U.S. patent application number 15/870258 was filed with the patent office on 2018-05-17 for systems and methods for transferring message data.
The applicant listed for this patent is Satori Worldwide, LLC. Invention is credited to Andrey Kushnir, Leonid Mosenkov, Maksim Terekhin.
Application Number | 20180139162 15/870258 |
Document ID | / |
Family ID | 56381799 |
Filed Date | 2018-05-17 |
United States Patent
Application |
20180139162 |
Kind Code |
A1 |
Kushnir; Andrey ; et
al. |
May 17, 2018 |
SYSTEMS AND METHODS FOR TRANSFERRING MESSAGE DATA
Abstract
Methods, systems, and apparatus, including computer programs
encoded on a computer storage medium, are described for providing
messages to client devices. In certain examples, the method
includes receiving a stream of messages at a client device, wherein
the stream of messages comprises a message transfer rate. The
method may also include determining, by one or more computer
processors, a download rate for an application client of the client
device, and providing, by the one or more computer processors, the
stream of messages to the application client at the message
transfer rate when the message transfer rate is less than or equal
to the download rate. The method may also include storing, by the
one or more computer processors, the stream of messages in a buffer
on the client device when the message transfer rate is greater than
the download rate.
Inventors: |
Kushnir; Andrey; (Sunnyvale,
CA) ; Terekhin; Maksim; (Ulyanovsk, RU) ;
Mosenkov; Leonid; (Ulyanovsk, RU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Satori Worldwide, LLC |
Palo Alto |
CA |
US |
|
|
Family ID: |
56381799 |
Appl. No.: |
15/870258 |
Filed: |
January 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15435915 |
Feb 17, 2017 |
9876745 |
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15870258 |
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15196597 |
Jun 29, 2016 |
9608953 |
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15435915 |
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14885034 |
Oct 16, 2015 |
9397973 |
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15196597 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 67/2857 20130101;
H04L 47/11 20130101; H04L 47/25 20130101; G06Q 10/107 20130101;
H04L 51/14 20130101 |
International
Class: |
H04L 12/58 20060101
H04L012/58; G06Q 10/10 20060101 G06Q010/10; H04L 29/08 20060101
H04L029/08; H04L 12/825 20060101 H04L012/825; H04L 12/801 20060101
H04L012/801 |
Claims
1. A method, comprising: receiving a stream of messages at a client
device, wherein the stream of messages comprises a message transfer
rate; determining, by one or more computer processors, a download
rate for an application client of the client device; providing, by
the one or more computer processors, the stream of messages to the
application client at the message transfer rate when the message
transfer rate is less than or equal to the download rate; and
storing, by the one or more computer processors, the stream of
messages in a buffer on the client device when the message transfer
rate is greater than the download rate.
2. The method of claim 1, wherein providing the stream of messages
to the application client at the message transfer rate comprises:
providing the stream of messages to the application client without
storing the messages in the buffer when the message transfer rate
is less than or equal to the download rate.
3. The method of claim 1, further comprising: monitoring download
capabilities of the application client; and based thereon,
determining that the application client is unable to download the
stream of messages at the message transfer rate.
4. The method of claim 1, further comprising: providing messages in
the buffer to the application client when the message transfer rate
is greater than the download rate.
5. The method of claim 1, further comprising: deleting messages
stored in the buffer when the buffer is full and the application
client is unable to download additional messages.
6. The method of claim 5, wherein messages stored in the buffer for
a longest period of time are deleted.
7. The method of claim 1, further comprising: allowing a stored
quantity of messages in the buffer to decrease when the message
transfer rate is less than or equal to the download rate.
8. The method of claim 7, further comprising: determining that the
stored quantity of messages in the buffer is zero; and in response,
providing the stream of messages to the application client at the
message transfer rate.
9. The method of claim 1, wherein messages are provided to the
application client in an order in which the messages are
received.
10. The method of claim 1, wherein the download rate corresponds to
a maximum rate at which the application client is able to download
messages.
11. A system, comprising: one or more computer processors
programmed to perform operations to: receive a stream of messages
at a client device, wherein the stream of messages comprises a
message transfer rate; determine a download rate for an application
client of the client device; provide the stream of messages to the
application client at the message transfer rate when the message
transfer rate is less than or equal to the download rate; and store
the stream of messages in a buffer on the client device when the
message transfer rate is greater than the download rate.
12. The system of claim 11, wherein to provide the stream of
messages to the application client at the message transfer rate the
one or more computer processors are further to: provide the stream
of messages to the application client without storing the messages
in the buffer when the message transfer rate is less than or equal
to the download rate.
13. The system of claim 11, wherein the operations are further to:
monitor download capabilities of the application client; and based
thereon, determine that the application client is unable to
download the stream of messages at the message transfer rate.
14. The system of claim 11, wherein the operations are further to:
provide messages in the buffer to the application client when the
message transfer rate is greater than the download rate.
15. The system of claim 11, wherein the operations are further to:
delete messages stored in the buffer when the buffer is full and
the application client is unable to download additional
messages.
16. The system of claim 15, wherein messages stored in the buffer
for a longest period of time are deleted.
17. The system of claim 11, wherein the operations are further to:
allow a stored quantity of messages in the buffer to decrease when
the message transfer rate is less than or equal to the download
rate.
18. The system of claim 17, wherein the operations are further to:
determine that the stored quantity of messages in the buffer is
zero; and in response, provide the stream of messages to the
application client at the message transfer rate.
19. The system of claim 11, wherein messages are provided to the
application client in an order in which the messages are
received.
20. A non-transitory computer-readable medium having instructions
stored thereon that, when executed by one or more computer
processors, cause the one or more computer processors to: receive a
stream of messages at a client device, wherein the stream of
messages comprises a message transfer rate; determine, by the one
or more computer processors, a download rate for an application
client of the client device; provide, by the one or more computer
processors, the stream of messages to the application client at the
message transfer rate when the message transfer rate is less than
or equal to the download rate; and store, by the one or more
computer processors, the stream of messages in a buffer on the
client device when the message transfer rate is greater than the
download rate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/435,915, filed Feb. 17, 2017, which is a continuation of
U.S. application Ser. No. 15/196,597, filed Jun. 29, 2016 (now U.S.
Pat. No. 9,608,953, issued Mar. 28, 2017), which is a continuation
of U.S. application Ser. No. 14/885,034, filed Oct. 16, 2015 (now
U.S. Pat. No. 9,397,973, issued Jul. 19, 2016), the entire contents
of each of which are hereby incorporated by reference.
BACKGROUND
[0002] This specification relates to a data communication system
and, in particular, a system that implements real-time, scalable
publish-subscribe messaging.
[0003] The publish-subscribe pattern (or "PubSub") is a data
communication messaging arrangement implemented by software systems
where so-called publishers publish messages to topics and so-called
subscribers receive the messages pertaining to particular topics to
which they are subscribed. There can be one or more publishers per
topic and publishers generally have no knowledge of what
subscribers, if any, will receive the published messages. Some
PubSub systems do not cache messages or have small caches meaning
that subscribers may not receive messages that were published
before the time of subscription to a particular topic. PubSub
systems can be susceptible to performance instability during surges
of message publications or as the number of subscribers to a
particular topic increases. Further, existing Pubsub systems may
attempt to process as many events and messages as possible on the
client device. This leads to performance degradation when the flow
of messages is too high for the client device.
SUMMARY
[0004] Examples of the systems and methods described herein are
used to process messages and other data received at client devices
of users. In instances when a messaging application on a client
device is unable to keep up with a rate at which messages are
received on the client device, the messages are diverted to a
buffer on the client device. The buffer then forwards the messages
to the messaging application, preferably in an order in which the
messages were received. The buffer stores the message data
temporarily and sends the messages to the messaging application at
a rate the messaging application is able to handle (e.g., a maximum
download rate for the messaging application). In general, the
buffer accumulates message data when the buffer receives messages
faster than the messages are forward from the buffer to the
messaging application. Likewise, the buffer stores fewer messages
when the buffer receives messages at a lower rate than the messages
are forwarded from the buffer to the messaging application.
Accordingly, the buffer is able to provide messages to the
messaging application at a rate that is suitable for the messaging
application, such that the messaging device receives messages in a
proper order and at a proper rate. This avoids problems associated
with prior systems in which a messaging application may receive
messages too quickly and, as a result, may drop certain messages
and/or crash due to overload.
[0005] In general, one aspect of the subject matter described in
this specification relates to a method. The method includes
performing, by one or more computers, the following steps:
receiving at a client device a stream of messages from a sender;
providing the stream of messages to a messaging application on the
client device at a desired message feed rate associated with the
sender; monitoring a message download rate of the stream of
messages by the messaging application; determining that the message
download rate is less than the desired message feed rate and, in
response, providing the stream of messages to a buffer on the
client device at the desired message feed rate, and sending the
stream of messages from the buffer to the messaging application at
the message download rate; determining that the message download
rate is greater than the desired message feed rate and, in
response, allowing a stored quantity of messages on the buffer to
decrease; and determining that the stored quantity of messages on
the buffer is zero and, in response, providing the stream of
messages to the messaging application at the desired message feed
rate.
[0006] In certain examples, the stream of messages corresponds to a
single channel in a PubSub system or, alternatively, to a plurality
of channels in a PubSub system. The buffer may include a plurality
of buffers, and each buffer in the plurality of buffers may
correspond to one channel in the plurality of channels. In various
instances, the sender is or includes an MX node in a PubSub system.
The desired message feed rate may correspond to a rate at which
messages are published in a PubSub system. In some implementations,
the download rate corresponds to a maximum rate at which the
messaging application is able to download messages. The download
rate may depend on, for example, a desired refresh rate for the
client device.
[0007] In some examples, sending the stream of messages from the
buffer to the client device may include sending messages in an
order in which the messages were received by the buffer. In
general, the stored quantity of messages on the buffer increases
(e.g., message data accumulates on the buffer) when the desired
message feed rate is greater than the message download rate. In
various examples, the stored quantity of messages on the buffer
decreases when the desired message feed rate is less than the
message download rate.
[0008] In another aspect, the subject matter of this disclosure
relates to a system that includes a non-transitory computer
readable medium having instructions stored thereon. The system also
includes a data processing apparatus configured to execute the
instructions to perform operations that include: receiving at a
client device a stream of messages from a sender; providing the
stream of messages to a messaging application on the client device
at a desired message feed rate associated with the sender;
monitoring a message download rate of the stream of messages by the
messaging application; determining that the message download rate
is less than the desired message feed rate and, in response,
providing the stream of messages to a buffer on the client device
at the desired message feed rate, and sending the stream of
messages from the buffer to the messaging application at the
message download rate; determining that the message download rate
is greater than the desired message feed rate and, in response,
allowing a stored quantity of messages on the buffer to decrease;
and determining that the stored quantity of messages on the buffer
is zero and, in response, providing the stream of messages to the
messaging application at the desired message feed rate.
[0009] In certain examples, the stream of messages corresponds to a
single channel in a PubSub system or, alternatively, to a plurality
of channels in a PubSub system. The buffer may include a plurality
of buffers, and each buffer in the plurality of buffers may
correspond to one channel in the plurality of channels. In various
instances, the sender is or includes an MX node in a PubSub system.
The desired message feed rate may correspond to a rate at which
messages are published in a PubSub system. In some implementations,
the download rate corresponds to a maximum rate at which the
messaging application is able to download messages. The download
rate may depend on, for example, a desired refresh rate for the
client device.
[0010] In some examples, sending the stream of messages from the
buffer to the client device may include sending messages in an
order in which the messages were received by the buffer. In
general, the stored quantity of messages on the buffer increases
(e.g., message data accumulates on the buffer) when the desired
message feed rate is greater than the message download rate. In
various examples, the stored quantity of messages on the buffer
decreases when the desired message feed rate is less than the
message download rate.
[0011] In another aspect, the subject matter described in this
specification can be embodied in a computer program product stored
in one or more non-transitory storage media for controlling a
processing mode of a data processing apparatus. The computer
program product is executable by the data processing apparatus to
cause the data processing apparatus to perform operations
including: receiving at a client device a stream of messages from a
sender; providing the stream of messages to a messaging application
on the client device at a desired message feed rate associated with
the sender; monitoring a message download rate of the stream of
messages by the messaging application; determining that the message
download rate is less than the desired message feed rate and, in
response, providing the stream of messages to a buffer on the
client device at the desired message feed rate, and sending the
stream of messages from the buffer to the messaging application at
the message download rate; determining that the message download
rate is greater than the desired message feed rate and, in
response, allowing a stored quantity of messages on the buffer to
decrease; and determining that the stored quantity of messages on
the buffer is zero and, in response, providing the stream of
messages to the messaging application at the desired message feed
rate.
[0012] In certain examples, the stream of messages corresponds to a
single channel in a PubSub system or, alternatively, to a plurality
of channels in a PubSub system. The buffer may include a plurality
of buffers, and each buffer in the plurality of buffers may
correspond to one channel in the plurality of channels. In various
instances, the sender is or includes an MX node in a PubSub system.
The desired message feed rate may correspond to a rate at which
messages are published in a PubSub system. In some implementations,
the download rate corresponds to a maximum rate at which the
messaging application is able to download messages. The download
rate may depend on, for example, a desired refresh rate for the
client device.
[0013] In some examples, sending the stream of messages from the
buffer to the client device may include sending messages in an
order in which the messages were received by the buffer. In
general, the stored quantity of messages on the buffer increases
(e.g., message data accumulates on the buffer) when the desired
message feed rate is greater than the message download rate. In
various examples, the stored quantity of messages on the buffer
decreases when the desired message feed rate is less than the
message download rate.
[0014] The details of one or more embodiments of the subject matter
described in this specification are set forth in the accompanying
drawings and the description below. Other features, aspects, and
advantages of the subject matter will become apparent from the
description, the drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1A illustrates an example system that supports the
PubSub communication pattern.
[0016] FIG. 1B illustrates functional layers of software on an
example client device.
[0017] FIG. 2 is a diagram of an example messaging system.
[0018] FIG. 3A is a data flow diagram of an example method for
writing data to a streamlet.
[0019] FIG. 3B is a data flow diagram of an example method for
reading data from a streamlet.
[0020] FIGS. 4A-4F are schematic diagrams of an example system for
providing message data to a client device.
[0021] FIG. 5 is a flowchart of an example method for providing
message data to a client device.
DETAILED DESCRIPTION
[0022] FIG. 1A illustrates an example system 100 that supports the
PubSub communication pattern. Publisher clients (e.g., Publisher 1)
can publish messages to named channels (e.g., "Channel 1") by way
of the system 100. A message can comprise any type of information
including one or more of the following: text, image content, sound
content, multimedia content, video content, binary data, and so on.
Other types of message data are possible. Subscriber clients (e.g.,
Subscriber 2) can subscribe to a named channel using the system 100
and start receiving messages which occur after the subscription
request or from a given position (e.g., a message number or time
offset). A client can be both a publisher and a subscriber.
[0023] Depending on the configuration, a PubSub system can be
categorized as follows: [0024] One to One (1:1). In this
configuration there is one publisher and one subscriber per
channel. A typical use case is private messaging. [0025] One to
Many (1:N). In this configuration there is one publisher and
multiple subscribers per channel. Typical use cases are
broadcasting messages (e.g., stock prices). [0026] Many to Many
(M:N). In this configuration there are many publishers publishing
to a single channel. The messages are then delivered to multiple
subscribers. Typical use cases are map applications.
[0027] There is no separate operation needed to create a named
channel. A channel is created implicitly when the channel is
subscribed to or when a message is published to the channel. In
some implementations, channel names can be qualified by a name
space. A name space comprises one or more channel names. Different
name spaces can have the same channel names without causing
ambiguity. The name space name can be a prefix of a channel name
where the name space and channel name are separated by a dot. In
some implementations, name spaces can be used when specifying
channel authorization settings. For instance, the messaging system
100 may have app1.foo and app1.system.notifications channels where
"app1" is the name of the name space. The system can allow clients
to subscribe and publish to the app1.foo channel. However, clients
can only subscribe to, but not publish to the
app1.system.notifications channel.
[0028] FIG. 1B illustrates functional layers of software on an
example client device. A client device (e.g., client 102) is a data
processing apparatus such as, for example, a personal computer, a
laptop computer, a tablet computer, a smart phone, a smart watch,
or a server computer. Other types of client devices are possible.
The application layer 104 comprises the end-user application(s)
that will integrate with the PubSub system 100. The messaging layer
106 is a programmatic interface for the application layer 104 to
utilize services of the system 100 such as channel subscription,
message publication, message retrieval, user authentication, and
user authorization. In some implementations, the messages passed to
and from the messaging layer 106 are encoded as JavaScript Object
Notation (JSON) objects. Other message encoding schemes are
possible.
[0029] The operating system 108 layer comprises the operating
system software on the client 102. In various implementations,
messages can be sent and received to/from the system 100 using
persistent or non-persistent connections. Persistent connections
can be created using, for example, network sockets. A transport
protocol such as TCP/IP layer 112 implements the Transport Control
Protocol/Internet Protocol communication with the system 100 that
can be used by the messaging layer 106 to send messages over
connections to the system 100. Other communication protocols are
possible including, for example, User Datagram Protocol (UDP). In
further implementations, an optional Transport Layer Security (TLS)
layer 110 can be employed to ensure the confidentiality of the
messages.
[0030] FIG. 2 is a diagram of an example messaging system 100. The
system 100 provides functionality for implementing PubSub
communication patterns. The system comprises software components
and storage that can be deployed at one or more data centers 122 in
one or more geographic locations, for example. The system comprises
MX nodes (e.g., MX nodes or multiplexer nodes 202, 204 and 206), Q
nodes (e.g., Q nodes or queue nodes 208, 210 and 212), one or more
channel manager nodes (e.g., channel managers 214, 215), and
optionally one or more C nodes (e.g., C nodes or cache nodes 220
and 222). Each node can execute in a virtual machine or on a
physical machine (e.g., a data processing apparatus). Each MX node
serves as a termination point for one or more publisher and/or
subscriber connections through the external network 216. The
internal communication among MX nodes, Q nodes, C nodes, and the
channel manager, is conducted over an internal network 218, for
example. By way of illustration, MX node 204 can be the terminus of
a subscriber connection from client 102. Each Q node buffers
channel data for consumption by the MX nodes. An ordered sequence
of messages published to a channel is a logical channel stream. For
example, if three clients publish messages to a given channel, the
combined messages published by the clients comprise a channel
stream. Messages can be ordered in a channel stream by time of
publication by the client, by time of receipt by an MX node, or by
time of receipt by a Q node. Other ways for ordering messages in a
channel stream are possible. In the case where more than one
message would be assigned to the same position in the order, one of
the messages can be chosen (e.g., randomly) to have a later
sequence in the order. Each channel manager node is responsible for
managing Q node load by splitting channel streams into so-called
streamlets. Streamlets are discussed further below. The optional C
nodes provide caching and load removal from the Q nodes.
[0031] In the example messaging system 100, one or more client
devices (publishers and/or subscribers) establish respective
persistent connections (e.g., TCP connections) to an MX node (e.g.,
MX node 204). The MX node serves as a termination point for these
connections. For instance, external messages (e.g., between
respective client devices and the MX node) carried by these
connections can be encoded based on an external protocol (e.g.,
JSON). The MX node terminates the external protocol and translates
the external messages to internal communication, and vice versa.
The MX nodes publish and subscribe to streamlets on behalf of
clients. In this way, an MX node can multiplex and merge requests
of client devices subscribing for or publishing to the same
channel, thus representing multiple client devices as one, instead
of one by one.
[0032] In the example messaging system 100, a Q node (e.g., Q node
208) can store one or more streamlets of one or more channel
streams. A streamlet is a data buffer for a portion of a channel
stream. A streamlet will close to writing when its storage is full.
A streamlet will close to reading and writing and be de-allocated
when its time-to-live (TTL) has expired. By way of illustration, a
streamlet can have a maximum size of 1 MB and a TTL of three
minutes. Different channels can have streamlets limited by
different TTLs. For instance, streamlets in one channel can exist
for up to three minutes, while streamlets in another channel can
exist for up to 10 minutes. In various implementations, a streamlet
corresponds to a computing process running on a Q node. The
computing process can be terminated after the streamlet's TTL has
expired, thus freeing up computing resources (for the streamlet)
back to the Q node, for example.
[0033] When receiving a publish request from a client device, an MX
node (e.g., MX node 204) makes a request to a channel manager
(e.g., channel manager 214) to grant access to a streamlet to write
the message being published. Note, however, that if the MX node has
already been granted write access to a streamlet for the channel
(and the channel has not been closed to writing), the MX node can
write the message to that streamlet without having to request a
grant to access the streamlet. Once a message is written to a
streamlet for a channel, the message can be read by MX nodes and
provided to subscribers of that channel.
[0034] Similarly, when receiving a channel subscription request
from a client device, an MX node makes a request to a channel
manager to grant access to a streamlet for the channel from which
messages are read. If the MX node has already been granted read
access to a streamlet for the channel (and the channel's TTL has
not been closed to reading), the MX node can read messages from the
streamlet without having to request a grant to access the
streamlet. The read messages can then be forwarded to client
devices that have subscribed to the channel. In various
implementations, messages read from streamlets are cached by MX
nodes so that MX nodes can reduce the number of times needed to
read from the streamlets.
[0035] By way of illustration, an MX node can request a grant from
the channel manager that allows the MX node to store a block of
data into a streamlet on a particular Q node that stores streamlets
of the particular channel. Example streamlet grant request and
grant data structures are as follows:
TABLE-US-00001 StreamletGrantRequest = { ''channel'': string( )
''mode'': ''read'' | ''write'' "position": 0 }
StreamletGrantResponse = { ''streamlet-id'': ''abcdef82734987'',
''limit-size'': 2000000, # 2 megabytes max ''limit-msgs'': 5000, #
5 thousand messages max ''limit-life'': 4000, # the grant is valid
for 4 seconds "q-node'': string( ) "position": 0 }
[0036] The StreamletGrantRequest data structure stores the name of
the stream channel and a mode indicating whether the MX node
intends on reading from or writing to the streamlet. The MX node
sends the StreamletGrantRequest to a channel manager node. The
channel manager node, in response, sends the MX node a
StreamletGrantResponse data structure. The StreamletGrantResponse
contains an identifier of the streamlet (streamlet-id), the maximum
size of the streamlet (limit-size), the maximum number of messages
that the streamlet can store (limit-msgs), the TTL (limit-life),
and an identifier of a Q node (q-node) on which the streamlet
resides. The StreamletGrantRequest and StreamletGrantResponse can
also have a position field that points to a position in a streamlet
(or a position in a channel) for reading from the streamlet.
[0037] A grant becomes invalid once the streamlet has closed. For
example, a streamlet is closed to reading and writing once the
streamlet's TTL has expired and a streamlet is closed to writing
when the streamlet's storage is full. When a grant becomes invalid,
the MX node can request a new grant from the channel manager to
read from or write to a streamlet. The new grant will reference a
different streamlet and will refer to the same or a different Q
node depending on where the new streamlet resides.
[0038] FIG. 3A is a data flow diagram of an example method for
writing data to a streamlet in various implementations. In FIG. 3A,
when an MX node (e.g., MX node 202) request to write to a streamlet
is granted by a channel manager (e.g., channel manager 214), as
described before, the MX node establishes a Transmission Control
Protocol (TCP) connection with the Q node (e.g., Q node 208)
identified in the grant response received from the channel manager
(302). A streamlet can be written concurrently by multiple write
grants (e.g., for messages published by multiple publisher
clients). Other types of connection protocols between the MX node
and the Q node are possible.
[0039] The MX node then sends a prepare-publish message with an
identifier of a streamlet that the MX node wants to write to the Q
node (304). The streamlet identifier and Q node identifier can be
provided by the channel manager in the write grant as described
earlier. The Q node hands over the message to a handler process 301
(e.g., a computing process running on the Q node) for the
identified streamlet (306). The handler process can send to the MX
node an acknowledgement (308). After receiving the acknowledgement,
the MX node starts writing (publishing) messages (e.g., 310, 312,
314, and 318) to the handler process, which in turns stores the
received data in the identified streamlet. The handler process can
also send acknowledgements (316, 320) to the MX node for the
received data. In some implementations, acknowledgements can be
piggy-backed or cumulative. For instance, the handler process can
send to the MX node an acknowledgement for every predetermined
amount of data received (e.g., for every 100 messages received), or
for every predetermined time period (e.g., for every one
millisecond). Other acknowledgement scheduling algorithms, such as
Nagle's algorithm, can be used.
[0040] If the streamlet can no longer accept published data (e.g.,
when the streamlet is full), the handler process sends a
Negative-Acknowledgement (NAK) message (330) indicating a problem,
following by an EOF (end-of-file) message (332). In this way, the
handler process closes the association with the MX node for the
publish grant. The MX node can then request a write grant for
another streamlet from a channel manager if the MX node has
additional messages to store.
[0041] FIG. 3B is a data flow diagram of an example method for
reading data from a streamlet in various implementations. In FIG.
3B, an MX node (e.g., MX node 204) sends to a channel manager
(e.g., channel manager 214) a request for reading a particular
channel starting from a particular message or time offset in the
channel. The channel manager returns to the MX node a read grant
including an identifier of a streamlet containing the particular
message, a position in the streamlet corresponding to the
particular message, and an identifier of a Q node (e.g., Q node
208) containing the particular streamlet. The MX node then
establishes a TCP connection with the Q node (352). Other types of
connection protocols between the MX node and the Q node are
possible.
[0042] The MX node then sends to the Q node a subscribe message
(354) with the identifier of the streamlet (in the Q node) and the
position in the streamlet from which the MX node wants to read
(356). The Q node hands over the subscribe message to a handler
process 351 for the streamlet (356). The handler process can send
to the MX node an acknowledgement (358). The handler process then
sends messages (360, 364, 366), starting at the position in the
streamlet, to the MX node. In some implementations, the handler
process can send all of the messages in the streamlet to the MX
node. After sending the last message in a particular streamlet, the
handler process can send a notification of the last message to the
MX node. The MX node can send to the channel manager another
request for another streamlet containing a next message in the
particular channel.
[0043] If the particular streamlet is closed (e.g., after its TTL
has expired), the handler process can send an unsubscribe message
(390), followed by an EOF message (392), to close the association
with the MX node for the read grant. The MX node can close the
association with the handler process when the MX node moves to
another streamlet for messages in the particular channel (e.g., as
instructed by the channel manager). The MX node can also close the
association with the handler process if the MX node receives an
unsubscribe message from a corresponding client device.
[0044] In various implementations, a streamlet can be written into
and read from at the same time instance. For instance, there can be
a valid read grant and a valid write grant at the same time
instance. In various implementations, a streamlet can be read
concurrently by multiple read grants (e.g., for channels subscribed
to by multiple publisher clients). The handler process of the
streamlet can order messages from concurrent write grants based on,
for example, time-of-arrival, and store the messages based on the
order. In this way, messages published to a channel from multiple
publisher clients can be serialized and stored in a streamlet of
the channel.
[0045] In the messaging system 100, one or more C nodes (e.g., C
node 220) can offload data transfers from one or more Q nodes. For
instance, if there are many MX nodes requesting streamlets from Q
nodes for a particular channel, the streamlets can be offloaded and
cached in one or more C nodes. The MX nodes (e.g., as instructed by
read grants from a channel manager) can read the streamlets from
the C nodes instead.
[0046] As described above, messages for a channel in the messaging
system 100 are ordered in a channel stream. A channel manager
(e.g., channel manager 214) splits the channel stream into
fixed-sized streamlets that each reside on a respective Q node. In
this way, storing a channel stream can be shared among many Q
nodes; each Q node stores a portion (one or more streamlets) of the
channel stream. More particularly, a streamlet can be stored in
registers and dynamic memory elements associated with a computing
process on a Q node, thus avoiding the need to access persistent,
slower storage devices such as hard disks. This results in faster
message access. The channel manager can also balance load among Q
nodes in the messaging system 100 by monitoring respective
workloads of the Q nodes and allocating streamlets in a way that
avoids overloading any one Q node.
[0047] In various implementations, a channel manager maintains a
list identifying each active streamlet, the respective Q node on
which the streamlet resides, an identification of the position of
the first message in the streamlet, and whether the streamlet is
closed for writing. In some implementations, Q nodes notify the
channel manager and any MX nodes that are publishing to a streamlet
that the streamlet is closed due to being full or when the
streamlet's TTL has expired. When a streamlet is closed, the
streamlet remains on the channel manager's list of active
streamlets until the streamlet's TTL has expired so that MX nodes
can continue to retrieve messages from the streamlet.
[0048] When an MX node requests a write grant for a given channel
and there is not a streamlet for the channel that can be written
to, the channel manager allocates a new streamlet on one of the Q
nodes and returns the identity of the streamlet and the Q node in
the StreamletGrantResponse. Otherwise, the channel manager returns
the identity of the currently open for writing streamlet and
corresponding Q node in the StreamletGrantResponse. MX nodes can
publish messages to the streamlet until the streamlet is full or
the streamlet's TTL has expired, after which a new streamlet can be
allocated by the channel manager.
[0049] When an MX node requests a read grant for a given channel
and there is not a streamlet for the channel that can be read from,
the channel manager allocates a new streamlet on one of the Q nodes
and returns the identity of the streamlet and the Q node in the
StreamletGrantResponse. Otherwise, the channel manager returns the
identity of the streamlet and Q node that contains the position
from which the MX node wishes to read. The Q node can then begin
sending messages to the MX node from the streamlet beginning at the
specified position until there are no more messages in the
streamlet to send. When a new message is published to a streamlet,
MX nodes that have subscribed to that streamlet will receive the
new message. If a streamlet's TTL has expired, the handler process
351 sends an EOF message (392) to any MX nodes that are subscribed
to the streamlet.
[0050] As described earlier in reference to FIG. 2, the messaging
system 100 can include multiple channel managers (e.g., channel
managers 214, 215). Multiple channel managers provide resiliency
and prevent single point of failure. For instance, one channel
manager can replicate lists of streamlets and current grants it
maintains to another "slave" channel manager. As for another
example, multiple channel managers can coordinate operations
between them using distributed consensus protocols, such as Paxos
or Raft protocols.
[0051] In various examples, systems and methods are provided for
monitoring and controlling the transfer of message data to client
devices. When sending a stream of messages to a client device, the
systems and methods may attempt to send the message stream at a
desired message transfer rate, which may correspond to, for
example, a desired refresh rate for the client device or a desired
number of bytes/second. During periods of high message traffic, the
client device may be unable to receive or download the message
stream at the desired message transfer rate. For example, a
download rate at the client device may be lower than the desired
message transfer rate. In such an instance, the message stream may
be diverted to a buffer which may store or accumulate message data
and pass the message data along to the client device, preferably in
the order in which the buffer received the message data. When the
buffer receives message data faster than the buffer transfers
message data to the client device (e.g., because the desired
message feed rate is greater than the download rate at the client
device), message data accumulates on the buffer. Likewise, when the
buffer transfers message data to the client device faster than it
receives message data (e.g., because the download rate at the
client device is greater than the desired message feed rate),
message data is removed from the buffer. When a number of messages
stored on the buffer is equal to zero, messages may again be sent
directly to the client device, without first being diverted to the
buffer.
[0052] FIG. 4A is an example system 400 for monitoring and
controlling a transfer of message data. The system 400 includes a
message sender 402 for sending messages to a client device 404. The
client device 404 includes a controller 405, a buffer 406, a
messaging application 407, and a sensor 408. The controller 405,
the buffer 406, and/or the sensor 408 are preferably implemented in
software. During operation of the system 400, the sender 402 (e.g.,
an MX node) transfers streams of messages to the client device 404
along an input path 409 to the controller 405. The messages pass
through the controller 405 and travel along primary path 410 to the
messaging application 407. The sensor 408 monitors a download rate
of the messages at the messaging application 407 and reports the
download rate to the controller 405 along a feedback path 412.
[0053] In general, the sender 402 transfers the message streams to
the client device 404 at a desired message feed rate. The desired
message feed rate may be or may correspond to, for example, a rate
at which the sender 402 is receiving message data to send to the
client device 404. When the sender 402 receives messages at a
higher rate, it may attempt to transfer the message streams to the
client device 404 at a correspondingly higher rate. In this way,
the desired message feed rate may fluctuate over time, according to
a number of messages being processed or handled by the sender
402.
[0054] In certain instances, the messaging application 407 is
unable to receive or download the message streams at the desired
message feed rate. When this happens, the sensor 408, which is
monitoring the download rate and capabilities of the messaging
application 407, instructs the controller 405 to stop sending the
messages along the primary path 410 and instead to divert the
messages to the buffer 406 along a buffer input path 414. The
messages are then forward from the buffer 406 to the messaging
application 407, along a buffer output path 416. The buffer 406 is
able to store or accumulate messages, and messages can therefore be
sent from the buffer 406 to the messaging application 407 at a rate
that is lower than the desired message feed rate. For example, the
rate at which messages are sent from the buffer 406 to the
messaging application 407 (referred to herein as a "buffer feed
rate") may be equal to a maximum download rate associated with the
messaging application 407 (e.g., a maximum rate at which the
messaging application 407 is capable of downloading messages). This
maximum download rate may be a fixed value (e.g., based on a
desired refresh rate for the messaging application 407 or the
client device 404) or it may vary over time. In some
implementations, the maximum download rate is monitored and
detected by the sensor 408.
[0055] In general, a rate at which the buffer 406 accumulates
messages is a function of the desired message feed rate and the
buffer feed rate. When the desired message feed rate exceeds the
buffer feed rate, a number of messages stored in the buffer 406
increases. When the desired message feed rate is less than the
buffer feed rate, the number of messages stored in the buffer 406
decreases.
[0056] The messaging application is preferably a software program
that a user of a client device uses to view or receive message
data. The messaging application may be, for example, a software
program for viewing or receiving text messages, email, news feeds,
images, music, video, or combinations thereof. The messaging
application may be implemented on any suitable client device,
including, for example, smart phones, tablet computers, personal
computers, and workstations.
[0057] FIGS. 4B through 4F show messages being delivered along the
primary path 410, the buffer input path 414, and the buffer output
path 416. In the example of FIG. 4B, the controller 405 is sending
a message M1 to the messaging application 407 along the primary
path 410. At this instant in time, the messaging application 407 is
able to download messages at a rate equal to the desired message
feed rate (e.g., the desired message feed rate is less than the
maximum download rate of the messaging application 407).
[0058] At a later time, referring to FIG. 4C, the controller 405
sends another message M2 to the messaging application 407 along the
primary path 410, but the download rate of the messaging
application 407 (e.g., as measured by the sensor 408) is less than
the desired message feed rate. To allow the sender 402 to continue
delivering messages at the desired message feed rate, the
controller 405 sends a subsequent message M3 to the buffer 406,
along the buffer input path 414.
[0059] At a further instance in time, referring to FIG. 4D, the
controller 405 continues to send messages to the buffer 406 along
the buffer input path 414, and the messages are, in turn, forwarded
from the buffer 406 to the messaging application 407 along the
buffer output path 416. At this time, message M3 is being sent from
the buffer 406 to the messaging application 407, and message M8 is
being sent from the controller 405 to the buffer 406. The buffer
406 is also storing messages M4 through M7, which were sent from
the controller 405 and received by the buffer 406 previously. The
desired message feed rate at this time is greater than the download
rate, and the number of messages stored on the buffer 406 is
increasing.
[0060] At a later time, referring to FIG. 4E, the buffer 406 is no
longer storing messages and message M8 has been sent from the
buffer 406 to the messaging application 407. At this time, the
desired message feed rate is less than the download rate of the
messaging application 407, and the number of messages stored on the
buffer 406 has decreased to zero. With the buffer 406 now empty and
the messaging application 407 able to download messages at the
desired feed rate, the controller 405 sends a next message M9
directly to the messaging application 407 along the primary path
410, as shown in FIG. 4F.
[0061] In various implementations, the desired message feed rate is
equal to the rate at which the sender 402 sends and receives
messages. The sender 402, which may be an MX node or other PubSub
system device, receives or obtains a stream of messages and
forwards the messages to the client device 404. The rate at which
the sender 402 forwards the messages may be equal to the rate at
which the sender 402 receives the messages. The sender 402
preferably forwards messages in an order in which the messages were
received.
[0062] In some instances, when the buffer 406 is full and the
messaging application 407 is unable to receive additional messages,
one or more messages (e.g., messages that have been stored by the
buffer for the longest period of time) may be deleted from the
buffer 406 without being sent to the messaging application 407.
Deleting the messages in this manner may avoid buffer bloat.
[0063] In certain examples, the system 400 utilizes a process
control scheme to obtain desired rates of message data transfer
from the sender 402 to the messaging application 407. The sensor
408 monitors the download rate at the messaging application 407 and
provides measured download rates to the controller 405 (e.g., along
the feedback path 412) and/or one or more other components of the
system 400. Likewise, the desired message feed rate is monitored by
the controller 405 and/or one or more other components of the
system 400. When the download rate is less than the desired message
feed rate (i.e., the messaging application 407 is unable to handle
a flowrate of messages it is receiving), the controller 405 or a
process controller used by the system 400 (e.g., within the client
device 404) diverts messages to the buffer 406, thereby relieving
message input demands on the messaging application 407. The
controller 405 continues to monitor the download rate and the
desired message feed rate. When the buffer 406 is empty and/or no
longer required to reduce the flow of messages to the client device
404, the controller 405 may resume sending messages directly to the
messaging application 407 along the primary path 410 (e.g., without
first passing message data through the buffer 406).
[0064] In alternative implementations, the system 400 may not
include the primary path 410 and may always send messages to the
messaging application 407 via the buffer 406, using the buffer
input path 414 and the buffer output path 416. In this arrangement,
when the desired message feed rate does not exceed the download
rate, the buffer 406 may not store message data and may instead
serve as a conduit through which messages are sent to the messaging
application 407. The buffer 406 may store messages, as needed, when
the desired message feed rate exceeds the download rate, as
described herein.
[0065] FIG. 5 is a flowchart of a method 500 of providing message
data to a client device in accordance with certain examples. A
stream of messages is received (step 501) at the client device from
a sender (e.g., an MX node in a PubSub system). The stream of
messages is provided (step 502) to a messaging application on the
client device at a desired message feed rate associated with the
sender. The desired message feed rate may be, for example, a rate
at which messages are published in a PubSub system. A message
download rate of the stream of messages by the messaging
application is monitored (step 504). A determination is made (step
506) that the message download rate is less than the desired
message feed rate. In response, the stream of messages is provided
(step 508) to a buffer for the client device at the desired message
feed rate, and the stream of messages is sent (step 510) from the
buffer to the messaging application at the message download rate. A
determination is made (step 512) that the message download rate is
greater than the desired message feed rate and, in response, a
stored quantity of messages on the buffer is allowed (step 514) to
decrease. A determination is made (step 516) that the stored
quantity of messages on the buffer is zero and, in response, the
stream of messages is provided (step 518) to the messaging
application at the desired message feed rate.
[0066] Embodiments of the subject matter and the operations
described in this specification can be implemented in digital
electronic circuitry, or in computer software, firmware, or
hardware, including the structures disclosed in this specification
and their structural equivalents, or in combinations of one or more
of them. Embodiments of the subject matter described in this
specification can be implemented as one or more computer programs,
i.e., one or more modules of computer program instructions, encoded
on computer storage medium for execution by, or to control the
operation of, data processing apparatus. Alternatively or in
addition, the program instructions can be encoded on an
artificially-generated propagated signal, e.g., a machine-generated
electrical, optical, or electromagnetic signal, that is generated
to encode information for transmission to suitable receiver
apparatus for execution by a data processing apparatus. A computer
storage medium can be, or be included in, a computer-readable
storage device, a computer-readable storage substrate, a random or
serial access memory array or device, or a combination of one or
more of them. Moreover, while a computer storage medium is not a
propagated signal, a computer storage medium can be a source or
destination of computer program instructions encoded in an
artificially-generated propagated signal. The computer storage
medium can also be, or be included in, one or more separate
physical components or media (e.g., multiple CDs, disks, or other
storage devices).
[0067] The operations described in this specification can be
implemented as operations performed by a data processing apparatus
on data stored on one or more computer-readable storage devices or
received from other sources.
[0068] The term "data processing apparatus" encompasses all kinds
of apparatus, devices, and machines for processing data, including
by way of example a programmable processor, a computer, a system on
a chip, or multiple ones, or combinations, of the foregoing. The
apparatus can include special purpose logic circuitry, e.g., an
FPGA (field programmable gate array) or an ASIC
(application-specific integrated circuit). The apparatus can also
include, in addition to hardware, code that creates an execution
environment for the computer program in question, e.g., code that
constitutes processor firmware, a protocol stack, a database
management system, an operating system, a cross-platform runtime
environment, a virtual machine, or a combination of one or more of
them. The apparatus and execution environment can realize various
different computing model infrastructures, such as web services,
distributed computing and grid computing infrastructures.
[0069] A computer program (also known as a program, software,
software application, script, or code) can be written in any form
of programming language, including compiled or interpreted
languages, declarative, procedural, or functional languages, and it
can be deployed in any form, including as a stand-alone program or
as a module, component, subroutine, object, or other unit suitable
for use in a computing environment. A computer program may, but
need not, correspond to a file in a file system. A program can be
stored in a portion of a file that holds other programs or data
(e.g., one or more scripts stored in a markup language resource),
in a single file dedicated to the program in question, or in
multiple coordinated files (e.g., files that store one or more
modules, sub-programs, or portions of code). A computer program can
be deployed to be executed on one computer or on multiple computers
that are located at one site or distributed across multiple sites
and interconnected by a communication network.
[0070] The processes and logic flows described in this
specification can be performed by one or more programmable
processors executing one or more computer programs to perform
actions by operating on input data and generating output. The
processes and logic flows can also be performed by, and apparatus
can also be implemented as, special purpose logic circuitry, e.g.,
an FPGA (field programmable gate array) or an ASIC
(application-specific integrated circuit).
[0071] Processors suitable for the execution of a computer program
include, by way of example, both general and special purpose
microprocessors, and any one or more processors of any kind of
digital computer. Generally, a processor will receive instructions
and data from a read-only memory or a random access memory or both.
The essential elements of a computer are a processor for performing
actions in accordance with instructions and one or more memory
devices for storing instructions and data. Generally, a computer
will also include, or be operatively coupled to receive data from
or transfer data to, or both, one or more mass storage devices for
storing data, e.g., magnetic disks, magneto-optical disks, optical
disks, or solid state drives. However, a computer need not have
such devices. Moreover, a computer can be embedded in another
device, e.g., a smart phone, a mobile audio or video player, a game
console, a Global Positioning System (GPS) receiver, or a portable
storage device (e.g., a universal serial bus (USB) flash drive), to
name just a few. Devices suitable for storing computer program
instructions and data include all forms of non-volatile memory,
media and memory devices, including, by way of example,
semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory
devices; magnetic disks, e.g., internal hard disks or removable
disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The
processor and the memory can be supplemented by, or incorporated
in, special purpose logic circuitry.
[0072] To provide for interaction with a user, embodiments of the
subject matter described in this specification can be implemented
on a computer having a display device, e.g., a CRT (cathode ray
tube) or LCD (liquid crystal display) monitor, for displaying
information to the user and a keyboard and a pointing device, e.g.,
a mouse, a trackball, a touchpad, or a stylus, by which the user
can provide input to the computer. Other kinds of devices can be
used to provide for interaction with a user as well; for example,
feedback provided to the user can be any form of sensory feedback,
e.g., visual feedback, auditory feedback, or tactile feedback; and
input from the user can be received in any form, including
acoustic, speech, or tactile input. In addition, a computer can
interact with a user by sending resources to and receiving
resources from a device that is used by the user; for example, by
sending web pages to a web browser on a user's client device in
response to requests received from the web browser.
[0073] Embodiments of the subject matter described in this
specification can be implemented in a computing system that
includes a back-end component, e.g., as a data server, or that
includes a middleware component, e.g., an application server, or
that includes a front-end component, e.g., a client computer having
a graphical user interface or a Web browser through which a user
can interact with an implementation of the subject matter described
in this specification, or any combination of one or more such
back-end, middleware, or front-end components. The components of
the system can be interconnected by any form or medium of digital
data communication, e.g., a communication network. Examples of
communication networks include a local area network ("LAN") and a
wide area network ("WAN"), an inter-network (e.g., the Internet),
and peer-to-peer networks (e.g., ad hoc peer-to-peer networks).
[0074] The computing system can include clients and servers. A
client and server are generally remote from each other and
typically interact through a communication network. The
relationship of client and server arises by virtue of computer
programs running on the respective computers and having a
client-server relationship to each other. In some embodiments, a
server transmits data (e.g., an HTML page) to a client device
(e.g., for purposes of displaying data to and receiving user input
from a user interacting with the client device). Data generated at
the client device (e.g., a result of the user interaction) can be
received from the client device at the server.
[0075] A system of one or more computers can be configured to
perform particular operations or actions by virtue of having
software, firmware, hardware, or a combination of them installed on
the system that in operation causes or cause the system to perform
the actions. One or more computer programs can be configured to
perform particular operations or actions by virtue of including
instructions that, when executed by data processing apparatus,
cause the apparatus to perform the actions.
[0076] While this specification contains many specific
implementation details, these should not be construed as
limitations on the scope of any inventions or of what may be
claimed, but rather as descriptions of features specific to
particular embodiments of particular inventions. Certain features
that are described in this specification in the context of separate
embodiments can also be implemented in combination in a single
embodiment. Conversely, various features that are described in the
context of a single embodiment can also be implemented in multiple
embodiments separately or in any suitable subcombination. Moreover,
although features may be described above as acting in certain
combinations and even initially claimed as such, one or more
features from a claimed combination can in some cases be excised
from the combination, and the claimed combination may be directed
to a subcombination or variation of a subcombination.
[0077] Similarly, while operations are depicted in the drawings in
a particular order, this should not be understood as requiring that
such operations be performed in the particular order shown or in
sequential order, or that all illustrated operations be performed,
to achieve desirable results. In certain circumstances,
multitasking and parallel processing may be advantageous. Moreover,
the separation of various system components in the embodiments
described above should not be understood as requiring such
separation in all embodiments, and it should be understood that the
described program components and systems can generally be
integrated together in a single software product or packaged into
multiple software products.
[0078] Thus, particular embodiments of the subject matter have been
described. Other embodiments are within the scope of the following
claims. In some cases, the actions recited in the claims can be
performed in a different order and still achieve desirable results.
In addition, the processes depicted in the accompanying figures do
not necessarily require the particular order shown, or sequential
order, to achieve desirable results. In certain implementations,
multitasking and parallel processing may be advantageous.
* * * * *