Changes between Version 2 and Version 3 of MasterSlaveCommunication

Timestamp:

05/31/12 09:47:39 (12 months ago)

Author:

sa1

Comment:

--

MasterSlaveCommunication

@@ -1 @@
-There is a new message-based protocol under development. This will replace the Twisted Perspective-Broker based protocol.
+There is a new message-based protocol under development. This will replace the Twisted Perspective-Broker based RPC protocol.
+= Current Protocol =
 For the current API,
 See: [http://buildbot.net/buildbot/docs/latest/developer/master-slave.html Master-Slave API]
 
-The developed protocol will be similar to the current API, but with incremental improvements.
-The current sequence diagram, if represented as messages, looks similar to this: 
+The current protocol sequence diagram, if represented as messages, looks similar to this: 
 
 [[Image(SequenceDiagram.png)]]
 
+Most remote calls are asynchronous.
+
+'''Initial Interaction''':
+
+Authentication: Currently the slave authenticates with the Twisted Cred (newcred) mechanism, using the username and password supplied to buildslave create-slave.
+
+After that the master requests information about the slave, via the remote methods {{{ remote_getSlaveInfo}}}, {{{ remote_getVersion}}}, and {{{ remote_getCommands}}}. 
+
+The SlaveInfo currently consists of the contents of the slave's info/ directory.[[BR}}
+This also contains the keys[[BR]]
+{{{environ}}}: copy of the slaves environment[[BR]]
+{{{system}}}: OS the slave is running (extracted from pythons os.name)[[BR]]
+{{{basedir}}}:base directory where slave is running[[BR]]
+
+
+{{{remote_getVersion}}} returns the version of slave.
+{{{remote_getCommands}}} returns the list of (name, version) for all commands the slave recognizes.
+These methods do not take any arguments.
+
+Next the master sets the builder list via {{{remote_setBuilderList}}}. This method, given a list of builders and their build directories, ensures that those builders, and only those builders, are running. It returns a set of {{{SlaveBuilder}}} objects.
+This method can be called later as well. 
+
+Then the master sets itself as master for each {{{SlaveBuilder}}} via remote_setMaster. This returns a reference to the master-side {{{SlaveBuilder}}}.
+
+'''Reactor Loop''': 
+
+The twisted event loop, or reactor, then waits for external triggers, such as Build. 
+
+On receiving the Build trigger, the master then runs commands on the {{{SlaveBuilder}}}.
+For documentation on commands see : [http://buildbot.net/buildbot/docs/latest/developer/cls-remotecommands.html#remotecommands Remote Commands][[BR]]
+For each of the commands, [[BR]]
+The command is started with {{{remote_startCommand}}}. This takes {{{stepref}}}, {{{stepId}}}, {{{command}}}, {{{args}}} as arguments.[[BR]]
+The command can be interrupted via an external trigger, which calls {{{remote_interruptCommand}}}. This method takes {{{stepID}}} and a reason {{{why}}} as arguments.
+
+The running command provides [http://buildbot.net/buildbot/docs/latest/developer/master-slave.html#updates Updates], sent as arguments to {{{remote_update}}} from the {{{SlaveBuilder}}} to the master, during execution.
+
+At the end of a command, the completion of the command is indicated by calling {{{remote_complete}}}, with failures as optional arguments.
+
+The master and slave(in versions greater than 0.8.3) can initiate the shutdown of a slave. The master can call {{{remote_shutdown}}} to shut down the slave, while the slave can also request for a graceful shutdown.
+
+= Proposed Protocol =
+
+The proposed protocol is message-based rather than RPC based.
+The protocol would be versioned. The initially planned changes are shown below. [[Image(ProposedSequenceDiagram.png)]]
+
 Changes will include reducing the number of roundtrips, support for several masters, a busy-signal from the slave, protocol versioning and other improvements.