wikid.pl
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Job execution framework
The wiki daemons have a job execution framework which allows ongoing jobs to run in a multiplexed way. The execution framework is persistent so that jobs will continue to execute after daemon or server restart. The work is stored in the global $::work array and the currently executing job's data is in the global $::job hash.
RPC
The wiki daemons now have RPC (Remote Procedure Call) capability which allows events to be propagated amongst peers and actions to be executed by remote request. The RPC method is robust and designed to account for the following key issues and requirements:
- Specific recipient or broadcast messages
- Messages keep trying until successfully propagated
- Messages are encrypted
The first use of wikid RPC is the doUpdateAccount action since changes to accounts must be securely and robustly replicated across all peers. Following is a description of the process that is carried out in response to a change in account information, either by a new account being created or an existing account's password being changed.
UpdateAccount propagation
When an account is created or updated in a wiki daemon's local wiki, the wiki will execute a PrefsPasswordAudit hook or a AddNewAccount hook which will then pass down the EventPipe into the wiki daemon and execute the onPrefsPasswordAudit or onAddNewAccount function, which then call doUpdateAccount with the appropriate arguments extracted from $::data.
In addition to calling doUpdateAccount which updates and synchronises the local unix and samba accounts, the action also calls rpcBroadcastAction so that the same update occurs on all peers (starting with $::peer). The rpcBroadcastAction function actually just calls rpcSendAction with an empty "To" parameter to indicate a broadcast message.
The rpcSendAction function starts a new "RpcSendAction" job in the persistent work hash so that the attempt to send the message can keep retrying periodically until successful in the case of outages. The job consists of just a main function (mainRpcSendAction) which does the periodic send attempts. The initial set up of the job is done in rpcSendAction rather than initRpcSendAction since the data must be encrypted before it gets stored in the persistent job hash. The action and arguments are first serialised into a string, encrypted using the $::netpass shared secret, and then converted to base64 so that the data can be supplied in URL's and command-line options.
The mainRpcSendAction function uses Net::Expect to connect to the remote peer using SSH and login with its own $::wikiuser and $::wikipass since that's guaranteed to have a corresponding unix account on all peers (but must be included in the AllowUsers clause of sshd_config). After it's shelled in it then executes the RPC by using the following syntax from the shell:
When wikid.pl is run with the --rpc option, it simply formats the data into an event called RpcDoAction which is sent into the wiki daemon through its proper port as if it were a normal MediaWiki event coming through the EventPipe, which results in the onRpcDoAction function being called.
Unlike other wikid event-handler functions, the $::data available to the onRpcDoAction handler is encrypted and so first needs to be converted back to an @args array (by base64 decoding, then decrypting with the shared $::netpass secret, then deserialising back into an array). If the action exists, then it is called along with the original arguments, otherwise an error is logged. If the action was broadcasted (having an empty "to" argument), then the same action and args will be sent to the next peer by calling rpcSendAction again at this point.
