Defining a FileLine Descriptor

A FileLine descriptor defines aspects of monitoring a text file. For each FileLine entry in the configuration, the Publisher master process JOBs a process that reads the monitored file line by line, executing a GT.M expression (an extrinsic function call) for each line read in order to gather relevant information. The FileLine process OPENs the monitored file with the FOLLOW deviceparameter and then READs individual lines (the GT.M equivalent of tail -f).

The syntax of a FileLine descriptor is

FileLine:{InfoDictID | InfoDictName}:[FileLineName]:[FileLineID]:{PublisherID | PublisherName}:Filename:[CheckCycle]:[Timeout]:[PieceSeparator]:[PreExpr]:[InfoExpr]:[PostExpr]
[Tip]InfoHub Internals

On starting up, a FileLine process executes its PreExpr, gathering any information provided, and logging an error if the data does not match the expected format, as described earlier. In the event that PreExpr does not return an error, the FileLine process OPENs the file using the FOLLOW deviceparameter, and sits on an untimed READ of the file. Every line read gets processed by InfoExpr, and the returned data placed into the InfoHub database. Triggers on ^InfoHubInfo provide asynchronous notification to Subscribers; this eliminates polling to provide the most efficient processing (all other actions, including commands to shutdown, are sent via asynchronous interrupt-driven messages). In response to a shutdown command, the FileLine process executes its PostExpr, which may provide summary information, as appropriate, before shutting down.

GT.M V6.0-002 is the minimum compatible version because InfoHub uses the FOLLOW deviceparameter functionality which was first introduced in V6.0-002. For information on installing GT.M, refer to "Installing GT.M" chapter of the UNIX Administration and Operations Guide.

Configuration stores FileLine specifications in the following node:

^InfoHubConfInfoHubID,"Publishers",PublisherID,BeginningSequenceNumber,​FileLineID)=​ EndingSequenceNumber]:​FileName:​InfoDictID:​FileLineName:​CheckCycle:​Timeout:​PieceSeparator]:​[PreExpr]:​[InfoExpr]:​[PostExpr]

PreExpr, InfoExpr, and PostExpr always execute with $ZGBLDIR pointing to the global directory in the temporary directory. The FileLine process logs gathered information in the InfoHub database using an extended reference.



This example configures two FileLine Gleaners, OpLog and AuthLog, as presented in the SimpleMonitor.conf configuration file in the ULFM Reference Implementation. The referenced PreExpr, InfoExpr, and PostExpr functions are implemented in "LogFileGleaner.m" (also available in the ULFM Reference Implementation), which provides a simple implementation of a gleaner that processes information from the system log.

Related Information: