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Comprehensive Guide on ErrorLogger Package Setup for Collective Logging

This tutorial provides an in-depth walkthrough of setting up the ErrorLogger package for collective error logging. The guide covers options, frameworks, destinations, thresholds, and limits, along with examples and documentation resources. Learn about key concepts like ErrorLogger, destinations, administrators, issuing messages, and setting up contexts. Discover how to control logging behavior, set up administrators, manage destinations, and handle thresholds and limits effectively. This tutorial is essential for code writers looking to enhance error logging practices.

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Comprehensive Guide on ErrorLogger Package Setup for Collective Logging

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  1. Tutorial on use of the ErrorLogger Package With introduction to setting up for “collective” error logging

  2. Viewpoints • “User” – the bulk of the code writers • Will explain all the options • Because there isn’t that much to cover! • “Framework” – sets up behavior • There are loads of control options • destinations • thresholds and limits • Will explain the most important ones • Please excuse use of web page/code transparencies

  3. Documentation resources • Web pages (from ZOOM page at ---www.fnal.gov/tf/zoom go to releases then ErrorLogger package • Examples in ErrorLogger/Test • BasicUsage • SampleFramework • BasicColl / BasicRecv

  4. 3 Key Concepts • ErrorLogger • This is what the “user” sees and uses • Set up by the framework • Normally a global or package-level variable • Conventionally called errlog • Destination(s) • Eladminstrator

  5. 3 Key Concepts • ErrorLogger • Destination(s) • Places where the logged output is to go • Can and normally willbe multiple destinations • ELoutput is the ordinary destination • Framework can set up multiple ELoutput dests, with different thresholds for logging messages etc. • ELstatistics is a special statistics-keeping destination • ELadminstrator

  6. 3 Key Concepts • ErrorLogger • Destination(s) • ELadminstrator • Framework instantiates this once • “singleton” pattern is used – impossible to have two • Acts as a hook to control overall logging behavior

  7. User • #include ErrorLogger/ErrorLog.h • probably done in framework, where errlog is made • Issuing messages • errlog ( severity, id ) << items << endmsg; • severity level • error id (a string) • additional items • anything you can << to an ostream is a valid item • multiple • endmsg • declares the end of a message • if this is omitted, next message will terminate anyway • web pages: How to & severity levels

  8. User • setSubroutine(“name”); • Optional • Framework can set subroutine • subroutine name is not required • “@SUBR=name” item in message does the same thing • ERRLOG macro • same syntax as errlog • but inserts line number and file name into message • No other options to learn.

  9. Framework • Instantiate an administrator • Make destination(s) • attach each destination to adminstrator • attaching returns a ELdestControl handle. • control thresholds and other destination properties using this handle • (See example)

  10. Framework • Set up errlog for each module • by using a different ErrorLog instance, each module can have its name used in messages, incurring no overhead when no messages are issued • Provide Context Supplier • Optional, but normally done • Allows appending run/event number to issued messages, without incurring overhead when no message is issued. • Control abort behavior • logger-> setAbortThreshold (ELhighestSeverity) • Cause statistics destination to output statistics • example output • See SampleFramework example • fairly complete spectrum of what can be done

  11. Framework • Thresholds and limits apply to each destination • Thresholds are severity levels, below which a distination won’t react to a message • Limits are by severity or message id for each destination, and can throttle the number of messages of that type displayed • logarithmic backoffs displaying past the limit • Context supplier is a function that returns a string to use when formatting needs a run/event context • logger.setContextSupplier( ELcontextSupplier s); • Follow the “mantra” in BasicFramework.cc example for how to set up the context supplier

  12. Collective Error Logging • New ELcollected destination derived from ELouput • So code setting up output destinations needs no superfluous mods • ELcollected captures severity level, id, text of each item, context, module, subroutine • Forms a buffer “data” and supplies to send(nbytes, data) method of a user-supplied ELsender object. • Could have different senders for different ELcollected destinations • send(nbytes, data) must transport the data to the server Server must then do errlog (nbytes, data) << endmsg; • See BasicColl / BasicRecv example

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