[GitHub] [trafficcontrol] jrushford opened a new pull request #3747: Adds the configuration parameter 'wrap_counters' to the astats_over_http plugin.

[GitBox <gi...@apache.org>]

jrushford opened a new pull request #3747: Adds the configuration parameter 'wrap_counters' to the  astats_over_http plugin.
URL: https://github.com/apache/trafficcontrol/pull/3747
 
 
   
   
   
   ## What does this PR (Pull Request) do?
   This PR adds a configuration parameter to the traffic server astats plugin.  The parameter 'wrap_counters' may be set to 'true' in the astats.config to insure that int64 type counters and signed integers do not present negative values once they increment beyond the INT64_MAX range.  The impetus for this this is to help in addressing the remap stats bug in traffic server.
   
   When traffic server core dumps, the remap stats indexes used to lookup particular counters in trafficserver become associated with the wrong stats due to a race condition that is triggered when traffic server is slammed with requests after it is restarted following a crash.  To mitigate this problem so that it does not happen, the remap stats plugin can be configured to create persistent statistics.  When this is done, all remap stats are loaded and created from persistent store in a controlled manner which avoids the race.  remap stats may be configured to create persistent stats using it's -p option in the plugin.config file.  When using this option, remap statistics will eventually wrap and show negative values once the INT64_MAX value is surpassed.  To prevent these negative values, the 'wrap_counters=true' parameter will cause the counters values to begin again at 0 and resume counting from there keeping the values positive in the INT64_MAX range.
   
   
   ## Which Traffic Control components are affected by this PR?
   traffic_server astats_over_http plugin
   
   The astats.config.example file has been updated as part of this PR to document the purpose and provides a 'wrap_counters' example.
   
   - CDN in a Box
   - Documentation
   - Grove
   - Traffic Control Client 
   - Traffic Monitor
   - Traffic Ops
   - Traffic Ops ORT
   - Traffic Portal
   - Traffic Router
   X Traffic Stats
   - Traffic Vault
   
   ## What is the best way to verify this PR?
   Add the 'wrap_counters=2' parameter in the astats.config file.  When a counter increments beyond INT64_MAX (9223372036854775807), the counter will wrap and start a 0 again rather than becoming negative.
   
   ## If this is a bug fix, what versions of Traffic Ops are affected?
   
   
   
   ## The following criteria are ALL met by this PR
   
   - [ ] This PR includes tests OR I have explained why tests are unnecessary
   - [X] This PR includes documentation OR I have explained why documentation is unnecessary
   - [ ] This PR includes an update to CHANGELOG.md OR such an update is not necessary
   - [X] This PR includes any and all required license headers
   - [ ] This PR ensures that database migration sequence is correct OR this PR does not include a database migration
   - [X] This PR **DOES NOT FIX A SERIOUS SECURITY VULNERABILITY** (see [the Apache Software Foundation's security guidelines](https://www.apache.org/security/) for details)
   
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