All perf counters stop being collected when any of faulty counters are specified to collect on Azure WebApps

[tukaef]

This is a consequence of #1685. When any of the counters in question is specified, the collector stops collecting the other counters after 5-6 successful iterations.

Repro Steps

1. Specify any of the following counters to collect:

• \.NET CLR Memory(??APP_CLR_PROC??)\# Total committed Bytes
• \ASP.NET Applications(??APP_W3SVC_PROC??)\Request Bytes In Total
• \ASP.NET Applications(??APP_W3SVC_PROC??)\Request Bytes Out Total

2. Specify any other counter, or just leave the default counters

Actual Behavior

After deploy, all counters apart from the faulty ones are collected and sent only 5-6 times (a few minutes). After that, nothing is collected (nor sent).

Expected Behavior

Non-faulty counters being collected successfully during the app lifetime.

Version Info

SDK Version : 2.12.1
.NET Version : 4.7
Hosting Info : Azure WebApps

[tukaef]

This is likely due to WebAppPerformanceCollector.RefreshCounters throwing an exception when PerformanceCollectorModule.EnsurePerformanceCountersRegistered is called. Since it's not caught on the way, we end up not updating lastRefreshTimestamp (line 369). Which in turn makes EnsurePerformanceCountersRegistered be always trying to refresh counters, and thus failing the whole iteration (timer tick) before any counters are collected.

Is it possible to catch the exception in WebAppPerformanceCollector.RefreshPerformanceCounter method? Could submit a PR if so.
This would be similar to what's implemented in StandardPerformanceCollector.

[TimothyMothra]

Hi, your explanation makes sense.
I don't have time to investigate this right now, but we would gladly accept your PR. :)

[cijothomas]

@tukaef Thanks for reporting and investigating the issue. Please submit a PR if you have time.