Do not log language metric in placeholder mode

[pragnagopa]

Do not log language metric in placeholder mode

azure-functions-host/src/WebJobs.Script/Host/ScriptHost.cs

Line 277 in af72576

_metricsLogger.LogEvent(string.Format(MetricEventNames.HostStartupRuntimeLanguage, _workerRuntime));

[pragnagopa]

cc @mhoeger @paulbatum

[pragnagopa]

Metric host.startup.runtime.language.dotnet is being emitted for non dotnet apps. This appears to be race condition during specialization. Needs investigation

[paulbatum]

I confirmed this by looking at a day's worth of telemetry from our cold start runners. This is going to be screwing up our analytics pipeline.

[pragnagopa]

cc - @brettsam
PR # #4356 fixes race condition during specialization. Need to revisit metrics issue where host.startup.runtime.language.dotnet is emitted after an app gets specialized.

[brettsam]

Do you have an example of the erroneous log? Are we logging this with the customer's app name and dotnet, even though it's not a dotnet app?

[pragnagopa]

An example of error metric: A Java app gets two metrics host.startup.runtime.language.dotnet and host.startup.runtime.language.java. Similarly a node app gets two metrics: host.startup.runtime.language.dotnet and host.startup.runtime.language.node

I will share kusto queries offline.

[pragnagopa]

PR #4210 addresses not logging language metric in placeholder mode. We still need to keep this issue active for investigating duplicate language metric logs

[fabiocav]

@pragnagopa can this be closed now?

[pragnagopa]

Yes. Thanks to @brettsam for fixing races during specialization!