Do not fail completely when re-registering metrics with the same name

[celandro]

Due to the way one of our legacy webapps integrates with spring, the spring context file is loaded 2 times instead of one. On the second time, it fails due to an IllegalArgumentException. This bug may be related to the other spring life cycle bug. This fix allows the reload to occur properly. This also handles more graceful accidental double registration of the same metrics.

My apologies for the long list of commits. I'm not sure how to reset my fork to your base

[ryantenney]

Would it be alright to simply not register the metrics the second time?

[celandro]

In theory yes. The real problem seems to be that the metrics registry is
not being recreated. If you provide me a proposed fix I can test it quickly.
On Dec 12, 2013 10:12 AM, "Ryan Tenney" [email protected] wrote:

Would it be alright to simply not register the metrics the second time?

—
Reply to this email directly or view it on GitHubhttps://github.com//pull/54#issuecomment-30446879
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[ryantenney]

So the metric registry mostly likely isn't being recreated because of the name attribute. If you provide a name to metric-registry it calls SharedMetricRegistries.getOrCreate(name) which persists the MetricRegistry outside of the Spring lifecycle. I did that so it would be easier to access the metric registry from outside of Spring (in a servlet or servlet filter for example) If you don't need that, removing the name attribute would ensure the registry is re-created when the spring context reloads.

[davidkarlsen]

I figured out some more, it only happens when I register the registry with a name like you say:
<metrics:metric-registry id="metricsRegistry" name="${metrics.registry.prefix}" />

But only when I have these added:

  <metrics:register metric-registry="metricsRegistry">
      <bean metrics:name="jvm.gc" class="com.codahale.metrics.jvm.GarbageCollectorMetricSet" />
      <bean metrics:name="jvm.classloading" class="com.codahale.metrics.jvm.ClassLoadingGaugeSet" />
      <bean metrics:name="jvm.memory" class="com.codahale.metrics.jvm.MemoryUsageGaugeSet" />
      <bean metrics:name="jvm.thread-states" class="com.codahale.metrics.jvm.ThreadStatesGaugeSet" />
      <bean metrics:name="jvm.fd.usage" class="com.codahale.metrics.jvm.FileDescriptorRatioGauge" />
  </metrics:register>