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https://issues.apache.org/jira/browse/SOLR-13700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16909041#comment-16909041
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Andrzej Bialecki  commented on SOLR-13700:
------------------------------------------

ad 1: yes, it's correct - the instances of these metrics are reused by all 
instances of respective plugins, so if the "old" instance was still processing 
an in-flight request it will still be counted, while the new instance may 
already handle new requests and use the same counters. It's perfectly ok.

ad 2: this seems like a confusion between referring to 
{{pkiAuthenticationPlugin}} (which stays unchanged) and 
{{authenticationPlugin}} (which may have changed). It's correct we don't need 
this here.

Also, I think the call to {{initializeMetrics}} should be done in each of 
{{initializeAuditloggerPlugin}} and {{initializeAuthenticationPlugin}}, then 
it's easier to avoid confusion because within the scope of these methods it's 
obvious that a new instance is created which needs to be initialized.

Also, I just spotted that both {{AuditLoggerPlugin.initializeMetrics}} and 
{{AuthenticationPlugin.initializeMetrics}} needlessly add metrics names to 
{{metricNames}} - this is already done as a part of each respective metric 
registration by using {{SolrInfoBean.this.registerName(name)}}.

> Race condition in initializing metrics for new security plugins when 
> security.json is modified
> ----------------------------------------------------------------------------------------------
>
>                 Key: SOLR-13700
>                 URL: https://issues.apache.org/jira/browse/SOLR-13700
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>            Reporter: Hoss Man
>            Assignee: Hoss Man
>            Priority: Major
>         Attachments: SOLR-13700.patch
>
>
> When new security plugins are initialized due to remote API requetss, there 
> is a delay between "registering" the new plugins for use in methods like 
> {{initializeAuthenticationPlugin()}} (by assigning them to CoreContainer's 
> volatile {{this.authenticationPlugin}} variable) and when the 
> {{initializeMetrics(..)}} method is called on these plugins, so that they 
> continue to use the existing {{Metric}} instances as the plugins they are 
> replacing.
> Because these security plugins maintain local refrences to these Metrics (and 
> don't "get" them from the MetricRegisty everytime they need to {{inc()}} 
> them) this means that there is short race condition situation such that 
> during the window of time after a new plugin instance is put into use, but 
> before  {{initializeMetrics(..)}} is called on them, at these plugins are 
> responsible for accepting/rejecting requests, and decisions in {{Metric}} 
> instances that are not registered and subsequently get thrown away (and GCed) 
> once the CoreContainer gets around to calling {{initializeMetrics(..)}} (and 
> the plugin starts using the pre-existing metric objects)
> ----
> This has some noticible impacts on auth tests on CPU constrained jenkins 
> machines (even after putting in place SOLR-13464 work arounds) that make 
> assertions about the metrics recorded.
> In real world situations, the impact of this bug on users is minor: for a few 
> micro/milli-seconds, requests may come in w/o being counted in the auth 
> metrics -- which may also result in descrepencies between the auth metrics 
> totals and the overall request metrics.  



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