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https://issues.apache.org/jira/browse/SOLR-7361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14505305#comment-14505305
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Mark Miller commented on SOLR-7361:
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bq. you might always have the cores up and running by the time you issue
requests
Other requests will block until the core is ready - what will that break? That
is how it works now if requests come in before the cores are loaded. Do you
have a concrete example?
bq. If we are breaking compat anyway, why not always break it
If the cores are just going to load quickly, I think it's simply nicer to wait
for them to load and only have outliers straggle in later, as the system did
work. Unless there are outliers, I think it's a nicer system experience. This
is a simple simulation of that approach.
It doesn't matter how long that wait is - you can set it to 0 and all the tests
will pass fine. You can certainly randomly set that to 0 in test runs.
> Main Jetty thread blocked by core loading delays HTTP listener from binding
> if core loading is slow
> ---------------------------------------------------------------------------------------------------
>
> Key: SOLR-7361
> URL: https://issues.apache.org/jira/browse/SOLR-7361
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Reporter: Timothy Potter
> Assignee: Mark Miller
> Fix For: Trunk, 5.2
>
> Attachments: SOLR-7361.patch, SOLR-7361.patch, SOLR-7361.patch,
> SOLR-7361.patch, SOLR-7361.patch
>
>
> During server startup, the CoreContainer uses an ExecutorService to load
> cores in multiple back-ground threads but then blocks until cores are loaded,
> see: CoreContainer#load around line 290 on trunk (invokeAll). From the
> JavaDoc on that method, we have:
> {quote}
> Executes the given tasks, returning a list of Futures holding their status
> and results when all complete. Future.isDone() is true for each element of
> the returned list.
> {quote}
> In other words, this is a blocking call.
> This delays the Jetty HTTP listener from binding and accepting requests until
> all cores are loaded. Do we need to block the main thread?
> Also, prior to this happening, the node is registered as a live node in ZK,
> which makes it a candidate for receiving requests from the Overseer, such as
> to service a create collection request. The problem of course is that the
> node listed in /live_nodes isn't accepting requests yet. So we either need to
> unblock the main thread during server loading or maybe wait longer before we
> register as a live node ... not sure which is the better way forward?
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