Chris M. Hostetter created SOLR-17744:
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Summary: Solr shutdown does not graceful close Jetty
requests/connections
Key: SOLR-17744
URL: https://issues.apache.org/jira/browse/SOLR-17744
Project: Solr
Issue Type: New Feature
Reporter: Chris M. Hostetter
Solr does a lot of work internally (via things like SolrCore reference
counting) to ensure that we "finish" in-flight requests on orderly shutdown
(ie: when the user has issued a "stop" command) – but it does not appear that
we are doing anything to ensure that *Jetty* managed resources will also wait
for in process requests to finish.
In particular, Jetty seems to abruptly close any existing & active network
connections to clients, even as Solr continues to process those requests and
try to write out the responses.
There are Jetty features to ensure that shutdown is genuinely "graceful"
(refusing new requests while letting existing ones finish) but Solr doesn't
appear to use/enable these features:
* In Jetty 10 & 11, this is apparently done using the {{StatisticsHandler}}
(as a wrapper around the main handler collection i think?)
** [https://github.com/jetty/jetty.project/issues/2076#issuecomment-353578130]
**
[https://javadoc.jetty.org/jetty-11/org/eclipse/jetty/server/handler/StatisticsHandler.html]
**
[https://jetty.org/docs/jetty/11/programming-guide/server/http.html#handler-use-util-stats-handler]
* In Jetty 12+ there is a {{graceful}} module that provides a
{{GracefulHandler}} (which seems like a slightly more robust version of what
{{StatisticsHandler}} does in jetty-10, but with less statistics tracking
overhead)
**
[https://jetty.org/docs/jetty/12/operations-guide/start/index.html#stop-graceful]
**
[https://jetty.org/docs/jetty/12/operations-guide/modules/standard.html#graceful]
The net result is that even during planned shutdown (or restart) of Solr nodes,
clients can get lots of errors.
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