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https://issues.apache.org/jira/browse/SOLR-13532?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16859330#comment-16859330
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Gus Heck commented on SOLR-13532:
---------------------------------
Hard coded timeouts are a general problem in several areas. I opened SOLR-13457
a little while ago to track these sorts of problems.
> Unable to start core recovery due to timeout in ping request
> ------------------------------------------------------------
>
> Key: SOLR-13532
> URL: https://issues.apache.org/jira/browse/SOLR-13532
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Affects Versions: 7.6
> Reporter: Suril Shah
> Priority: Major
>
> Discovered following issue with the core recovery:
> * Core recovery is not being initialized and throwing following exception
> message :
> {code:java}
> 2019-06-07 00:53:12.436 INFO
> (recoveryExecutor-4-thread-1-processing-n:<solr_ip>:8983_solr
> x:<collection_name>_shard41_replica_n2777 c:<collection_name> s:shard41
> r:core_node2778) x:<collection_name>_shard41_replica_n2777
> o.a.s.c.RecoveryStrategy Failed to connect leader http://<solr_ip>:8983/solr
> on recovery, try again{code}
> * Above error occurs when ping request takes time more than a timeout period
> which is hard-coded to one second in solr source code. However In a general
> production setting it is common to have ping time more than one second,
> hence, the core recovery never starts and exception is thrown.
> * Also the other major concern is that this exception is logged as an info
> message, hence it is very difficult to identify the error if info logging is
> not enabled.
> * Please refer to following code snippet from the [source
> code|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java#L789-L803]
> to understand the above issue.
> {code:java}
> try (HttpSolrClient httpSolrClient = new
> HttpSolrClient.Builder(leaderReplica.getCoreUrl())
> .withSocketTimeout(1000)
> .withConnectionTimeout(1000)
>
> .withHttpClient(cc.getUpdateShardHandler().getRecoveryOnlyHttpClient())
> .build()) {
> SolrPingResponse resp = httpSolrClient.ping();
> return leaderReplica;
> } catch (IOException e) {
> log.info("Failed to connect leader {} on recovery, try again",
> leaderReplica.getBaseUrl());
> Thread.sleep(500);
> } catch (Exception e) {
> if (e.getCause() instanceof IOException) {
> log.info("Failed to connect leader {} on recovery, try again",
> leaderReplica.getBaseUrl());
> Thread.sleep(500);
> } else {
> return leaderReplica;
> }
> }
> {code}
> The above issue will have high impact in production level clusters, since
> cores not being able to recover may lead to data loss.
> Following improvements would be really helpful:
> 1. The [timeout for ping
> request|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java#L790-L791]
> in *RecoveryStrategy.java* should be configurable and the defaults set to
> high values like 15seconds.
> 2. The exception message in [line
> 797|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java#L797]
> and [line
> 801|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/cloud/RecoveryStrategy.java#L801]
> in *RecoveryStrategy.java* should be logged as *error* messages instead of
> *info* messages
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