[jira] [Created] (SOLR-13532) Unable to start core recovery due to timeout in ping request

["Suril Shah (JIRA)" <ji...@apache.org>]

Suril Shah created SOLR-13532:
---------------------------------

             Summary: 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
      Security Level: Public (Default Security Level. Issues are Public)
          Components: SolrCloud
    Affects Versions: 7.6
            Reporter: Suril Shah


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);
        }
{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.
 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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