[jira] [Created] (SOLR-9925) Child documents missing from replicas during parallel delete+add

["Dan Sirotzke (JIRA)" <ji...@apache.org>]

Dan Sirotzke created SOLR-9925:
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             Summary: Child documents missing from replicas during parallel delete+add
                 Key: SOLR-9925
                 URL: https://issues.apache.org/jira/browse/SOLR-9925
             Project: Solr
          Issue Type: Bug
      Security Level: Public (Default Security Level. Issues are Public)
    Affects Versions: 6.3, 5.5.2
         Environment: Java 1.8 (OpenJDK) on both CentOS 6.7 and Ubuntu 16.04.1
            Reporter: Dan Sirotzke


When pushing documents to Solr in parallel, doing a delete-by-query and then add for the same set of IDs within each thread results in some of the replicas missing some of the child documents.  All the parent documents are successfully replicated.

This appears to trigger some sort of race condition, since:

* Documents are never missing from the leader.
* Documents _might_ be missing from the replicas.
* When they are missing, the number and which documents are different for each replica and each run.
* It happens more easily with large documents; my test script needs a huge number of documents to trigger it a small number of times, whereas it happens ~5% of the time on our dataset.
* We're currently on Solr 5.5.2, but I've also managed to trigger it on 6.3.0
* When not running anything in parallel, this doesn't occur.

Quick aside, since this is surely the first thing that will jump out:  We can't just do an update due to to the uniqueKey/_root_ issue behind SOLR-5211.



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