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https://issues.apache.org/jira/browse/SOLR-13045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16712293#comment-16712293
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Jason Gerlowski edited comment on SOLR-13045 at 12/7/18 3:21 AM:
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Looking at {{testCreateCollectionAddReplica}} first. I'm still in the early
stages of looking into this, but I think I see some things pointing to this
being a sim-framework issue, as opposed to being a production problem. I'm not
super familiar with the sim-framework though, so I'll try and give some detail
here in case anyone with more context can correct me and save me from a
potential red-herring.
*TL;DR* I believe this to be a test-framework bug related to how the
SimClusterStateProvider caches clusterstate values.
The test starts by creating a collection using a specific policy. Maybe 1 time
in 10 it'll fail in a {{CloudTestUtils.waitForState}} call. On these failures,
this {{waitForState}} call fails because the collection (supposedly) doesn't
have a leader:
{code}
last coll state:
DocCollection(testCreateCollectionAddReplica//clusterstate.json/5)={
"replicationFactor":"1",
"pullReplicas":"0",
"router":{"name":"compositeId"},
"maxShardsPerNode":"1",
"autoAddReplicas":"false",
"nrtReplicas":"1",
"tlogReplicas":"0",
"autoCreated":"true",
"policy":"c1",
"shards":{"shard1":{
"replicas":{"core_node1":{
"core":"testCreateCollectionAddReplica_shard1_replica_n1",
"SEARCHER.searcher.maxDoc":0,
"SEARCHER.searcher.deletedDocs":0,
"INDEX.sizeInBytes":10240,
"node_name":"127.0.0.1:10068_solr",
"state":"active",
"type":"NRT",
"INDEX.sizeInGB":9.5367431640625E-6,
"SEARCHER.searcher.numDocs":0}},
"range":"80000000-7fffffff",
"state":"active"}}}
{code}
But other statements in the logs indicate that this collection *does* have a
leader. We get this series of messages right as the test ends:
{code}
14445 INFO
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.SolrTestCaseJ4 ###Ending testCreateCollectionAddReplica
14446 DEBUG
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimClusterStateProvider ** creating new collection states,
currentVersion=6
14446 INFO
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimClusterStateProvider JEGERLOW: Saving clusterstate
14446 DEBUG
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimClusterStateProvider ** saved cluster state version 6
14446 INFO
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimSolrCloudTestCase #######################################
############ CLUSTER STATE ############
#######################################
## Live nodes: 2
## Empty nodes: 1
## Dead nodes: 0
## Collections:
## * testCreateCollectionAddReplica
## shardsTotal 1
## shardsState {active=1}
## shardsWithoutLeader 0
{code}
One thing that stands out to me are the different clusterstate versions in play
here. The log snippets above show information from {{/clusterstate.json/5}},
and {{/clusterstate.json/6}} respectively.
I looked into {{SimClusterStateProvider}} and noticed that it caches the
cluster state locally (see
[here|https://github.com/apache/lucene-solr/blob/75b183196798232aa6f2dcaaaab117f309119053/solr/core/src/test/org/apache/solr/cloud/autoscaling/sim/SimClusterStateProvider.java#L2086])
and warns readers that the cache must be explicitly cleared before new changes
become visible. With this caching temporarily disabled the test failure
disappeared. (Or at least, I couldn't trigger it in 2000 runs). I suspect
that the test failure is caused by either (1) some codepath not properly
clearing/resetting this clusterstate cache, or (2) a subtler synchronization
bug in how this cache is locked down.
was (Author: gerlowskija):
Looking at {{testCreateCollectionAddReplica}} first. I'm still in the early
stages of looking into this, but I think I see some things pointing to this
being a sim-framework issue, as opposed to being a production problem. I'm not
super familiar with the sim-framework though, so I'll try and give some detail
here in case anyone with more context can correct me and save me from a
potential red-herring.
*TL;DR* I believe this to be a test-framework bug related to how the
SimClusterStateProvider caches clusterstate values.
The test starts by creating a collection using a specific policy. Maybe 1 time
in 10 it'll fail in a {{CloudTestUtils.waitForState}} call. On these failures,
this {{waitForState}} call fails because the collection (supposedly) doesn't
have a leader:
{code}
last coll state:
DocCollection(testCreateCollectionAddReplica//clusterstate.json/5)={
"replicationFactor":"1",
"pullReplicas":"0",
"router":{"name":"compositeId"},
"maxShardsPerNode":"1",
"autoAddReplicas":"false",
"nrtReplicas":"1",
"tlogReplicas":"0",
"autoCreated":"true",
"policy":"c1",
"shards":{"shard1":{
"replicas":{"core_node1":{
"core":"testCreateCollectionAddReplica_shard1_replica_n1",
"SEARCHER.searcher.maxDoc":0,
"SEARCHER.searcher.deletedDocs":0,
"INDEX.sizeInBytes":10240,
"node_name":"127.0.0.1:10068_solr",
"state":"active",
"type":"NRT",
"INDEX.sizeInGB":9.5367431640625E-6,
"SEARCHER.searcher.numDocs":0}},
"range":"80000000-7fffffff",
"state":"active"}}}
{code}
But other statements in the logs indicate that this collection *does* have a
leader. We get this series of messages right as the test ends:
{code}
14445 INFO
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.SolrTestCaseJ4 ###Ending testCreateCollectionAddReplica
14446 DEBUG
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimClusterStateProvider ** creating new collection states,
currentVersion=6
14446 INFO
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimClusterStateProvider JEGERLOW: Saving clusterstate
14446 DEBUG
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimClusterStateProvider ** saved cluster state version 6
14446 INFO
(TEST-TestSimPolicyCloud.testCreateCollectionAddReplica-seed#[6FE5447E15D3DD6F])
[ ] o.a.s.c.a.s.SimSolrCloudTestCase #######################################
############ CLUSTER STATE ############
#######################################
## Live nodes: 2
## Empty nodes: 1
## Dead nodes: 0
## Collections:
## * testCreateCollectionAddReplica
## shardsTotal 1
## shardsState {active=1}
## shardsWithoutLeader 0
{code}
One thing that stands out to me are the different clusterstate versions in play
here. The log snippets above show information from {{/clusterstate.json/5}},
and {{/clusterstate.json/6}} respectively.
I looked into {{SimClusterStateProvider}} and noticed that it caches the
cluster state locally (see
[here|https://github.com/apache/lucene-solr/blob/75b183196798232aa6f2dcaaaab117f309119053/solr/core/src/test/org/apache/solr/cloud/autoscaling/sim/SimClusterStateProvider.java#L2086]
and warns readers that the cache must be explicitly cleared before new changes
become visible. With this caching temporarily disabled the test failure
disappeared. (Or at least, I couldn't trigger it in 2000 runs). I suspect
that the test failure is caused by either (1) some codepath not properly
clearing/resetting this clusterstate cache, or (2) a subtler synchronization
bug in how this cache is locked down.
> Harden TestSimPolicyCloud
> -------------------------
>
> Key: SOLR-13045
> URL: https://issues.apache.org/jira/browse/SOLR-13045
> Project: Solr
> Issue Type: Test
> Security Level: Public(Default Security Level. Issues are Public)
> Components: AutoScaling
> Affects Versions: master (8.0)
> Reporter: Jason Gerlowski
> Priority: Major
>
> Several tests in TestSimPolicyCloud, but especially
> {{testCreateCollectionAddReplica}}, have some flaky behavior, even after
> Mark's recent test-fix commit. This JIRA covers looking into and (hopefully)
> fixing this test failure.
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