Favourite filters REST Resource consumes large amount of memory when user has large number of filters

Summary

If some user has many favourite filters, REST API call /rest/api/2/filter/favourite triggered by him will use large amount of memory (200MB+) and that causes high JVM memory pressure. In case of many simultaneous requests this could cause OOM and JVM/JIRA crash.

Environment

• User with many favourite filters: 100+

Steps to Reproduce

1. Create many filters
2. Register the filters as your favourite ones
3. Open Issue Navigator (check left sidebar)
   • or do REST API call /rest/api/2/filter/favourite directly

Expected Results

No performance problem happens.

Actual Results

JVM heap memory pressure (causes FullGC). Specific thread can allocate 200MB+ of memory.

Notes

• Thread dump will show the following stack-trace for the thread which loads /rest/api/2/filter/favourite, part related to com.atlassian.jira.rest.v2.search.FilterBean

  ...
  	at com.atlassian.jira.rest.v2.search.UserListResolver.getShareCount(UserListResolver.java:137)
  	at com.atlassian.jira.rest.v2.search.UserBeanListWrapper.<init>(UserBeanListWrapper.java:40)
  	at com.atlassian.jira.rest.v2.search.FilterBeanBuilder.build(FilterBeanBuilder.java:173)
  	at com.atlassian.jira.rest.v2.search.FilterResource$SearchRequestToFilterBean.apply(FilterResource.java:650)
  	at com.atlassian.jira.rest.v2.search.FilterResource$SearchRequestToFilterBean.apply(FilterResource.java:622)
  	at com.google.common.collect.Iterators$8.next(Iterators.java:812)
  	at com.google.common.collect.Lists.newArrayList(Lists.java:139)
  	at com.google.common.collect.Lists.newArrayList(Lists.java:119)
  	at com.atlassian.jira.rest.v2.search.FilterResource.getFavouriteFilters(FilterResource.java:422)
  ..
  

• Each FilterBean object (corresponds to favourite filter) is around 2.8MB, so having 100 of them will use ~300MB of memory.
• Heap dump will show large memory consumed by org.apache.tomcat.util.threads.TaskThread
  • Snippet from dominator tree with 350 favourite filters:

    Object / Stack Frame	Name	Shallow Heap	Retained Heap
    org.apache.tomcat.util.threads.TaskThread @ 0x235d499d8	http-nio-8080-exec-1061 url:/jira/rest/api/2/filter/f...	128	961,473,680
    org.apache.tomcat.util.threads.TaskThread @ 0x235d49b98	http-nio-8080-exec-1059 url:/jira/rest/api/2/filter/f...	128	863,698,080

Workaround

• Reduce number of favourite filters
• Set dark feature com.atlassian.jira.rest.v2.search.UserListResolver.getShareCount.disabled flag, that will always return sharedUsers.size: 0 in JSON response, eg:

  sharedUsers: {
   size: 0,
   items: [ ],
   max-results: 1000,
   start-index: 0,
   end-index: 0
  },
  

  • API break. Since after change /rest/api/2/filter/favourite API doesn't return a correct number of the share count there is a risk that it will affect some other functionality.

Note on fix

• The issue was work-arounded in 7.2.12, 7.6.1 and 7.7 by introducing an extra query param enableSharedUsers to /rest/api/2/filter/favourite and /rest/api/2/filter/id to show that users shouldn't be calculated.
  • By default, this param is true, so endpoints are fully backwards compatible. So that still can cause the mentioned problem
  • We've started using this param in JIRA itself ( issue-nav uses enableSharedUsers=false), so the problem should be fixed for JIRA.