Breaking changes

• Snapshot/Restore:
  • Url repository should respect repo.path for file urls #11687

Enhancements

• Exceptions:
  • Reduce the size of the XContent parsing exception #11642
• REST:
  • Create Snapshot: remove _create from POST path to match PUT #11928 (issue: #11897)
  • Add rewrite query parameter to the indices.validate_query API spec #11580 (issue: #10147)
• Snapshot/Restore:
  • Add validation of snapshot FileInfo during parsing #12108
  • Add snapshot name validation logic to all snapshot operations #11617
• Term Vectors:
  • Only load term statistics if required #11737
• Upgrade:
  
  • Upgrade groovy from 2.4.0 to 2.4.4 #12288

Bug fixes

• Core:
  • Throw LockObtainFailedException exception when we can't lock index directory #12203
  • Only clear open search ctx if the index is delete or closed via API #12199 (issue: #12116)
  • Workaround deadlock on Codec initialisation #11837 (issue: #11170)
  • Consistently add one more maxMerge in ConcurrentMergeSchedulerProvider #11613
• Highlighting:
  • Fix exception for plain highlighter and huge terms for Lucene 4.x #11683 (issue: #11599)
• Index APIs:
  • Use IndexWriter.hasPendingChanges() to detect if a flush is needed. #12146 (issue: #12134)
• Internal:
  • Fix FieldDataTermsFilter.equals. #11835 (issue: #11779)
  • Add a null-check for XContentBuilder#field for BigDecimals #11790 (issue: #11699)
  • AsyncShardFetch can hang if there are new nodes in cluster state #11615
• Logging:
  • Use task's class name if not a TimedPrioritizeRunnable #11610
• More Like This:
  • Fix potentially unpositioned enum #12066
• Packaging:
  • Fix endless looping if starting fails #11836
  • Postrm script should not fail #11678 (issue: #11373)
  • Create PID_DIR in init.d script #11674 (issue: #11594)
• Percolator:
  • Support filtering percolator queries by date using now #12215 (issue: #12185)
  • Fail nicely if nested query with inner_hits is used in a percolator query #11793 (issue: #11672)
• Query DSL:
  • CommonTermsQuery fix for ignored coordination factor #11780 (issue: #11730)
  • Fix support for _name in some queries #11694
• Scroll:
  • Append the shard top docs in such a way to prevent AOOBE #11978 (issue: #7926)
• Search:
  • Free all pending search contexts if index is closed or removed #12180 (issue: #12116)
• Settings:
  • Do not prompt for node name twice #11668 (issue: #11564)
• Shadow Replicas:
  • Return empty CommitID from ShadowEngine#flush #11554
• Snapshot/Restore:
  • Add url repository whitelist - backport of #11687 to 1.6 and 1.7 #12241
  • Improve repository verification failure message #11925 (issue: #11922)
  • Aborting snapshot might not abort snapshot of shards in very early stages in the snapshot process #11839 (issue: #11756)
  • Improve logging of repository verification exceptions. #11763 (issue: #11760)
• Stats:
  • Fix wrong reused file bytes in Recovery API reports #11965 (issue: #11876)
  • Fix RecoveryState timestamps #11871 (issue: #11870)

Regression

• More Like This:
  • Support for deprecated percent_terms_to_match REST parameter #11736 (issues: #11572, #11574)
  • Add back support for deprectated percent_terms_to_match REST parameter #11574 (issue: #11572)