Breaking changes

• Allocation:
  • Default delayed allocation timeout to 1m from 0 #12166

New features

• Allocation:
  • Optional Delayed Allocation on Node leave #11712
• Recovery:
  • Add basic recovery prioritization to GatewayAllocator #11975 (issue: #11787)

Enhancements

• Allocation:
  • Simplify ShardRouting and centralize move to unassigned #11634
• Cluster:
  • Remove scheduled routing #11776
  • Reset registeredNextDelaySetting on reroute #11759
  • Add Unassigned meta data #11653
• Exceptions:
  • Reduce the size of the XContent parsing exception #11642
• Internal:
  • Remove reroute with no reassign #11804
  • Mark store as corrupted instead of deleting state file on engine failure #11769
• 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)
• Search:
  • Search preference based on node specification #11464 (issue: #5925)
• Snapshot/Restore:
  • Backport to 1.7 - Snapshot info should contain version of elasticsearch that created the snapshot #12162 (issues: #11980, #11985)
  • Add validation of snapshot FileInfo during parsing #12108
• Term Vectors:
  • Only load term statistics if required #11737
• Upgrade:
  
  • Upgrade groovy from 2.4.0 to 2.4.4 #12288

Bug fixes

• Allocation:
  • Shard Started messages should be matched using an exact match #11999
  • Reroute after node join is processed #11960 (issues: #11776, #11923)
• 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)
• Discovery:
  • ZenDiscovery: #11960 failed to remove eager reroute from node join #12019
• 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)
• More Like This:
  • Fix potentially unpositioned enum #12066
• Packaging:
  • Fix endless looping if starting fails #11836
  • 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)
• 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:
  • Fail engine without marking it as corrupt when recovering on SharedFS #11933 (issue: #11788)
• 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)