Breaking changes

• Plugins:
  • Don't overwrite plugin configuration when removing/upgrading plugins #7890 (issue: #5064)

New features

• Aggregations:
  • Return the sum of the doc counts of other buckets in terms aggregations. #8213
• Cat API:
  • show open and closed indices in _cat/indices #7936 (issue: #7907)
• Circuit Breakers:
  • Allow setting individual breakers to "noop" breakers #8135
  • Add NoopCircuitBreaker used in NoneCircuitBreakerService #8063
• Upgrade API:
  • Add API to upgrade old Lucene indices to the latest version #7922 (issue: #7884)

Enhancements

• Circuit Breakers:
  • Log if CircuitBreaker is tripping #8050
• Deprecation:
  • MLT Field Query #8253
• Discovery:
  • Improve handling of multicast binding exceptions #8243 (issue: #8225)
  • Simplify discovery node initialization if version is unknown #8055 (issue: #8051)
  • Remove MasterFaultDetection.Listener.notListedOnMaster #7995
  • Only accept unicast pings when started #7950
  • Add a finalize round to multicast pinging #7924
• FunctionScore:
  • RandomScoreFunction now accepts long, as well a strings. #8311 (issue: #8267)
• Indexing:
  • Raise maximum index name length to 255 bytes #8158 (issue: #8079)
• Internal:
  • Use a 1024 byte minimum weight for filter cache entries #8304 (issues: #8249, #8268)
  • Make indexQueryParserService available from ParseContext #8252 (issue: #8248)
  • Allow to configure custom thread pools #8247
  • Expose concurrency_level setting on all caches #8112 (issue: #7836)
  • Don't let took be negative. #7968
  • Upgrade to Jackson 2.4.2 #7934 (issue: #7932)
  • Clarify when a shard search request gets created to be only used locally #7855
  • Force execution of delete index requests #7799
  • Refactor the Translog.read(Location) method #7780
  • Nest original exception while creating NoShardAvailableActionException #7757 (issue: #7756)
• Java API:
  • Enabled overriding the request headers in the clients #8258
• Logs:
  • Change log level for mpercolate #8306
• MLT Query:
  • Support for when all fields are deprecated #8067
• Netty:
  • Support binding on multiple host/port pair #8098
• Packaging:
  • Introduce elasticsearch.in.bat (i.e. es.in for Windows) #8244 (issue: #8237)
  • Use the new command line syntax in the init script #5033
• Parent/child:
  • Reduce memory usage in top children query #8165 (issue: #8160)
• Percolator:
  • Added missing percolate API parameters to the rest spec #7173 (issue: #3380)
• Query DSL:
  • Throw parsing exception if terms filter or query has more than one field #5137 (issue: #5014)
• Resiliency:
  • Be more conservative if index.version.created is not set #8018
  • Perform write consistency check just before writing on the primary shard #7873
• Search:
  • Reduce memory usage during fetch source sub phase #8138
• Settings:
  • Validates bool values in yaml for node settings #8186 (issue: #8097)
• Snapshot/Restore:
  • Add repository validation #7680 (issue: #7096)
• Stats :
  • Add time in index throttle to stats. #7896 (issue: #7861)

Bug fixes

• Aggregations:
  • The children agg didn't take deleted document into account #8180
  • Fixes scripted metrics aggregation when used as a sub aggregation #8037 (issue: #8036)
  • Makes script params consistent with other APIs in scripted_metric #7969
  • Significant terms can throw error on index with deleted docs. #7960 (issue: #7951)
• Allocation:
  • Enable ClusterInfoService by default #8206
• Bulk API:
  • Handle failed request when auto create index is disabled #8163 (issue: #8125)
• Completion Suggester:
  • Fix CompletionFieldMapper to correctly parse weight #8197 (issue: #8090)
• Discovery:
  • Improve the lifecycle management of the join control thread in zen discovery. #8327
• Geo:
  • Fix IndexedGeoBoundingBoxFilter to not modify the bits of other filters. #8325
• Indexed Scripts/Templates:
  • GetIndexedScript call can deadlock #8266
• Internal:
  • When corruption strikes, don't create exceptions with circular references #8331
  • Fixed bitset filter cache leftover in nested filter #8303
  • Bind each AllocationDecider as a singleton #8272
  • Add current translog ID to commit meta before closing #8245
  • Cleanup non nested filter to not flip the FixedBitSet returned by the wrapped filter. #8232 (issue: #8227)
  • Make "noop" request breaker a non-dynamic setting #8179
  • Move the child filter over to the fixed bitset cache. #8171
  • In fixed bitset service fix order where the warmer listener is added. #8168 (issue: #8140)
  • Dynamic changes to max_merge_count are now picked up by index throttling #8136 (issue: #8132)
  • Only schedule another refresh if refresh_interval is positive #8087 (issue: #8085)
  • Don't handle FNF exceptions when reading snapshot #8086
  • Fix serialization of PendingClusterTask.timeInQueue. #8077
  • Fix location information for loggers #8052 (issue: #5130)
  • Make close() synchronized during node shutdown #7885
• MLT Query:
  • fix percent_terms_to_match #7754
• Mapping:
  • Throw exception if null_value is set to null #7978 (issue: #7273)
• Netty:
  • Add HTTP pipelining support #8299 (issue: #2665)
• Packaging:
  • Export JAVA_HOME in RPM init script #5434
• Parent/child:
  • Check if there is a search context, otherwise throw a query parse exception. #8177 (issue: #8031)
  • has_parent filter must take parent filter into account when executing the inner query/filter #8020 (issue: #7362)
• Plugins:
  • Support usage of ES_JAVA_OPTS in plugin commands #8288
• Query DSL:
  • Make simple_query_string leniency more fine-grained #8162 (issue: #7967)
• Resiliency:
  • Don't catch FNF/NSF exception when reading metadata #8207
• Scripting:
  • Clear the GroovyClassLoader cache before compiling #8062 (issues: #7658, #8073)
  • Fix NPE in ScriptService when script file with no extension is deleted #7953 (issue: #7689)
• Search:
  • Passing fieddata_fields as a non array causes OOM #8203
• Snapshot/Restore:
  • Fix snapshotting of a single closed index #8047 (issue: #8046)
  • Make it possible to delete snapshots with missing metadata file #7981 (issue: #7980)
  • Make sure indices cannot be renamed into restored aliases #7918 (issue: #7915)
• Upgrade API:
  • Fix upgrade logic to check for major version bump. #8013