* fix: stop druid on unhandled curator exceptions

* catch exceptions when stopping lifecycle

* Unified configuration doc page

* Rename to index.md, update redirects

* PR comments

* PR comments

* PR comment

* New docs intro

* PR comments

* Fix arch diagram

* PR comment

* PR comment

* PR comment

* Add keepSegmentGranularity for compactionTask

* fix build

* createIoConfig method

* fix build

* fix build

* address comments

* fix build

* update redis-cache documentation

added clarifying info on setup and enablement

* added link

* Add docs for virtual columns and transform specs

* PR Comments

* PR comment

* Separate hadoop and native batch docs more

* Rebase with parallel batch

* PR comments

* New quickstart and tutorials

* PR comments

* Fix tranquility

* Unified API doc page

* PR comments

* Fix metadata endpoint

* Cache: Add maxEntrySize config.

The idea is this makes it more feasible to cache query types that
can potentially generate large result sets, like groupBy and select,
without fear of writing too much to the cache per query.

Includes a refactor of cache population code in CachingQueryRunner and
CachingClusteredClient, such that they now use the same CachePopulator
interface with two implementations: one for foreground and one for
background.

The main reason for splitting the foreground / background impls is
that the foreground impl can have a more effective implementation of
maxEntrySize. It can stop retaining subvalues for the cache early.

* Add CachePopulatorStats.

* Fix whitespace.

* Fix docs.

* Fix various tests.

* Add tests.

* Fix tests.

* Better tests

* Remove conflict markers.

* Fix licenses.

* Native parallel indexing without shuffle

* fix build

* fix ci

* fix ingestion without intervals

* fix retry

* fix retry

* add it test

* use chat handler

* fix build

* add docs

* fix ITUnionQueryTest

* fix failures

* disable metrics reporting

* working

* Fix split of static-s3 firehose

* Add endpoints to supervisor task and a unit test for endpoints

* increase timeout in test

* Added doc

* Address comments

* Fix overlapping locks

* address comments

* Fix static s3 firehose

* Fix test

* fix build

* fix test

* fix typo in docs

* add missing maxBytesInMemory to doc

* address comments

* fix race in test

* fix test

* Rename to ParallelIndexSupervisorTask

* fix teamcity

* address comments

* Fix license

* addressing comments

* addressing comments

* indexTaskClient-based segmentAllocator instead of CountingActionBasedSegmentAllocator

* Fix race in TaskMonitor and move HTTP endpoints to supervisorTask from runner

* Add more javadocs

* use StringUtils.nonStrictFormat for logging

* fix typo and remove unused class

* fix tests

* change package

* fix strict build

* tmp

* Fix overlord api according to the recent change in master

* Fix it test

* order using IncrementalIndexRowComparator at persist time when rollup is disabled, allowing increased effectiveness of dimension compression, resolves #6066

* fix stuff from review

Fix IllegalArgumentException in TaskLockBox.syncFromStorage() when updating from 0.12.x to 0.12.2 (#6086)

* Fix TaskLockBox.syncFromStorage() when updating from 0.12.x to 0.12.2

* Make the priority of taskLock nullable

* fix test

* fix build

* validate baseDataSource non-empty string in DerivativeDataSourceMetadata; added a test

* added another test for validating null baseDataSource

* restored the arguments check order

* Part 2 of changes for SQL Compatible Null Handling

* Review comments - break lines longer than 120 characters

* review comments

* review comments

* fix license

* fix test failure

* fix CalciteQueryTest failure

* Null Handling - Review comments

* review comments

* review comments

* fix checkstyle

* fix checkstyle

* remove unrelated change

* fix test failure

* fix failing test

* fix travis failures

* Make StringLast and StringFirst aggregators nullable and fix travis failures

* Optimize per-segment queries

* Always optimize, add unit test

* PR comments

* Only run IntervalDimFilter optimization on __time column

* PR comments

* Checkstyle fix

* Add test for non __time column

* Add lastString and firstString aggregators extension

* Remove duplicated class

* Move first-last-string doc page to extensions-contrib

* Fix ObjectStrategy compare method

* Fix doc bad aggregatos type name

* Create FoldingAggregatorFactory classes to fix SegmentMetadataQuery

* Add getMaxStringBytes() method to support JSON serialization

* Fix null pointer exception at segment creation phase when the string value is null

* Control the valueSelector object class on BufferAggregators

* Perform all improvements

* Add java doc on SerializablePairLongStringSerde

* Refactor ObjectStraty compare method

* Remove unused ;

* Add aggregateCombiner unit tests. Rename BufferAggregators unit tests

* Remove unused imports

* Add license header

* Add class name to java doc class serde

* Throw exception if value is unsupported class type

* Move first-last-string extension into druid core

* Update druid core docs

* Fix null pointer exception when pair->string is null

* Add null control unit tests

* Remove unused imports

* Add first/last string folding aggregator on AggregatorsModule to support segment metadata query

* Change SerializablePairLongString to extend SerializablePair

* Change vars from public to private

* Convert vars to primitive type

* Clarify compare comment

* Change IllegalStateException to ISE

* Remove TODO comments

* Control possible null pointer exception

* Add @Nullable annotation

* Remove empty line

* Remove unused parameter type

* Improve AggregatorCombiner javadocs

* Add filterNullValues option at StringLast and StringFirst aggregators

* Add filterNullValues option at agg documentation

* Fix checkstyle

* Update header license

* Fix StringFirstAggregatorFactory.VALUE_COMPARATOR

* Fix StringFirstAggregatorCombiner

* Fix if condition at StringFirstAggregateCombiner

* Remove filterNullValues from string first/last aggregators

* Add isReset flag in FirstAggregatorCombiner

* Change Arrays.asList to Collections.singletonList

* Prohibit Lists.newArrayList() with a single argument

* Test fixes

* Add Javadoc to Node constructor

* Fix CombiningFirehoseFactory with IngestSegmentFirehoseFactory in IndexTask

* Make recursive

* Revert "Fix a bug in GroupByQueryEngine (#6062)"

This reverts commit f3595c93.

* Revert "Add definition of 'NONE' to queryGranularity in ingestion.index doc (#6073)"

This reverts commit 7f89c729.

* Revert "skip travis on doc only changes (#6061)"

This reverts commit 66af403f.

* Fix 'auto' encoded longs + compression serializer
Fixes #6044

changes:
* Fixes `VSizeLongSerde` serializers to treat 'close' as 'flush' when used with `BlockLayoutColumnarLongsSerializer`, allowing unwritten values to be flushed to the buffer when the block is compressed
* Add exhaustive unit test that flexes a variety of value sizes, row counts, and compression strategies to catch issues such as these
:

* refactor LongSerializer close to be named flush instead

* revert and just make new serializers per block

* Remove some unnecessary task storage internal APIs.

- Remove MetadataStorageActionHandler's getInactiveStatusesSince and getActiveEntriesWithStatus.
- Remove TaskStorage's getCreatedDateTimeAndDataSource.
- Remove TaskStorageQueryAdapter's getCreatedTime, and getCreatedDateAndDataSource.
- Migrated all callers to getActiveTaskInfo and getCompletedTaskInfo.

This has one side effect: since getActiveTaskInfo (new) warns and continues when it
sees unreadable tasks, but getActiveEntriesWithStatus threw an exception when it
encountered those, it means that after this patch bad tasks will be ignored when
syncing from metadata storage rather than causing an exception to be thrown.

IMO, this is an improvement, since the most likely reason for bad tasks is either:

- A new version introduced an additional validation, and a pre-existing task doesn't
  pass it.
- You are rolling back from a newer version to an older version.

In both cases, I believe you would want to skip tasks that can't be deserialized,
rather than blocking overlord startup.

* Remove unused import.

* Fix formatting.

* Fix formatting.

* Add meaning of granularity = None to queryGranularity

* Fix format

* skip travis on doc only changes

* more selective ignoring of examples folder

* CompactionTask: Reject empty intervals on construction.

They don't make sense anyway, and it's better to fail fast.

* Switch API.

Fixes #6063.

Class org.apache.hadoop.conf.Configuration inside extensions should be used with caution.
By default, the configuration uses the context class loader of the current thread set to the
class loader used to load the application. Because of isolation between the application and
extensions we must explicitely set the class loader to extension class loader to be able
load classes specified in hadoop configuration file.

* Various changes about druid-services module

* Patch improvements from reviewer

* Add ToArrayCallWithZeroLengthArrayArgument & ArraysAsListWithZeroOrOneArgument into inspection profile

* Fix ArraysAsListWithZeroOrOneArgument

* Fix conflict

* Fix ToArrayCallWithZeroLengthArrayArgument

* Fix AliEqualsAvoidNull

* Remove blank line

* Remove unused import clauses

* Fix code style in TopNQueryRunnerTest

* Fix conflict

* Don't use Collections.singletonList when converting the type of array type

* Add argLine into maven-surefire-plugin in druid-process module & increase the timeout value for testMoveSegment testcase

* Roll back the latest commit

* Add java.io.File#toURL() into druid-forbidden-apis

* Using Boolean.parseBoolean instead of Boolean.valueOf for CliCoordinator#isOverlord

* Add a new regexp element into stylecode xml file

* Fix style error for new regexp

* Set the level of ArraysAsListWithZeroOrOneArgument as WARNING

* Fix style error for new regexp

* Add option BY_LEVEL for ToArrayCallWithZeroLengthArrayArgument in inspection profile

* Roll back the level as ToArrayCallWithZeroLengthArrayArgument as ERROR

* Add toArray(new Object[0]) regexp into checkstyle config file & fix them

* Set the level of ArraysAsListWithZeroOrOneArgument as ERROR & Roll back the level of ToArrayCallWithZeroLengthArrayArgument as WARNING until Youtrack fix it

* Add a comment for string equals regexp in checkstyle config

* Fix code format

* Add RedundantTypeArguments as ERROR level inspection

* Fix cannot resolve symbol datasource

See issue #6030

* Remove the unsafe loop from the benchmark

* Removing unused variables

Similar issue to https://github.com/apache/incubator-druid/issues/6028.