[[breaking-changes-3.0]]
== Breaking changes in 3.0

This section discusses the changes that you need to be aware of when migrating
your application to Elasticsearch 3.0.

* <<breaking_30_search_changes>>
* <<breaking_30_rest_api_changes>>
* <<breaking_30_parent_child_changes>>
* <<breaking_30_settings_changes>>
* <<breaking_30_mapping_changes>>
* <<breaking_30_plugins>>
* <<breaking_30_java_api_changes>>
* <<breaking_30_cache_concurrency>>
* <<breaking_30_non_loopback>>
* <<breaking_30_thread_pool>>
* <<breaking_30_allocation>>
* <<breaking_30_percolator>>
* <<breaking_30_packaging>>
* <<breaking_30_scripting>>
* <<breaking_30_term_vectors>>

[[breaking_30_search_changes]]
=== Warmers

Thanks to several changes like doc values by default or disk-based norms,
warmers have become quite useless. As a consequence, warmers and the warmer
API have been removed: it is not possible anymore to register queries that
will run before a new IndexSearcher is published.

Don't worry if you have warmers defined on your indices, they will simply be
ignored when upgrading to 3.0.

=== Search changes

==== `search_type=count` removed

The `count` search type was deprecated since version 2.0.0 and is now removed.
In order to get the same benefits, you just need to set the value of the `size`
parameter to `0`.

For instance, the following request:

[source,sh]
---------------
GET /my_index/_search?search_type=count
{
  "aggs": {
    "my_terms": {
       "terms": {
         "field": "foo"
       }
     }
  }
}
---------------

can be replaced with:

[source,sh]
---------------
GET /my_index/_search
{
  "size": 0,
  "aggs": {
    "my_terms": {
       "terms": {
         "field": "foo"
       }
     }
  }
}
---------------

==== `search_type=scan` removed

The `scan` search type was deprecated since version 2.1.0 and is now removed.
All benefits from this search type can now be achieved by doing a scroll
request that sorts documents in `_doc` order, for instance:

[source,sh]
---------------
GET /my_index/_search?scroll=2m
{
  "sort": [
    "_doc"
  ]
}
---------------

Scroll requests sorted by `_doc` have been optimized to more efficiently resume
from where the previous request stopped, so this will have the same performance
characteristics as the former `scan` search type.

[[breaking_30_rest_api_changes]]
=== REST API changes

==== search exists api removed

The search exists api has been removed in favour of using the search api with
`size` set to `0` and `terminate_after` set to `1`.

==== `/_optimize` endpoint removed

The deprecated `/_optimize` endpoint has been removed. The `/_forcemerge`
endpoint should be used in lieu of optimize.

The `GET` HTTP verb for `/_forcemerge` is no longer supported, please use the
`POST` HTTP verb.

==== Deprecated queries removed

The following deprecated queries have been removed:
* `filtered`: use `bool` query instead, which supports `filter` clauses too
* `and`: use `must` clauses in a `bool` query instead
* `or`: use should clauses in a `bool` query instead
* `limit`: use `terminate_after` parameter instead
* `fquery`: obsolete after filters and queries have been merged
* `query`: obsolete after filters and queries have been merged

==== Unified fuzziness parameter

* Removed support for the deprecated `min_similarity` parameter in `fuzzy query`, in favour of `similarity`.
* Removed support for the deprecated `fuzzy_min_sim` parameter in `query_string` query, in favour of `similarity`.
* Removed support for the deprecated `edit_distance` parameter in completion suggester, in favour of `similarity`.

==== indices query

Removed support for the deprecated `filter` and `no_match_filter` fields in `indices` query,
in favour of `query` and `no_match_query`.

==== nested query

Removed support for the deprecated `filter` fields in `nested` query, in favour of `query`.

==== terms query

Removed support for the deprecated `minimum_should_match` and `disable_coord` in `terms` query, use `bool` query instead.
Removed also support for the deprecated `execution` parameter.

==== function_score query

Removed support for the top level `filter` element in `function_score` query, replaced by `query`.

==== highlighters

Removed support for multiple highlighter names, the only supported ones are: `plain`, `fvh` and `postings`.

==== top level filter

Removed support for the deprecated top level `filter` in the search api, replaced by `post_filter`.

==== `query_binary` and `filter_binary` removed

Removed support for the undocumented `query_binary` and `filter_binary` sections of a search request.

==== `span_near`'s' `collect_payloads` deprecated

Payloads are now loaded when needed.

[[breaking_30_parent_child_changes]]
=== Parent/Child changes

The `children` aggregation, parent child inner hits and `has_child` and `has_parent` queries will not work on indices
with `_parent` field mapping created before version `2.0.0`. The data of these indices need to be re-indexed into a new index.

The format of the join between parent and child documents have changed with the `2.0.0` release. The old
format can't read from version `3.0.0` and onwards. The new format allows for a much more efficient and
scalable join between parent and child documents and the join data structures are stored on disk
data structures as opposed as before the join data structures were stored in the jvm heap space.

==== `score_type` has been removed

The `score_type` option has been removed from the `has_child` and `has_parent` queries in favour of the `score_mode` option
which does the exact same thing.

==== `sum` score mode removed

The `sum` score mode has been removed in favour of the `total` mode which does the same and is already available in
previous versions.

==== `max_children` option

When `max_children` was set to `0` on the `has_child` query then there was no upper limit on how many children documents
are allowed to match. This has changed and `0` now really means to zero child documents are allowed. If no upper limit
is needed then the `max_children` option shouldn't be defined at all on the `has_child` query.

==== `_parent` field no longer indexed

The join between parent and child documents no longer relies on indexed fields and therefor from `3.0.0` onwards
the `_parent` indexed field won't be indexed. In order to find documents that referrer to a specific parent id
the new `parent_id` query can be used. The get response and hits inside the search response remain to include
the parent id under the `_parent` key.

[[breaking_30_settings_changes]]
=== Settings changes

From Elasticsearch 3.0 on all settings are validated before they are applied. Node level and default index
level settings are validated on node startup, dynamic cluster and index setting are validated before they are updated/added
to the cluster state. Every setting must be a _known_ setting or in other words all settings must be registered with the
node or transport client they are used with. This implies that plugins that define custom settings must register all of their
settings during pluging loading using the `SettingsModule#registerSettings(Setting)` method.

==== Node settings

The `name` setting has been removed and is replaced by `node.name`. Usage of `-Dname=some_node_name` is not supported
anymore.

==== Transport Settings

All settings with a `netty` infix have been replaced by their already existing `transport` synonyms. For instance `transport.netty.bind_host` is
no longer supported and should be replaced by the superseding setting `transport.bind_host`.

==== Analysis settings

The `index.analysis.analyzer.default_index` analyzer is not supported anymore.
If you wish to change the analyzer to use for indexing, change the
`index.analysis.analyzer.default` analyzer instead.

==== Ping timeout settings

Previously, there were three settings for the ping timeout: `discovery.zen.initial_ping_timeout`,
`discovery.zen.ping.timeout` and `discovery.zen.ping_timeout`. The former two have been removed and
the only setting key for the ping timeout is now `discovery.zen.ping_timeout`. The default value for
ping timeouts remains at three seconds.

==== Recovery settings

Recovery settings deprecated in 1.x have been removed:

 * `index.shard.recovery.translog_size` is superseded by `indices.recovery.translog_size`
 * `index.shard.recovery.translog_ops` is superseded by `indices.recovery.translog_ops`
 * `index.shard.recovery.file_chunk_size` is superseded by `indices.recovery.file_chunk_size`
 * `index.shard.recovery.concurrent_streams` is superseded by `indices.recovery.concurrent_streams`
 * `index.shard.recovery.concurrent_small_file_streams` is superseded by `indices.recovery.concurrent_small_file_streams`
 * `indices.recovery.max_size_per_sec` is superseded by `indices.recovery.max_bytes_per_sec`

If you are using any of these settings please take the time and review their purpose. All of the settings above are considered
_expert settings_ and should only be used if absolutely necessary. If you have set any of the above setting as persistent
cluster settings please use the settings update API and set their superseded keys accordingly.

The following settings have been removed without replacement

 * `indices.recovery.concurrent_small_file_streams` - recoveries are now single threaded. The number of concurrent outgoing recoveries are throttled via allocation deciders
 * `indices.recovery.concurrent_file_streams` - recoveries are now single threaded. The number of concurrent outgoing recoveries are throttled via allocation deciders

==== Translog settings

The `index.translog.flush_threshold_ops` setting is not supported anymore. In order to control flushes based on the transaction log
growth use `index.translog.flush_threshold_size` instead. Changing the translog type with `index.translog.fs.type` is not supported
anymore, the `buffered` implementation is now the only available option and uses a fixed `8kb` buffer.

The translog by default is fsynced on a request basis such that the ability to fsync on every operation is not necessary anymore. In-fact it can
be a performance bottleneck and it's trappy since it enabled by a special value set on `index.translog.sync_interval`. `index.translog.sync_interval`
now doesn't accept a value less than `100ms` which prevents fsyncing too often if async durability is enabled. The special value `0` is not supported anymore.

==== Request Cache Settings

The deprecated settings `index.cache.query.enable` and `indices.cache.query.size` have been removed and are replaced with
`index.requests.cache.enable` and `indices.requests.cache.size` respectively.

==== Allocation settings

Allocation settings deprecated in 1.x have been removed:

 * `cluster.routing.allocation.concurrent_recoveries` is superseded by `cluster.routing.allocation.node_concurrent_recoveries`

Please change the setting in your configuration files or in the clusterstate to use the new settings instead.

==== Similarity settings

The 'default' similarity has been renamed to 'classic'.

==== Indexing settings

`indices.memory.min_shard_index_buffer_size` and `indices.memory.max_shard_index_buffer_size` are removed since Elasticsearch now allows any one shard to any
amount of heap as long as the total indexing buffer heap used across all shards is below the node's `indices.memory.index_buffer_size` (default: 10% of the JVM heap)

[[breaking_30_mapping_changes]]
=== Mapping changes

==== Default doc values settings

Doc values are now also on by default on numeric and boolean fields that are
not indexed.

==== Transform removed

The `transform` feature from mappings has been removed. It made issues very hard to debug.

==== Default number mappings

When a floating-point number is encountered, it is now dynamically mapped as a
float by default instead of a double. The reasoning is that floats should be
more than enough for most cases but would decrease storage requirements
significantly.

==== `index` property

On all types but `string`, the `index` property now only accepts `true`/`false`
instead of `not_analyzed`/`no`. The `string` field still accepts
`analyzed`/`not_analyzed`/`no`.

==== `_source`'s `format` option

The `_source` mapping does not support the `format` option anymore. This option
will still be accepted for indices created before the upgrade to 3.0 for backward
compatibility, but it will have no effect. Indices created on or after 3.0 will
reject this option.

==== Object notation

Core types don't support the object notation anymore, which allowed to provide
values as follows:

[source,json]
-----
{
  "value": "field_value",
  "boost": 42
}
----

==== `fielddata.format`

Setting `fielddata.format: doc_values` in the mappings used to implicitly
enable doc values on a field. This no longer works: the only way to enable or
disable doc values is by using the `doc_values` property of mappings.


[[breaking_30_plugins]]
=== Plugin changes

The command `bin/plugin` has been renamed to `bin/elasticsearch-plugin`.

==== Site plugins removed

Site plugins have been removed. It is recommended to migrate site plugins to Kibana plugins.

==== Multicast plugin removed

Multicast has been removed. Use unicast discovery, or one of the cloud discovery plugins.

==== Plugins with custom query implementations

Plugins implementing custom queries need to implement the `fromXContent(QueryParseContext)` method in their
`QueryParser` subclass rather than `parse`. This method will take care of parsing the query from `XContent` format
into an intermediate query representation that can be streamed between the nodes in binary format, effectively the
query object used in the java api. Also, the query parser needs to implement the `getBuilderPrototype` method that
returns a prototype of the `NamedWriteable` query, which allows to deserialize an incoming query by calling
`readFrom(StreamInput)` against it, which will create a new object, see usages of `Writeable`. The `QueryParser`
also needs to declare the generic type of the query that it supports and it's able to parse.
The query object can then transform itself into a lucene query through the new `toQuery(QueryShardContext)` method,
which returns a lucene query to be executed on the data node.

Similarly, plugins implementing custom score functions need to implement the `fromXContent(QueryParseContext)`
method in their `ScoreFunctionParser` subclass rather than `parse`. This method will take care of parsing
the function from `XContent` format into an intermediate function representation that can be streamed between
the nodes in binary format, effectively the function object used in the java api. Also, the query parser needs
to implement the `getBuilderPrototype` method that returns a prototype of the `NamedWriteable` function, which
allows to deserialize an incoming function by calling `readFrom(StreamInput)` against it, which will create a
new object, see usages of `Writeable`. The `ScoreFunctionParser` also needs to declare the generic type of the
function that it supports and it's able to parse. The function object can then transform itself into a lucene
function through the new `toFunction(QueryShardContext)` method, which returns a lucene function to be executed
on the data node.

==== Cloud AWS plugin changes

Cloud AWS plugin has been split in two plugins:

* {plugins}/discovery-ec2.html[Discovery EC2 plugin]
* {plugins}/repository-s3.html[Repository S3 plugin]

Proxy settings for both plugins have been renamed:

* from `cloud.aws.proxy_host` to `cloud.aws.proxy.host`
* from `cloud.aws.ec2.proxy_host` to `cloud.aws.ec2.proxy.host`
* from `cloud.aws.s3.proxy_host` to `cloud.aws.s3.proxy.host`
* from `cloud.aws.proxy_port` to `cloud.aws.proxy.port`
* from `cloud.aws.ec2.proxy_port` to `cloud.aws.ec2.proxy.port`
* from `cloud.aws.s3.proxy_port` to `cloud.aws.s3.proxy.port`

==== Cloud Azure plugin changes

Cloud Azure plugin has been split in three plugins:

* {plugins}/discovery-azure.html[Discovery Azure plugin]
* {plugins}/repository-azure.html[Repository Azure plugin]
* {plugins}/store-smb.html[Store SMB plugin]

If you were using the `cloud-azure` plugin for snapshot and restore, you had in `elasticsearch.yml`:

[source,yaml]
-----
cloud:
    azure:
        storage:
            account: your_azure_storage_account
            key: your_azure_storage_key
-----

You need to give a unique id to the storage details now as you can define multiple storage accounts:

[source,yaml]
-----
cloud:
    azure:
        storage:
            my_account:
                account: your_azure_storage_account
                key: your_azure_storage_key
-----


==== Cloud GCE plugin changes

Cloud GCE plugin has been renamed to {plugins}/discovery-gce.html[Discovery GCE plugin].

[[breaking_30_java_api_changes]]
=== Java API changes

==== Count api has been removed

The deprecated count api has been removed from the Java api, use the search api instead and set size to 0.

The following call

[source,java]
-----
client.prepareCount(indices).setQuery(query).get();
-----

can be replaced with

[source,java]
-----
client.prepareSearch(indices).setSource(new SearchSourceBuilder().size(0).query(query)).get();
-----

==== BoostingQueryBuilder

Removed setters for mandatory positive/negative query. Both arguments now have
to be supplied at construction time already and have to be non-null.

==== SpanContainingQueryBuilder

Removed setters for mandatory big/little inner span queries. Both arguments now have
to be supplied at construction time already and have to be non-null. Updated
static factory methods in QueryBuilders accordingly.

==== SpanOrQueryBuilder

Making sure that query contains at least one clause by making initial clause mandatory
in constructor.

==== SpanNearQueryBuilder

Removed setter for mandatory slop parameter, needs to be set in constructor now. Also
making sure that query contains at least one clause by making initial clause mandatory
in constructor. Updated the static factory methods in QueryBuilders accordingly.

==== SpanNotQueryBuilder

Removed setter for mandatory include/exclude span query clause, needs to be set in constructor now.
Updated the static factory methods in QueryBuilders and tests accordingly.

==== SpanWithinQueryBuilder

Removed setters for mandatory big/little inner span queries. Both arguments now have
to be supplied at construction time already and have to be non-null. Updated
static factory methods in QueryBuilders accordingly.

==== QueryFilterBuilder

Removed the setter `queryName(String queryName)` since this field is not supported
in this type of query. Use `FQueryFilterBuilder.queryName(String queryName)` instead
when in need to wrap a named query as a filter.

==== WrapperQueryBuilder

Removed `wrapperQueryBuilder(byte[] source, int offset, int length)`. Instead simply
use  `wrapperQueryBuilder(byte[] source)`. Updated the static factory methods in
QueryBuilders accordingly.

==== QueryStringQueryBuilder

Removed ability to pass in boost value using `field(String field)` method in form e.g. `field^2`.
Use the `field(String, float)` method instead.

==== Operator

Removed the enums called `Operator` from `MatchQueryBuilder`, `QueryStringQueryBuilder`,
`SimpleQueryStringBuilder`, and `CommonTermsQueryBuilder` in favour of using the enum
defined in `org.elasticsearch.index.query.Operator` in an effort to consolidate the
codebase and avoid duplication.

==== queryName and boost support

Support for `queryName` and `boost` has been streamlined to all of the queries. That is
a breaking change till queries get sent over the network as serialized json rather
than in `Streamable` format. In fact whenever additional fields are added to the json
representation of the query, older nodes might throw error when they find unknown fields.

==== InnerHitsBuilder

InnerHitsBuilder now has a dedicated addParentChildInnerHits and addNestedInnerHits methods
to differentiate between inner hits for nested vs. parent / child documents. This change
makes the type / path parameter mandatory.

==== MatchQueryBuilder

Moving MatchQueryBuilder.Type and MatchQueryBuilder.ZeroTermsQuery enum to MatchQuery.Type.
Also reusing new Operator enum.

==== MoreLikeThisQueryBuilder

Removed `MoreLikeThisQueryBuilder.Item#id(String id)`, `Item#doc(BytesReference doc)`,
`Item#doc(XContentBuilder doc)`. Use provided constructors instead.

Removed `MoreLikeThisQueryBuilder#addLike` in favor of texts and/or items being provided
at construction time. Using arrays there instead of lists now.

Removed `MoreLikeThisQueryBuilder#addUnlike` in favor to using the `unlike` methods
which take arrays as arguments now rather than the lists used before.

The deprecated `docs(Item... docs)`, `ignoreLike(Item... docs)`,
`ignoreLike(String... likeText)`, `addItem(Item... likeItems)` have been removed.

==== GeoDistanceQueryBuilder

Removing individual setters for lon() and lat() values, both values should be set together
 using point(lon, lat).

==== GeoDistanceRangeQueryBuilder

Removing setters for to(Object ...) and from(Object ...) in favour of the only two allowed input
arguments (String, Number). Removing setter for center point (point(), geohash()) because parameter
is mandatory and should already be set in constructor.
Also removing setters for lt(), lte(), gt(), gte() since they can all be replaced by equivallent
calls to to/from() and inludeLower()/includeUpper().

==== GeoPolygonQueryBuilder

Require shell of polygon already to be specified in constructor instead of adding it pointwise.
This enables validation, but makes it necessary to remove the addPoint() methods.

==== MultiMatchQueryBuilder

Moving MultiMatchQueryBuilder.ZeroTermsQuery enum to MatchQuery.ZeroTermsQuery.
Also reusing new Operator enum.

Removed ability to pass in boost value using `field(String field)` method in form e.g. `field^2`.
Use the `field(String, float)` method instead.

==== MissingQueryBuilder

The MissingQueryBuilder which was deprecated in 2.2.0 is removed. As a replacement use ExistsQueryBuilder
inside a mustNot() clause. So instead of using `new ExistsQueryBuilder(name)` now use
`new BoolQueryBuilder().mustNot(new ExistsQueryBuilder(name))`.

==== NotQueryBuilder

The NotQueryBuilder which was deprecated in 2.1.0 is removed. As a replacement use BoolQueryBuilder
with added mustNot() clause. So instead of using `new NotQueryBuilder(filter)` now use
`new BoolQueryBuilder().mustNot(filter)`.

==== TermsQueryBuilder

Remove the setter for `termsLookup()`, making it only possible to either use a TermsLookup object or
individual values at construction time. Also moving individual settings for the TermsLookup (lookupIndex,
lookupType, lookupId, lookupPath) to the separate TermsLookup class, using constructor only and moving
checks for validation there. Removed `TermsLookupQueryBuilder` in favour of `TermsQueryBuilder`.

==== FunctionScoreQueryBuilder

`add` methods have been removed, all filters and functions must be provided as constructor arguments by
creating an array of `FunctionScoreQueryBuilder.FilterFunctionBuilder` objects, containing one element
for each filter/function pair.

`scoreMode` and `boostMode` can only be provided using corresponding enum members instead
of string values: see `FilterFunctionScoreQuery.ScoreMode` and `CombineFunction`.

`CombineFunction.MULT` has been renamed to `MULTIPLY`.

==== IdsQueryBuilder

For simplicity, only one way of adding the ids to the existing list (empty by default)  is left: `addIds(String...)`

==== DocumentAlreadyExistsException removed

`DocumentAlreadyExistsException` is removed and a `VersionConflictException` is thrown instead (with a better
error description). This will influence code that use the `IndexRequest.opType()` or `IndexRequest.create()`
to index a document only if it doesn't already exist.

==== ShapeBuilders

`InternalLineStringBuilder` is removed in favour of `LineStringBuilder`, `InternalPolygonBuilder` in favour of PolygonBuilder` and `Ring` has been replaced with `LineStringBuilder`. Also the abstract base classes `BaseLineStringBuilder` and `BasePolygonBuilder` haven been merged with their corresponding implementations.

==== RescoreBuilder

`RecoreBuilder.Rescorer` was merged with `RescoreBuilder`, which now is an abstract superclass. QueryRescoreBuilder currently is its only implementation.

==== PhraseSuggestionBuilder

The inner DirectCandidateGenerator class has been moved out to its own class called DirectCandidateGeneratorBuilder.

[[breaking_30_cache_concurrency]]
=== Cache concurrency level settings removed

Two cache concurrency level settings `indices.requests.cache.concurrency_level` and
`indices.fielddata.cache.concurrency_level` because they no longer apply to the cache implementation used for the
request cache and the field data cache.

[[breaking_30_non_loopback]]
=== Remove bind option of `non_loopback`

This setting would arbitrarily pick the first interface not marked as loopback. Instead, specify by address
scope (e.g. `_local_,_site_` for all loopback and private network addresses) or by explicit interface names,
hostnames, or addresses.

[[breaking_30_thread_pool]]
=== Forbid changing of thread pool types

Previously, <<modules-threadpool,thread pool types>> could be dynamically adjusted. The thread pool type effectively
controls the backing queue for the thread pool and modifying this is an expert setting with minimal practical benefits
and high risk of being misused. The ability to change the thread pool type for any thread pool has been removed; do note
that it is still possible to adjust relevant thread pool parameters for each of the thread pools (e.g., depending on
the thread pool type, `keep_alive`, `queue_size`, etc.).

[[breaking_30_cpu_stats]]
=== System CPU stats

The recent CPU usage (as a percent) has been added to the OS stats
reported under the node stats API and the cat nodes API. The breaking
change here is that there is a new object in the `os` object in the node
stats response. This object is called `cpu` and includes "percent" and
`load_average` as fields. This moves the `load_average` field that was
previously a top-level field in the `os` object to the `cpu` object. The
format of the `load_average` field has changed to an object with fields
`1m`, `5m`, and `15m` representing the one-minute, five-minute and
fifteen-minute loads respectively. If any of these fields are not present,
it indicates that the corresponding value is not available.

In the cat nodes API response, the `cpu` field is output by default. The
previous `load` field has been removed and is replaced by `load_1m`,
`load_5m`, and `load_15m` which represent the one-minute, five-minute
and fifteen-minute loads respectively. The field will be null if the
corresponding value is not available.

Finally, the API for `org.elasticsearch.monitor.os.OsStats` has
changed. The `getLoadAverage` method has been removed. The value for
this can now be obtained from `OsStats.Cpu#getLoadAverage` but it is no
longer a double and is instead an object encapsulating the one-minute,
five-minute and fifteen-minute load averages. Additionally, the recent
CPU usage can be obtained from `OsStats.Cpu#getPercent`.

=== Fields option
Only stored fields are retrievable with this option.
The fields option won't be able to load non stored fields from _source anymore.

[[breaking_30_allocation]]
=== Primary shard allocation

Previously, primary shards were only assigned if a quorum of shard copies were found (configurable using
`index.recovery.initial_shards`, now deprecated). In case where a primary had only a single replica, quorum was defined
to be a single shard. This meant that any shard copy of an index with replication factor 1 could become primary, even it
was a stale copy of the data on disk. This is now fixed by using allocation IDs.

Allocation IDs assign unique identifiers to shard copies. This allows the cluster to differentiate between multiple
copies of the same data and track which shards have been active, so that after a cluster restart, shard copies
containing only the most recent data can become primaries.

=== Indices Shard Stores command

By using allocation IDs instead of version numbers to identify shard copies for primary shard allocation, the former versioning scheme
has become obsolete. This is reflected in the indices-shards-stores.html[Indices Shard Stores API]. A new field `allocation_id` replaces the
former `version` field in the result of the Indices Shard Stores command. This field is available for all shard copies that have been either
created with the current version of Elasticsearch or have been active in a cluster running a current version of Elasticsearch. For legacy
shard copies that have not been active in a current version of Elasticsearch, a `legacy_version` field is available instead (equivalent to
the former `version` field).

=== Reroute commands

The reroute command `allocate` has been split into two distinct commands `allocate_replica` and `allocate_empty_primary`.
This was done as we introduced a new `allocate_stale_primary` command. The new `allocate_replica` command corresponds to the
old `allocate` command  with `allow_primary` set to false. The new `allocate_empty_primary` command corresponds to the old
`allocate` command with `allow_primary` set to true.

==== `index.shared_filesystem.recover_on_any_node` changes

The behavior of `index.shared_filesystem.recover_on_any_node = true` has been changed. Previously, in the case where no
shard copies could be found, an arbitrary node was chosen by potentially ignoring allocation deciders. Now, we take
balancing into account but don't assign the shard if the allocation deciders are not satisfied. The behavior has also changed
in the case where shard copies can be found. Previously, a node not holding the shard copy was chosen if none of the nodes
holding shard copies were satisfying the allocation deciders. Now, the shard will be assigned to a node having a shard copy,
even if none of the nodes holding a shard copy satisfy the allocation deciders.

[[breaking_30_percolator]]
=== Percolator

Adding percolator queries and modifications to existing percolator queries are no longer visible in immediately
to the percolator. A refresh is required to run before the changes are visible to the percolator.

The reason that this has changed is that on newly created indices the percolator automatically indexes the query terms
and these query terms are used at percolate time to reduce the amount of queries the percolate API needs evaluate.
This optimization didn't work in the percolate API mode where modifications to queries are immediately visible.

The percolator by defaults sets the `size` option to `10` whereas before this was set to unlimited.

The percolate api can no longer accept documents that have fields that don't exist in the mapping.

When percolating an existing document then specifying a document in the source of the percolate request is not allowed
any more.

The percolate api no longer modifies the mappings. Before the percolate api could be used to dynamically introduce new
fields to the mappings based on the fields in the document being percolated. This no longer works, because these
unmapped fields are not persisted in the mapping.

Percolator documents are no longer excluded from the search response.

[[breaking_30_packaging]]
=== Packaging

==== Default logging using systemd (since Elasticsearch 2.2.0)

In previous versions of Elasticsearch, the default logging
configuration routed standard output to /dev/null and standard error to
the journal. However, there are often critical error messages at
startup that are logged to standard output rather than standard error
and these error messages would be lost to the nether. The default has
changed to now route standard output to the journal and standard error
to inherit this setting (these are the defaults for systemd). These
settings can be modified by editing the elasticsearch.service file.

[[breaking_30_scripting]]
=== Scripting

==== Script mode settings

Previously script mode settings (e.g., "script.inline: true",
"script.engine.groovy.inline.aggs: false", etc.) accepted the values
`on`, `true`, `1`, and `yes` for enabling a scripting mode, and the
values `off`, `false`, `0`, and `no` for disabling a scripting mode.
The variants `on`, `1`, and `yes ` for enabling and `off`, `0`,
and `no` for disabling are no longer supported.

[[breaking_30_term_vectors]]
=== Term vectors

The term vectors APIs no longer persist unmapped fields in the mappings.

The `dfs` parameter has been removed completely, term vectors don't support
distributed document frequencies anymore.
