[[breaking_50_settings_changes]]
=== Settings changes

From Elasticsearch 5.0 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. All settings must have been
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 plugin loading using the `SettingsModule#registerSettings(Setting)`
method.

==== Index Level Settings

In previous versions Elasticsearch allowed to specify index level setting
as _defaults_ on the node level, inside the `elasticsearch.yaml` file or even via
command-line parameters. From Elasticsearch 5.0 on only selected settings like
for instance `index.codec` can be set on the node level. All other settings must be
set on each individual index. To set default values on every index, index templates
should be used instead.

==== Node settings

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

==== Node attribute settings

Node level attributes used for allocation filtering, forced awareness or other node identification / grouping
must be prefixed with `node.attr`. In previous versions it was possible to specify node attributes with the `node.`
prefix. All node attributes except of `node.master`, `node.data` and `node.ingest` must be moved to the new `node.attr.`
namespace.

==== Node types settings

The `node.client` setting has been removed. A node with such a setting set will not
start up. Instead, each node role needs to be set separately using the existing
`node.master`, `node.data` and `node.ingest` supported static settings.

==== Gateway settings

The `gateway.format` setting for configuring global and index state serialization
format has been removed. By default, `smile` is used as the format.

==== 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All settings with a `netty` infix have been replaced by their already existing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`.

==== Security manager settings

The option to disable the security manager `security.manager.enabled` has been
removed. In order to grant special permissions to elasticsearch users must
edit the local Java Security Policy.

==== Network settings

The `_non_loopback_` value for settings like `network.host` 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.

==== 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. 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.).

==== Threadpool settings

The `suggest` threadpool has been removed, now suggest requests use the
`search` threadpool.

==== 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 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.


`discovery.zen.master_election.filter_client` and `discovery.zen.master_election.filter_data` have
been removed in favor of the new `discovery.zen.master_election.ignore_non_master_pings`. This setting control how ping responses
are interpreted during master election and should be used with care and only in extreme cases. See documentation for details.

==== 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 to 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 after every `index`, `create`, `update`,
`delete`, or `bulk` request.  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`.
Now, `index.translog.sync_interval`  doesn't accept a value less than `100ms`
which prevents fsyncing too often if async durability is enabled. The special
value `0` is no longer supported.

`index.translog.interval` has been removed.

==== 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.

`indices.requests.cache.clean_interval` has been replaced with
`indices.cache.clean_interval` and is no longer supported.

==== Field Data Cache Settings

The `indices.fielddata.cache.clean_interval` setting has been replaced with
`indices.cache.clean_interval`.

==== Allocation settings

The `cluster.routing.allocation.concurrent_recoveries` setting has been
replaced with `cluster.routing.allocation.node_concurrent_recoveries`.

==== Similarity settings

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

==== Indexing settings

The `indices.memory.min_shard_index_buffer_size` and
`indices.memory.max_shard_index_buffer_size` have been removed as
Elasticsearch now allows any one shard to use  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` (defaults to 10% of the JVM heap).

==== Removed es.max-open-files

Setting the system property es.max-open-files to true to get
Elasticsearch to print the number of maximum open files for the
Elasticsearch process has been removed. This same information can be
obtained from the <<cluster-nodes-info>> API, and a warning is logged
on startup if it is set too low.

==== Removed es.netty.gathering

Disabling Netty from using NIO gathering could be done via the escape
hatch of setting the system property "es.netty.gathering" to "false".
Time has proven enabling gathering by default is a non-issue and this
non-documented setting has been removed.

==== Removed es.useLinkedTransferQueue

The system property `es.useLinkedTransferQueue` could be used to
control the queue implementation used in the cluster service and the
handling of ping responses during discovery. This was an undocumented
setting and has been removed.

==== 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.

==== Using system properties to configure Elasticsearch

Elasticsearch can no longer be configured by setting system properties.
Instead, use `-Ename.of.setting=value.of.setting`.

==== Removed using double-dashes to configure Elasticsearch

Elasticsearch could previously be configured on the command line by
setting settings via `--name.of.setting value.of.setting`. This feature
has been removed. Instead, use `-Ename.of.setting=value.of.setting`.

==== Discovery Settings

The `discovery.zen.minimum_master_node` must be set for nodes that have
`network.host`, `network.bind_host`, `network.publish_host`,
`transport.host`, `transport.bind_host`, or `transport.publish_host`
configuration options set. We see those nodes as in "production" mode
and thus require the setting.

==== Realtime get setting

The `action.get.realtime` setting has been removed. This setting was
a fallback realtime setting for the get and mget APIs when realtime
wasn't specified. Now if the parameter isn't specified we always
default to true.

=== Script settings

==== Indexed script settings

Due to the fact that indexed script has been replaced by stored
scripts the following settings have been replaced to:

* `script.indexed` has been replaced by `script.stored`
* `script.engine.*.indexed.aggs` has been replaced by `script.engine.*.stored.aggs` (where `*` represents the script language, like `groovy`, `mustache`, `plainless` etc.)
* `script.engine.*.indexed.mapping` has been replaced by `script.engine.*.stored.mapping` (where `*` represents the script language, like `groovy`, `mustache`, `plainless` etc.)
* `script.engine.*.indexed.search` has been replaced by `script.engine.*.stored.search` (where `*` represents the script language, like `groovy`, `mustache`, `plainless` etc.)
* `script.engine.*.indexed.update` has been replaced by `script.engine.*.stored.update` (where `*` represents the script language, like `groovy`, `mustache`, `plainless` etc.)
* `script.engine.*.indexed.plugin` has been replaced by `script.engine.*.stored.plugin` (where `*` represents the script language, like `groovy`, `mustache`, `plainless` etc.)

==== Script mode settings

Previously script mode settings (e.g., "script.inline: true",
"script.engine.groovy.inline.aggs: false", etc.) accepted a wide range of
"truthy" or "falsy" values. This is now much stricter and supports only the
`true` and `false` options.


==== Script sandbox settings removed

Prior to 5.0 a third option could be specified for the `script.inline` and
`script.stored` settings ("sandbox"). This has been removed, You can now only
set `script.line: true` or `script.stored: true`.

==== Search settings

The setting `index.query.bool.max_clause_count` has been removed. In order to
set the maximum number of boolean clauses `indices.query.bool.max_clause_count`
should be used instead.
