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Fluent::Plugin::Elasticsearch, a plugin for Fluentd

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Send your logs to Elasticsearch (and search them with Kibana maybe?)

Note: For Amazon Elasticsearch Service please consider using fluent-plugin-aws-elasticsearch-service

Current maintainers: @cosmo0920


fluent-plugin-elasticsearch fluentd ruby
>= 2.0.0 >= v0.14.20 >= 2.1
< 2.0.0 >= v0.12.0 >= 1.9

NOTE: For v0.12 version, you should use 1.x.y version. Please send patch into v0.12 branch if you encountered 1.x version's bug.

NOTE: This documentation is for fluent-plugin-elasticsearch 2.x or later. For 1.x documentation, please see v0.12 branch.


$ gem install fluent-plugin-elasticsearch


In your Fluentd configuration, use @type elasticsearch. Additional configuration is optional, default values would look like this:

<match my.logs>
  @type elasticsearch
  host localhost
  port 9200
  index_name fluentd
  type_name fluentd

Index templates

This plugin creates Elasticsearch indices by merely writing to them. Consider using Index Templates to gain control of what get indexed and how. See this example for a good starting point.



emit_error_for_missing_id true

When write_operation is configured to anything other then index, setting this value to true will cause the plugin to emit_error_event of any records which do not include an _id field. The default (false) behavior is to silently drop the records.


hosts host1:port1,host2:port2,host3:port3

You can specify multiple Elasticsearch hosts with separator ",".

If you specify multiple hosts, this plugin will load balance updates to Elasticsearch. This is an elasticsearch-ruby feature, the default strategy is round-robin. Note: If you will use scheme https, do not include "https://" in your hosts ie. host "https://domain", this will cause ES cluster to be unreachable and you will recieve an error "Can not reach Elasticsearch cluster"

Note: Up until v2.8.5, it was allowed to embed the username/password in the URL. However, this syntax is deprecated as of v2.8.6 because it was found to cause serious connection problems (See #394). Please migrate your settings to use the user and password field (described below) instead.

user, password, path, scheme, ssl_verify

If you specify this option, port options are ignored.

user demo
password secret
path /elastic_search/
scheme https

You can specify user and password for HTTP Basic authentication.

And this plugin will escape required URL encoded characters within %{} placeholders.

user %{demo+}
password %{@secret}

Specify ssl_verify false to skip ssl verification (defaults to true)


logstash_format true # defaults to false

This is meant to make writing data into Elasticsearch indices compatible to what Logstash calls them. By doing this, one could take advantage of Kibana. See logstash_prefix and logstash_dateformat to customize this index name pattern. The index name will be #{logstash_prefix}-#{formated_date}

⚠️ Setting this option to true will ignore the index_name setting. The default index name prefix is logstash-.


include_timestamp true # defaults to false

Adds a @timestamp field to the log, following all settings logstash_format does, except without the restrictions on index_name. This allows one to log to an alias in Elasticsearch and utilize the rollover API.


logstash_prefix mylogs # defaults to "logstash"


logstash_prefix_separator _ # defaults to "-"


The strftime format to generate index target index name when logstash_format is set to true. By default, the records are inserted into index logstash-YYYY.MM.DD. This option, alongwith logstash_prefix lets us insert into specified index like mylogs-YYYYMM for a monthly index.

logstash_dateformat %Y.%m. # defaults to "%Y.%m.%d"


Only in ES >= 5.x is available to use this parameter. This param is to set a pipeline id of your elasticsearch to be added into the request, you can configure ingest node. For more information: [Ingest node]

pipeline pipeline_id


The format of the time stamp field (@timestamp or what you specify with time_key). This parameter only has an effect when logstash_format is true as it only affects the name of the index we write to. Please see Time#strftime for information about the value of this format.

Setting this to a known format can vastly improve your log ingestion speed if all most of your logs are in the same format. If there is an error parsing this format the timestamp will default to the ingestion time. If you are on Ruby 2.0 or later you can get a further performance improvment by installing the "strptime" gem: fluent-gem install strptime.

For example to parse ISO8601 times with sub-second precision:

time_key_format %Y-%m-%dT%H:%M:%S.%N%z


Should the record not include a time_key, define the degree of sub-second time precision to preserve from the time portion of the routed event.

For example, should your input plugin not include a time_key in the record but it able to pass a time to the router when emitting the event (AWS CloudWatch events are an example of this), then this setting will allow you to preserve the sub-second time resolution of those events. This is the case for: fluent-plugin-cloudwatch-ingest.


By default, when inserting records in Logstash format, @timestamp is dynamically created with the time at log ingestion. If you'd like to use a custom time, include an @timestamp with your record.

{"@timestamp": "2014-04-07T000:00:00-00:00"}

You can specify an option time_key (like the option described in tail Input Plugin) to replace @timestamp key.

Suppose you have settings

logstash_format true
time_key vtm

Your input is:

  "title": "developer",
  "vtm": "2014-12-19T08:01:03Z"

The output will be

  "title": "developer",
  "@timestamp": "2014-12-19T08:01:03Z",
  "vtm": "2014-12-19T08:01:03Z"

See time_key_exclude_timestamp to avoid adding @timestamp.


time_key_exclude_timestamp false

By default, setting time_key will copy the value to an additional field @timestamp. When setting time_key_exclude_timestamp true, no additional field will be added.


utc_index true

By default, the records inserted into index logstash-YYMMDD with UTC (Coordinated Universal Time). This option allows to use local time if you describe utc_index to false.


Tell this plugin to find the index name to write to in the record under this key in preference to other mechanisms. Key can be specified as path to nested record using dot ('.') as a separator.

If it is present in the record (and the value is non falsey) the value will be used as the index name to write to and then removed from the record before output; if it is not found then it will use logstash_format or index_name settings as configured.

Suppose you have the following settings

target_index_key @target_index
index_name fallback

If your input is:

  "title": "developer",
  "@timestamp": "2014-12-19T08:01:03Z",
  "@target_index": "logstash-2014.12.19"

The output would be

  "title": "developer",
  "@timestamp": "2014-12-19T08:01:03Z",

and this record will be written to the specified index (logstash-2014.12.19) rather than fallback.


Similar to target_index_key config, find the type name to write to in the record under this key (or nested record). If key not found in record - fallback to type_name (default "fluentd").


The name of the template to define. If a template by the name given is already present, it will be left unchanged, unless template_overwrite is set, in which case the template will be updated.

This parameter along with template_file allow the plugin to behave similarly to Logstash (it installs a template at creation time) so that raw records are available. See

template_file must also be specified.


The path to the file containing the template to install.

template_name must also be specified.


Specify index templates in form of hash. Can contain multiple templates.

templates { "template_name_1": "path_to_template_1_file", "template_name_2": "path_to_template_2_file"}

If template_file and template_name are set, then this parameter will be ignored.


Specify the string and its value to be replaced in form of hash. Can contain multiple templates.

customize_template {"string_1": "subs_value_1", "string_2": "subs_value_2"}

If template_file and template_name are set, then this parameter will be in effect otherwise ignored.


index_prefix mylogs # defaults to "logstash"

If customize_template is set, then this parameter will be in effect otherwise ignored.


Always update the template, even if it already exists.

template_overwrite true # defaults to false

One of template_file or templates must also be specified if this is set.


You can specify times of retry putting template.

This is useful when Elasticsearch plugin cannot connect Elasticsearch to put template. Usually, booting up clustered Elasticsearch containers are much slower than launching Fluentd container.

max_retry_putting_template 15 # defaults to 10


You can specify HTTP request timeout.

This is useful when Elasticsearch cannot return response for bulk request within the default of 5 seconds.

request_timeout 15s # defaults to 5s


You can tune how the elasticsearch-transport host reloading feature works. By default it will reload the host list from the server every 10,000th request to spread the load. This can be an issue if your Elasticsearch cluster is behind a Reverse Proxy, as Fluentd process may not have direct network access to the Elasticsearch nodes.

reload_connections false # defaults to true


Indicates that the elasticsearch-transport will try to reload the nodes addresses if there is a failure while making the request, this can be useful to quickly remove a dead node from the list of addresses.

reload_on_failure true # defaults to false


You can set in the elasticsearch-transport how often dead connections from the elasticsearch-transport's pool will be resurrected.

resurrect_after 5s # defaults to 60s

include_tag_key, tag_key

include_tag_key true # defaults to false
tag_key tag # defaults to tag

This will add the Fluentd tag in the JSON record. For instance, if you have a config like this:

<match my.logs>
  @type elasticsearch
  include_tag_key true
  tag_key _key

The record inserted into Elasticsearch would be

{"_key": "my.logs", "name": "Johnny Doeie"}


id_key request_id # use "request_id" field as a record id in ES

By default, all records inserted into Elasticsearch get a random _id. This option allows to use a field in the record as an identifier.

This following record {"name": "Johnny", "request_id": "87d89af7daffad6"} will trigger the following Elasticsearch command

{ "index" : { "_index": "logstash-2013.01.01", "_type": "fluentd", "_id": "87d89af7daffad6" } }
{ "name": "Johnny", "request_id": "87d89af7daffad6" }

Fluentd re-emits events that failed to be indexed/ingested in Elasticsearch with a new and unique _id value, this means that congested Elasticsearch clusters that reject events (due to command queue overflow, for example) will cause Fluentd to re-emit the event with a new _id, however Elasticsearch may actually process both (or more) attempts (with some delay) and create duplicate events in the index (since each have a unique _id value), one possible workaround is to use the fluent-plugin-genhashvalue plugin to generate a unique _hash key in the record of each event, this _hash record can be used as the id_key to prevent Elasticsearch from creating deplicate events.

id_key _hash

Example configuration for fluent-plugin-genhashvalue (review the documentation of the plugin for more details)

<filter logs.**>
  @type genhashvalue
  keys sessionid,requestid
  hash_type md5    # md5/sha1/sha256/sha512
  base64_enc true
  base91_enc false
  set_key _hash
  separator _
  inc_time_as_key true
  inc_tag_as_key true

⚠️ In order to avoid hash-collisions and loosing data careful consideration is required when choosing the keys in the event record that should be used to calculate the hash

Using nested key

Nested key specifying syntax is also supported.

With the following configuration

id_key $.nested.request_id

and the following nested record

{"nested":{"name": "Johnny", "request_id": "87d89af7daffad6"}}

will trigger the following Elasticsearch command


⚠️ Note that Hash flattening may be conflict nested record feature.


parent_key a_parent # use "a_parent" field value to set _parent in elasticsearch command

If your input is

{ "name": "Johnny", "a_parent": "my_parent" }

Elasticsearch command would be

{ "index" : { "_index": "****", "_type": "****", "_id": "****", "_parent": "my_parent" } }
{ "name": "Johnny", "a_parent": "my_parent" }

if parent_key is not configed or the parent_key is absent in input record, nothing will happen.

Using nested key

Nested key specifying syntax is also supported.

With the following configuration

parent_key $.nested.a_parent

and the following nested record

{"nested":{ "name": "Johnny", "a_parent": "my_parent" }}

will trigger the following Elasticsearch command


⚠️ Note that Hash flattening may be conflict nested record feature.


Similar to parent_key config, will add _routing into elasticsearch command if routing_key is set and the field does exist in input event.


parent_key a_parent
routing_key a_routing
remove_keys a_parent, a_routing # a_parent and a_routing fields won't be sent to elasticsearch


Remove keys on update will not update the configured keys in elasticsearch when a record is being updated. This setting only has any effect if the write operation is update or upsert.

If the write setting is upsert then these keys are only removed if the record is being updated, if the record does not exist (by id) then all of the keys are indexed.

remove_keys_on_update foo,bar


This setting allows remove_keys_on_update to be configured with a key in each record, in much the same way as target_index_key works. The configured key is removed before indexing in elasticsearch. If both remove_keys_on_update and remove_keys_on_update_key is present in the record then the keys in record are used, if the remove_keys_on_update_key is not present then the value of remove_keys_on_update is used as a fallback.

remove_keys_on_update_key keys_to_skip


This setting allows custom routing of messages in response to bulk request failures. The default behavior is to emit failed records using the same tag that was provided. When set to a value other then nil, failed messages are emitted with the specified tag:

retry_tag 'retry_es'

NOTE: retry_tag is optional. If you would rather use labels to reroute retries, add a label (e.g '@label @SOMELABEL') to your fluent elasticsearch plugin configuration. Retry records are, by default, submitted for retry to the ROOT label, which means records will flow through your fluentd pipeline from the beginning. This may nor may not be a problem if the pipeline is idempotent - that is - you can process a record again with no changes. Use tagging or labeling to ensure your retry records are not processed again by your fluentd processing pipeline.


The write_operation can be any of:

Operation Description
index (default) new data is added while existing data (based on its id) is replaced (reindexed).
create adds new data - if the data already exists (based on its id), the op is skipped.
update updates existing data (based on its id). If no data is found, the op is skipped.
upsert known as merge or insert if the data does not exist, updates if the data exists (based on its id).

Please note, id is required in create, update, and upsert scenario. Without id, the message will be dropped.


With logstash_format true, elasticsearch plugin parses timestamp field for generating index name. If the record has invalid timestamp value, this plugin emits an error event to @ERROR label with time_parse_error_tag configured tag.

Default value is Fluent::ElasticsearchOutput::TimeParser.error for backward compatibility. :: separated tag is not good for tag routing because some plugins assume tag is separated by .. We recommend to set this parameter like time_parse_error_tag es_plugin.output.time.error. We will change default value to . separated tag.


Indicates that the plugin should reset connection on any error (reconnect on next send). By default it will reconnect only on "host unreachable exceptions". We recommended to set this true in the presence of elasticsearch shield.

reconnect_on_error true # defaults to false


This is debugging purpose option to enable to obtain transporter layer log. Default value is false for backward compatibility.

We recommend to set this true if you start to debug this plugin.

with_transporter_log true


With content_type application/x-ndjson, elasticsearch plugin adds application/x-ndjson as Content-Type in payload.

Default value is application/json which is default Content-Type of Elasticsearch requests. If you will not use template, it recommends to set content_type application/x-ndjson.

content_type application/x-ndjson


With this option set to true, Fluentd manifests the index name in the request URL (rather than in the request body). You can use this option to enforce an URL-based access control.

include_index_in_url true


With http_backend typhoeus, elasticsearch plugin uses typhoeus faraday http backend. Typhoeus can handle HTTP keepalive.

Default value is excon which is default http_backend of elasticsearch plugin.

http_backend typhoeus


With default beavior, Elasticsearch client uses Yajl as JSON encoder/decoder. Oj is the alternative high performance JSON encoder/decoder. When this parameter sets as true, Elasticsearch client uses Oj as JSON encoder/decoder.

Default value is false.

prefer_oj_serializer true

Client/host certificate options

Need to verify Elasticsearch's certificate? You can use the following parameter to specify a CA instead of using an environment variable.

ca_file /path/to/your/ca/cert

Does your Elasticsearch cluster want to verify client connections? You can specify the following parameters to use your client certificate, key, and key password for your connection.

client_cert /path/to/your/client/cert
client_key /path/to/your/private/key
client_key_pass password

If you want to configure SSL/TLS version, you can specify ssl_version parameter.

ssl_version TLSv1_2 # or [SSLv23, TLSv1, TLSv1_1]

⚠️ If SSL/TLS enabled, it might have to be required to set ssl_version.

Proxy Support

Starting with version 0.8.0, this gem uses excon, which supports proxy with environment variables -

Buffer options

fluentd-plugin-elasticsearch extends Fluentd's builtin Output plugin and use compat_parameters plugin helper. It adds the following options:

buffer_type memory
flush_interval 60s
retry_limit 17
retry_wait 1.0
num_threads 1

The value for option buffer_chunk_limit should not exceed value http.max_content_length in your Elasticsearch setup (by default it is 100mb).

Note: If you use or evaluate Fluentd v0.14, you can use <buffer> directive to specify buffer configuration, too. In more detail, please refer to the buffer configuration options for v0.14

Note: If you use disable_retry_limit in v0.12 or retry_forever in v0.14 or later, please be careful to consume memory inexhaustibly.

Hash flattening

Elasticsearch will complain if you send object and concrete values to the same field. For example, you might have logs that look this, from different places:

{"people" => 100} {"people" => {"some" => "thing"}}

The second log line will be rejected by the Elasticsearch parser because objects and concrete values can't live in the same field. To combat this, you can enable hash flattening.

flatten_hashes true
flatten_hashes_separator _

This will produce elasticsearch output that looks like this: {"people_some" => "thing"}

Note that the flattener does not deal with arrays at this time.

Generate Hash ID

By default, the fluentd elasticsearch plugin does not emit records with a _id field, leaving it to Elasticsearch to generate a unique _id as the record is indexed. When an Elasticsearch cluster is congested and begins to take longer to respond than the configured request_timeout, the fluentd elasticsearch plugin will re-send the same bulk request. Since Elasticsearch can't tell its actually the same request, all documents in the request are indexed again resulting in duplicate data. In certain scenarios, this can result in essentially and infinite loop generating multiple copies of the same data.

The bundled elasticsearch_genid filter can generate a unique _hash key for each record, this key may be passed to the id_key parameter in the elasticsearch plugin to communicate to Elasticsearch the uniqueness of the requests so that duplicates will be rejected or simply replace the existing records. Here is a sample config:

<filter **>
  @type elasticsearch_genid
  hash_id_key _hash    # storing generated hash id key (default is _hash)
<match **>
  @type elasticsearch
  id_key _hash # specify same key name which is specified in hash_id_key
  remove_keys _hash # Elasticsearch doesn't like keys that start with _
  # other settings are ommitted.

Sniffer Class Name

The default Sniffer used by the Elasticsearch::Transport class works well when Fluentd has a direct connection to all of the Elasticsearch servers and can make effective use of the _nodes API. This doesn't work well when Fluentd must connect through a load balancer or proxy. The parameter sniffer_class_name gives you the ability to provide your own Sniffer class to implement whatever connection reload logic you require. In addition, there is a new Fluent::Plugin::ElasticsearchSimpleSniffer class which reuses the hosts given in the configuration, which is typically the hostname of the load balancer or proxy. For example, a configuration like this would cause connections to logging-es to reload every 100 operations:

host logging-es
port 9200
reload_connections true
sniffer_class_name Fluent::Plugin::ElasticsearchSimpleSniffer
reload_after 100

Reload After

When reload_connections true, this is the integer number of operations after which the plugin will reload the connections. The default value is 10000.

Validate Client Version

When you use mismatched Elasticsearch server and client libraries, fluent-plugin-elasticsearch cannot send data into Elasticsearch. The default value is false.

validate_client_version true

Not seeing a config you need?

We try to keep the scope of this plugin small and not add too many configuration options. If you think an option would be useful to others, feel free to open an issue or contribute a Pull Request.

Alternatively, consider using fluent-plugin-forest. For example, to configure multiple tags to be sent to different Elasticsearch indices:

<match my.logs.*>
  @type forest
  subtype elasticsearch
  remove_prefix my.logs
    logstash_prefix ${tag}
    # ...

And yet another option is described in Dynamic Configuration section.

Note: If you use or evaluate Fluentd v0.14, you can use builtin placeholders. In more detail, please refer to Placeholders section.

Dynamic configuration

If you want configurations to depend on information in messages, you can use elasticsearch_dynamic. This is an experimental variation of the Elasticsearch plugin allows configuration values to be specified in ways such as the below:

<match my.logs.*>
  @type elasticsearch_dynamic
  hosts ${record['host1']}:9200,${record['host2']}:9200
  index_name my_index.${}
  logstash_prefix ${tag_parts[3]}
  port ${9200+rand(4)}
  index_name ${tag_parts[2]}-${}

Please note, this uses Ruby's eval for every message, so there are performance and security implications.


v0.14 placeholders can handle ${tag} for tag, %Y%m%d like strftime format, and custom record keys like as record["mykey"].

Note that custom chunk key is diffrent notations for record_reformer and record_modifier. They uses record["some_key"] to specify placeholders, but this feature uses ${key1}, ${key2} notation. And tag, time, and some arbitrary keys must be included in buffer directive attributes.

They are used as below:


<match my.logs>
  @type elasticsearch
  index_name elastic.${tag} #=> replaced with each event's tag. e.g.) elastic.test.tag
  <buffer tag>
    @type memory
  # <snip>


<match my.logs>
  @type elasticsearch
  index_name elastic.%Y%m%d #=> e.g.) elastic.20170811
  <buffer tag, time>
    @type memory
    timekey 3600
  # <snip>

custom key

records = {key1: "value1", key2: "value2"}
<match my.logs>
  @type elasticsearch
  index_name elastic.${key1}.${key2} # => e.g.) elastic.value1.value2
  <buffer tag, key1, key2>
    @type memory
  # <snip>

Multi workers

Since Fluentd v0.14, multi workers feature had been implemented to increase throughput with multiple processes. This feature allows Fluentd processes to use one or more CPUs. This feature will be enabled by the following system configuration:

  workers N # where N is a natural number (N >= 1).


If you have a question, open an Issue.


There are usually a few feature requests, tagged Easy, Normal and Hard. Feel free to work on any one of them.

Pull Requests are welcomed.

Pull Request Graph

Running tests

Install dev dependencies:

$ gem install bundler
$ bundle install
$ bundle exec rake test