Reindex APIedit

Copies documents from one index to another.

Reindex requires _source to be enabled for all documents in the source index.

You must set up the destination index before calling _reindex. Reindex does not copy the settings from the source index. Mappings, shard counts, replicas, and so on must be configured ahead of time.

POST _reindex
{
  "source": {
    "index": "twitter"
  },
  "dest": {
    "index": "new_twitter"
  }
}

Requestedit

POST /_reindex

Descriptionedit

Extracts the document source from the source index and indexes the documents into the destination index. You can copy all documents to the destination index, or reindex a subset of the documents.

Just like _update_by_query, _reindex gets a snapshot of the source index but its target must be a different index so version conflicts are unlikely. The dest element can be configured like the index API to control optimistic concurrency control. Omitting version_type or setting it to internal causes Elasticsearch to blindly dump documents into the target, overwriting any that happen to have the same ID.

Setting version_type to external causes Elasticsearch to preserve the version from the source, create any documents that are missing, and update any documents that have an older version in the destination index than they do in the source index.

Setting op_type to create causes _reindex to only create missing documents in the target index. All existing documents will cause a version conflict.

By default, version conflicts abort the _reindex process. To continue reindexing if there are conflicts, set the "conflicts" request body parameter to proceed. In this case, the response includes a count of the version conflicts that were encountered. Note that the handling of other error types is unaffected by the "conflicts" parameter.

Running reindex asynchronouslyedit

If the request contains wait_for_completion=false, Elasticsearch performs some preflight checks, launches the request, and returns a task you can use to cancel or get the status of the task. Elasticsearch creates a record of this task as a document at .tasks/task/${taskId}. When you are done with a task, you should delete the task document so Elasticsearch can reclaim the space.

Reindexing many indicesedit

If you have many indices to reindex it is generally better to reindex them one at a time rather than using a glob pattern to pick up many indices. That way you can resume the process if there are any errors by removing the partially completed index and starting over at that index. It also makes parallelizing the process fairly simple: split the list of indices to reindex and run each list in parallel.

One-off bash scripts seem to work nicely for this:

for index in i1 i2 i3 i4 i5; do
  curl -HContent-Type:application/json -XPOST localhost:9200/_reindex?pretty -d'{
    "source": {
      "index": "'$index'"
    },
    "dest": {
      "index": "'$index'-reindexed"
    }
  }'
done

Throttlingedit

Set requests_per_second to any positive decimal number (1.4, 6, 1000, etc.) to throttle the rate at which _reindex issues batches of index operations. Requests are throttled by padding each batch with a wait time. To disable throttling, set requests_per_second to -1.

The throttling is done by waiting between batches so that the scroll that _reindex uses internally can be given a timeout that takes into account the padding. The padding time is the difference between the batch size divided by the requests_per_second and the time spent writing. By default the batch size is 1000, so if requests_per_second is set to 500:

target_time = 1000 / 500 per second = 2 seconds
wait_time = target_time - write_time = 2 seconds - .5 seconds = 1.5 seconds

Since the batch is issued as a single _bulk request, large batch sizes cause Elasticsearch to create many requests and then wait for a while before starting the next set. This is "bursty" instead of "smooth".

Rethrottlingedit

The value of requests_per_second can be changed on a running reindex using the _rethrottle API:

POST _reindex/r1A2WoRbTwKZ516z6NEs5A:36619/_rethrottle?requests_per_second=-1

The task ID can be found using the tasks API.

Just like when setting it on the Reindex API, requests_per_second can be either -1 to disable throttling or any decimal number like 1.7 or 12 to throttle to that level. Rethrottling that speeds up the query takes effect immediately, but rethrottling that slows down the query will take effect after completing the current batch. This prevents scroll timeouts.

Slicingedit

Reindex supports Sliced Scroll to parallelize the reindexing process. This parallelization can improve efficiency and provide a convenient way to break the request down into smaller parts.

Reindexing from remote clusters does not support manual or automatic slicing.

Manual slicingedit

Slice a reindex request manually by providing a slice id and total number of slices to each request:

POST _reindex
{
  "source": {
    "index": "twitter",
    "slice": {
      "id": 0,
      "max": 2
    }
  },
  "dest": {
    "index": "new_twitter"
  }
}
POST _reindex
{
  "source": {
    "index": "twitter",
    "slice": {
      "id": 1,
      "max": 2
    }
  },
  "dest": {
    "index": "new_twitter"
  }
}

You can verify this works by:

GET _refresh
POST new_twitter/_search?size=0&filter_path=hits.total

which results in a sensible total like this one:

{
  "hits": {
    "total" : {
        "value": 120,
        "relation": "eq"
    }
  }
}
Automatic slicingedit

You can also let _reindex automatically parallelize using Sliced Scroll to slice on _id. Use slices to specify the number of slices to use:

POST _reindex?slices=5&refresh
{
  "source": {
    "index": "twitter"
  },
  "dest": {
    "index": "new_twitter"
  }
}

You can also this verify works by:

POST new_twitter/_search?size=0&filter_path=hits.total

which results in a sensible total like this one:

{
  "hits": {
    "total" : {
        "value": 120,
        "relation": "eq"
    }
  }
}

Setting slices to auto will let Elasticsearch choose the number of slices to use. This setting will use one slice per shard, up to a certain limit. If there are multiple source indices, it will choose the number of slices based on the index with the smallest number of shards.

Adding slices to _reindex just automates the manual process used in the section above, creating sub-requests which means it has some quirks:

  • You can see these requests in the Tasks APIs. These sub-requests are "child" tasks of the task for the request with slices.
  • Fetching the status of the task for the request with slices only contains the status of completed slices.
  • These sub-requests are individually addressable for things like cancelation and rethrottling.
  • Rethrottling the request with slices will rethrottle the unfinished sub-request proportionally.
  • Canceling the request with slices will cancel each sub-request.
  • Due to the nature of slices each sub-request won’t get a perfectly even portion of the documents. All documents will be addressed, but some slices may be larger than others. Expect larger slices to have a more even distribution.
  • Parameters like requests_per_second and max_docs on a request with slices are distributed proportionally to each sub-request. Combine that with the point above about distribution being uneven and you should conclude that using max_docs with slices might not result in exactly max_docs documents being reindexed.
  • Each sub-request gets a slightly different snapshot of the source index, though these are all taken at approximately the same time.
Picking the number of slicesedit

If slicing automatically, setting slices to auto will choose a reasonable number for most indices. If slicing manually or otherwise tuning automatic slicing, use these guidelines.

Query performance is most efficient when the number of slices is equal to the number of shards in the index. If that number is large (e.g. 500), choose a lower number as too many slices will hurt performance. Setting slices higher than the number of shards generally does not improve efficiency and adds overhead.

Indexing performance scales linearly across available resources with the number of slices.

Whether query or indexing performance dominates the runtime depends on the documents being reindexed and cluster resources.

Reindex routingedit

By default if _reindex sees a document with routing then the routing is preserved unless it’s changed by the script. You can set routing on the dest request to change this:

keep
Sets the routing on the bulk request sent for each match to the routing on the match. This is the default value.
discard
Sets the routing on the bulk request sent for each match to null.
=<some text>
Sets the routing on the bulk request sent for each match to all text after the =.

For example, you can use the following request to copy all documents from the source index with the company name cat into the dest index with routing set to cat.

POST _reindex
{
  "source": {
    "index": "source",
    "query": {
      "match": {
        "company": "cat"
      }
    }
  },
  "dest": {
    "index": "dest",
    "routing": "=cat"
  }
}

By default _reindex uses scroll batches of 1000. You can change the batch size with the size field in the source element:

POST _reindex
{
  "source": {
    "index": "source",
    "size": 100
  },
  "dest": {
    "index": "dest",
    "routing": "=cat"
  }
}

Reindex can also use the Ingest node feature by specifying a pipeline like this:

POST _reindex
{
  "source": {
    "index": "source"
  },
  "dest": {
    "index": "dest",
    "pipeline": "some_ingest_pipeline"
  }
}

Query parametersedit

refresh
(Optional, enum) If true, Elasticsearch refreshes the affected shards to make this operation visible to search, if wait_for then wait for a refresh to make this operation visible to search, if false do nothing with refreshes. Valid values: true, false, wait_for. Default: false.
timeout
(Optional, time units) Specifies the period of time to wait for a response. If no response is received before the timeout expires, the request fails and returns an error. Defaults to 30s.
wait_for_active_shards

(Optional, string) The number of shard copies that must be active before proceeding with the operation. Set to all or any positive integer up to the total number of shards in the index (number_of_replicas+1). Default: 1, the primary shard.

See Active shards.

wait_for_completion
(Optional, boolean) If true, the request blocks until the operation is complete. Defaults to true.
requests_per_second
(Optional, integer) The throttle for this request in sub-requests per second. -1 means no throttle. Defaults to 0.
scroll
(Optional, time units) Specifies how long a consistent view of the index should be maintained for scrolled search.
slices
(Optional, integer) The number of slices this task should be divided into. Defaults to 1 meaning the task isn’t sliced into subtasks.
max_docs
(Optional, integer) Maximum number of documents to process. Defaults to all documents.

Request bodyedit

conflicts
(Optional, enum) Set to proceed to continue reindexing even if there are conflicts. Defaults to abort.
source
index
(Required, string) The name of the index you are copying from. Also accepts a comma-separated list of indices to reindex from multiple sources.
max_docs
(Optional, integer) The maximum number of documents to reindex.
query
(Optional, query object) Specifies the documents to reindex using the Query DSL.
remote
host
(Optional, string) The URL for the remote instance of Elasticsearch that you want to index from. Required when indexing from remote.
username
(Optional, string) The username to use for authentication with the remote host.
password
(Optional, string) The password to use for authentication with the remote host.
socket_timeout
(Optional, time units) The remote socket read timeout. Defaults to 30 seconds.
connect_timeout
(Optional, time units) The remote connection timeout. Defaults to 30 seconds.
size
{Optional, integer) The number of documents to index per batch. Use when indexing from remote to ensure that the batches fit within the on-heap buffer, which defaults to a maximum size of 100 MB.
slice
id
(Optional, integer) Slice ID for manual slicing.
max
(Optional, integer) Total number of slices.
sort
(Optional, list) A comma-separated list of <field>:<direction> pairs to sort by before indexing. Use in conjunction with max_docs to control what documents are reindexed.
_source
(Optional, string) If true reindexes all source fields. Set to a list to reindex select fields. Defaults to true.
dest
index
(Required, string) The name of the index you are copying to.
version_type
(Optional, enum) The versioning to use for the indexing operation. Valid values: internal, external, external_gt, external_gte. See Version types for more information.
op_type
(Optional, enum) Set to create to only index documents that do not already exist (put if absent). Valid values: index, create. Defaults to index.
script
source
(Optional, string) The script to run to update the document source or metadata when reindexing.
lang
(Optional, enum) The script language: painless, expression, mustache, java. For more information, see Scripting.

Response bodyedit

took
(integer) The total milliseconds the entire operation took.
timed_out
{boolean) This flag is set to true if any of the requests executed during the reindex timed out.
total
(integer) The number of documents that were successfully processed.
updated
(integer) The number of documents that were successfully updated, i.e. a document with same ID already existed prior to reindex updating it.
created
(integer) The number of documents that were successfully created.
deleted
(integer) The number of documents that were successfully deleted.
batches
(integer) The number of scroll responses pulled back by the reindex.
noops
(integer) The number of documents that were ignored because the script used for the reindex returned a noop value for ctx.op.
version_conflicts
{integer)The number of version conflicts that reindex hit.
retries
(integer) The number of retries attempted by reindex. bulk is the number of bulk actions retried and search is the number of search actions retried.
throttled_millis
(integer) Number of milliseconds the request slept to conform to requests_per_second.
requests_per_second
(integer) The number of requests per second effectively executed during the reindex.
throttled_until_millis
(integer) This field should always be equal to zero in a _reindex response. It only has meaning when using the Task API, where it indicates the next time (in milliseconds since epoch) a throttled request will be executed again in order to conform to requests_per_second.
failures
(array) Array of failures if there were any unrecoverable errors during the process. If this is non-empty then the request aborted because of those failures. Reindex is implemented using batches and any failure causes the entire process to abort but all failures in the current batch are collected into the array. You can use the conflicts option to prevent reindex from aborting on version conflicts.

Examplesedit

Reindex select documents with a queryedit

You can limit the documents by adding a query to the source. For example, the following request only copies tweets made by kimchy into new_twitter:

POST _reindex
{
  "source": {
    "index": "twitter",
    "query": {
      "term": {
        "user": "kimchy"
      }
    }
  },
  "dest": {
    "index": "new_twitter"
  }
}

Reindex select documents with sortedit

You can limit the number of processed documents by setting max_docs. For example, this request copies a single document from twitter to new_twitter:

POST _reindex
{
  "max_docs": 1,
  "source": {
    "index": "twitter"
  },
  "dest": {
    "index": "new_twitter"
  }
}

You can use sort in conjunction with max_docs to select the documents you want to reindex. Sorting makes the scroll less efficient but in some contexts it’s worth it. If possible, it’s better to use a more selective query instead of max_docs and sort.

For example, following request copies 10000 documents from twitter into new_twitter:

POST _reindex
{
  "max_docs": 10000,
  "source": {
    "index": "twitter",
    "sort": { "date": "desc" }
  },
  "dest": {
    "index": "new_twitter"
  }
}

Reindex from multiple indicesedit

The index attribute in source can be a list, allowing you to copy from lots of sources in one request. This will copy documents from the twitter and blog indices:

POST _reindex
{
  "source": {
    "index": ["twitter", "blog"]
  },
  "dest": {
    "index": "all_together"
  }
}

The Reindex API makes no effort to handle ID collisions so the last document written will "win" but the order isn’t usually predictable so it is not a good idea to rely on this behavior. Instead, make sure that IDs are unique using a script.

Reindex select fields with a source filteredit

You can use source filtering to reindex a subset of the fields in the original documents. For example, the following request only reindexes the user and _doc fields of each document:

POST _reindex
{
  "source": {
    "index": "twitter",
    "_source": ["user", "_doc"]
  },
  "dest": {
    "index": "new_twitter"
  }
}

Reindex to change the name of a fieldedit

_reindex can be used to build a copy of an index with renamed fields. Say you create an index containing documents that look like this:

POST test/_doc/1?refresh
{
  "text": "words words",
  "flag": "foo"
}

but you don’t like the name flag and want to replace it with tag. _reindex can create the other index for you:

POST _reindex
{
  "source": {
    "index": "test"
  },
  "dest": {
    "index": "test2"
  },
  "script": {
    "source": "ctx._source.tag = ctx._source.remove(\"flag\")"
  }
}

Now you can get the new document:

GET test2/_doc/1

which will return:

{
  "found": true,
  "_id": "1",
  "_index": "test2",
  "_version": 1,
  "_seq_no": 44,
  "_primary_term": 1,
  "_source": {
    "text": "words words",
    "tag": "foo"
  }
}

Reindex daily indicesedit

You can use _reindex in combination with Painless to reindex daily indices to apply a new template to the existing documents.

Assuming you have indices that contain documents like:

PUT metricbeat-2016.05.30/_doc/1?refresh
{"system.cpu.idle.pct": 0.908}
PUT metricbeat-2016.05.31/_doc/1?refresh
{"system.cpu.idle.pct": 0.105}

The new template for the metricbeat-* indices is already loaded into Elasticsearch, but it applies only to the newly created indices. Painless can be used to reindex the existing documents and apply the new template.

The script below extracts the date from the index name and creates a new index with -1 appended. All data from metricbeat-2016.05.31 will be reindexed into metricbeat-2016.05.31-1.

POST _reindex
{
  "source": {
    "index": "metricbeat-*"
  },
  "dest": {
    "index": "metricbeat"
  },
  "script": {
    "lang": "painless",
    "source": "ctx._index = 'metricbeat-' + (ctx._index.substring('metricbeat-'.length(), ctx._index.length())) + '-1'"
  }
}

All documents from the previous metricbeat indices can now be found in the *-1 indices.

GET metricbeat-2016.05.30-1/_doc/1
GET metricbeat-2016.05.31-1/_doc/1

The previous method can also be used in conjunction with changing a field name to load only the existing data into the new index and rename any fields if needed.

Extract a random subset of an indexedit

_reindex can be used to extract a random subset of an index for testing:

POST _reindex
{
  "max_docs": 10,
  "source": {
    "index": "twitter",
    "query": {
      "function_score" : {
        "query" : { "match_all": {} },
        "random_score" : {}
      }
    },
    "sort": "_score"    
  },
  "dest": {
    "index": "random_twitter"
  }
}

_reindex defaults to sorting by _doc so random_score will not have any effect unless you override the sort to _score.

Modify documents during reindexingedit

Like _update_by_query, _reindex supports a script that modifies the document. Unlike _update_by_query, the script is allowed to modify the document’s metadata. This example bumps the version of the source document:

POST _reindex
{
  "source": {
    "index": "twitter"
  },
  "dest": {
    "index": "new_twitter",
    "version_type": "external"
  },
  "script": {
    "source": "if (ctx._source.foo == 'bar') {ctx._version++; ctx._source.remove('foo')}",
    "lang": "painless"
  }
}

Just as in _update_by_query, you can set ctx.op to change the operation that is executed on the destination index:

noop
Set ctx.op = "noop" if your script decides that the document doesn’t have to be indexed in the destination index. This no operation will be reported in the noop counter in the response body.
delete
Set ctx.op = "delete" if your script decides that the document must be deleted from the destination index. The deletion will be reported in the deleted counter in the response body.

Setting ctx.op to anything else will return an error, as will setting any other field in ctx.

Think of the possibilities! Just be careful; you are able to change:

  • _id
  • _index
  • _version
  • _routing

Setting _version to null or clearing it from the ctx map is just like not sending the version in an indexing request; it will cause the document to be overwritten in the target index regardless of the version on the target or the version type you use in the _reindex request.

Reindex from remoteedit

Reindex supports reindexing from a remote Elasticsearch cluster:

POST _reindex
{
  "source": {
    "remote": {
      "host": "http://otherhost:9200",
      "username": "user",
      "password": "pass"
    },
    "index": "source",
    "query": {
      "match": {
        "test": "data"
      }
    }
  },
  "dest": {
    "index": "dest"
  }
}

The host parameter must contain a scheme, host, port (e.g. https://otherhost:9200), and optional path (e.g. https://otherhost:9200/proxy). The username and password parameters are optional, and when they are present _reindex will connect to the remote Elasticsearch node using basic auth. Be sure to use https when using basic auth or the password will be sent in plain text. There are a range of settings available to configure the behaviour of the https connection.

Remote hosts have to be explicitly whitelisted in elasticsearch.yml using the reindex.remote.whitelist property. It can be set to a comma delimited list of allowed remote host and port combinations (e.g. otherhost:9200, another:9200, 127.0.10.*:9200, localhost:*). Scheme is ignored by the whitelist — only host and port are used, for example:

reindex.remote.whitelist: "otherhost:9200, another:9200, 127.0.10.*:9200, localhost:*"

The whitelist must be configured on any nodes that will coordinate the reindex.

This feature should work with remote clusters of any version of Elasticsearch you are likely to find. This should allow you to upgrade from any version of Elasticsearch to the current version by reindexing from a cluster of the old version.

To enable queries sent to older versions of Elasticsearch the query parameter is sent directly to the remote host without validation or modification.

Reindexing from remote clusters does not support manual or automatic slicing.

Reindexing from a remote server uses an on-heap buffer that defaults to a maximum size of 100mb. If the remote index includes very large documents you’ll need to use a smaller batch size. The example below sets the batch size to 10 which is very, very small.

POST _reindex
{
  "source": {
    "remote": {
      "host": "http://otherhost:9200"
    },
    "index": "source",
    "size": 10,
    "query": {
      "match": {
        "test": "data"
      }
    }
  },
  "dest": {
    "index": "dest"
  }
}

It is also possible to set the socket read timeout on the remote connection with the socket_timeout field and the connection timeout with the connect_timeout field. Both default to 30 seconds. This example sets the socket read timeout to one minute and the connection timeout to 10 seconds:

POST _reindex
{
  "source": {
    "remote": {
      "host": "http://otherhost:9200",
      "socket_timeout": "1m",
      "connect_timeout": "10s"
    },
    "index": "source",
    "query": {
      "match": {
        "test": "data"
      }
    }
  },
  "dest": {
    "index": "dest"
  }
}

Configuring SSL parametersedit

Reindex from remote supports configurable SSL settings. These must be specified in the elasticsearch.yml file, with the exception of the secure settings, which you add in the Elasticsearch keystore. It is not possible to configure SSL in the body of the _reindex request.

The following settings are supported:

reindex.ssl.certificate_authorities
List of paths to PEM encoded certificate files that should be trusted. You cannot specify both reindex.ssl.certificate_authorities and reindex.ssl.truststore.path.
reindex.ssl.truststore.path
The path to the Java Keystore file that contains the certificates to trust. This keystore can be in "JKS" or "PKCS#12" format. You cannot specify both reindex.ssl.certificate_authorities and reindex.ssl.truststore.path.
reindex.ssl.truststore.password
The password to the truststore (reindex.ssl.truststore.path). This setting cannot be used with reindex.ssl.truststore.secure_password.
reindex.ssl.truststore.secure_password (Secure)
The password to the truststore (reindex.ssl.truststore.path). This setting cannot be used with reindex.ssl.truststore.password.
reindex.ssl.truststore.type
The type of the truststore (reindex.ssl.truststore.path). Must be either jks or PKCS12. If the truststore path ends in ".p12", ".pfx" or "pkcs12", this setting defaults to PKCS12. Otherwise, it defaults to jks.
reindex.ssl.verification_mode
Indicates the type of verification to protect against man in the middle attacks and certificate forgery. One of full (verify the hostname and the certificate path), certificate (verify the certificate path, but not the hostname) or none (perform no verification - this is strongly discouraged in production environments). Defaults to full.
reindex.ssl.certificate
Specifies the path to the PEM encoded certificate (or certificate chain) to be used for HTTP client authentication (if required by the remote cluster) This setting requires that reindex.ssl.key also be set. You cannot specify both reindex.ssl.certificate and reindex.ssl.keystore.path.
reindex.ssl.key
Specifies the path to the PEM encoded private key associated with the certificate used for client authentication (reindex.ssl.certificate). You cannot specify both reindex.ssl.key and reindex.ssl.keystore.path.
reindex.ssl.key_passphrase
Specifies the passphrase to decrypt the PEM encoded private key (reindex.ssl.key) if it is encrypted. Cannot be used with reindex.ssl.secure_key_passphrase.
reindex.ssl.secure_key_passphrase (Secure)
Specifies the passphrase to decrypt the PEM encoded private key (reindex.ssl.key) if it is encrypted. Cannot be used with reindex.ssl.key_passphrase.
reindex.ssl.keystore.path
Specifies the path to the keystore that contains a private key and certificate to be used for HTTP client authentication (if required by the remote cluster). This keystore can be in "JKS" or "PKCS#12" format. You cannot specify both reindex.ssl.key and reindex.ssl.keystore.path.
reindex.ssl.keystore.type
The type of the keystore (reindex.ssl.keystore.path). Must be either jks or PKCS12. If the keystore path ends in ".p12", ".pfx" or "pkcs12", this setting defaults to PKCS12. Otherwise, it defaults to jks.
reindex.ssl.keystore.password
The password to the keystore (reindex.ssl.keystore.path). This setting cannot be used with reindex.ssl.keystore.secure_password.
reindex.ssl.keystore.secure_password (Secure)
The password to the keystore (reindex.ssl.keystore.path). This setting cannot be used with reindex.ssl.keystore.password.
reindex.ssl.keystore.key_password
The password for the key in the keystore (reindex.ssl.keystore.path). Defaults to the keystore password. This setting cannot be used with reindex.ssl.keystore.secure_key_password.
reindex.ssl.keystore.secure_key_password (Secure)
The password for the key in the keystore (reindex.ssl.keystore.path). Defaults to the keystore password. This setting cannot be used with reindex.ssl.keystore.key_password.