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How to use scripts
editHow to use scripts
editWherever scripting is supported in the Elasticsearch API, the syntax follows the same pattern:
The language the script is written in, which defaults to |
|
The script itself which may be specified as |
|
Any named parameters that should be passed into the script. |
For example, the following script is used in a search request to return a scripted field:
PUT my_index/my_type/1 { "my_field": 5 } GET my_index/_search { "script_fields": { "my_doubled_field": { "script": { "lang": "expression", "source": "doc['my_field'] * multiplier", "params": { "multiplier": 2 } } } } }
Script Parameters
edit-
lang
-
Specifies the language the script is written in. Defaults to
painless
but may be set to any of languages listed in Scripting. The default language may be changed in theelasticsearch.yml
config file by settingscript.default_lang
to the appropriate language. -
source
,id
,file
-
Specifies the source of the script. An
inline
script is specified withsource
as in the example above, astored
script is specified withid
and is retrieved from the cluster state (see Stored Scripts), and afile
script is retrieved from a file in theconfig/scripts
directory (see File Scripts).While languages like
expression
andpainless
can be used out of the box as inline or stored scripts, other languages likegroovy
can only be specified asfile
unless you first adjust the default scripting security settings. -
params
- Specifies any named parameters that are passed into the script as variables.
Prefer parameters
The first time Elasticsearch sees a new script, it compiles it and stores the compiled version in a cache. Compilation can be a heavy process.
If you need to pass variables into the script, you should pass them in as
named params
instead of hard-coding values into the script itself. For
example, if you want to be able to multiply a field value by different
multipliers, don’t hard-code the multiplier into the script:
"source": "doc['my_field'] * 2"
Instead, pass it in as a named parameter:
"source": "doc['my_field'] * multiplier", "params": { "multiplier": 2 }
The first version has to be recompiled every time the multiplier changes. The second version is only compiled once.
If you compile too many unique scripts within a small amount of time,
Elasticsearch will reject the new dynamic scripts with a
circuit_breaking_exception
error. By default, up to 15 inline scripts per
minute will be compiled. You can change this setting dynamically by setting
script.max_compilations_per_minute
.
File-based Scripts
editTo increase security, non-sandboxed languages can only be specified in script
files stored on every node in the cluster. File scripts must be saved in the
scripts
directory whose default location depends on whether you use the
zip
/tar.gz
($ES_HOME/config/scripts/
),
RPM, or Debian package. The default may be
changed with the path.scripts
setting.
The languages which are assumed to be safe by default are: painless
,
expression
, and mustache
(used for search and query templates).
Any files placed in the scripts
directory will be compiled automatically
when the node starts up and then every 60 seconds thereafter.
The file should be named as follows: {script-name}.{lang}
. For instance,
the following example creates a Groovy script called calculate-score
:
cat "Math.log(_score * 2) + params.my_modifier" > config/scripts/calculate_score.painless
This script can be used as follows:
GET my_index/_search { "query": { "script": { "script": { "lang": "painless", "file": "calculate_score", "params": { "my_modifier": 2 } } } } }
The language of the script, which should correspond with the script file suffix. |
|
The name of the script, which should be the name of the file. |
The script
directory may contain sub-directories, in which case the
hierarchy of directories is flattened and concatenated with underscores. A
script in group1/group2/my_script.groovy
should use group1_group2_myscript
as the file
name.
Automatic script reloading
editThe scripts
directory will be rescanned every 60s
(configurable with the
resource.reload.interval
setting) and new, changed, or removed scripts will
be compiled, updated, or deleted from the script cache.
Script reloading can be completely disabled by setting
script.auto_reload_enabled
to false
.
Stored Scripts
editScripts may be stored in and retrieved from the cluster state using the
_scripts
end-point.
Deprecated Namespace
editThe namespace for stored scripts using both lang
and id
as a unique
identifier has been deprecated. The new namespace for stored scripts will
only use id
. Stored scripts with the same id
, but different lang
's
will no longer be allowed in 6.0. To comply with the new namespace for
stored scripts, existing stored scripts should be deleted and put again.
Any scripts that share an id
but have different `lang`s will need to
be re-named. For example, take the following:
"id": "example", "lang": "painless" "id": "example", "lang": "expressions"
The above scripts will conflict under the new namespace since the id’s are
the same. At least one will have to be re-named to comply with the new
namespace of only id
.
As a final caveat, stored search templates and stored scripts share
the same namespace, so if a search template has the same id
as a
stored script, one of the two will have to be re-named as well using
delete and put requests.
Request Examples
editThe following are examples of using a stored script that lives at
/_scripts/{id}
.
First, create the script called calculate-score
in the cluster state:
POST _scripts/calculate-score { "script": { "lang": "painless", "source": "Math.log(_score * 2) + params.my_modifier" } }
This same script can be retrieved with:
GET _scripts/calculate-score
Stored scripts can be used by specifying the id
of the script and passing values for the stored parameters using params
, as follows:
GET _search { "query": { "script": { "script": { "id": "calculate-score", "params": { "my_modifier": 2 } } } } }
And deleted with:
DELETE _scripts/calculate-score
Script Caching
editAll scripts are cached by default so that they only need to be recompiled
when updates occur. File scripts keep a static cache and will always reside
in memory. Both inline and stored scripts are stored in a cache that can evict
residing scripts. By default, scripts do not have a time-based expiration, but
you can change this behavior by using the script.cache.expire
setting.
You can configure the size of this cache by using the script.cache.max_size
setting.
By default, the cache size is 100
.
The size of stored scripts is limited to 65,535 bytes. This can be
changed by setting script.max_size_in_bytes
setting to increase that soft
limit, but if scripts are really large then alternatives like
native scripts should be considered instead.