63 lines
3.5 KiB
Plaintext
63 lines
3.5 KiB
Plaintext
[[transform-script]]
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==== Script Transform
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A <<transform, Transform>> that executes a script on the current payload in the watch execution context
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and replaces it with a newly generated one. The following snippet shows how a simple script transform can be defined on the watch level:
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[source,json]
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.Simple Script Transform
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--------------------------------------------------
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{
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...
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"transform" : {
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"script" : "return [ time : ctx.trigger.scheduled_time ]" <1>
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}
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...
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}
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--------------------------------------------------
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<1> A simple `groovy` script that creates a new payload with a single `time` field holding the scheduled time.
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NOTE: The executed script may either return a valid model that is the equivalent of a Java(TM) Map or a JSON object (you
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will need to consult the documentation of the specific scripting language to find out what this construct is). Any
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other value that is returned will be assigned and accessible to/via the `_value` variable.
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As seen above, the `script` may hold a string value in which case it will be treated as the script itself and the default
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elasticsearch script languages will be assumed (as described {ref}/modules-scripting.html#modules-scripting[here]). It
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is possible to have more control over the scripting languages and also utilize pre-registered/pre-configured scripts
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in elasticsearch. For this, the `script` field will be defined as an object, and the following table lists the possible
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settings that can be configured:
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[[transform-script-settings]]
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.Script Transform Settings
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[options="header"]
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|======
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| Name |Required | Default | Description
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| `inline` | yes* | - | When using an inline script, this field holds the script itself.
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| `file` | yes* | - | When refering to a script file, this field holds the name of the file.
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| `id` | yes* | - | When refering to an indexed script, this field holds the id of the script.
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| `lang` | no | `groovy` | The script language
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| `params` | no | - | Additional parameters/variables that are accessible by the script
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|======
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* When using the object notation of the script, one (and only one) of `inline`, `file` or `id` fields must be defined
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NOTE: In addition to the provided `params`, the scripts also have access to the <<watch-execution-context, Standard Watch Execution Context Parameters>>
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===== Script Type
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IMPORTANT: When suing `inline` scripts, if you're running Elasticsearch 1.3.8 or above, or 1.4.3 or above,
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you will need to explicitly {ref}/modules-scripting.html#enable-dynamic-scripting[enable dynamic scripts]
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in `elasticsearch.yml`.
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As indicated by the table above, it is possible to utilize the full scripting support in elasticsearch and to base the script
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on pre-registered indexed scripts or pre-defined scripts in file. Please note, for security reasons, starting from elasticsearch
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`v1.4.3`, inline groovy scripts are disabled by default. Furthermore, it is considered a best practice to pre-define the script
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in stored files. To read more about elasticsearch search scripting support and possible related vulnerabilities, please
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see {ref}/modules-scripting.html[here].
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TIP: The `script` transform is often useful when used in combination with the <<transform-script, `search`>>
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transform, where the script can extract only the significant data from a search result, and by that, keep the payload
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minimal. This can be achieved with the <<transform-chain, `chain`>> transform.
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