148 lines
4.8 KiB
Plaintext
148 lines
4.8 KiB
Plaintext
[[condition-script]]
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=== Script Condition
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A watch <<condition, condition>> that evaluates a script. The default scripting
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language is `painless`. You can use any of the scripting languages supported by
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Elasticsearch as long as the language supports evaluating expressions to Boolean
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values. Note that the `mustache` and `expression` languages are too limited to be
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used by this condition. For more information, see {ref}/modules-scripting.html[Scripting]
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in the Elasticsearch Reference.
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==== Using a Script Condition
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The following snippet configures an inline `script` condition that always returns
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`true`:
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[source,js]
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--------------------------------------------------
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"condition" : {
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"script" : "return true"
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}
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--------------------------------------------------
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This example defines a script as a simple string. This format is actually a
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shortcut for defining an <<condition-script-inline, inline>> script. The
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formal definition of a script is an object that specifies the script type and
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optional language and parameter values. If the `lang` attribute is omitted, the
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language defaults to `painless`. Elasticsearch supports two types of scripts,
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<<condition-script-inline, Inline>> and <<condition-script-stored, Stored>>.
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For example, the following snippet shows a formal definition of an `inline`
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script that explicitly specifies the language and defines a single script
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parameter, `result`:
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[source,js]
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--------------------------------------------------
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"condition" : {
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"script" : {
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"source" : "return result",
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"lang" : "painless",
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"params" : {
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"result" : true
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}
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}
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}
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--------------------------------------------------
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[[condition-script-inline]]
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==== Inline Scripts
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Inline scripts are scripts that are defined in the condition itself. The
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following snippet shows the formal configuration of a simple painless script that
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always returns `true`.
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[source,js]
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--------------------------------------------------
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"condition" : {
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"script" : {
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"source" : "return true"
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}
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}
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--------------------------------------------------
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[[condition-script-stored]]
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==== Stored Scripts
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Stored scripts refer to scripts that were {ref}/modules-scripting-using.html#modules-scripting-stored-scripts[stored]
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in Elasticsearch. The following snippet shows how to refer to a script by its `id`:
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[source,js]
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--------------------------------------------------
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"condition" : {
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"script" : {
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"id" : "my_script"
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}
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}
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--------------------------------------------------
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As with <<condition-script-inline, Inline>>
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scripts, you can also specify the script language and parameters:
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[source,js]
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--------------------------------------------------
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"condition" : {
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"script" : {
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"id" : "my_script",
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"lang" : "javascript",
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"params" : { "color" : "red" }
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}
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}
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--------------------------------------------------
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[[accessing-watch-payload]]
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==== Accessing the Watch Payload
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A script can access the current watch execution context, including the payload
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data, as well as any parameters passed in through the condition definition.
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For example, the following snippet defines a watch that uses a <<input-search, `search` input>>
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and uses a `script` condition to check if the number of hits is above a specified
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threshold:
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[source,js]
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--------------------------------------------------
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{
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"input" : {
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"search" : {
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"indices" : "log-events",
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"body" : {
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"size" : 0,
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"query" : { "match" : { "status" : "error" } }
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}
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}
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},
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"condition" : {
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"script" : {
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"source" : "return ctx.payload.hits.total > threshold",
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"params" : {
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"threshold" : 5
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}
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}
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}
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}
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--------------------------------------------------
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When you're using a scripted condition to evaluate an Elasticsearch response,
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keep in mind that the fields in the response are no longer in their native data
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types. For example, the `@timestamp` in the response is a string, rather than a
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`DateTime`. To compare the response `@timestamp` against the `ctx.execution_time`,
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you need to parse the `@timestamp` string into a `DateTime`. For example:
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[source,js]
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--------------------------------------------------
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org.elasticsearch.common.joda.time.DateTime.parse(@timestamp)
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--------------------------------------------------
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You can reference the following variables in the watch context:
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[options="header"]
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|======
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| Name | Description
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| `ctx.watch_id` | The id of the watch that is currently executing.
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| `ctx.execution_time` | The time execution of this watch started.
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| `ctx.trigger.triggered_time` | The time this watch was triggered.
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| `ctx.trigger.scheduled_time` | The time this watch was supposed to be triggered.
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| `ctx.metadata.*` | Any metadata associated with the watch.
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| `ctx.payload.*` | The payload data loaded by the watch's input.
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|======
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