95 lines
2.5 KiB
Plaintext
95 lines
2.5 KiB
Plaintext
[role="xpack"]
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[[input-chain]]
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=== Chain Input
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Use the `chain` input to load data from multiple sources into the watch
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execution context when the watch is triggered. The inputs in a chain
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are processed in order and the data loaded by an input can be accessed by the
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subsequent inputs in the chain.
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The `chain` input enables you perform actions based on data from multiple
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sources. You can also use the data collected by one input to load data
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from another source.
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For example, the following chain input loads data from an HTTP server using the
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path set by a `simple` input:
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[source,js]
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--------------------------------------------------
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"input" : {
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"chain" : {
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"inputs" : [ <1>
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{
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"first" : {
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"simple" : { "path" : "/_search" }
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}
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},
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{
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"second" : {
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"http" : {
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"request" : {
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"host" : "localhost",
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"port" : 9200,
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"path" : "{{ctx.payload.first.path}}" <2>
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}
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}
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}
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}
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]
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}
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}
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--------------------------------------------------
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// NOTCONSOLE
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<1> The inputs in a chain are specified as an array to guarantee the order in
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which the inputs are processed. (JSON does not guarantee the order of
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arbitrary objects.)
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<2> Loads the `path` set by the `first` input.
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==== Accessing Chained Input Data
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To reference data loaded by a particular input, you use the input's name,
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`ctx.payload.<input-name>.<value>`.
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==== Transforming Chained Input Data
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In certain use-cases the output of the first input should be used as input
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in a subsequent input. This requires you to do a transform, before you pass
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the data on to the next input.
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In order to achieve this you can use a transform input between the two
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specified inputs, see the following example. Note, that the first input will
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still be available in its original form in `ctx.payload.first`.
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[source,js]
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--------------------------------------------------
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"input" : {
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"chain" : {
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"inputs" : [ <1>
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{
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"first" : {
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"simple" : { "path" : "/_search" }
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}
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},
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{
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"second" : {
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"transform" : {
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"script" : "return [ 'path' : ctx.payload.first.path + '/' ]"
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}
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}
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},
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{
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"third" : {
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"http" : {
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"request" : {
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"host" : "localhost",
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"port" : 9200,
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"path" : "{{ctx.payload.second.path}}" <2>
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}
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}
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}
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}
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]
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}
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}
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--------------------------------------------------
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// NOTCONSOLE |