[[customizing-watches]]
== Customizing Watches

Now that you've seen how to set up simple watches to <<watch-log-data, watch your log data>>
and <<watch-cluster-status, monitor your cluster health>>, let's take a closer
look at how you can customize a watch by modifying its <<changing-inputs, inputs>>,
<<changing-conditions, conditions>>, <<using-transforms, transforms>>, and
<<customizing-actions, actions>>.

[[changing-inputs]]
=== Changing Inputs

The Watch Input is called when the watch triggered to load an initial payload.
This payload is stored in the _Watch Execution Context_ and from then on is
available for other watch elements to access (e.g. watch conditions can
be evaluated based on the data in this payload).

{watcher} supports four types of inputs <<loading-static-data, simple>>,
<<loading-search-results, search>>, <<loading-http-data, http>>, and
<<input-chain, chain>>.

[[loading-static-data]]
==== Loading a Static Payload with the Simple Input

To load static data into the watch payload for testing purposes, you can use the
<<input-simple, simple>> input. For example, the following input stores three
fields in the payload:

[source,js]
-------------------------------------
"input" : {
  "simple" : {
    "color"  : "red",
    "status" : "error",
    "count"  : 3
  }
}
-------------------------------------

See <<input-simple>> for more details.

[[loading-search-results]]
==== Loading a Payload from Elasticsearch with the Search Input

You can use the `search` input to load Elasticsearch search results as the watch
initial payload.

A <<input-search, search>> input contains a `request` object that specifies the
indices you want to search, the {ref}/search-request-search-type.html[search type],
and the search request body. The `body` field of a search input is the same as
the body of an Elasticsearch `_search` request, making the full Elaticsearch
Query DSL available for you to use.

For example, the following `search` input loads the latest VIX quote:

[source,js]
--------------------------------------------------
{
  "input" : {
    "search" : {
      "request" : {
        "indices" : [ "<stock-quotes-{now/d}>" ], <1>
        "body" : {
          "size" : 1,
          "sort" : {
            "timestamp" : { "order" : "desc"}
          },
          "query" : {
            "term" : { "symbol" : "vix"}
          }
        }
      }
    }
  }
}
--------------------------------------------------
<1> Will resolve to today's daily quotes index

See <<input-search>> for more details.

[[loading-http-data]]
==== Loading a Payload from a remote HTTP Service with HTTP Input

Use the `http` input to issue a HTTP request and load the returned response as
the watch initial payload. This input expects the response body content type
to either be JSON or YAML.

For example, the following `http` input loads the current weather forecast for
Amsterdam using http://openweathermap.org/appid[OpenWeatherMap] online service:

[source,js]
--------------------------------------------------
{
  "input" : {
    "http" : {
      "request" : {
        "url" : "http://api.openweathermap.org/data/2.5/weather",
        "params" : {
          "lat" : "52.374031",
          "lon" : "4.88969",
          "appid" : "<your openweathermap appid>"
        }
      }
    }
  }
}
--------------------------------------------------

See <<input-http>> for more details.

[[chaining-inputs]]
==== Chaining Inputs

You can create an <<input-chain, input chain>> to load data from multiple sources
into a watch payload. The inputs in a chain are processed in order, so the the
data loaded by one input can be used by subsequent inputs.

See <<input-chain>> for more details.

[[changing-conditions]]
=== Changing Conditions

The Watch Condition is evaluated as part of the watch execution. The condition
determines whether the actions associated with the watch should execute or not.

{watcher} supports four types of conditions <<condition-always, always>>,
<<condition-never, never>>, <<condition-compare, compare>>,  and
<<condition-script, script>>.

The first two are pretty self-explanatory--they are shortcuts for setting a
watch's condition to `true` or `false`.

==== Simple Value Comparison with the Compare Condition

The `compare` condition enables you to perform simple comparisons against values
in the Watch payload. While you can also do this with a `script` condition, with
`compare` you can define inline comparisons without having to enable dynamic
scripting.

For example, the following compare condition checks to see if the `search` input
returned any hits:

[source,js]
--------------------------------------------------
"condition" : {
    "compare" : { "ctx.payload.hits.total" : { "gt" : 0 }}
  },
--------------------------------------------------

See <<condition-compare>> for more details.

==== Powerful Comparison Logic with the Script Condition

For more complex conditional logic you can use the `script` condition. The
`script` condition accepts a script that when executed returns `true` (indicating
the condition is met) or `false` (indicating the condition is not met). The script
language defaults to the default script language in Elasticsearch, but you can
also use any other supported language in the system.

NOTE: Starting with 5.0, Elasticsearch is shipped with the new
      {ref}/modules-scripting-painless.html[Painless] scripting language.
      Painless was created and designed specifically for use in Elasticsearch.
      Beyond providing an extensive feature set, its biggest trait is that it's
      properly sandboxed and safe to use anywhere in the system (including in
      {watcher}) without the need to enable dynamic scripting.

For example, the following `script` condition checks if the change in the latest
VIX quote loaded by the `http` input is either greater than 5% or lower than -5%:

[source,js]
--------------------------------------------------
"condition" : {
  "script" : {
    "source" : "Math.abs(ctx.payload.hits.hits[0]._source.ChangePercent) > 5",
    "lang" : "painless"
  }
}
--------------------------------------------------

See <<condition-script>> for more details.

[[using-transforms]]
=== Using Transforms

Transforms are constructs in a watch that can change the current payload
associated with the watch execution context.

{watcher} supports three types of transforms <<transform-search, search>>,
<<transform-script, script>> and <<transform-chain, chain>>. A `search` transform
replaces the existing payload with the response of a new search request. You can
use `script` transforms to modify the existing payload. A `chain` transform
enables you to perform a series of `search` and `script` transforms.

See <<transform>> for more details.

[[customizing-actions]]
=== Customizing Actions

Actions are associated with a watch and are executed as part of the watch execution
only when the watch condition is met.

{watcher} supports the following action types: <<actions-email, email>>,
<<actions-slack, slack>>, <<actions-hipchat, hipchat>>, <<actions-pagerduty, pagerduty>>,
<<actions-index, index>>, <<actions-logging, logging>>, and <<actions-webhook, webhook>>.

To use the `email` action, you need to <<configuring-email, configure an email account>>
in `elasticsearch.yml` that {watcher} can use to send email. Your custom email
messages can be plain text or styled using HTML. You can include information from
the watch execution payload using <<templates, templates>>, as well as attach the
entire watch payload to the message.

For example, the following email action uses a template in the email body and
attaches the payload data to the message:

[source,js]
--------------------------------------------------
"actions" : {
  "send_email" : { <1>
    "email" : { <2>
      "to" : "<username>@<domainname>",
      "subject" : "Watcher Notification",
      "body" : "{{ctx.payload.hits.total}} error logs found",
      "attachments" : {
        "data_attachment" : {
          "data" : {
            "format" : "json"
          }
        }
      }
    }
  }
}
--------------------------------------------------
<1> The id of the action
<2> The action type, in this case it's an `email` action

Another example for an action is the `webhook` action. This enables you to send
a request to any external webservice. For example, the following `webhook` action
creates a new issue in GitHub

[source,js]
--------------------------------------------------
"actions" : {
  "create_github_issue" : {
    "webhook" : {
      "method" : "POST",
      "url" : "https://api.github.com/repos/<owner>/<repo>/issues", <1>
      "body" : "{
        \"title\": \"Found errors in 'contact.html'\",
        \"body\": \"Found {{ctx.payload.hits.total}} errors in this page in the last 5 minutes\",
        \"assignee\": \"web-admin\",
        \"labels\": [ \"bug\", \"sev2\" ]
      }",
      "auth" : {
        "basic" : {
          "username" : "<username>", <2>
          "password" : "<password>" <3>
        }
      }
    }
  }
}
--------------------------------------------------
<1> `<owner>` is the owner of the GitHub repo and `<repo>` is the name of the repo.
<2> The username that creates the issue
<3> The password of that user

To learn how to create other actions see <<actions>>.
