[[watcher-getting-started]]
== Getting Started with {watcher}

{Watcher} is automatically enabled when you <<installing-xpack, install
{xpack}>> into Elasticsearch and Kibana.

[[watch-log-data]]
To set up a watch to start sending alerts:

* <<log-add-input, Schedule the watch and define an input>>.
* <<log-add-condition, Add a condition>> that checks to see if an alert
needs to be sent.
* <<log-take-action, Configure an action>> to send an alert when the
condition is met.

[float]
[[log-add-input]]
=== Schedule the Watch and Define an Input

A watch {xpack-ref}/trigger-schedule.html[schedule] controls how often a watch is triggered.
The watch {xpack-ref}/input.html[input] gets the data that you want to evaluate.

To periodically search log data and load the results into the
watch, you could use an {xpack-ref}/trigger-schedule.html#schedule-interval[interval] schedule and a
{xpack-ref}/input-search.html[search] input. For example, the following Watch searches
the `logs` index for errors every 10 seconds:

[source,js]
------------------------------------------------------------
PUT _xpack/watcher/watch/log_error_watch
{
  "trigger" : {
    "schedule" : { "interval" : "10s" } <1>
  },
  "input" : {
    "search" : {
      "request" : {
        "indices" : [ "logs" ],
        "body" : {
          "query" : {
            "match" : { "message": "error" }
          }
        }
      }
    }
  }
}
------------------------------------------------------------
// CONSOLE
<1> Schedules are typically configured to run less frequently. This example sets
    the interval to 10 seconds so you can easily see the watches being triggered.
    Since this watch runs so frequently, don't forget to <<log-delete, delete the watch>>
    when you're done experimenting.

If you check the watch history you'll see that the watch is being triggered every
10 seconds. However, the search isn't returning any results so nothing is loaded
into the watch payload.

For example, the following request retrieves the last ten watch executions (watch
records) from the watch history:

[source,js]
------------------------------------------------------------
GET .watcher-history*/_search?pretty
{
  "sort" : [
    { "result.execution_time" : "desc" }
  ]
}
------------------------------------------------------------
// CONSOLE
// TEST[continued]

[float]
[[log-add-condition]]
=== Add a Condition

A {xpack-ref}/condition.html[condition] evaluates the data you've loaded into the watch and
determines if any action is required. Now that you've loaded log errors into
the watch, you can define a condition that checks to see if any errors were
found.

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

[source,js]
--------------------------------------------------
PUT _xpack/watcher/watch/log_error_watch
{
  "trigger" : { "schedule" : { "interval" : "10s" }},
  "input" : {
    "search" : {
      "request" : {
        "indices" : [ "logs" ],
        "body" : {
          "query" : {
            "match" : { "message": "error" }
          }
        }
      }
    }
  },
  "condition" : {
    "compare" : { "ctx.payload.hits.total" : { "gt" : 0 }} <1>
  }
}
--------------------------------------------------
// CONSOLE
<1> The {xpack-ref}/condition-compare.html[compare] condition lets you easily compare against
    values in the execution context.

For this compare condition to evaluate to `true`, you need to add an event
to the `logs` index that contains an error. For example, the following request
adds a 404 error to the `logs` index:

[source,js]
--------------------------------------------------
POST logs/event
{
    "timestamp" : "2015-05-17T18:12:07.613Z",
    "request" : "GET index.html",
    "status_code" : 404,
    "message" : "Error: File not found"
}
--------------------------------------------------
// CONSOLE
// TEST[continued]

Once you add this event, the next time the watch executes its condition will
evaluate to `true`. The condition result is recorded as part of the
`watch_record` each time the watch executes, so you can verify whether or
not the condition was met by searching the watch history:

[source,js]
--------------------------------------------------
GET .watcher-history*/_search?pretty
{
  "query" : {
    "bool" : {
      "must" : [
        { "match" : { "result.condition.met" : true }},
        { "range" : { "result.execution_time" : { "from" : "now-10s" }}}
      ]
    }
  }
}
--------------------------------------------------
// CONSOLE
// TEST[continued]

[float]
[[log-take-action]]
=== Configure an Action

Recording watch records in the watch history is nice, but the real power of
{watcher} is being able to do something when the watch condition is met. A
watch's {xpack-ref}/actions.html[actions]  define what to do when the watch condition
evaluates to `true`. You can send emails, call third-party webhooks, write
documents to an Elasticsearch index, or log messages to the standard
Elasticsearch log files.

For example, the following action writes a message to the Elasticsearch
log when an error is detected.

[source,js]
--------------------------------------------------
PUT _xpack/watcher/watch/log_error_watch
{
  "trigger" : { "schedule" : { "interval" : "10s" }},
  "input" : {
    "search" : {
      "request" : {
        "indices" : [ "logs" ],
        "body" : {
          "query" : {
            "match" : { "message": "error" }
          }
        }
      }
    }
  },
  "condition" : {
    "compare" : { "ctx.payload.hits.total" : { "gt" : 0 }}
  },
  "actions" : {
    "log_error" : {
      "logging" : {
        "text" : "Found {{ctx.payload.hits.total}} errors in the logs"
      }
    }
  }
}
--------------------------------------------------
// CONSOLE

[float]
[[log-delete]]
=== Delete the Watch

Since the `log_error_watch` is configured to run every 10 seconds, make sure you
delete it when you're done experimenting. Otherwise, the noise from this sample
watch will make it hard to see what else is going on in your watch history and
log file.

To remove the watch, use the {ref}/watcher-api-delete-watch.html[DELETE watch API]:

[source,js]
--------------------------------------------------
DELETE _xpack/watcher/watch/log_error_watch
--------------------------------------------------
// CONSOLE
// TEST[continued]

[float]
[[required-security-privileges]]
=== Required Security Privileges
To enable users to create and manipulate watches, assign them the `watcher_admin`
security role. Watcher admins can also view watches, watch history, and triggered
watches.

To allow users to view watches and the watch history, assign them the `watcher_user`
security role. Watcher users cannot create or manipulate watches; they are only
allowed to execute read-only watch operations.

[float]
[[next-steps]]
=== Where to Go Next

* See {xpack-ref}/how-watcher-works.html[How {watcher} Works] for more information about the
anatomy of a watch and the watch lifecycle.
* See {xpack-ref}/example-watches.html[Example Watches] for more examples of setting up
a watch.
* See the https://github.com/elastic/examples/tree/master/Alerting[Example
Watches] in the Elastic Examples repo for additional sample watches you can use
as a starting point for building custom watches.
