[[input-http]]
=== HTTP Input

Use the `http` input to submit a request to an HTTP endpoint and load the
response into the watch execution context when the watch is triggered. See
<<http-input-attributes, Input Attributes>> for all of the supported attributes.

With the `http` input, you can:

* Query external Elasticsearch clusters. The `http` input provides a way 
  to submit search requests to clusters other than the one {watcher} is running 
  on. This is useful when you're running a dedicated {watcher} cluster or if you 
  need to search clusters that are running different Elasticsearch versions.

* Query Elasticsearch APIs other than the search API. For example, you might want
  to load data from the {ref}/cluster-nodes-stats.html[Nodes Stats], 
  {ref}/cluster-health.html[Cluster Health] or {ref}/cluster-state.html[Cluster 
  State] APIs.

* Query external web services. The `http` input enables you to load data from
  any service that exposes an HTTP endpoint. This provides a bridge
  between Elasticsearch clusters and other systems.

==== Querying External Elasticsearch Clusters

To query an external Elasticsearch cluster, you specify the cluster's
`host` and `port` attributes and the index's search endpoint as the `path`. 
If you omit the search body, the request returns all documents in the specified
index: 

[source,js]
--------------------------------------------------
"input" : {
  "http" : {
    "request" : {
      "host" : "example.com",
      "port" : 9200,
      "path" : "/idx/_search"
    }
  }
}
--------------------------------------------------

You can use the full Elasticsearch {ref}/query-dsl.html[Query DSL] to perform
more sophisticated searches. For example, the following `http` input retrieves 
all documents that contain `event` in the `category` field:

[source,js]
--------------------------------------------------
"input" : {
  "http" : {
    "request" : {
      "host" : "host.domain",
      "port" : 9200,
      "path" : "/idx/_search",
      "body" :  "{\"query\" :  {  \"match\" : { \"category\" : \"event\"}}}"
    }
  }
}
--------------------------------------------------

==== Calling Elasticsearch APIs

To load the data from other Elasticsearch APIs, specify the API
endpoint as the `path` attribute. Use the `params` attribute to specify
query string parameters. For example, the following `http` input 
calls the {ref}/cluster-stats.html[Cluster 
Stats] API and enables the `human` attribute:

[source,js]
--------------------------------------------------
"input" : {
  "http" : {
    "request" : {
      "host" : "host.domain",
      "port" : "9200",
      "path" : "/_cluster/stats",
      "params" : {
        "human" : "true" <1>
      }
    }
  }
}
--------------------------------------------------
<1> Enabling this attribute returns the `bytes` values in the response in human
    readable format.

[[input-http-auth-basic-example]]
==== Calling External Web Services

You can use `http` input to get data from any external web service. The `http`
input supports basic authentication. For example, the following input provides
a username and password to access `myservice`:

[source,js]
--------------------------------------------------
"input" : {
  "http" : {
    "request" : {
      "host" : "host.domain",
      "port" : "9200",
      "path" : "/myservice",
      "auth" : {
        "basic" : {
          "username" : "user",
          "password" : "pass"
        }
      }
    }
  }
}
--------------------------------------------------

You can also pass in service-specific API keys and other information
through the `params` attribute. For example, the following `http` 
input loads the current weather forecast for Amsterdam from the
http://openweathermap.org/appid[OpenWeatherMap] 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>"
      }
    }
  }
}
--------------------------------------------------

==== Using Templates

The `http` input supports templating. You can use <<templates, templates>> when
specifying the `path`, `body`, header values, and parameter values.

For example, the following snippet uses templates to specify what index to query
and restrict the results to documents added within the last five minutes:

[source,js]
--------------------------------------------------
"input" : {
  "http" : {
    "request" : {
      "host" : "host.domain",
      "port" : 9200,
      "path" : "/{{ctx.watch_id}}/_search",
      "body" : "{\"query\" : {\"range\": {\"@timestamp\" : {\"from\": \"{{ctx.trigger.triggered_time}}||-5m\",\"to\": \"{{ctx.trigger.triggered_time}}\"}}}}"
      }
    }
  }
--------------------------------------------------

==== Accessing the HTTP Response

If the response body is formatted in  JSON or YAML, it is parsed and loaded into
the execution context. If the response body is not formatted in JSON or YAML, it 
is loaded into the payload's `_value` field. 

Conditions, transforms, and actions access the response data through the 
execution context. For example, if the response contains a `message` 
object, you can use `ctx.payload.message` to access the message data. 

In addition all the headers from the response can be accessed using the
`ctx.payload._headers` field as well as the HTTP status code of the response using
`ctx.payload._status_code`.

      
[[http-input-attributes]]
==== HTTP Input Attributes

[cols=",^,^,", options="header"]
|======
| Name                          | Required | Default | Description

| `request.scheme`              | no       | http    | Url scheme. Valid values are: `http` or `https`.

| `request.host`                | yes      | -       | The host to connect to.

| `request.port`                | yes      | -       | The port the http service is listening on.

| `request.path`                | no       | -       | The URL path. The path can be static text or contain `mustache`
                                                       <<templates, templates>>. URL query string parameters must be
                                                       specified via the `request.params` attribute.

| `request.method`              | no       | get     | The HTTP method. Supported values are: `head`, `get`, `post`,
                                                       `put` and `delete`.

| `request.headers`             | no       | -       | The HTTP request headers. The header values can be static text
                                                       or include `mustache` <<templates, templates>>.

| `request.params`              | no       | -       | The URL query string parameters. The parameter values can be
                                                       static text or contain `mustache` <<templates, templates>>.

| `request.url`                 | no       | -       | Allows you to set `request.scheme`, `request.host`, `request.port`
                                                       and `request.params` add once by specifying a real URL, like
                                                       `https://www.example.org:1234/mypath?foo=bar`. May not be combined
                                                       with on of those four parameters. As those parameters are set,
                                                       specifying them individually might overwrite them.

| `request.auth`                | no       | -       | Authentication related HTTP headers. Currently, only basic
                                                       authentication is supported.

| `request.proxy.host`          | no       | -       | The proxy host to use when connecting to the host.

| `request.proxy.port`          | no       | -       | The proxy port to use when connecting to the host.

| `request.connection_timeout`  | no       | 10s     | The timeout for setting up the http connection. If the connection
                                                       could not be set up within this time, the input will timeout and
                                                       fail.

| `request.read_timeout`        | no       | 10s     | The timeout for reading data from http connection. If no response
                                                       was received within this time, the input will timeout and fail.
                                                      

| `request.body`                | no       | -       | The HTTP request body. The body can be static text or include
                                                       `mustache` <<templates, templates>>.

| `extract`                     | no       | -       | A array of JSON keys to extract from the input response and
                                                       use as payload. In cases when an input generates a large
                                                       response this can be used to filter the relevant piece of
                                                       the response to be used as payload.

| `response_content_type`       | no       | json    | The expected content type the response body will contain.
                                                       Supported values are `json`, `yaml` and `text`. If the
                                                       format is `text` the `extract` attribute cannot exist.
                                                       Note that this overrides the header that is returned in the
                                                       HTTP response. If this is set to `text` the body of the
                                                       response will be assigned and accessible to/via the `_value`
                                                       variable of the payload.
|======

You can reference the following variables in the execution context when
specifying the `path`, `params`, `headers` and `body` values:

[options="header"]
|======
| Name                         | Description
| `ctx.watch_id`               | The id of the watch that is currently executing.
| `ctx.execution_time`         | The time execution of this watch started.
| `ctx.trigger.triggered_time` | The time this watch was triggered.
| `ctx.trigger.scheduled_time` | The time this watch was supposed to be triggered.
| `ctx.metadata.*`             | Any metadata associated with the watch.
|======
