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HTTP backend

Module description

This module is a backend of mod_event_pusher that enables forwarding certain events (messages, presence, etc.) via HTTP to external services such as push (by mobile, email or SMS), big data, or analytics services.

How it works

The module hooks on all packets sent by connected users. When the hook is triggered, the module:

  • runs a callback module's should_make_req/6 function to see if a notification should be sent
  • runs a callback module's prepare_headers/7 to get http headers to be used
  • runs a callback module's prepare_body/7
  • sends a POST request composed of {Host::binary(), Sender::binary(), Receiver::binary(), Message::binary()} to the http notification server

You can make multiple configuration entries for this backend to handle more complicated pushing scenarios (e.g. sending various types of messages to different backends).

Callback module

To find out what and how to send MongooseIM calls the following callback module's functions: Mod:should_make_req(Acc::mongoose_acc:t(), Dir::in|out, Packet::xmlel(), From::jid(), To::jid(), Opts :: [{atom(), term()}]).

Mod:prepare_headers(Acc::mongoose_acc:t(), Dir::in|out, Host::jid:lserver(), Message::binary(), Sender::jid:luser(), Receiver::luser(), Opts :: [{atom(), term()}]).

Mod:prepare_body(Acc::mongoose_acc:t(), Dir::in|out, Host::jid:lserver(), Message::binary(), Sender::jid:luser(), Receiver::luser(), Opts :: [{atom(), term()}]).

By default it uses the function in mod_event_pusher_http itself, which ships all non-empty chat messages.

Prerequisites

This module uses a connection pool created by mongoose_http_client. It must be defined in the outgoing_pools settings.

Options

modules.mod_event_pusher_http.pool_name

  • Syntax: non-empty string
  • Default: "http_pool"
  • Example: pool_name = "http_pool"

Name of the pool to use (as defined in outgoing_pools).

modules.mod_event_pusher_http.path

  • Syntax: string
  • Default: ""
  • Example: path = "/notifications"

Path part of an URL to which a request should be sent (will be appended to the pool's prefix path).

modules.mod_event_pusher_http.callback_module

  • Syntax: string
  • Default: "mod_event_pusher_http_defaults"
  • Example: callback_module = "mod_event_pusher_http_notifications"

Name of a module which should be used to check whether a notification should be sent.

Example configuration

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[outgoing_pools.http.http_pool]
  scope = "global"
  workers = 50

  [outgoing_pools.http.http_pool.connection]
    host = "https://localhost:8000"
    path_prefix = "/webservice"
    request_timeout = 2000

[modules.mod_event_pusher.backend.http]
  pool_name = "http_pool"
  path = "/notifications"

Notifications will be POSTed to http://localhost:8000/webservice/notifications.

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[[modules.mod_event_pusher.backend.http]]
  pool_name = "http_pool"
  path = "/notifications"
  callback_module = "mod_event_pusher_http_notifications"

[[modules.mod_event_pusher.backend.http]]
  pool_name = "http_pool"
  path = "/alerts"
  callback_module = "mod_event_pusher_http_alerts"

Here, some notifications will be POSTed to http://localhost:8000/webservice/notifications and some to http://localhost:8000/webservice/alerts, depending on implementation of should_make_req/6 in the two callback modules.

Default payload format

The default HTTP event pusher sends a POST request with Content-Type application/x-www-form-urlencoded. The form has the following fields: * author: username of the user who authored the message * server: name of the server from where the message originates * receiver: username of the user who the message is for * message: content of <body> element of the message

The contents of the author, server and receiver fields are processed by stringprep. As a result, these values are all lower case.

Example

Below is an example of what the body of an HTTP POST request can look like: 

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"author=alice&server=localhost&receiver=bob&message=Hi, Bob!"

Metrics

If you'd like to learn more about metrics in MongooseIM, please visit MongooseIM metrics page.

Name Type Description (when it gets incremented)
[Host, mod_event_pusher_http, sent] spiral An HTTP notification is sent successfully.
[Host, mod_event_pusher_http, failed] spiral An HTTP notification failed.
[Host, mod_event_pusher_http, response_time] histogram Does not include timings of failed requests.