View Source Phoenix.PubSub (Phoenix.PubSub v2.1.3)
Realtime Publisher/Subscriber service.
getting-started
Getting started
You start Phoenix.PubSub directly in your supervision tree:
{Phoenix.PubSub, name: :my_pubsub}You can now use the functions in this module to subscribe and broadcast messages:
iex> alias Phoenix.PubSub
iex> PubSub.subscribe(:my_pubsub, "user:123")
:ok
iex> Process.info(self(), :messages)
{:messages, []}
iex> PubSub.broadcast(:my_pubsub, "user:123", {:user_update, %{id: 123, name: "Shane"}})
:ok
iex> Process.info(self(), :messages)
{:messages, [{:user_update, %{id: 123, name: "Shane"}}]}
adapters
Adapters
Phoenix PubSub was designed to be flexible and support multiple backends. There are two officially supported backends:
Phoenix.PubSub.PG2- the default adapter that ships as part of Phoenix.PubSub. It uses Distributed Elixir, directly exchanging notifications between servers. It supports a:pool_sizeoption to be given alongside the name, defaults to1. Note the:pool_sizemust be the same throughout the cluster, therefore don't configure the pool size based onSystem.schedulers_online/1, especially if you are using machines with different specs.Phoenix.PubSub.Redis- uses Redis to exchange data between servers. It requires the:phoenix_pubsub_redisdependency.
See Phoenix.PubSub.Adapter to implement a custom adapter.
custom-dispatching
Custom dispatching
Phoenix.PubSub allows developers to perform custom dispatching
by passing a dispatcher module which is responsible for local
message deliveries.
The dispatcher must be available on all nodes running the PubSub
system. The dispatch/3 function of the given module will be
invoked with the subscriptions entries, the broadcaster identifier
(either a pid or :none), and the message to broadcast.
You may want to use the dispatcher to perform special delivery for
certain subscriptions. This can be done by passing the :metadata
option during subscriptions. For instance, Phoenix Channels use a
custom value to provide "fastlaning", allowing messages broadcast
to thousands or even millions of users to be encoded once and written
directly to sockets instead of being encoded per channel.
Link to this section Summary
Functions
Raising version of broadcast/4.
Broadcasts message on given topic across the whole cluster.
Raising version of broadcast_from/5.
Broadcasts message on given topic from the given process across the whole cluster.
Returns a child specification for pubsub with the given options.
Raising version of direct_broadcast/5.
Broadcasts message on given topic to a given node.
Broadcasts message on given topic only for the current node.
Broadcasts message on given topic from a given process only for the current node.
Returns the node name of the PubSub server.
Subscribes the caller to the PubSub adapter's topic.
Unsubscribes the caller from the PubSub adapter's topic.
Link to this section Types
Link to this section Functions
@spec broadcast!(t(), topic(), message(), dispatcher()) :: :ok
Raising version of broadcast/4.
@spec broadcast(t(), topic(), message(), dispatcher()) :: :ok | {:error, term()}
Broadcasts message on given topic across the whole cluster.
pubsub- The name of the pubsub systemtopic- The topic to broadcast to, ie:"users:123"message- The payload of the broadcast
A custom dispatcher may also be given as a fourth, optional argument. See the "Custom dispatching" section in the module documentation.
broadcast_from!(pubsub, from, topic, message, dispatcher \\ __MODULE__)
View Source@spec broadcast_from!(t(), pid(), topic(), message(), dispatcher()) :: :ok
Raising version of broadcast_from/5.
broadcast_from(pubsub, from, topic, message, dispatcher \\ __MODULE__)
View SourceBroadcasts message on given topic from the given process across the whole cluster.
pubsub- The name of the pubsub systemfrom- The pid that will send the messagetopic- The topic to broadcast to, ie:"users:123"message- The payload of the broadcast
The default dispatcher will broadcast the message to all subscribers except for the process that initiated the broadcast.
A custom dispatcher may also be given as a fifth, optional argument. See the "Custom dispatching" section in the module documentation.
@spec child_spec(keyword()) :: Supervisor.child_spec()
Returns a child specification for pubsub with the given options.
The :name is required as part of options. The remaining options
are described below.
options
Options
:name- the name of the pubsub to be started:adapter- the adapter to use (defaults toPhoenix.PubSub.PG2):pool_size- number of pubsub partitions to launch (defaults to one partition for every 4 cores)
direct_broadcast!(node_name, pubsub, topic, message, dispatcher \\ __MODULE__)
View Source@spec direct_broadcast!(node_name(), t(), topic(), message(), dispatcher()) :: :ok
Raising version of direct_broadcast/5.
direct_broadcast(node_name, pubsub, topic, message, dispatcher \\ __MODULE__)
View SourceBroadcasts message on given topic to a given node.
node_name- The target node namepubsub- The name of the pubsub systemtopic- The topic to broadcast to, ie:"users:123"message- The payload of the broadcast
DO NOT use this function if you wish to broadcast to the current
node, as it is always serialized, use local_broadcast/4 instead.
A custom dispatcher may also be given as a fifth, optional argument. See the "Custom dispatching" section in the module documentation.
@spec local_broadcast(t(), topic(), message(), dispatcher()) :: :ok
Broadcasts message on given topic only for the current node.
pubsub- The name of the pubsub systemtopic- The topic to broadcast to, ie:"users:123"message- The payload of the broadcast
A custom dispatcher may also be given as a fourth, optional argument. See the "Custom dispatching" section in the module documentation.
local_broadcast_from(pubsub, from, topic, message, dispatcher \\ __MODULE__)
View Source@spec local_broadcast_from(t(), pid(), topic(), message(), dispatcher()) :: :ok
Broadcasts message on given topic from a given process only for the current node.
pubsub- The name of the pubsub systemfrom- The pid that will send the messagetopic- The topic to broadcast to, ie:"users:123"message- The payload of the broadcast
The default dispatcher will broadcast the message to all subscribers except for the process that initiated the broadcast.
A custom dispatcher may also be given as a fifth, optional argument. See the "Custom dispatching" section in the module documentation.
Returns the node name of the PubSub server.
Subscribes the caller to the PubSub adapter's topic.
pubsub- The name of the pubsub systemtopic- The topic to subscribe to, for example:"users:123"opts- The optional list of options. See below.
duplicate-subscriptions
Duplicate Subscriptions
Callers should only subscribe to a given topic a single time.
Duplicate subscriptions for a Pid/topic pair are allowed and
will cause duplicate events to be sent; however, when using
Phoenix.PubSub.unsubscribe/2, all duplicate subscriptions
will be dropped.
options
Options
:metadata- provides metadata to be attached to this subscription. The metadata can be used by custom dispatching mechanisms. See the "Custom dispatching" section in the module documentation
Unsubscribes the caller from the PubSub adapter's topic.