hare v0.2.2 Hare.Publisher behaviour
A behaviour module for implementing AMQP publisher processes.
The Hare.Publisher
module provides a way to create processes that hold,
monitor, and restart a channel in case of failure, exports a function to publish
messages to an exchange, and some callbacks to hook into the process lifecycle.
An example Hare.Publisher
process that only sends every other message:
defmodule MyPublisher do
use Hare.Publisher
def start_link(conn, config, opts \ []) do
Hare.Publisher.start_link(__MODULE__, conn, config, :ok, opts)
end
def publish(publisher, payload, routing_key) do
Hare.Publisher.publish(publisher, payload, routing_key)
end
def init(:ok) do
{:ok, %{last_ignored: false}}
end
def before_publication(_payload, _routing_key, _opts, %{last_ignored: false}) do
{:ignore, %{last_ignored: true}}
end
def before_publication(_payload, _routing_key, _opts, %{last_ignored: true}) do
{:ok, %{last_ignored: false}}
end
end
Channel handling
When the Hare.Publisher
starts with start_link/5
it runs the init/1
callback
and responds with {:ok, pid}
on success, like a GenServer.
After starting the process it attempts to open a channel on the given connection. It monitors the channel, and in case of failure it tries to reopen again and again on the same connection.
Context setup
The context setup process for a publisher is to declare its exchange.
Every time a channel is open the context is set up, meaning that the exchange is declared through the new channel based on the given configuration.
The configuration must be a Keyword.t
that may contain a single key: :exchange
whose value is the configuration for the Hare.Context.Action.DeclareExchange
.
Check it for more detailed information. If the :exchange
key is omited, the
default exchange will be used.
Summary
Functions
See Hare.Actor.call/2
See Hare.Actor.call/3
See Hare.Actor.cast/2
Publishes a message to an exchange through the Hare.Publisher
process
See Hare.Actor.reply/2
Starts a Hare.Publisher
process linked to the current process
Callbacks
Called after a message has been published to the exchange
Called before a message will be published to the exchange
Called when the process receives a cast message sent by cast/3
. This
callback has the same arguments as the GenServer
equivalent and the
:noreply
and :stop
return tuples behave the same
Called when the publisher process has successfully opened AMQP channel
Called when the AMQP publisher has been disconnected from the AMQP broker
Called when the process receives a message
Called when the publisher process is first started. start_link/5
will block
until it returns
This callback is the same as the GenServer
equivalent and is called when the
process terminates. The first argument is the reason the process is about
to exit with
Types
Functions
publish(GenServer.server, payload :: term, routing_key, opts) :: :ok
Publishes a message to an exchange through the Hare.Publisher
process.
start_link(module, GenServer.server, config, initial :: term, GenServer.options) :: GenServer.on_start
Starts a Hare.Publisher
process linked to the current process.
This function is used to start a Hare.Publisher
process in a supervision
tree. The process will be started by calling init
with the given initial
value.
Arguments:
mod
- the module that defines the server callbacks (like GenServer)conn
- the pid of aHare.Core.Conn
processconfig
- the configuration of the publisher (describing the exchange to declare)initial
- the value that will be given toinit/1
opts
- the GenServer options
Callbacks
after_publication(payload, routing_key, opts :: term, state) :: {:ok, state} | {:stop, reason :: term, state}
Called after a message has been published to the exchange.
It receives as argument the message payload, the routing key, the options for that publication and the internal state.
Returning {:ok, state}
will enter the main loop with the given state.
Returning {:stop, reason, state}
will terminate the
main loop and call terminate(reason, state)
before the process exits with
reason reason
.
before_publication(message, routing_key, opts :: term, state) :: {:ok, state} | {:ok, payload, routing_key, opts :: term, state} | {:ignore, state} | {:stop, reason :: term, state}
Called before a message will be published to the exchange.
It receives as argument the message payload, the routing key, the options for that publication and the internal state.
Returning {:ok, state}
will cause the message to be sent with no
modification, and enter the main loop with the given state.
Returning {:ok, payload, routing_key, opts, state}
will cause the
given payload, routing key and options to be used instead of the original
ones, and enter the main loop with the given state.
Returning {:ignore, state}
will ignore that message and enter the main loop
again with the given state.
Returning {:stop, reason, state}
will not send the message, terminate the
main loop and call terminate(reason, state)
before the process exits with
reason reason
.
Called when the process receives a call message sent by call/3
. This
callback has the same arguments as the GenServer
equivalent and the
:reply
, :noreply
and :stop
return tuples behave the same.
Called when the process receives a cast message sent by cast/3
. This
callback has the same arguments as the GenServer
equivalent and the
:noreply
and :stop
return tuples behave the same.
Called when the publisher process has successfully opened AMQP channel.
Returning {:noreply, state}
will cause the process to enter the main loop
with the given state.
Returning {:stop, reason, state}
will terminate the main loop and call
terminate(reason, state)
before the process exits with reason reason
.
Called when the AMQP publisher has been disconnected from the AMQP broker.
Returning {:noreply, state}
causes the process to enter the main loop with
the given state. The publisher will not be able to send any new messages until
connection to AMQP broker is established again.
Returning {:stop, reason, state}
will terminate the main loop and call
terminate(reason, state)
before the process exits with reason reason
.
Called when the process receives a message.
Returning {:noreply, state}
will causes the process to enter the main loop
with the given state.
Returning {:stop, reason, state}
will not send the message, terminate the
main loop and call terminate(reason, state)
before the process exits with
reason reason
.
Called when the publisher process is first started. start_link/5
will block
until it returns.
It receives as argument the fourth argument given to start_link/5
.
Returning {:ok, state}
will cause start_link/5
to return {:ok, pid}
and attempt to open a channel on the given connection and declare the exchange.
After that it will enter the main loop with state
as its internal state.
Returning :ignore
will cause start_link/5
to return :ignore
and the
process will exit normally without entering the loop, opening a channel or calling
terminate/2
.
Returning {:stop, reason}
will cause start_link/5
to return {:error, reason}
and
the process will exit with reason reason
without entering the loop, opening a channel,
or calling terminate/2
.