gen_rmq v0.2.1 GenRMQ.Consumer behaviour
A behaviour module for implementing the RabbitMQ consumer.
It will:
- setup RabbitMQ connection / channel and keep them in a state
- create (if does not exist) a queue and bind it to an exchange
- create deadletter queue and exchange
- handle reconnections
- call
handle_message
callback on every message delivery
Summary
Functions
Acknowledges given message
Returns a specification to start this module under a supervisor
Requeues / rejects given message
Starts GenRMQ.Consumer
process with given callback module linked to the current
process
Synchronously stops the consumer with a given reason
Functions
Specs
ack(message :: GenRMQ.Message.t) :: :ok
Acknowledges given message
message
- GenRMQ.Message
struct
Specs
reject(message :: GenRMQ.Message.t, requeue :: Boolean.t) :: :ok
Requeues / rejects given message
message
- GenRMQ.Message
struct
requeue
- indicates if message should be requeued
Starts GenRMQ.Consumer
process with given callback module linked to the current
process
module
- callback module implementing GenRMQ.Consumer
behaviour
Options
:name
- used for name registration
Return values
If the consumer is successfully created and initialized, this function returns
{:ok, pid}
, where pid
is the PID of the consumer. If a process with the
specified consumer name already exists, this function returns
{:error, {:already_started, pid}}
with the PID of that process.
Examples:
GenRMQ.Consumer.start_link(Consumer, name: :consumer)
Specs
stop(name :: Atom.t | Pit.t, reason :: Any.t) :: :ok
Synchronously stops the consumer with a given reason
name
- pid or name of the consumer to stop
reason
- reason of the termination
Examples:
GenRMQ.Consumer.stop(:consumer, :normal)
Callbacks
Specs
consumer_tag :: String.t
Invoked to provide consumer tag
Examples:
def consumer_tag() do
"hostname-app-version-consumer"
end
Specs
handle_message(message :: GenRMQ.Message.t) :: :ok
Invoked on message delivery
message
- GenRMQ.Message
struct
Examples:
def handle_message(message) do
# Do something with message and acknowledge it
GenRMQ.Consumer.ack(message)
end
Specs
Invoked to provide consumer configuration
Return values
Mandatory:
uri
- RabbitMQ uri
queue
- the name of the queue to consume.
If does not exist it will be created
exchange
- the name of the exchange to which queue
should be bind.
If does not exist it will be created
routing_key
- queue binding key
prefetch_count
- limit the number of unacknowledged messages
Optional:
queue_ttl
- controls for how long a queue can be unused before it is
automatically deleted. Unused means the queue has no consumers,
the queue has not been redeclared, and basic.get has not been invoked
for a duration of at least the expiration period
concurrency
- defines if handle_message
callback is called
in seperate process using spawn
function. By default concurrency is enabled. To disable, set it to false
retry_delay_function
- custom retry delay function. Called when the connection to
the broker cannot be established. Receives the connection attempt as an argument (>= 1)
and is expected to wait for some time.
With this callback you can for example do exponential backoff.
The default implementation is a linear delay starting with 1 second step.
reconnect
- defines if consumer should reconnect on connection termination.
By default reconnection is enabled.
deadletter
- defines if consumer should setup deadletter exchange and queue.
deadletter_queue
- defines name of the deadletter queue.
deadletter_exchange
- defines name of the deadletter exchange.
Examples:
def init() do
[
queue: "gen_rmq_in_queue",
exchange: "gen_rmq_exchange",
routing_key: "#",
prefetch_count: "10",
uri: "amqp://guest:guest@localhost:5672",
concurrency: true,
queue_ttl: 5000,
retry_delay_function: fn attempt -> :timer.sleep(1000 * attempt) end,
reconnect: true,
deadletter: true,
deadletter_queue: "gen_rmq_in_queue_error",
deadletter_exchange: "gen_rmq_exchange.deadletter"
]
end