Dispatch
A distributed service registry built on top of phoenix_pubsub.
Requests are dispatched to one or more services based on hashed keys.
Installation
- Add dispatch to your list of dependencies in
mix.exs:
def deps do
[
{:dispatch, "~> 0.2.0"}
]
endUsage
Configuration
Configure the registry:
config :dispatch,
pubsub: [name: Dispatch.PubSub,
adapter: Phoenix.PubSub.PG2,
opts: [pool_size: 1]],
registry: [log_level: :debug,
broadcast_period: 25,
max_silent_periods: 3]When the application is started, a supervisor with be started supervising a pubsub adapter with the name and options specified. One can also customize the tracker options for the registry.
Register a service
iex> {:ok, service_pid} = Agent.start_link(fn -> 1 end) # Use your real service here
iex> Dispatch.Registry.add_service(:uploader, service_pid)
{:ok, "g20AAAAI9+IQ28ngDfM="}In this example, :uploader is the type of the service.
Retrieve all services for a service type
iex> Dispatch.Registry.get_services(:uploader)
[{#PID<0.166.0>,
%{node: :"[email protected]", phx_ref: "g20AAAAIHAHuxydO084=",
phx_ref_prev: "g20AAAAI4oU3ICYcsoQ=", state: :online}}]This retrieves all of the services info.
Finding a service for a key
iex> Dispatch.Registry.find_service(:uploader, "file.png")
{:ok, :"[email protected]", #PID<0.153.0>}
Using find_service/2 returns a tuple in the form {:ok, node, pid} where
node is the node that owns the service pid. If no service can be
found then {:error, reason} is returned.
Finding a list of count service instances for a particular key
iex> Dispatch.Registry.find_multi_service(2, :uploader, "file.png")
[{:ok, :"[email protected]", #PID<0.153.0>}, {:ok, :"[email protected]", #PID<0.145.0>}]Convenience API
The Service module can be used to automatically handle registration of a service
based on a GenServer.
Call Service.init within your GenServer's init function.
def init(_) do
:ok = Dispatch.Service.init(type: :uploader)
{:ok, %{}}
endThis will use the type provided to attach a service to the configured registry pid.
Use Dispatch.Service.cast and Dispatch.Service.call to route the GenServer cast or call
to the appropriate service based on the key provided.
Use Dispatch.Service.multi_cast to send cast messages to several service instances at once.
Dispatch.Service.multi_call calls several service instances and waits
for all the responses before returning.
# File is a map with the format %{name: "file.png", contents: "test file"}
def upload(file)
Dispatch.Service.cast(:uploader, file.name, {:upload, file})
end
def download(file)
Dispatch.Service.call(:uploader, file.name, {:download, file})
end
def handle_cast({:upload, file}, state) do
Logger.info("Uploading #{file.name}")
{:noreply, Map.put(state, file.name, file.contents)}
end
def handle_call({:download, %{name: name}}, from, state) do
Logger.info("Downloading #{name}")
{:reply, {:ok, Map.get(state, name}}, state}
end