Component v0.2.2 Component.Strategy.Pooled View Source
Implement a named pool of services. The current implementation delegates the heavy lifting to poolboy
Usage
To create the service:
Create a module that implements the API you want. This API will be expressed as a set of public functions. Each function will automatically receive the current state in a variable (by default named
state
). There is not need to declare this as a parameter.why?. If a function wants to change the state, it must end with a call to theset_state/2
function (which will have been imported into your module automatically).For this example, we'll call the module
Workers
.Add the line
use Component.Strategy.Pooled
to the top of this module.Adjust the other options if required.
To start the pool:
Workers.initialize()
or
Workers.initialize(initial_state)
Claim a worker using
worker = Workers.create()
Call functions in the module using
result = Workers.some_function(worker, other_args) ...
When you're finished with the worker, call
Workers.destroy(worker)
(The create
and destroy
functions correspond to poolboy's
checkout
and checkin
. We use these names for consistency with
other strategies.)
Example
defmodule FaceDetector do
using Component.Strategy.Pooled,
state: %{ algorithm: ViolaJones },
state_name: :options,
pool: [ min: 3, max: 10 ]
def recognize(image) do
# calls to OpenCV or whatever...
end
end
Options
You can pass a keyword list to use Component.Strategy.Pooled:
state:
valueThe default value for the initial state of all workers. Can be overridden (again for all workers) by passing a value to
initialize()
state_name:
atomThe default name for the state variable is (unimaginatively)
state
. Usestate_name
to override this. For example, the previous example named the stateoptions
, and inside therecognize
function your could writeoptions.algorithm
to look up the algorithm to use.name:
atomThe default name for the pool is the name of the module that defines it. Use
name:
to change this.pool: [
options]
Set options for the service pool. One or more of:
min: n
The minimum number of workers that should be active, and by extension the number of workers started when the pool is run. Default is 2.
max: n
The maximum number of workers. If all workers are busy and a new request arrives, a new worker will be started to handle it if the current worker count is less than
max
. Excess idle workers will be quietly killed off in the background. Default value is(min+1)*2
.
showcode:
booleanIf truthy, dump a representation of the generated code to STDOUT during compilation.
timeout:
integer or floatSpecify the timeout to be used when the client calls workers in the pool. If all workers are busy, and none becomes free in that time, an OTP exception is raised. An integer specifies the timeout in milliseconds, and a float in seconds (so 1.5 is the same as 1500).