Handler

Got a function that might get out of hand? Let the Handler run it in its own process and it will "take care of" the process if things get out of hand.

Usage

Handler.run(fn -> 1 + 1 end)
# => 2
Handler.run(fn -> :timer.sleep(61_000) end)
# => {:error, %Handler.Timeout{message: "process ran for longer than 60000ms"}}
Handler.run(fn -> load_tons_of_data_into_memory() end)
# => {:error, %Handler.OOM{message: "process tried to use more than 10485760 bytes of memory"}}
Handler.run(fn -> Process.exit(self(), :i_am_ded) end)
# => {:error, %Handler.ProcessExit{message: "process exited with :i_am_ded"}}

By default Handler puts a limit of 60sec and 10MB of heap space on the function you are running. You can change these limits by passing the optional second argument.

# Set 100MB heap limit and 2sec time limit
Handler.run(fn -> 1 + 1 end, max_heap_bytes: 100 * 1024 * 1024, max_ms: 2_000)
# => 2

Pool Limits

You can also use Handler to manage a shared pool of resources. If there are not enough resources available to run your function, you'll get back a {:reject, exception} value.

First start a supervised pool somewhere in your application tree.

config = %Handler.Pool{
  max_workers: 20,
  max_memory_bytes: 5 * 1024 * 1024 * 1024,
  name: :my_pool
}

children = [
  {Handler.Pool, config}
]

opts = [strategy: :one_for_one, name: Peg.Supervisor]
Supervisor.start_link(children, opts)

Now that you have a pool being supervised, you can kick off some where from other parts of your project.

Handler.Pool.run(:my_pool, fn -> danger_will_robinson() end, [max_heap_bytes: 1024 * 1024])