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workers_manager.ex
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workers_manager.ex
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defmodule Verk.WorkersManager do
@moduledoc """
A WorkersManager assign jobs to workers from a pool (handled by poolboy) monitoring the job.
It interacts with the related QueueManager to request jobs and to schedule jobs to be retried
"""
use GenServer
require Logger
alias Verk.Events
@default_timeout 1000
defmodule State do
defstruct [:queue_name, :pool_name, :queue_manager_name, :pool_size, :monitors]
end
@doc """
Returns the atom that represents the WorkersManager of the `queue`
"""
@spec name(binary | atom) :: atom
def name(queue) do
String.to_atom("#{queue}.workers_manager")
end
@doc false
def start_link(name, queue_name, queue_manager_name, pool_name, pool_size) do
GenServer.start_link(__MODULE__, [name, queue_name, queue_manager_name, pool_name, pool_size], name: name)
end
@doc """
List running jobs
Example:
[%{ process: #PID<0.186.0>, job: %Verk.Job{...}, started_at: %Timex.DateTime{...}} ]
"""
@spec running_jobs(binary | atom) :: Map.t
def running_jobs(queue, limit \\ 100) do
match_spec = [{{:"$1", :_, :"$2", :_, :"$3"}, [], [{{:"$1", :"$2", :"$3"}}]}]
case :ets.select(name(queue), match_spec, limit) do
:'$end_of_table' -> []
{ jobs, _continuation } ->
for { pid, job, started_at } <- jobs do
%{ process: pid, job: job, started_at: started_at }
end
end
end
@process_info_keys [:current_stacktrace, :initial_call, :reductions, :status]
@doc """
List information about the process that is currently running a `job_id`
"""
@spec inspect_worker(binary | atom, binary) :: { :ok, Map.t } | { :error, :not_found }
def inspect_worker(queue, job_id) do
case :ets.match(name(queue), { :'$1', job_id, :'$2', :_, :'$3' }) do
[] -> { :error, :not_found }
[[pid, job, started_at]] ->
info = Process.info(pid, @process_info_keys)
if info do
{ :ok, %{ process: pid, job: job, started_at: started_at, info: info } }
else
{ :error, :not_found }
end
end
end
@doc """
Create a table to monitor workers saving data about the assigned queue/pool
"""
def init([name, queue_name, queue_manager_name, pool_name, size]) do
monitors = :ets.new(name, [:named_table, read_concurrency: true])
state = %State{ queue_name: queue_name,
queue_manager_name: queue_manager_name,
pool_name: pool_name,
pool_size: size,
monitors: monitors }
send self, :enqueue_inprogress
Logger.info "Workers Manager started for queue #{queue_name}"
{ :ok, state }
end
@doc false
def handle_info(:enqueue_inprogress, state) do
:ok = Verk.QueueManager.enqueue_inprogress(state.queue_manager_name)
{ :noreply, state, 0 }
end
def handle_info(:timeout, state) do
free_workers = free_workers(state.monitors, state.pool_size)
if free_workers != 0 do
case Verk.QueueManager.dequeue(state.queue_manager_name, free_workers) do
jobs when is_list(jobs) ->
for job <- jobs, do: Verk.Job.decode!(job) |> start_job(state)
reason ->
Logger.error("Failed to fetch a job. Reason: #{inspect reason}")
end
{ :noreply, state, @default_timeout }
else
{ :noreply, state }
end
end
# Possible reasons to receive a :DOWN message:
# * :normal - The worker finished the job but :done message did not arrive
# * :failed - The worker failed the job but :failed message did not arrive
# * {reason, stack } - The worker crashed and it has a stacktrace
# * reason - The worker crashed and it doesn't have have a stacktrace
def handle_info({ :DOWN, mref, _, worker, :normal }, state) do
case :ets.lookup(state.monitors, worker) do
[{ ^worker, _job_id, job, ^mref, start_time}] ->
succeed(job, start_time, worker, mref, state.monitors, state.queue_manager_name)
_ -> Logger.warn "Worker finished but such worker was not monitored #{inspect(worker)}"
end
{ :noreply, state, 0 }
end
def handle_info({ :DOWN, mref, _, worker, :failed }, state) do
handle_down!(mref, worker, :failed, [], state)
{ :noreply, state, 0 }
end
def handle_info({ :DOWN, mref, _, worker, { reason, stack } }, state) do
handle_down!(mref, worker, reason, stack, state)
{ :noreply, state, 0 }
end
def handle_info({ :DOWN, mref, _, worker, reason }, state) do
handle_down!(mref, worker, reason, [], state)
{ :noreply, state, 0 }
end
defp handle_down!(mref, worker, reason, stack, state) do
Logger.debug "Worker got down, reason: #{inspect reason}, #{inspect([mref, worker])}"
case :ets.lookup(state.monitors, worker) do
[{ ^worker, _job_id, job, ^mref, start_time}] ->
exception = RuntimeError.exception(inspect(reason))
fail(job, start_time, worker, mref, state.monitors, state.queue_manager_name, exception, stack)
error -> Logger.warn "Worker got down but it was not found, error: #{inspect error}"
end
end
@doc false
def handle_cast({ :done, worker, job_id }, state) do
case :ets.lookup(state.monitors, worker) do
[{ ^worker, ^job_id, job, mref, start_time}] ->
succeed(job, start_time, worker, mref, state.monitors, state.queue_manager_name)
_ -> Logger.warn "#{job_id} finished but no worker was monitored"
end
{ :noreply, state, 0 }
end
def handle_cast({ :failed, worker, job_id, exception, stacktrace }, state) do
Logger.debug "Job failed reason: #{inspect exception}"
case :ets.lookup(state.monitors, worker) do
[{ ^worker, ^job_id, job, mref, start_time}] ->
fail(job, start_time, worker, mref, state.monitors, state.queue_manager_name, exception, stacktrace)
_ -> Logger.warn "#{job_id} failed but no worker was monitored"
end
{ :noreply, state, 0 }
end
defp succeed(job, start_time, worker, mref, monitors, queue_manager_name) do
Verk.QueueManager.ack(queue_manager_name, job)
Verk.Log.done(job, start_time, worker)
demonitor!(monitors, worker, mref)
notify!(%Events.JobFinished{ job: job, finished_at: Timex.Date.now })
end
defp fail(job, start_time, worker, mref, monitors, queue_manager_name, exception, stacktrace) do
Verk.Log.fail(job, start_time, worker)
demonitor!(monitors, worker, mref)
:ok = Verk.QueueManager.retry(queue_manager_name, job, exception, stacktrace)
:ok = Verk.QueueManager.ack(queue_manager_name, job)
notify!(%Events.JobFailed{ job: job, failed_at: Timex.Date.now, exception: exception, stacktrace: stacktrace })
end
defp start_job(job = %Verk.Job{ jid: job_id, class: module, args: args }, state) do
case :poolboy.checkout(state.pool_name, false) do
worker when is_pid(worker)->
monitor!(state.monitors, worker, job)
Verk.Log.start(job, worker)
ask_to_perform(worker, job_id, module, args)
notify!(%Events.JobStarted{ job: job, started_at: Timex.Date.now })
end
end
defp demonitor!(monitors, worker, mref) do
true = Process.demonitor(mref, [:flush])
true = :ets.delete(monitors, worker)
end
defp monitor!(monitors, worker, job = %Verk.Job{ jid: job_id }) do
mref = Process.monitor(worker)
now = Timex.Date.now
true = :ets.insert(monitors, { worker, job_id, job, mref, now })
end
@doc false
def terminate(reason, _state) do
Logger.error "Manager terminating, reason: #{inspect reason}"
:ok
end
defp notify!(event) do
:ok = GenEvent.ack_notify(Verk.EventManager, event)
end
defp free_workers(monitors, size) do
size - :ets.info(monitors, :size)
end
defp ask_to_perform(worker, job_id, module, args) do
Verk.Worker.perform_async(worker, self, module, args, job_id)
end
end