Class: Concurrent::FixedThreadPool
- Inherits:
-
ThreadPoolExecutor
- Object
- ThreadPoolExecutor
- Concurrent::FixedThreadPool
- Defined in:
- lib/concurrent-ruby/concurrent/executor/fixed_thread_pool.rb
Overview
Failure to properly shutdown a thread pool can lead to unpredictable results. Please read Shutting Down Thread Pools for more information.
A thread pool that reuses a fixed number of threads operating off an unbounded queue.
At any point, at most num_threads
will be active processing tasks. When all threads are busy new
tasks #post
to the thread pool are enqueued until a thread becomes available.
Should a thread crash for any reason the thread will immediately be removed
from the pool and replaced.
The API and behavior of this class are based on Java's FixedThreadPool
Thread Pool Options
Thread pools support several configuration options:
idletime
: The number of seconds that a thread may be idle before being reclaimed.name
: The name of the executor (optional). Printed in the executor's#to_s
output and a<name>-worker-<id>
name is given to its threads if supported by used Ruby implementation.<id>
is uniq for each thread.max_queue
: The maximum number of tasks that may be waiting in the work queue at any one time. When the queue size reachesmax_queue
and no new threads can be created, subsequent tasks will be rejected in accordance with the configuredfallback_policy
.auto_terminate
: When true (default), the threads started will be marked as daemon.fallback_policy
: The policy defining how rejected tasks are handled.
Three fallback policies are supported:
:abort
: Raise aRejectedExecutionError
exception and discard the task.:discard
: Discard the task and return false.:caller_runs
: Execute the task on the calling thread.
Shutting Down Thread Pools
Killing a thread pool while tasks are still being processed, either by calling
the #kill
method or at application exit, will have unpredictable results. There
is no way for the thread pool to know what resources are being used by the
in-progress tasks. When those tasks are killed the impact on those resources
cannot be predicted. The best practice is to explicitly shutdown all thread
pools using the provided methods:
- Call
#shutdown
to initiate an orderly termination of all in-progress tasks - Call
#wait_for_termination
with an appropriate timeout interval an allow the orderly shutdown to complete - Call
#kill
only when the thread pool fails to shutdown in the allotted time
On some runtime platforms (most notably the JVM) the application will not
exit until all thread pools have been shutdown. To prevent applications from
"hanging" on exit, all threads can be marked as daemon according to the
:auto_terminate
option.
pool1 = Concurrent::FixedThreadPool.new(5) # threads will be marked as daemon
pool2 = Concurrent::FixedThreadPool.new(5, auto_terminate: false) # mark threads as non-daemon
Instance Method Summary collapse
-
#initialize(num_threads, opts = {}) ⇒ FixedThreadPool
constructor
Create a new thread pool.
Constructor Details
#initialize(num_threads, opts = {}) ⇒ FixedThreadPool
Create a new thread pool.
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# File 'lib/concurrent-ruby/concurrent/executor/fixed_thread_pool.rb', line 194 def initialize(num_threads, opts = {}) raise ArgumentError.new('number of threads must be greater than zero') if num_threads.to_i < 1 defaults = { max_queue: DEFAULT_MAX_QUEUE_SIZE, idletime: DEFAULT_THREAD_IDLETIMEOUT } overrides = { min_threads: num_threads, max_threads: num_threads } super(defaults.merge(opts).merge(overrides)) end |