Class: ThreadPool
Defined in: core/src/threads/ThreadPool.ts:73
The ThreadPool class provides an interface for managing a pool of execution threads that can be used for parallel
code execution. ThreadPool is a wrapper to the worker_threads API to add support for multiple Worker instances.
By default, the pool will create n workers corresponding to the number of CPUs (physical + virtual) on the system.
There are two ways to start worker threads with the pool.
The first way is to set the entry option when calling the start() function. This will create a instance of the
worker_threads APIs Worker class with the specified file as the entry point. Note that this file must be of
type JavaScript (.js extension) as the underlying system does not support loading TypeScript. If the args option
is set, the value will be passed in as the workerData to the entry file.
The second way to start a worker thread is by setting the worker argument when calling the start() function. The
specified worker file must contain a default export. The default export must be a class definition which
extends the ThreadWorker abstract class interface. The file can be either JavaScript or TypeScript. When using
this method the start() function will return only when all worker instances in each thread of the pool has
successfully returned from its start() function. When the args option is set, the value(s) will be passed in to
the constructor on instantiation by the thread executor.
When the restartOnExit option is specified, the pool will automatically recreate and start a worker thread on
the exit event.
This class exposes worker messages via the on() callback handler function. Registering a callback handler via
on() will propogate all messages from all underlying threads in the pool.
Constructors
Constructor
new ThreadPool(
max?,logger?):ThreadPool
Defined in: core/src/threads/ThreadPool.ts:117
Creates a new ThreadPool instance with the specified defaults.
Parameters
max?
number = 0
The maximum number of threads to create. Default is os.cpus().length.
logger?
any
The Winston logger instance to forward all worker thread logs to.
Returns
ThreadPool
Properties
workers
readonlyworkers:Worker[]
Defined in: core/src/threads/ThreadPool.ts:89
The list of active worker threads.
Accessors
max
Get Signature
get max():
number
Defined in: core/src/threads/ThreadPool.ts:100
The maximum number of threads that can be created by the pool.
Returns
number
size
Get Signature
get size():
number
Defined in: core/src/threads/ThreadPool.ts:107
The number of active threads in the pool.
Returns
number
Methods
on()
on(
type,func):void
Defined in: core/src/threads/ThreadPool.ts:418
Registers a new callback function to be notified when the given event type is fired.
Parameters
type
string
The event type to be notified of. Possible values are: error, exit and message.
func
The callback function to register.
Returns
void
send()
send(
msg):void
Defined in: core/src/threads/ThreadPool.ts:431
Sends the provided message to the next available worker thread. Messages are sent in a round-robin order.
Parameters
msg
any
The message to send the next available worker thread.
Returns
void
sendAll()
sendAll(
msg):void
Defined in: core/src/threads/ThreadPool.ts:456
Sends the provided message to all worker threads in the pool. Workers that have already exited (e.g.
crashed with no restartOnExit) are silently skipped rather than throwing, so one dead worker doesn't
prevent delivery to every worker after it in the array.
Parameters
msg
any
The message to send to all workers.
Returns
void
sendTo()
sendTo(
id,msg):void
Defined in: core/src/threads/ThreadPool.ts:469
Sends the provided message to the worker thread with the specified id.
Parameters
id
number
The id of the thread to send the message to.
msg
any
The message to send the next available worker thread.
Returns
void
start()
start(
options?,num?):Promise<void>
Defined in: core/src/threads/ThreadPool.ts:238
Initializes the thread pool with the initial worker threads and begins execution.
Parameters
options?
The options to use when creating the worker thread.
num?
number = ...
The number of initial threads to create, cannot be greater than max. Default is max.
Returns
Promise<void>
stop()
stop():
Promise<void>
Defined in: core/src/threads/ThreadPool.ts:371
Stops all running thread executions. Each worker is given ThreadPool.STOP_GRACE_PERIOD_MS to gracefully
finish its own stop() and exit on its own before being force-terminated.
Returns
Promise<void>