VirtualExecutor implements a light‐weight view onto existing Executor.

Synopsis

Declared in <folly/executors/VirtualExecutor.h>

class VirtualExecutor
    : public DefaultKeepAliveExecutor

Description

Multiple VirtualExecutors can be backed by a single Executor.

VirtualExecutor's destructor blocks until all tasks scheduled through it are complete. Executor's destructor also blocks until all VirtualExecutors backed by it are released.

Base Classes

Name

Description

DefaultKeepAliveExecutor

An Executor accepts units of work with add(), which should be threadsafe.

Types

Name

Description

WeakRefExecutor

Marker base for the weak‐reference executor wrappers.

Type Aliases

Name

Description

KeepAlive

Alias for ExecutorKeepAlive, a safe pointer to an Executor.

Member Functions

Name

Description

VirtualExecutor [constructor]

Constructors

~VirtualExecutor [destructor] [virtual]

Destroys the executor, blocking until all scheduled tasks complete.

operator= [deleted]

Copy assignment operator (deleted).

add [virtual]

Schedules a function to run on the backing executor.

addWithPriority [virtual]

Schedules a function to run on the backing executor at the given priority.

getNumPriorities [virtual]

Returns the number of priority levels supported by the backing executor.

weakRef

Returns a weak keep‐alive to this executor.

Static Member Functions

Name

Description

getKeepAliveToken

getKeepAliveToken overloads

getWeakRef

Returns a weak keep‐alive to executor that does not extend its lifetime.

invokeCatchingExns

Invokes f, logging and swallowing any exception it throws.

Static Data Members

Name

Description

HI_PRI

Highest schedulable priority.

LO_PRI

Lowest schedulable priority.

MID_PRI

Medium (default) schedulable priority.

Protected Member Functions

Name

Description

joinAndResetKeepAlive

Joins the keep‐alive, then reinstates a fresh one so the executor is reusable.

joinKeepAlive

Releases this executor's own keep‐alive and waits for all others to drain.

keepAliveAcquire [virtual]

Acquire a keep alive token. Should return false if keep‐alive mechanism is not supported.

keepAliveRelease [virtual]

Release a keep alive token previously acquired by keepAliveAcquire(). Will never be called if keepAliveAcquire() returns false.

Protected Static Member Functions

Name

Description

isKeepAliveDummy

Returns true if the KeepAlive is constructed from an executor that does not support the keep alive ref‐counting functionality

keepAliveAcquire

Acquires a keep‐alive reference on executor.

keepAliveRelease

Releases a keep‐alive reference on executor.

makeKeepAlive

Makes a counted (non‐dummy, non‐alias) keep‐alive referring to executor.

Non-Member Functions

Name

Description

async_tracing::logFutureVia

Trace hook invoked when a Future is rescheduled onto an executor.

async_tracing::logGetGlobalCPUExecutor

Trace hook invoked when the global CPU executor is retrieved.

async_tracing::logGetImmutableCPUExecutor

Trace hook invoked when the immutable CPU executor is retrieved.

async_tracing::logSemiFutureVia

Trace hook invoked when a SemiFuture is rescheduled onto an executor.

async_tracing::logSetGlobalCPUExecutor

Trace hook invoked when the global CPU executor is set.

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