qmi.core.thread

Implementation of the QMI_Thread class.

Functions

check_in_main_thread()

Check that this function is called in the main thread.

Classes

QMI_Thread()

A QMI_Thread is an abstract base class for all threads used within QMI.

qmi.core.thread.check_in_main_thread() → None

Check that this function is called in the main thread.

Raises:

QMI_WrongThreadException – If the function is called from any thread other than the main thread.

class qmi.core.thread.QMI_Thread

A QMI_Thread is an abstract base class for all threads used within QMI.

The added value compared to Python’s threading.Thread class is that it provides a way to request thread shutdown (via the shutdown method).

QMI_Thread instances are initialized to be Python ‘daemon’ threads. This is done to prevent a deadlock when the Python process terminates; the Python interpreter effectively performs a ‘join()’ on non-daemon threads at shutdown, prior even to running atexit handlers.

Unfortunately, the shutdown process cannot be reliably hooked. By making the QMI_Threads daemonic, we ensure that we get to the execution of the at-exit handlers, which will properly tear down any remaining QMI_Contexts; This will shut down all active QMI_Threads in an orderly way.

The QMI_Thread class currently has three specializations:

• _EventDrivenThread in qmi.core.messaging;

• _RpcThread in qmi.core.rpc;

• _TaskThread in qmi.core.task.

Important

QMI_Threads are part of the core QMI machinery. They should not be instantiated directly by QMI users. QMI users should use QMI_Tasks instead.

run() → None

The run() method must be overridden by derived classes.

shutdown() → None

Command the thread to terminate orderly, as soon as possible.

After calling shutdown(), the usual thing to do is call join() to join up with the thread.

The shutdown() function can also be called during Python cleanup, see the documentation of the join() method above.

property daemon

A boolean value indicating whether this thread is a daemon thread.

This must be set before start() is called, otherwise RuntimeError is raised. Its initial value is inherited from the creating thread; the main thread is not a daemon thread and therefore all threads created in the main thread default to daemon = False.

The entire Python program exits when only daemon threads are left.

getName()

Return a string used for identification purposes only.

This method is deprecated, use the name attribute instead.

property ident

Thread identifier of this thread or None if it has not been started.

This is a nonzero integer. See the get_ident() function. Thread identifiers may be recycled when a thread exits and another thread is created. The identifier is available even after the thread has exited.

isDaemon()

Return whether this thread is a daemon.

This method is deprecated, use the daemon attribute instead.

is_alive()

Return whether the thread is alive.

This method returns True just before the run() method starts until just after the run() method terminates. See also the module function enumerate().

join(timeout=None)

Wait until the thread terminates.

This blocks the calling thread until the thread whose join() method is called terminates – either normally or through an unhandled exception or until the optional timeout occurs.

When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions thereof). As join() always returns None, you must call is_alive() after join() to decide whether a timeout happened – if the thread is still alive, the join() call timed out.

When the timeout argument is not present or None, the operation will block until the thread terminates.

A thread can be join()ed many times.

join() raises a RuntimeError if an attempt is made to join the current thread as that would cause a deadlock. It is also an error to join() a thread before it has been started and attempts to do so raises the same exception.

property name

A string used for identification purposes only.

It has no semantics. Multiple threads may be given the same name. The initial name is set by the constructor.

property native_id

Native integral thread ID of this thread, or None if it has not been started.

This is a non-negative integer. See the get_native_id() function. This represents the Thread ID as reported by the kernel.

setDaemon(daemonic)

Set whether this thread is a daemon.

This method is deprecated, use the .daemon property instead.

setName(name)

Set the name string for this thread.

This method is deprecated, use the name attribute instead.

start()

Start the thread’s activity.

It must be called at most once per thread object. It arranges for the object’s run() method to be invoked in a separate thread of control.

This method will raise a RuntimeError if called more than once on the same thread object.