tornado.process — Utilities for multiple processes¶

Utilities for working with multiple processes, including both forkingthe server into multiple processes and managing subprocesses.

exception tornado.process.CalledProcessError[源代码]

An alias for subprocess.CalledProcessError.
tornado.process.cpucount()[源代码]

Returns the number of processors on this machine.
tornado.process.fork_processes(_num_processes, max_restarts=100)[源代码]

Starts multiple worker processes.

If numprocesses is None or <= 0, we detect the number of coresavailable on this machine and fork that number of childprocesses. If num_processes is given and > 0, we fork thatspecific number of sub-processes.

Since we use processes and not threads, there is no shared memorybetween any server code.

Note that multiple processes are not compatible with the autoreloadmodule (or the autoreload=True option to tornado.web.Applicationwhich defaults to True when debug=True).When using multiple processes, no IOLoops can be created orreferenced until after the call to fork_processes.

In each child process, fork_processes returns its _task id, anumber between 0 and numprocesses. Processes that exitabnormally (due to a signal or non-zero exit status) are restartedwith the same id (up to max_restarts times). In the parentprocess, fork_processes returns None if all child processeshave exited normally, but will otherwise only exit by throwing anexception.
tornado.process.task_id()[源代码]

Returns the current task id, if any.

Returns None if this process was not created by fork_processes.
_class tornado.process.Subprocess(*args, **kwargs)[源代码]

Wraps subprocess.Popen with IOStream support.

The constructor is the same as subprocess.Popen with the followingadditions:

- stdin, stdout, and stderr may have the valuetornado.process.Subprocess.STREAM, which will make the correspondingattribute of the resulting Subprocess a PipeIOStream.
- A new keyword argument ioloop may be used to pass in an IOLoop.
The Subprocess.STREAM option and the set_exit_callback andwait_for_exit methods do not work on Windows. There istherefore no reason to use this class instead ofsubprocess.Popen on that platform.


在 4.1 版更改: The io_loop argument is deprecated.

set_exit_callback(_callback)[源代码]

Runs callback when this process exits.

The callback takes one argument, the return code of the process.

This method uses a SIGCHLD handler, which is a global settingand may conflict if you have other libraries trying to handle thesame signal. If you are using more than one IOLoop it maybe necessary to call Subprocess.initialize first to designateone IOLoop to run the signal handlers.

In many cases a close callback on the stdout or stderr streamscan be used as an alternative to an exit callback if thesignal handler is causing a problem.
waitfor_exit(_raise_error=True)[源代码]

Returns a Future which resolves when the process exits.

Usage:



  1. ret = yield proc.waitfor_exit()




This is a coroutine-friendly alternative to set_exit_callback(and a replacement for the blocking subprocess.Popen.wait).

By default, raises subprocess.CalledProcessError if the processhas a non-zero exit status. Use wait_for_exit(raise_error=False)to suppress this behavior and return the exit status without raising.


4.2 新版功能.

_classmethod initialize(io_loop=None)[源代码]

Initializes the SIGCHLD handler.

The signal handler is run on an IOLoop to avoid locking issues.Note that the IOLoop used for signal handling need not be thesame one used by individual Subprocess objects (as long as theIOLoops are each running in separate threads).


在 4.1 版更改: The ioloop argument is deprecated.

_classmethod uninitialize()[源代码]

Removes the SIGCHLD handler.

原文:

https://tornado-zh-cn.readthedocs.io/zh_CN/latest/process.html