This Multi-Processing Module (MPM) is the default for the
Windows NT operating systems. It uses a single control process
which launches a single child process which in turn creates
threads to handle requests
Capacity is configured using the
ThreadsPerChild directive,
which sets the maximum number of concurrent client connections.
By default, this MPM uses advanced Windows APIs for accepting
new client connections. In some configurations, third-party products
may interfere with this implementation, with the following messages
written to the web server log:
Child: Encountered too many AcceptEx faults accepting client connections.
winnt_mpm: falling back to 'AcceptFilter none'.
The MPM falls back to a safer implementation, but some client requests
were not processed correctly. In order to avoid this error, use
AcceptFilter with accept filter
none.
AcceptFilter http none
AcceptFilter https none
In Apache httpd 2.0 and 2.2,
Win32DisableAcceptEx was used for this purpose.
The WinNT MPM differs from the Unix MPMs such as worker and event
in several areas:
- When a child process is exiting due to shutdown, restart, or
MaxConnectionsPerChild,
active requests in the exiting process have
TimeOut seconds to finish before
processing is aborted. Alternate types of restart and shutdown are not
implemented.
- New child processes read the configuration files instead of
inheriting the configuration from the parent. The behavior will
be the same as on Unix if the child process is created at startup
or restart, but if a child process is created because the prior
one crashed or reached
MaxConnectionsPerChild,
any pending changes to the configuration will become active in the
child at that point, and the parent and child will be using a
different configuration. If planned configuration changes have been
partially implemented and the current configuration cannot be
parsed, the replacement child process cannot start up and the server
will halt. Because of this behavior, configuration files should not
be changed until the time of a server restart.
- The
monitor and fatal_exception hooks
are not currently implemented.
- AcceptFilter is implemented in the MPM
and has a different type of control over handling of new connections.
(Refer to the AcceptFilter
documentation for details.)