5.2 Starting the Server in Single-Process Mode
When
developing new code, it is often
helpful to run the server in single-process mode. This is most often
used to find bugs in code that seems to work fine when the server
starts, but refuses to work correctly after a few requests have been
made. It also helps to uncover problems related to collisions between
module names.
Running in single-process mode inhibits the server from automatically
running in the background. This allows it to more easily be run under
the control of a debugger. The -X switch is used
to enable this mode:
panic% /home/httpd/httpd_perl/bin/httpd_perl -X
With the -X switch, the server runs in the
foreground of the shell, so it can be
killed
by typing Ctrl-C. You can run it in the background by appending an
ampersand:
panic% /home/httpd/httpd_perl/bin/httpd_perl -X &
Note that in -X (single-process) mode, the
server will run very slowly when fetching images. Because only one
request can be served at a time, requests for images normally done in
parallel by the browser will now be serialized, making the page
display slower.
|
If Netscape is being used as the test browser while
the server is running in single-process mode, the HTTP
protocol's
KeepAlive feature gets in the way. Netscape
tries to open multiple connections and keep them all open, as this
should be faster for browsing. But because there is only one server
process listening, each connection has to time out before the next
one succeeds. Turn off KeepAlive in
httpd.conf to avoid this effect while testing.
Assuming you use width and
height image size parameters in your HTML files,
Netscape will be able to render the page without the images, so you
can press the browser's Stop button after a few
seconds to speed up page display. It's always good
practice to specify width and
height image size parameters.
|
Also note that when running with -X, the control
messages that the parent server normally writes to
error_log (e.g., "server
started", "server
stopped", etc.) will not be written anywhere.
httpd -X causes the server to handle all
requests itself without forking any children, so there is no
controlling parent to write the status messages.
Usually Ctrl-C is used to kill a server running in single process
mode, but Ctrl-C doesn't constitute a clean
shutdown. httpd.pid doesn't get
removed, so the next time the server is started, the message:
[warn] pid file /home/httpd/httpd_perl/logs/httpd.pid
overwritten -- Unclean shutdown of previous Apache run?
will appear in error_log. You can ignore this
warning; there's nothing to worry about.
|
