A descriptor, also commonly called a file handle is
+an object that a program uses to read or write an open file, or open
+network socket, or a variety of other devices. It is represented
+by an integer, and you may be familiar with stdin,
+stdout, and stderr which are descriptors 0,
+1, and 2 respectively.
+Apache needs a descriptor for each log file, plus one for each
+network socket that it listens on, plus a handful of others. Libraries
+that Apache uses may also require descriptors. Normal programs don't
+open up many descriptors at all, and so there are some latent problems
+that you may experience should you start running Apache with many
+descriptors (i.e. with many virtual hosts).
+
+
The operating system enforces a limit on the number of descriptors +that a program can have open at a time. There are typically three limits +involved here. One is a kernel limitation, depending on your operating +system you will either be able to tune the number of descriptors available +to higher numbers (this is frequently called FD_SETSIZE). Or you +may be stuck with a (relatively) low amount. The second limit is called +the hard resource limit, and it is sometimes set by root in an +obscure operating system file, but frequently is the same as the kernel +limit. The third limit is called the soft +resource limit. The soft limit is always less than or equal to +the hard limit. For example, the hard limit may be 1024, but the soft +limit only 64. Any user can raise their soft limit up to the hard limit. +Root can raise the hard limit up to the system maximum limit. The soft +limit is the actual limit that is used when enforcing the maximum number +of files a process can have open. + +
To summarize: + +
+ #open files <= soft limit <= hard limit <= kernel limit +
You control the hard and soft limits using the limit (csh)
+or ulimit (sh) directives. See the respective man pages
+for more information. For example you can probably use
+ulimit -n unlimited to raise your soft limit up to the
+hard limit. You should include this command in a shell script which
+starts your webserver.
+
+
Unfortunately, it's not always this simple. As mentioned above, +you will probably run into some system limitations that will need to be +worked around somehow. Work was done in version 1.2.1 to improve the +situation somewhat. Here is a partial list of systems and workarounds +(assuming you are using 1.2.1 or later): + +
-DFD_SETSIZE=nnn to
+ EXTRA_CFLAGS (where nnn is the number of descriptors
+ you wish to support, keep it less than the hard limit). But it
+ will run into trouble if more than approximately 240 Listen
+ directives are used. This may be cured by rebuilding your kernel
+ with a higher FD_SETSIZE.
+
+
+ FD_SETSIZE and rebuild. But the extra
+ Listen limitation doesn't exist.
+
+
+ -DHIGH_SLACK_LINE=256 added to
+ EXTRA_CFLAGS. You will be limited to approximately
+ 240 error logs if you do this.
+
+
+ In addition to the problems described above there are problems with +many libraries that Apache uses. The most common example is the bind +DNS resolver library that is used by pretty much every unix, which +fails if it ends up with a descriptor above 256. We suspect there +are other libraries that similar limitations. So the code as of 1.2.1 +takes a defensive stance and tries to save descriptors less than 16 +for use while processing each request. This is called the low +slack line. + +
Note that this shouldn't waste descriptors. If you really are pushing +the limits and Apache can't get a descriptor above 16 when it wants +it, it will settle for one below 16. + +
In extreme situations you may want to lower the low slack line,
+but you shouldn't ever need to. For example, lowering it can
+increase the limits 240 described above under Solaris and BSDI 2.0.
+But you'll play a delicate balancing game with the descriptors needed
+to serve a request. Should you want to play this game, the compile
+time parameter is LOW_SLACK_LINE and there's a tiny
+bit of documentation in the header file httpd.h.
+
+
Finally, if you suspect that all this slack stuff is causing you
+problems, you can disable it. Add -DNO_SLACK to
+EXTRA_CFLAGS and rebuild. But please report it to
+our Bug
+Report Page so that
+we can investigate.
+
+
+
+
diff --git a/APACHE_1_2_X/htdocs/manual/new_features_1_3.html b/APACHE_1_2_X/htdocs/manual/new_features_1_3.html
new file mode 100644
index 00000000000..855cc382d67
--- /dev/null
+++ b/APACHE_1_2_X/htdocs/manual/new_features_1_3.html
@@ -0,0 +1,48 @@
+
+
New features with this release, as extensions of the Apache +functionality. Because the core code has changed so +significantly, there are certain liberties that earlier versions of +Apache (and the NCSA daemon) took that recent Apache versions are +pickier about - please check the compatibility notes if you have any +problems.
+In addition to a number of bug fixes and internal performance +enhancements, Apache +1.2 has the following specific new user features:
+ +