[GitHub] flimzy commented on a change in pull request #169: Improve docs on increasing max file handle limits

[gi...@git.apache.org]

flimzy commented on a change in pull request #169: Improve docs on increasing max file handle limits
URL: https://github.com/apache/couchdb-documentation/pull/169#discussion_r142001611
 
 

 ##########
 File path: src/maintenance/performance.rst
 ##########
 @@ -120,20 +120,44 @@ explanation`_.
 .. _this tip for a possible workaround: http://erlang.org/pipermail/erlang-questions/2011-December/063119.html
 .. _this thread for a deeper explanation: http://erlang.org/pipermail/erlang-questions/2011-October/061971.html
 
-PAM and ulimit
---------------
+Maximum open file descriptors (ulimit)
+--------------------------------------
 
-Finally, most \*nix operating systems impose various resource limits on every
-process. If your system is set up to use the Pluggable Authentication Modules
-(`PAM`_) system, increasing this limit is straightforward. For example,
-creating a file named ``/etc/security/limits.d/100-couchdb.conf`` with the
-following contents will ensure that CouchDB can open enough file descriptors
-to service your increased maximum open databases and Erlang ports::
+Most \*nix operating systems impose various resource limits on every process.
+The method of increasing these limits varies, depending on your init system and
+particular os release. The default value for many OSes is 1024 or 4096. On a
+system with many databases or many views, CouchDB can very rapidly hit this
+limit.
+
+If your system is set up to use the Pluggable Authentication Modules (`PAM`_)
+system (as is the cate with nearly all modern Linuxes), increasing this limit
+is straightforward. For example, creating a file named
+``/etc/security/limits.d/100-couchdb.conf`` with the following contents will
+ensure that CouchDB can open up to 4096 file descriptors at once::
 
     #<domain>    <type>    <item>    <value>
     couchdb      hard      nofile    4096
     couchdb      soft      nofile    4096
 
+You may also have to edit the ``/etc/pam.d/common-session`` and
+``/etc/pam.d/common-session-noninteractive`` files to add the line::
+
+    session required pam_limits.so
+
+if it is not already present.
+
+For systemd-based Linuxes (such as CentOS/RHEL 7, Ubuntu 16.04+, Debian jessie
 
 Review comment:
   Maybe include the Debian version number, not just codename?
 
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