systemd,manual: set LimitNOFILE=65536
A typical OS imposed limit is 1024 open FD, which can bee too low when
there are hundreds of concurrent voice calls.
In systemd service file, set a super high limit of 65536.
In osmo-mgw's user manual, add section 'Configure limits' describing
this in detail.
Related: OS#6256
Related: osmo-bsc I26c4058484b11ff1d035a919bf88824c3af14e71
Change-Id: I46512517bc3b5bb90cac7643e7ac73afba398d36
diff --git a/contrib/systemd/osmo-mgw.service b/contrib/systemd/osmo-mgw.service
index b187e1a..03f40ff 100644
--- a/contrib/systemd/osmo-mgw.service
+++ b/contrib/systemd/osmo-mgw.service
@@ -5,6 +5,7 @@
[Service]
Type=simple
+LimitNOFILE=65536
StateDirectory=osmocom
WorkingDirectory=%S/osmocom
Restart=always
diff --git a/doc/manuals/chapters/running.adoc b/doc/manuals/chapters/running.adoc
index c178e31..e3bab4d 100644
--- a/doc/manuals/chapters/running.adoc
+++ b/doc/manuals/chapters/running.adoc
@@ -23,3 +23,20 @@
Disable colors for logging to stderr. This has mostly been
deprecated by VTY based logging configuration, see <<logging>>
for more information.
+
+
+=== Configure limits
+
+When servicing hundreds of media endpoints, it may be necessary to adjust the
+operating system's limit on open file descriptors for the osmo-mgw process. A
+typical default limit imposed by operating systems is 1024; this would be
+exceeded by, for example, about 256 active voice calls with 4 RTP/RTPC ports
+each, sockets for other interfaces not considered yet.
+
+It should be ok to set an OS limit on open file descriptors as high as 65536
+for osmo-mgw, which practically rules out failure from running out of file
+descriptors anywhere (<16,000 active calls).
+
+When using systemd, the file descriptor limit may be adjusted in the service
+file by the `LimitNOFILE` setting ("Number of Open FILE descriptors"). OsmoMGW
+ships a systemd service file with a high LimitNOFILE setting.