memcached: Add a Memcached image

The 10MB of overhead memory were estimated from this output in a
running memcached container:

  # ps aux
  USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
  root         1  0.0  0.0  20300  2124 ?        S    20:57   0:00 /bin/bash
  memcach+   184  0.0  0.0 323124  1112 ?        Ssl  20:58   0:00 /usr/bin/memcached -d -p 11211 -U 11211 -m 128 -c 1024 -u
  root       224  0.0  0.0  25064   440 ?        S    20:58   0:00 supervising syslog-ng
  root       225  0.3  0.0 124708  3620 ?        Ssl  20:58   0:00 /usr/sbin/syslog-ng --persist-file /var/lib/syslog-ng/sysl
  root       263  0.0  0.0  18632   804 ?        Ss   20:58   0:00 /usr/sbin/cron
  root       300  0.0  0.0  15440  1148 ?        R+   20:58   0:00 ps aux

Less Bash and ps, that's 1112 + 3620 + 804 = 5.5MB of resident memory,
so 10MB seemed like a safe buffer.

diff --git a/README.md b/README.md
index 77f65169f020b708783c858b5480a4b97aaadbd1..f11c5cb7f11e392d9b980485479e83970d4d3e14 100644 (file)
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@ The dependency graph is:
         `-- gentoo-en-us  (adds locale)
             `-- gentoo-syslog  (adds syslog-ng and associates)
                 |-- buildbot  (adds a Buildbot master and slave)
+                |-- memcached  (adds Memcached)
                 |-- nginx  (adds Nginx)
                 |   `-- kibana  (adds Kibana)
                 |-- postgresql  (adds PostgreSQL)

diff --git a/build.sh b/build.sh
index 55dcbb3ad7baa66b94318548fcfaa94926d86cbc..d4ad779adbb27385249c3009dbb95a5586d5a76e 100755 (executable)
--- a/build.sh
+++ b/build.sh
@@ -44,6 +44,7 @@ REPOS="${REPOS:-
        gentoo-java
        buildbot
        elasticsearch
+       memcached
        nginx
        kibana
        postgresql

diff --git a/memcached/Dockerfile.template b/memcached/Dockerfile.template
new file mode 100644 (file)
index 0000000..4522fcb
--- /dev/null
+++ b/memcached/Dockerfile.template
@@ -0,0 +1,36 @@
+# Copyright (C) 2013 W. Trevor King <wking@tremily.us>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+FROM NAMESPACE/gentoo-syslog:TAG
+MAINTAINER A. U. Thor <author@example.com>
+#VOLUME ["PORTAGE:/usr/portage:ro", "PORTAGE/distfiles:/usr/portage/distfiles:rw"]
+RUN emerge -v net-misc/memcached
+RUN eselect news read new
+RUN rc-update add memcached default
+
+# Container networking happens automatically
+RUN sed -i 's/need net$/use net/' /etc/init.d/*
+
+CMD sed -i "s/^MEMUSAGE=.*/MEMUSAGE=\"${MEMUSAGE}\"/" /etc/conf.d/memcached && rc default && tail -F /var/log/messages
+EXPOSE 11211

diff --git a/memcached/README.md b/memcached/README.md
new file mode 100644 (file)
index 0000000..7b27cec
--- /dev/null
+++ b/memcached/README.md
@@ -0,0 +1,22 @@
+Run this [Memcached][] image with:
+
+    $ docker run -d -name memcached-0 -m 128m -e MEMUSAGE=118 wking/memcached
+
+The 10MB difference between container memory and the
+Memcached-specific `MEMUSAGE` limit gives some overhead for the
+`memcached` process itself and auxilliary processes to ensure that
+`MEMUSAGE` stops us before we hit “out of memory” errors.
+
+Then [link][linking] to it from your client container:
+
+    $ docker run -link memcached-0:memcached your-client
+
+Inside your client, use the `MEMCACHED_PORT` environment variable
+(which should be something like `tcp://172.17.0.8:11211`) to configure
+your client's Memcached connection.  Linking like this *does not*
+expose the port on your host interface (that's what `-p` is for).  You
+can spin up as many Memcached containers as you like (`memcached-1`,
+`memcached-2`, …), and link to any of them from any client container.
+
+[Memcached]: http://memcached.org/
+[linking]: http://docs.docker.io/en/latest/use/port_redirection/#linking-a-container