Merge pull request #2041 from mfournier/contrib-docker

Add sample Dockerfile & LD_PRELOAD wrapper to contrib

diff --git a/contrib/README b/contrib/README
index 5f401f0..6e2ea19 100644 (file)
--- a/contrib/README
+++ b/contrib/README
@@ -49,6 +49,21 @@ should look something like this:
   datadir: "/var/lib/collectd/rrd/"
   libdir: "/usr/lib/collectd/"
 
+docker/
+-------
+Sample docker setup using an LD_PRELOAD wrapper to redirect system calls
+accessing /proc and /sys to prefixed bind-mounts inside the container.
+
+Drop your collectd configuration snippets in the
+contrib/docker/collectd.conf.d/ directory, and build an image including them:
+ $ docker build -t my_collectd ./contrib/docker/
+
+Then run it with the required bind-mounts:
+ $ docker run -it --rm \
+    -v /proc:/rootfs/proc:ro -v /sys:/rootfs/sys:ro \
+    --name collectd my_collectd
+ $ docker exec -it collectd collectdctl listval
+
 exec-munin.px
 -------------
   Script to be used with the exec-plugin (see collectd-exec(5) for details)

diff --git a/contrib/docker/50docker-apt-conf b/contrib/docker/50docker-apt-conf
new file mode 100644 (file)
index 0000000..3f898b3
--- /dev/null
+++ b/contrib/docker/50docker-apt-conf
@@ -0,0 +1,4 @@
+APT::Install-Recommends "0";
+APT::Install-Suggests "0";
+APT::Get::Assume-Yes "1";
+APT::Get::AutomaticRemove "1";

diff --git a/contrib/docker/Dockerfile b/contrib/docker/Dockerfile
new file mode 100644 (file)
index 0000000..a691f2e
--- /dev/null
+++ b/contrib/docker/Dockerfile
@@ -0,0 +1,24 @@
+FROM debian:stable
+
+ENV DEBIAN_FRONTEND noninteractive
+COPY 50docker-apt-conf /etc/apt/apt.conf.d/
+
+COPY rootfs_prefix/ /usr/src/rootfs_prefix/
+
+RUN apt-get update \
+ && apt-get upgrade \
+ && apt-get install \
+    collectd-core \
+    collectd-utils \
+    build-essential \
+ && make -C /usr/src/rootfs_prefix/ \
+ && apt-get --purge remove build-essential \
+ && apt-get clean \
+ && rm -rf /var/lib/apt/lists/*
+
+COPY collectd.conf /etc/collectd/collectd.conf
+COPY collectd.conf.d /etc/collectd/collectd.conf.d
+
+ENV LD_PRELOAD /usr/src/rootfs_prefix/rootfs_prefix.so
+
+CMD [ "/usr/sbin/collectd", "-f"]

diff --git a/contrib/docker/collectd.conf b/contrib/docker/collectd.conf
new file mode 100644 (file)
index 0000000..bbcd079
--- /dev/null
+++ b/contrib/docker/collectd.conf
@@ -0,0 +1,16 @@
+LoadPlugin logfile
+<Plugin logfile>
+       LogLevel "info"
+       File STDOUT
+       Timestamp true
+       PrintSeverity true
+</Plugin>
+
+LoadPlugin unixsock
+<Plugin unixsock>
+        SocketGroup "nogroup"
+</Plugin>
+
+<Include "/etc/collectd/collectd.conf.d">
+        Filter "*.conf"
+</Include>

diff --git a/contrib/docker/collectd.conf.d/sample.conf b/contrib/docker/collectd.conf.d/sample.conf
new file mode 100644 (file)
index 0000000..cbd7ce1
--- /dev/null
+++ b/contrib/docker/collectd.conf.d/sample.conf
@@ -0,0 +1,4 @@
+LoadPlugin cpu
+LoadPlugin memory
+LoadPlugin disk
+LoadPlugin df

diff --git a/contrib/docker/rootfs_prefix/Makefile b/contrib/docker/rootfs_prefix/Makefile
new file mode 100644 (file)
index 0000000..f26bebd
--- /dev/null
+++ b/contrib/docker/rootfs_prefix/Makefile
@@ -0,0 +1,2 @@
+rootfs_prefix.so: rootfs_prefix.c
+       $(CC) -Wall -Werror -fPIC -shared -o rootfs_prefix.so rootfs_prefix.c -ldl

diff --git a/contrib/docker/rootfs_prefix/rootfs_prefix.c b/contrib/docker/rootfs_prefix/rootfs_prefix.c
new file mode 100644 (file)
index 0000000..d41f062
--- /dev/null
+++ b/contrib/docker/rootfs_prefix/rootfs_prefix.c
@@ -0,0 +1,63 @@
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <error.h>
+#include <dlfcn.h>
+#include <string.h>
+#include <errno.h>
+#include <dirent.h>
+
+#define PREFIX "/rootfs"
+#define BUFSIZE 256
+
+const char *add_prefix(const char *orig, char *prefixed) {
+       int status;
+       int errno;
+
+       if ((strncmp(orig, "/proc", 5) == 0) ||
+               (strncmp(orig, "/sys", 4) == 0)) {
+
+               status = snprintf(prefixed, BUFSIZE, "%s%s", PREFIX, orig);
+               if ((unsigned int)status >= BUFSIZE) {
+                       error(status, ENAMETOOLONG, "'%s' got truncated when adding '%s' prefix: '%s'",
+                               orig, PREFIX, prefixed);
+                       return orig;
+               } else if (status < 1) {
+                       error(status, errno, "adding '%s' prefix to file path failed: '%s' -> '%s'",
+                               PREFIX, orig, prefixed);
+                       return orig;
+               } else {
+                       return (const char*) prefixed;
+               }
+
+       } else {
+               return orig;
+       }
+}
+
+FILE *fopen(const char *path, const char *mode) {
+       char filename[BUFSIZE] = "\0";
+
+       FILE *(*original_fopen)(const char*, const char*);
+       original_fopen = dlsym(RTLD_NEXT, "fopen");
+
+       return (*original_fopen)(add_prefix(path, filename), mode);
+}
+
+DIR *opendir(const char *name) {
+       char filename[BUFSIZE] = "\0";
+
+       DIR *(*original_opendir)(const char*);
+       original_opendir = dlsym(RTLD_NEXT, "opendir");
+
+       return (*original_opendir)(add_prefix(name, filename));
+}
+
+int *open(const char *pathname, int flags) {
+       char filename[BUFSIZE] = "\0";
+
+       int *(*original_open)(const char*, int);
+       original_open = dlsym(RTLD_NEXT, "open");
+
+       return (*original_open)(add_prefix(pathname, filename), flags);
+}