Dockerfile: adding a worker CMD entrypoint

Dockerfile

@@ -1,15 +1,20 @@
 FROM ubuntu:14.04.2
 MAINTAINER Bryan Latten <latten@adobe.com>
 
+# Use in multi-phase builds, when an init process requests for the container to gracefully exit, so that it may be committed
 ENV SIGNAL_BUILD_STOP 99
 
+# Used with alternative CMD (worker.sh), leverages supervisor to maintain long-running processes
+ENV CONTAINER_ROLE=web
+
 # Install pre-reqs, security updates
 RUN apt-get update && \
     apt-get upgrade -yq && \
     apt-get -yq install \
         openssl=1.0.1f-1ubuntu2.15 \
         ca-certificates=20141019ubuntu0.14.04.1 \
         software-properties-common \
+        supervisor \
         nano
 
 # Install latest nginx-stable

README.md

@@ -17,3 +17,10 @@ To inject things into the runtime process, add shell scripts (ending in .sh) int
 
 - If script terminates with a non-zero exit code, container will stop, terminating with the script's exit code, unless...
 - If script terminates with exit code of $SIGNAL_BUILD_STOP (99), this will signal the container to stop cleanly. This can be used for multi-stage builds that can be committed
+
+
+### Long-running processes (workers)
+
+`docker run {image_id} /worker.sh 3 /bin/binary -parameters -that -binary -receives`
+
+Runs 3 copies of `/bin/binary` that receives any arguments as parameters

container/root/init.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+RUN_SCRIPTS=/run.d
+STATUS=0
+
+# Run shell scripts (ending in .sh) in run.d directory
+
+# When .sh run scripts fail (exit non-zero), container run will fail
+# NOTE: if a .sh script exits with 99, this is a stop signal, container must exit cleanly
+
+for file in $RUN_SCRIPTS/*.sh; do
+
+  echo "[init] executing ${file}"
+
+  /bin/bash $file
+
+  STATUS=$?  # Captures exit code from script that was run
+
+  if [[ $STATUS == $SIGNAL_BUILD_STOP ]]
+  then
+    echo "[init] exit signalled - ${file}"
+    exit $STATUS
+  fi
+
+  if [[ $STATUS != 0 ]]
+  then
+    echo "[init] failed executing - ${file}"
+    exit $STATUS
+  fi
+
+done

container/root/run.d/10-nginx.sh

@@ -5,13 +5,13 @@ CONFIG_SERVER=/etc/nginx/nginx.conf
 echo '[nginx] setting sensible defaults'
 
 # Configure nginx to use as many workers as there are cores for the running container
+# NOTE: worker_processes is only replaced when *not* set to auto
 sed -i "s/worker_processes [0-9]\+/worker_processes $(nproc)/" $CONFIG_SERVER
 sed -i "s/worker_connections [0-9]\+/worker_connections 1024/" $CONFIG_SERVER
 
 # Uncomment prod-level tokens (none)
 sed -i "s/\#\ server_tokens/server_tokens/" $CONFIG_SERVER
 
-
 echo '[nginx] piping logs to STDOUT'
 
 # Set access/error log, and use them as a placeholder for injecting log_format key

container/root/run.sh

@@ -1,33 +1,23 @@
 #!/bin/bash
-RUN_SCRIPTS=/run.d
-STATUS=0
 
-# Run shell scripts (ending in .sh) in run.d directory
+# Begin startup sequence
+/init.sh
 
-# When .sh run scripts fail (exit non-zero), container run will fail
-# NOTE: if a .sh script exits with 99, this is our stop signal, container will exit cleanly
+STATUS=$?  # Captures exit code from script that was run
 
-for file in $RUN_SCRIPTS/*.sh; do
+# TODO this exit code detection is also present in worker.sh, needs to be combined
+if [[ $STATUS == $SIGNAL_BUILD_STOP ]]
+then
+  echo "[run] container exit requested"
+  exit # Exit cleanly
+fi
 
-  echo "[run.d] executing ${file}"
-
-  /bin/bash $file
-
-  STATUS=$?  # Captures exit code from script that was run
-
-  if [[ $STATUS == 99 ]]
-  then
-    echo "[run.d] exit signalled - ${file}"
-    exit # Exit cleanly
-  fi
-
-  if [[ $STATUS != 0 ]]
-  then
-    echo "[run.d] failed executing - ${file}"
-    exit $STATUS
-  fi
-
-done
+if [[ $STATUS != 0 ]]
+then
+  echo "[run] failed to init"
+  exit $STATUS
+fi
 
+# Primary command - starting webserver
 echo "[nginx] start (foreground)"
 exec /usr/sbin/nginx -g "daemon off;"

container/root/worker.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+
+# Entrypoint for utilizing as a worker pool instead of a web server
+# Based on configuration, can run multiple instances of a single worker process
+
+SUPERVISOR_CONF=/etc/supervisor/conf.d/worker.conf
+
+# Signal to init processes to avoid any webserver startup
+export CONTAINER_ROLE='worker'
+
+# Begin startup sequence
+/init.sh
+
+STATUS=$?  # Captures exit code from script that was run
+
+# TODO this exit code detection is also present in run.sh, needs to be combined
+if [[ $STATUS == $SIGNAL_BUILD_STOP ]]
+then
+  echo "[worker] container exit requested"
+  exit # Exit cleanly
+fi
+
+if [[ $STATUS != 0 ]]
+then
+  echo "[worker] failed to init"
+  exit $STATUS
+fi
+
+
+WORKER_QUANTITY=$1
+
+# Rebuild worker command as properly escaped parameters from shifted input args
+# @see http://stackoverflow.com/questions/7535677/bash-passing-paths-with-spaces-as-parameters
+shift
+WORKER_COMMAND="$@"
+
+if [ -z "$WORKER_COMMAND" ]
+then
+  echo "[worker] command is required, exiting"
+  exit 1
+fi
+
+echo "[worker] command: '${WORKER_COMMAND}' quantity: ${WORKER_QUANTITY}"
+
+echo "\
+[program:worker]
+command=${WORKER_COMMAND}
+process_name=%(program_name)s%(process_num)s
+numprocs=${WORKER_QUANTITY}
+autorestart=true
+redirect_stderr=true
+stdout_logfile=/dev/stdout" > $SUPERVISOR_CONF
+
+echo "[worker] entering supervisor"
+
+# Primary command - starting supervisor after writing with worker program config file
+exec /usr/bin/supervisord -c /etc/supervisor/supervisord.conf --nodaemon