Complete support for dynamic container names (#231)

* Allow setting NGINX_DOCKER_GEN_CONTAINER from a label
* Find labeled cid in runtime instead of startup time

Author: Helder Correia

README.md

@@ -30,10 +30,10 @@ $ docker run -d -p 80:80 -p 443:443 \
     -v /etc/nginx/vhost.d \
     -v /usr/share/nginx/html \
     -v /var/run/docker.sock:/tmp/docker.sock:ro \
-    --label com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true \
+    --label com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy \
     jwilder/nginx-proxy
 ```
-The "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true" label is needed so that the letsencrypt container knows which nginx proxy container to use.
+The "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy" label is needed so that the letsencrypt container knows which nginx proxy container to use.
 
 * Second start this container:
 ```bash
@@ -63,7 +63,7 @@ To run nginx proxy as a separate container you'll need:
 curl https://raw.githubusercontent.com/jwilder/nginx-proxy/master/nginx.tmpl > /path/to/nginx.tmpl
 ```
 
-2) Set the `NGINX_DOCKER_GEN_CONTAINER` environment variable to the name or id of the docker-gen container.
+2) Use the `com.github.jrcs.letsencrypt_nginx_proxy_companion.docker_gen` label on the docker-gen container, or explicitly set the `NGINX_DOCKER_GEN_CONTAINER` environment variable to the name or id of that container.
 
 Examples:
 
@@ -75,7 +75,7 @@ $ docker run -d -p 80:80 -p 443:443 \
     -v /etc/nginx/vhost.d \
     -v /usr/share/nginx/html \
     -v /path/to/certs:/etc/nginx/certs:ro \
-    --label com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true \
+    --label com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy \
     nginx
 ```
 
@@ -86,23 +86,25 @@ $ docker run -d \
     --volumes-from nginx \
     -v /path/to/nginx.tmpl:/etc/docker-gen/templates/nginx.tmpl:ro \
     -v /var/run/docker.sock:/tmp/docker.sock:ro \
+    --label com.github.jrcs.letsencrypt_nginx_proxy_companion.docker_gen \
     jwilder/docker-gen \
     -notify-sighup nginx -watch -wait 5s:30s /etc/docker-gen/templates/nginx.tmpl /etc/nginx/conf.d/default.conf
 ```
 
-* Then start this container (NGINX_DOCKER_GEN_CONTAINER variable must contain the docker-gen container name or id):
+* Then start this container:
 ```bash
 $ docker run -d \
     --name nginx-letsencrypt \
-    -e "NGINX_DOCKER_GEN_CONTAINER=nginx-gen" \
     --volumes-from nginx \
     -v /path/to/certs:/etc/nginx/certs:rw \
     -v /var/run/docker.sock:/var/run/docker.sock:ro \
     jrcs/letsencrypt-nginx-proxy-companion
 ```
-Then start any containers to be proxied as described previously.
 
-* If for some reason you can't use the docker --volumes-from option, you can specify the name or id of the nginx container with `NGINX_PROXY_CONTAINER` variable.
+* Then start any containers to be proxied as described previously.
+
+Note: If the docker-gen container name is static and you want to explicitly set it, use `-e NGINX_DOCKER_GEN_CONTAINER=nginx-gen`. The same thing is true with the nginx container (`-e NGINX_PROXY_CONTAINER=nginx`).
+
 
 #### Let's Encrypt
 
@@ -161,7 +163,9 @@ $ docker run -d \
 
 * `REUSE_KEY` - Set it to `true` to make simp_le reuse previously generated private key instead of creating a new one on certificate renewal. Recommended if you intend to use HPKP.
 
-* The "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true" label - set this label on the nginx-proxy container to tell the docker-letsencrypt-nginx-proxy-companion container to use it as the proxy.
+* The "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy" label - set this label on the nginx-proxy container to tell the docker-letsencrypt-nginx-proxy-companion container to use it as the proxy.
+
+* The "com.github.jrcs.letsencrypt_nginx_proxy_companion.docker_gen" label - set this label on the docker-gen container to tell the docker-letsencrypt-nginx-proxy-companion container to use it as the docker-gen when it's split from nginx (separate containers).
 
 * `ACME_TOS_HASH` - Let´s you pass an alternative TOS hash to simp_le, to support other CA´s ACME implentation.
 
@@ -172,5 +176,5 @@ If you want other examples how to use this container, look at:
 * [Evert Ramos's Examples](https://github.com/evertramos/docker-compose-letsencrypt-nginx-proxy-companion) - using docker-compose version '3'
 * [Karl Fathi's Examples](https://github.com/fatk/docker-letsencrypt-nginx-proxy-companion-examples)
 * [More examples from Karl](https://github.com/pixelfordinner/pixelcloud-docker-apps/tree/master/nginx-proxy)
-* [George Ilyes' Examples](https://github.com/gilyes/docker-nginx-letsencrypt-sample) 
+* [George Ilyes' Examples](https://github.com/gilyes/docker-nginx-letsencrypt-sample)
 * [Dmitry's simple docker-compose example](https://github.com/dmitrym0/simple-lets-encrypt-docker-compose-sample)

app/entrypoint.sh

@@ -33,12 +33,7 @@ function get_nginx_proxy_cid {
             break
         fi
     done
-    # Check if any container has been labelled as the nginx proxy container.
-    local labeled_cid=$(docker_api "/containers/json" | jq -r '.[] | select( .Labels["com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy"] == "true")|.Id')
-    if [[ ! -z "${labeled_cid:-}" ]]; then
-        export NGINX_PROXY_CONTAINER=$labeled_cid
-    fi
-    if [[ -z "${NGINX_PROXY_CONTAINER:-}" ]]; then
+    if [[ -z "$(nginx_proxy_container)" ]]; then
         echo "Error: can't get nginx-proxy container id !" >&2
         echo "Check that you use the --volumes-from option to mount volumes from the nginx-proxy or label the nginx proxy container to use with 'com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true'." >&2
         exit 1
@@ -79,7 +74,7 @@ source /app/functions.sh
 
 if [[ "$*" == "/bin/bash /app/start.sh" ]]; then
     check_docker_socket
-    if [[ -z "${NGINX_DOCKER_GEN_CONTAINER:-}" ]]; then
+    if [[ -z "$(docker_gen_container)" ]]; then
         [[ -z "${NGINX_PROXY_CONTAINER:-}" ]] && get_nginx_proxy_cid
     fi
     check_writable_directory '/etc/nginx/certs'

app/functions.sh

@@ -67,21 +67,37 @@ function docker_kill {
     docker_api "/containers/$id/kill?signal=$signal" "POST"
 }
 
+function labeled_cid {
+    docker_api "/containers/json" | jq -r '.[] | select(.Labels["'$1'"])|.Id'
+}
+
+function docker_gen_container {
+    echo ${NGINX_DOCKER_GEN_CONTAINER:-$(labeled_cid com.github.jrcs.letsencrypt_nginx_proxy_companion.docker_gen)}
+}
+
+function nginx_proxy_container {
+    echo ${NGINX_PROXY_CONTAINER:-$(labeled_cid com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy)}
+}
+
 ## Nginx
 reload_nginx() {
-    if [[ -n "${NGINX_DOCKER_GEN_CONTAINER:-}" ]]; then
+    local _docker_gen_container=$(docker_gen_container)
+    local _nginx_proxy_container=$(nginx_proxy_container)
+
+    if [[ -n "${_docker_gen_container:-}" ]]; then
         # Using docker-gen and nginx in separate container
-        echo "Reloading nginx docker-gen (using separate container ${NGINX_DOCKER_GEN_CONTAINER})..."
-        docker_kill "$NGINX_DOCKER_GEN_CONTAINER" SIGHUP
-        if [[ -n "${NGINX_PROXY_CONTAINER:-}" ]]; then
+        echo "Reloading nginx docker-gen (using separate container ${_docker_gen_container})..."
+        docker_kill "${_docker_gen_container}" SIGHUP
+
+        if [[ -n "${_nginx_proxy_container:-}" ]]; then
             # Reloading nginx in case only certificates had been renewed
-            echo "Reloading nginx (using separate container ${NGINX_PROXY_CONTAINER})..."
-            docker_kill "$NGINX_PROXY_CONTAINER" SIGHUP
+            echo "Reloading nginx (using separate container ${_nginx_proxy_container})..."
+            docker_kill "${_nginx_proxy_container}" SIGHUP
         fi
     else
-        if [[ -n "${NGINX_PROXY_CONTAINER:-}" ]]; then
-            echo "Reloading nginx proxy..."
-            docker_exec "$NGINX_PROXY_CONTAINER" \
+        if [[ -n "${_nginx_proxy_container:-}" ]]; then
+            echo "Reloading nginx proxy (${_nginx_proxy_container})..."
+            docker_exec "${_nginx_proxy_container}" \
                         '[ "sh", "-c", "/usr/local/bin/docker-gen -only-exposed /app/nginx.tmpl /etc/nginx/conf.d/default.conf; /usr/sbin/nginx -s reload" ]'
         fi
     fi