Add healthcheck endpoint, set default ENV in Dockerfile

Dockerfile

@@ -1,7 +1,18 @@
 FROM nginx:alpine
 
+ENV SERVER_NAME='localhost' \
+    SERVER_REDIRECT_PATH='$request_uri' \
+    SERVER_REDIRECT_SCHEME='$redirect_scheme' \
+    SERVER_ACCESS_LOG='/dev/stdout' \
+    SERVER_ERROR_LOG='/dev/stderr' \
+    SERVER_HEALTHCHECK_ENABLED=0 \
+    SERVER_HEALTHCHECK_RESPONSE_CODE=200 \
+    SERVER_HEALTHCHECK_RESPONSE_BODY='alive' \
+    SERVER_HEALTHCHECK_PATH='healthcheck'
+
 ADD run.sh /run.sh
 ADD default.conf /etc/nginx/conf.d/default.conf
+ADD healthcheck.conf /etc/nginx/includes/healthcheck.conf
 
 RUN chmod +x /run.sh
 

README.md

@@ -33,6 +33,15 @@ A very simple container to redirect HTTP traffic to another server, based on `ng
    - if not set /dev/stdout is used
 - `SERVER_ERROR_LOG` - optionally define the location where nginx will write its error log
    - if not set /dev/stderr is used
+- `SERVER_HEALTHCHECK_ENABLED` - optionally enable a static healthcheck endpoint by setting `SERVER_HEALTHCHECK_ENABLED=1`
+   - useful for deploying to Kubernetes or similar infrastructure where readiness needs to be confirmed and monitored
+   - disabled by default
+- `SERVER_HEALTHCHECK_PATH` - optionally override the location of the healthcheck endpoint
+   - defaults to `/healthcheck`
+- `SERVER_HEALTHCHECK_RESPONSE_CODE` - optionally override the status code of the healthcheck endpoint response
+   - defaults to `200`
+- `SERVER_HEALTHCHECK_RESPONSE_BODY` - optionally override the body of the healthcheck endpoint response
+   - defaults to `alive`
 
 See also `docker-compose.yml` file.
 

default.conf

@@ -7,16 +7,18 @@ server {
     listen       80;
     server_name  ${SERVER_NAME};
 
-    # cherry picked from https://github.com/schmunk42/docker-nginx-redirect/pull/8
-    if ($request_method = POST) {
-        return ${SERVER_REDIRECT_POST_CODE} ${SERVER_REDIRECT_SCHEME}://${SERVER_REDIRECT}${SERVER_REDIRECT_PATH};
-    }
+    location / {
+        # cherry picked from https://github.com/schmunk42/docker-nginx-redirect/pull/8
+        if ($request_method = POST) {
+            return ${SERVER_REDIRECT_POST_CODE} ${SERVER_REDIRECT_SCHEME}://${SERVER_REDIRECT}${SERVER_REDIRECT_PATH};
+        }
 
-    if ($request_method ~ PUT|PATCH|DELETE) {
-        return ${SERVER_REDIRECT_PUT_PATCH_DELETE_CODE} ${SERVER_REDIRECT_SCHEME}://${SERVER_REDIRECT}${SERVER_REDIRECT_PATH};
-    }
+        if ($request_method ~ PUT|PATCH|DELETE) {
+            return ${SERVER_REDIRECT_PUT_PATCH_DELETE_CODE} ${SERVER_REDIRECT_SCHEME}://${SERVER_REDIRECT}${SERVER_REDIRECT_PATH};
+        }
 
-    return ${SERVER_REDIRECT_CODE} ${SERVER_REDIRECT_SCHEME}://${SERVER_REDIRECT}${SERVER_REDIRECT_PATH};
+        return ${SERVER_REDIRECT_CODE} ${SERVER_REDIRECT_SCHEME}://${SERVER_REDIRECT}${SERVER_REDIRECT_PATH};
+    }
 
     # redirect server error pages to the static page /50x.html
     #
@@ -25,4 +27,5 @@ server {
         root   /usr/share/nginx/html;
     }
 
+    ${HEALTHCHECK_LOCATION_BLOCK}
 }

docker-compose.yml

@@ -26,3 +26,5 @@ to:
     # optionally define the location for the nginx error log
     # if not set /dev/stderr is used
     #- SERVER_ERROR_LOG=/dev/null
+    # optionally enable the healthcheck endpoint
+    #- SERVER_HEALTHCHECK_ENABLED=1

healthcheck.conf

@@ -0,0 +1,5 @@
+# return status code 200 on healthcheck route
+location = /${SERVER_HEALTHCHECK_PATH} {
+    return ${SERVER_HEALTHCHECK_RESPONSE_CODE} ${SERVER_HEALTHCHECK_RESPONSE_BODY};
+    add_header Content-Type text/plain;
+}

run.sh

@@ -5,11 +5,6 @@ if [ ! -n "$SERVER_REDIRECT" ] ; then
     exit 1
 fi
 
-# set server name from optional ENV var
-if [ ! -n "$SERVER_NAME" ] ; then
-    SERVER_NAME='localhost'
-fi
-
 # set redirect code from optional ENV var
 # allowed Status Codes are: 301, 302, 303, 307, 308
 expr match "$SERVER_REDIRECT_CODE" '30[12378]$' > /dev/null || SERVER_REDIRECT_CODE='301'
@@ -20,26 +15,6 @@ expr match "$SERVER_REDIRECT_POST_CODE" '30[12378]$' > /dev/null || SERVER_REDIR
 # set redirect code from optional ENV var for PUT, PATCH and DELETE requests
 expr match "$SERVER_REDIRECT_PUT_PATCH_DELETE_CODE" '30[12378]$' > /dev/null || SERVER_REDIRECT_PUT_PATCH_DELETE_CODE=$SERVER_REDIRECT_CODE
 
-# set redirect path from optional ENV var
-if [ ! -n "$SERVER_REDIRECT_PATH" ] ; then
-    SERVER_REDIRECT_PATH='$request_uri'
-fi
-
-# set redirect scheme from optional ENV var
-if [ ! -n "$SERVER_REDIRECT_SCHEME" ] ; then
-    SERVER_REDIRECT_SCHEME='$redirect_scheme'
-fi
-
-# set access log location from optional ENV var
-if [ ! -n "$SERVER_ACCESS_LOG" ] ; then
-    SERVER_ACCESS_LOG='/dev/stdout'
-fi
-
-# set error log location from optional ENV var
-if [ ! -n "$SERVER_ERROR_LOG" ] ; then
-    SERVER_ERROR_LOG='/dev/stderr'
-fi
-
 sed -i "s|\${SERVER_REDIRECT}|${SERVER_REDIRECT}|" /etc/nginx/conf.d/default.conf
 sed -i "s|\${SERVER_NAME}|${SERVER_NAME}|" /etc/nginx/conf.d/default.conf
 sed -i "s|\${SERVER_REDIRECT_CODE}|${SERVER_REDIRECT_CODE}|" /etc/nginx/conf.d/default.conf
@@ -48,6 +23,17 @@ sed -i "s|\${SERVER_REDIRECT_PUT_PATCH_DELETE_CODE}|${SERVER_REDIRECT_PUT_PATCH_
 sed -i "s|\${SERVER_REDIRECT_PATH}|${SERVER_REDIRECT_PATH}|" /etc/nginx/conf.d/default.conf
 sed -i "s|\${SERVER_REDIRECT_SCHEME}|${SERVER_REDIRECT_SCHEME}|" /etc/nginx/conf.d/default.conf
 
+# optionally add healthcheck endpoint
+if [ $SERVER_HEALTHCHECK_ENABLED = 1 ]; then
+    sed -i "s|\${HEALTHCHECK_LOCATION_BLOCK}|include includes/healthcheck.conf;|" /etc/nginx/conf.d/default.conf
+
+    sed -i "s|\${SERVER_HEALTHCHECK_PATH}|${SERVER_HEALTHCHECK_PATH}|" /etc/nginx/includes/healthcheck.conf
+    sed -i "s|\${SERVER_HEALTHCHECK_RESPONSE_CODE}|${SERVER_HEALTHCHECK_RESPONSE_CODE}|" /etc/nginx/includes/healthcheck.conf
+    sed -i "s|\${SERVER_HEALTHCHECK_RESPONSE_BODY}|${SERVER_HEALTHCHECK_RESPONSE_BODY}|" /etc/nginx/includes/healthcheck.conf
+else
+    sed -i "s|\${HEALTHCHECK_LOCATION_BLOCK}||" /etc/nginx/conf.d/default.conf
+fi
+
 ln -sfT "$SERVER_ACCESS_LOG" /var/log/nginx/access.log
 ln -sfT "$SERVER_ERROR_LOG" /var/log/nginx/error.log