add entrypoint, if MCROUTER_CONFIG_PATH undefined then use the defaul…

…t one written to /etc/mcrouter/mcrouter.json

simplify entrypoint. bundle the default mcrouter.json with the Docker image, and now allow to point at an alternative location for the mcrouter json config file

mcrouter/scripts/docker/Dockerfile.ubuntu-packaged

@@ -1,10 +1,12 @@
 FROM ubuntu:xenial
 
-RUN DEBIAN_FRONTEND=noninteractive \
-    apt-get update && \
-    apt-get install -yq \
-        wget \
-        apt-transport-https
+RUN set -xe \
+        && buildDeps=" \
+                wget \
+                apt-transport-https" \
+        && DEBIAN_FRONTEND=noninteractive \
+           apt-get update \
+        && apt-get install -y $buildDeps 
 
 COPY ["container/ubuntu-packaged/", "/"]
 
@@ -17,3 +19,5 @@ RUN wget -qO- \
            apt-get install -yq mcrouter --no-install-recommends  \
         && apt-get purge -y --autoremove -o APT::AutoRemove::RecommendsImportant=false wget apt-transport-https \
         && apt-get autoremove && apt-get autoclean && rm -rf /var/lib/apt-lists/*
+
+ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]

mcrouter/scripts/docker/container/ubuntu-packaged/mcrouter.json

@@ -0,0 +1,10 @@
+{
+  "pools": {
+    "A": {
+      "servers": [
+        "127.0.0.1:5001"
+      ]
+    }
+  },
+  "route": "PoolRoute|A"
+}

mcrouter/scripts/docker/container/ubuntu-packaged/usr/local/bin/entrypoint.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+set -o errexit
+
+
+function run_mcrouter() {
+        local CONFIG_PATH=$1
+        mcrouter \
+        --config file:${CONFIG_PATH} \
+        -p "${MCROUTER_LISTEN_PORT:-5000}"
+}
+
+
+if [ -z "${MCROUTER_CONFIG_PATH}" ]; then
+  echo "MCROUTER_CONFIG_PATH undefined! Using bundled default ..."
+  export MCROUTER_CONFIG_PATH=/etc/mcrouter/mcrouter.json
+fi
+
+run_mcrouter "${MCROUTER_CONFIG_PATH}" "$@"