use pm2 for multi processing management

Dockerfile

 FROM node:8-slim
 
-RUN apt-get update && apt-get install -y wget --no-install-recommends \
-    && apt-get update \
-    && rm -rf /var/lib/apt/lists/* \
-    && apt-get purge --auto-remove -y curl \
-    && rm -rf /src/*.deb
-
 WORKDIR /usr/src/app/linstt-poc
 
 COPY package.json .
 COPY yarn.lock .
 
-RUN yarn install
+RUN npm install pm2 -g
+#RUN yarn install
 
 COPY . /usr/src/app/linstt-poc
 
 RUN /usr/src/app/linstt-poc/ssl/generateDockerCert.sh
 
-CMD ["yarn", "start"]
+#CMD ["yarn", "start"]
+CMD ["pm2-docker", "process.yml"]

process.yml

+apps:
+  - script : app.js
+    instances: 4
+    exec_mode: cluster
+    watch  : true
+    env    :
+      NODE_ENV: development
+    env_production:
+      NODE_ENV: production