NodeJS

Using nodemon

NodeJS applications can be restarted when a source file changes using tools like nodemon. Let’s look at an example microservice, with the following directory service:

.
├── Dockerfile
├── k8s.yaml
└── src
    ├── package.json
    └── server.js

A typical local development workflow would be to execute nodemon server.js inside the src directory. nodemon will start watching the files and runs the web-server. Whenever you edit server.js or any other js files, nodemon will reload the server with the latest code.

We can replicate the same workflow on a Hasura cluster also. Let’s see how we can modify the typical Dockerfile for the above microservice to include nodemon and enable live reloading.

# Step 1: Pulls a simple ubuntu image with node 8 installed in it
FROM node:8

# Step 2: install nodemon
RUN npm install -g nodemon

# Step 3: Make a new directory called "src"
RUN mkdir /src

# Step 4: Copy the package.json file from your local directory and paste it inside the container, inside the src directory
COPY src/package.json /src/package.json

# Step 5: cd into the src directory and run npm install to install application dependencies
RUN cd /src && npm install

# Step 6: Add all source code into the src directory from your local src directory
ADD src /src

# Step 7: Set src as our current work directory
WORKDIR /src

# Step 8: run the nodemon command
CMD ["nodemon", "server.js"]

As per step 6, we are copying the src directory from the local system into the /src of the container. Also, in step 8, we are starting a server using nodemon. Once you commit and push this dockerfile, the microservice is running nodemon and will restart for any changes to server.js and related files.

Next step is to start the sync command which continuously copies the required files to the container as and when they change. As we mentioned earlier, the dockerfile indicates that the local src directory is copied over as /src. So, we execute the following command (assuming the microservice name is api):

$ hasura microservice sync api microservices/api/src:/src

Keep the command running in a terminal. Open the microservice in a browser, using another terminal window:

$ hasura microservice open api

Make some changes to server.js and save. Voila! You can see that it changes live in the browser tab.

« previous | next »
Want to contribute or report missing content? Check out the github repo for docs.
Powered by Sphinx. Copyright © 2019 Hasura.