NodeJS Production Deployment Best Practice

Question

I'm looking for ways in which to deploy some web services into production in a consistent and timely manner.

I'm currently implementing a deployment pipeline that will end with a manual deployment action of a specific version of the software to a number of virtual machines provisioned by Ansible. The idea is to provision x number of instances using version A whilst already having y number of instances running version B. Then image and flick the traffic over. The same mechanism should allow me to scale new vms in a set using the image I already made.

I have considered the following options but was wondering if theres something I'm overlooking:

1. TGZ

The CI environment would build a tarball from a project that has passed unit tests and integration tests. Optionally depednencies would be bundled (removing the need to run npm install on the production machine and relying on network connectivity to public or private npm repository).

My main issue here is that any dependencies that depend on system libraries would be build on a different machine (albeit the same image). I don't like this.

1. NPM

The CI environment would publish to a private NPM repository and the Ansible deployment script would check out a specific version after provisioning. Again this suffers from a reliance on external services being available when you want to deploy. I dont like this.

1. Git

Any system dependent modules become globally installed as part of provisioning and all other dependencies are checked into the repository. This gives me the flexibility of being able to do differential deployments whereby just the deltas are pushed and the application daemon can be restarted automatically by the process manager almost instantly. Dependencies are then absolutely locked down.

This would mean that theres no need to spinning up new VM unless to scale. Deployments can be pushed straight to all active instances.

Answer 1

First and foremost, regardless of the deployment method, you need to make sure you don't drop requests while deploying new code. One simple approach is removing the node from a load balancer prior to switchover. Before doing so, you may also want to try and evaluate if there are pending requests, open connections, or anything else negatively impacted by premature termination. Or perhaps something like the up module.

Most people would not recommend source controlling your modules. It seems that a .tgz with your node_modules already filled in from an npm install while utilizing a bundledDependencies declaration in your package.json might cover all your concerns. With this approach, an npm install on your nodes will not download and install everything again. Though, it will rebuild node-gyp implementations which may cover your system library concern.

You can also make use of git tags to more easily keep track of versions with specific dependencies and payloads. Manually deploying the code may get tedious, you may want to consider automating the routine while iterating over x amount of known server entries in a database from an interface. docker.io may be of interest.