Lecture: DevOps - application
=============================


This repository contains the [application](./app/README.md) that should be used as *deployable workload* for the
[exercise](https://github.com/lucendio/lecture-devops-material/blob/master/assignments/exercise.md) implementation.  


### Getting started 

For more information regarding the app, please take a look into its [README](./app/README.md).

The `Makefile` in this directory can be seen as the main entry point for this repository. It's meant to locally run the
application and mess around with the source code in order to better understand how it works and to be able to tear it
apart if necessary.
Additionally, it documents various invocations that may help you adapting this application as *workload* for the exercise. 

**_Please note, that the `Makefile` is only meant to showcase steps that are usually needed to be taken in order to
automate the deployment lifecycle of such an application and code base.
It is NOT recommended to invoke `make` targets from the CI/CD, but rather to utilize platform-specific interfaces 
(e.g. `.gitlab-ci.yml`, `Jenkinsfile`, etc.), which may then invoke commands shown in the `make` target or in the `scripts`
 section of one of the `package.json` files._**


### Prerequisites

The following software must be installed and available in your `${PATH}`:

* `node` ([NodeJS](https://nodejs.org/en/download)): latest v14
* `npm` ([npm](https://www.npmjs.com/get-npm)): latest v6
* `mongod` ([MongoDB](https://docs.mongodb.com/manual/installation/)): latest v4.2

*NOTE: the application in this repository has not been tested with versions newer than that*

Choose for yourself how you want to install these dependencies. Perhaps you can use the package manager
available on your operating system, or maybe you prefer using container images. 


### Commands

The following commands are available from the root directory:


#### `make install`

* installs all dependencies via `npm` for *server* and *client*


#### `make build`

1. copies server source into some empty location
2. copies dependency manifest (`package*`) into the same location right next to the server source
3. installs server dependencies
4. builds client code (requires client dependencies to be installed already) and puts it next to the server source into   


#### `make test`

*NOTE: requires a MongoDB service already ro be running (see `MONGODB_URL` in target on where it's assumed to be running)*

* runs client & server tests in [CI mode](https://jestjs.io/docs/en/cli.html#--ci) (exits regardless of the test outcome; closed tty)


#### `make dev-test-client`

*NOTE: only demonstrates a use case during local development and are not meant to run in any other context (e.g. automation)*

* runs client tests in a local development mode


#### `make dev-start-db`

*NOTE: only demonstrates a use case during local development and are not meant to run in any other context (e.g. automation)*

* starts a local MongoDB service


#### `make dev-start-app`

*NOTE (1): only demonstrates a use case during local development and are not meant to run in any other context (e.g. automation)*
*NOTE (2): it might be desired to first start a database service (e.g. `make dev-start-db`)*

* builds client
* starts server in development mode with development configuration


#### `make run`

*NOTE (1): showcases plain executable invocation with a shared parent process. Press `Ctrl+C` to send termination signal.*
*NOTE (2): in reality those two services would always be invoked independently and __never__ share a parent process!*

* starts a MongoDB service as a child process with an explicit inline-configuration
* starts the application service with variables being set in a way so that they are only *visible* to that invocation
  (as an alternative to the configuration file `app/server/dev.env` that is used to set environment variables)
* blocks terminal and keeps it as output device until termination signal is being send.


#### `make clean`

* removes all `node_modules` dependencies that have been installed locally via `npm`
* removes other temporarily created folder in `.local`