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https://github.com/bruno-garcia/hub-like-docker-compose

Wiring up through docker-compose a test environment for the Hub project
https://github.com/bruno-garcia/hub-like-docker-compose

angular-cli angular4 asp-net-core docker docker-compose mongodb mssql redis

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Wiring up through docker-compose a test environment for the Hub project

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# PoC for a docker-compose containing all dependencies of the Hub project



The objective of this repo is to serve as a PoC for a set of Dockerfile/compose that could aid 

in bootstrapping an integration environment for automated tests for a non public project called Hub.

For this PoC, a simplified version of this project will be recreated. The goal is simply to reach 

all dependencies. In other words: it's all dummy code.



The repo is composed of an Angular 4 SPA, backed by a web API written 

in C# and .NET Core 2.0. This API backend has 3 external dependencies: MongoDB, Redis and yet 

another web API called Envoy. Envoy is backed by a SQL Server database.



        +--------------------+

        | SPA                |

        | Angular CLI 1.3.0  |

        | Docker: nginx      |

        +----------+---------+

                   |

                   |                  +---------------------+

    +--------------v--------------+-->+ Redis               |

    | API                         |   | Docker: redis:alpine|

    | .NET Core 2.0 Preview 2     |   +---------------------+

    | Docker: dotnet:2.0-runtime  |   +---------------------+

    +--------------+--------------+-->+ MongoDB             |

                   |                  | Docker: mongo:3.4.7 |

                   |                  +---------------------+

    +--------------v--------------+

    | Envoy                       |

    | .NET Core 1.1               |

    | Docker: dotnet:1.1-runtime  |

    +--------------+--------------+

                   |

                   |

    +--------------v--------------+

    | SQL Server                  |

    | mssql on Linux              |

    | Docker: mssql-server-linux  |

    +-----------------------------+



### A few findings while settings this up:



#### StackExchange.Redis on .NET Core 1.1:

The Api project could not be done with .NET Core 1.1 due to [StackExchange.Redis not supporting DNS 

resolution on Linux](https://github.com/StackExchange/StackExchange.Redis/issues/463).

That's an issue due to the container linking by name. It will fail with:



`This platform does not support connecting sockets to DNS endpoints via the instance Connect and ConnectAsync methods, due to the potential for a host name to map to multiple IP addresses and sockets becoming invalid for use after a failed connect attempt. Use the static ConnectAsync method, or provide to the instance methods the specific IPAddress desired.`



.NET Core 2.0 solves this problem but it's still Preview 2. 



#### Angular CLI 1.3.0 environment configuration

Been able to set environment variables on docker-compose.yml or at Dockerfile or finally directly on 

the shell before running something is extremely powerful. With the .NET Core apps one could even override 

those settings with command-line arguments. 



Unfortunately, Angular CLI 1.3.0 doesn't support accessing environment variables.

Ideally, access to `process.env` at build time from `environment.ts` would do the job.

There's [a discussion going on](https://github.com/angular/angular-cli/issues/4318) on Angular CLI repo, hopefully support will

be added soon.

Until that, one of the work around proposed could be used. For this PoC I decided to add a `docker` environment.

This way, before running `docker-compose up`, the configuration file `environment.docker.ts` can be patched 

with the desired external api endpoint (e.g: http://docker-host-address:5000)



#### Exposing containers

Notice all containers listed on `docker-compose.yml` have a `ports:` section. That is simply to ease

testability from outside of the docker network. It allows hitting any of those services through the 

docker host address.



#### Dockerfile: Empty array on CMD

For the .NET Core applications, it's possible to override the configuration by passing arguments to the 

executable. For example, the 'api' project could run from a development machine while using all 

dependencies bootstrapped through `docker-compose up`:



`C:\>dotnet run -- Redis=athens.lan:6379 Envoy=http://athens.lan:5001 Mongo=mongodb://athens.lan:27017/^?connectTimeoutMS=2000`



- `athens.lan` is the hostname of the Docker host.

- ^ is the escape character for the Windows cmd



To achieve that, the .NET application has to take command line arguments into its ConfigurationBuilder:



`.AddCommandLine(args)` from `Microsoft.Extensions.Configuration.CommandLine` package.

- [See example](https://github.com/bruno-garcia/hub-like-docker-compose/blob/master/api/Program.cs)



In order to pass arguments to a container, after the `ENTRYPOINT`, it's required to define a `CMD`.

With an empty array:



`CMD []`

- [See example](https://github.com/bruno-garcia/hub-like-docker-compose/blob/master/api/Dockerfile)



Nothing is provided to the executable by default. While still able to change configuration without

the need to rebuild the image:



`$ docker run -ti hublike_api Redis=athens.lan:6379 Envoy=http://athens.lan:5001 Mongo=mongodb://athens.lan:27017/\?connectTimeoutMS=2000`

- \ is the escape character in bash