MissionControl

CLI as a middleware for your web apps and microservices

Example web site with MC console: https://mc-sample.azurewebsites.net/

UNDER DEVELOPMENT - alpha version

Why

Often we want to add some kind of interaction with our application. For example:

purge cache
check some background tasks
state of objects or queues
resources consumption
add new user to database, update database records
etc

MissionControl serves CLI web terminal on a dedicated URL and executes custom commands created by application developer. There are some generic commands already bundled with this library, like list-commands, help and diagnostics. Custom commands are easy to add by just implementing an interface or adding an attribute, and MissonControl will handle the rest.

How it works

just a middleware for any .NET Core app
serves CLI UI interface on dedicated URL (/mc by default)
automatically registers all commands/handlers in the app

Installation and configuration

In Startup.cs register services and add a middleware:

public void ConfigureServices(IServiceCollection services)
{
    // registers internal dependencies, scans this assemly for commands
    services.AddMissionControl();
}

public void Configure(IApplicationBuilder app)
{
    // registers /mc endpoint
    app.UseMissingControl();
}

With custom configuration:

all assemblies that contains commands and command handlers
Url where CLI is served
authentication callback - add your own request authentication to prevent execution of commands in production

public void ConfigureServices(IServiceCollection services)
{
    // assemblies where commands and handlers are located
    services.AddMissionControl(typeof(PurgeCacheCommand).Assembly, typeof(ListActiveUsersCommand).Assembly);
}

public void Configure(IApplicationBuilder app)
{
    app.UseMissingControl(opt =>
    {
        opt.Url = "/mc";
        opt.Authentication = req => true; // this allows all requests, but add authentication for production deployments! 
    });
}

Basic example

Simple command and handler example:

// Gets exposed to CLI as a command:
// > say-hi -name=Batman -foo=123
[CliCommand("say-hi", "Say Hi!")]
public class SayHiCommand : CliCommand
{
    public string Name { get; set; }

    [CliArg(required: false, help: "Attribute is optional")]
    public int Foo { get;set; }
}

public class SayHiHandler: ICliCommandHandler<SayHiCommand>
{
    // IService is resolved with standard asp.net ioc
    public SayHiHandler(IService service) { }

    public async Task<CliResponse> Handle(SayHiCommand command)
    {
        await DoSomeAsyncWork();
        return new TextResponse($"Computer says hi to {command.Name}!");
    }
}

Invoked in CLI console with:

> say-hi -name=Hackerman
Computer says hi to Hackerman!
> _

Available response types

TextResponse: simple text message
ErrorResponse: text message with error UI
MultipleResponses: async (chunked) responses
TableResponse: collection of objects rendered as a table

Multiple responses

Sometimes you want to "stream" responses back to the client while executing some long-running task on the server.
For multiple responses we can yield strings:

[CliCommand("multi-resp", "Multiple responses example")]
public class MultipleResponsesCommand : CliCommand {  }

public class MultipleResponsesHandler : ICliCommandHandler<MultipleResponsesCommand>
{
    public async Task<CliResponse> Handle(MultipleResponsesCommand command)
    {
        await service.DoSomething();
        
        // here we can "stream" partial responses back to the CLI terminal
        // use async callback in MultipleResponses constructor:
        return new MultipleResponses(async yield =>
        {
            await yield.ReturnAsync("Response 1");
            await Task.Delay(2000);
            await yield.ReturnAsync("Response 2");
            await Task.Delay(2000);
            await yield.ReturnAsync("Response 3 - done.");
        });
    }
}

CLI output, with 2sec delay between each response line:

> multi-resp
Response 1
Response 2
Response 3 - done.
> _

Included commands

Standard commands bundled with MC:

list-commands: displayes a list of registered commands
server-info: system information

every command can be invoked with -help argument. Handler will not be executed, but list of command arguments and its descriptions will be displayed in the console.