ServiceUpdater/UpdateWorker.cs

using System.Diagnostics;

namespace ServiceUpdater;

public sealed class UpdateWorker(UpdaterConfig config) {

    private int LastExitCode { get; set; }
    
    public async IAsyncEnumerable<string> UpdateService(string serviceName) {
        yield return $"Starting update for {serviceName}";

        await foreach (var line in RunProcess(serviceName, "compose pull")) {
            yield return line;
        }

        if (LastExitCode != 0)
            yield break;

        yield return $"Downloaded changes for {serviceName}";

        await foreach (var line in RunProcess(serviceName, "compose up -d --remove-orphans")) {
            yield return line;
        }
    }

    private async IAsyncEnumerable<string> RunProcess(string folder, string arguments) {
        var process = new Process {
            StartInfo = new() {
                FileName = "docker",
                Arguments = arguments,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                UseShellExecute = false,
                WorkingDirectory = Path.Combine(config.ServicesRoot, folder)
            }
        };

        process.Start();

        var output = process.StandardOutput.ReadLineAsync();
        var error = process.StandardError.ReadLineAsync();

        while (true) {
            var completed = await Task.WhenAny(output, error);

            if (completed == output) {
                var line = await output;
                if (line == null) break;
                yield return line;
                output = process.StandardOutput.ReadLineAsync();
            }
            else {
                var line = await error;
                if (line == null) break;
                yield return line;
                error = process.StandardError.ReadLineAsync();
            }
        }

        await process.WaitForExitAsync();
        LastExitCode = process.ExitCode;
    }
}