EngineManager.cs

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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net.Http;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
 
using Microsoft.Extensions.Logging;
 
using Tgstation.Server.Api.Models;
using Tgstation.Server.Common.Extensions;
using Tgstation.Server.Host.Components.Events;
using Tgstation.Server.Host.IO;
using Tgstation.Server.Host.Jobs;
using Tgstation.Server.Host.Utils;
 
namespace Tgstation.Server.Host.Components.Engine
{
    sealed class EngineManager : IEngineManager
    {
        const string VersionFileName = "Version.txt";
 
        const string ActiveVersionFileName = "ActiveVersion.txt";
 
        public EngineVersion? ActiveVersion { get; private set; }
 
        public IReadOnlyList<EngineVersion> InstalledVersions
        {
            get
            {
                lock (installedVersions)
                    return installedVersions.Keys.ToList();
            }
        }
 
        readonly IIOManager ioManager;
 
        readonly IEngineInstaller engineInstaller;
 
        readonly IEventConsumer eventConsumer;
 
        readonly ILogger<EngineManager> logger;
 
        readonly Dictionary<EngineVersion, ReferenceCountingContainer<IEngineInstallation, EngineExecutableLock>> installedVersions;
 
        readonly SemaphoreSlim changeDeleteSemaphore;
 
        volatile TaskCompletionSource activeVersionChanged;
 
        static void CheckVersionParameter(EngineVersion version)
        {
            ArgumentNullException.ThrowIfNull(version);
 
            if (!version.Engine.HasValue)
                throw new InvalidOperationException("version.Engine cannot be null!");
 
            if (version.CustomIteration == 0)
                throw new InvalidOperationException("version.CustomIteration cannot be 0!");
        }
 
        public EngineManager(IIOManager ioManager, IEngineInstaller engineInstaller, IEventConsumer eventConsumer, ILogger<EngineManager> logger)
        {
            this.ioManager = ioManager ?? throw new ArgumentNullException(nameof(ioManager));
            this.engineInstaller = engineInstaller ?? throw new ArgumentNullException(nameof(engineInstaller));
            this.eventConsumer = eventConsumer ?? throw new ArgumentNullException(nameof(eventConsumer));
            this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
 
            installedVersions = new Dictionary<EngineVersion, ReferenceCountingContainer<IEngineInstallation, EngineExecutableLock>>();
            changeDeleteSemaphore = new SemaphoreSlim(1);
            activeVersionChanged = new TaskCompletionSource();
        }
 
        public void Dispose() => changeDeleteSemaphore.Dispose();
 
        public async ValueTask ChangeVersion(
            JobProgressReporter? progressReporter,
            EngineVersion version,
            Stream? customVersionStream,
            bool allowInstallation,
            CancellationToken cancellationToken)
        {
            CheckVersionParameter(version);
 
            using (await SemaphoreSlimContext.Lock(changeDeleteSemaphore, cancellationToken))
            {
                using var installLock = await AssertAndLockVersion(
                    progressReporter,
                    version,
                    customVersionStream,
                    false,
                    allowInstallation,
                    cancellationToken);
 
                // We reparse the version because it could be changed after a custom install.
                version = new EngineVersion(installLock.Version);
 
                var stringVersion = version.ToString();
                await ioManager.WriteAllBytes(ActiveVersionFileName, Encoding.UTF8.GetBytes(stringVersion), cancellationToken);
                await eventConsumer.HandleEvent(
                    EventType.EngineActiveVersionChange,
                    new List<string?>
                    {
                        ActiveVersion?.ToString(),
                        stringVersion,
                    },
                    false,
                    cancellationToken);
 
                ActiveVersion = version;
 
                logger.LogInformation("Active version changed to {version}", version);
                var oldTcs = Interlocked.Exchange(ref activeVersionChanged, new TaskCompletionSource());
                oldTcs.SetResult();
            }
        }
 
        public async ValueTask<IEngineExecutableLock> UseExecutables(EngineVersion? requiredVersion, string? trustDmbFullPath, CancellationToken cancellationToken)
        {
            logger.LogTrace(
                "Acquiring lock on BYOND version {version}...",
                requiredVersion?.ToString() ?? $"{ActiveVersion} (active)");
            var versionToUse = requiredVersion ?? ActiveVersion ?? throw new JobException(ErrorCode.EngineNoVersionsInstalled);
            var installLock = await AssertAndLockVersion(
                null,
                versionToUse,
                null,
                requiredVersion != null,
                true,
                cancellationToken);
            try
            {
                if (trustDmbFullPath != null)
                    await engineInstaller.TrustDmbPath(installLock.Version, trustDmbFullPath, cancellationToken);
 
                return installLock;
            }
            catch
            {
                installLock.Dispose();
                throw;
            }
        }
 
        public async ValueTask DeleteVersion(JobProgressReporter progressReporter, EngineVersion version, CancellationToken cancellationToken)
        {
            ArgumentNullException.ThrowIfNull(progressReporter);
 
            CheckVersionParameter(version);
 
            logger.LogTrace("DeleteVersion {version}", version);
 
            var activeVersion = ActiveVersion;
            if (activeVersion != null && version.Equals(activeVersion))
                throw new JobException(ErrorCode.EngineCannotDeleteActiveVersion);
 
            ReferenceCountingContainer<IEngineInstallation, EngineExecutableLock> container;
            logger.LogTrace("Waiting to acquire installedVersions lock...");
            lock (installedVersions)
            {
                if (!installedVersions.TryGetValue(version, out var containerNullable))
                {
                    logger.LogTrace("Version {version} already deleted.", version);
                    return;
                }
 
                container = containerNullable;
                logger.LogTrace("Installation container acquired for deletion");
            }
 
            progressReporter.StageName = "Waiting for version to not be in use...";
            while (true)
            {
                var containerTask = container.OnZeroReferences;
 
                // We also want to check when the active version changes in case we need to fail the job because of that.
                Task activeVersionUpdate;
                using (await SemaphoreSlimContext.Lock(changeDeleteSemaphore, cancellationToken))
                    activeVersionUpdate = activeVersionChanged.Task;
 
                logger.LogTrace("Waiting for container.OnZeroReferences or switch of active version...");
                await Task.WhenAny(
                    containerTask,
                    activeVersionUpdate)
                    .WaitAsync(cancellationToken);
 
                if (containerTask.IsCompleted)
                    logger.LogTrace("All locks for version {version} are gone", version);
                else
                    logger.LogTrace("activeVersion changed, we may have to wait again. Acquiring semaphore...");
 
                using (await SemaphoreSlimContext.Lock(changeDeleteSemaphore, cancellationToken))
                {
                    // check again because it could have become the active version.
                    activeVersion = ActiveVersion;
                    if (activeVersion != null && version.Equals(activeVersion))
                        throw new JobException(ErrorCode.EngineCannotDeleteActiveVersion);
 
                    bool proceed;
                    logger.LogTrace("Locking installedVersions...");
                    lock (installedVersions)
                    {
                        proceed = container.OnZeroReferences.IsCompleted;
                        if (proceed)
                            if (!installedVersions.TryGetValue(version, out var newerContainer))
                                logger.LogWarning("Unable to remove engine installation {version} from list! Is there a duplicate job running?", version);
                            else
                            {
                                if (container != newerContainer)
                                {
                                    // Okay let me get this straight, there was a duplicate delete job, it ran before us after we grabbed the container, AND another installation of the same version completed?
                                    // I know realistically this is practically impossible, but god damn that small possiblility
                                    // best thing to do is check we exclusively own the newer container
                                    logger.LogDebug("Extreme race condition encountered, applying concentrated copium...");
                                    container = newerContainer;
                                    proceed = container.OnZeroReferences.IsCompleted;
                                }
 
                                if (proceed)
                                {
                                    logger.LogTrace("Proceeding with installation deletion...");
                                    installedVersions.Remove(version);
                                }
                            }
                    }
 
                    if (proceed)
                    {
                        logger.LogInformation("Deleting version {version}...", version);
                        progressReporter.StageName = "Deleting installation...";
 
                        // delete the version file first, because we will know not to re-discover the installation if it's not present and it will get cleaned on reboot
                        var installPath = version.ToString();
                        await ioManager.DeleteFile(
                            ioManager.ConcatPath(installPath, VersionFileName),
                            cancellationToken);
                        await ioManager.DeleteDirectory(installPath, cancellationToken);
                        return;
                    }
 
                    if (containerTask.IsCompleted)
                        logger.LogDebug(
                            "Another lock was acquired before we could remove version {version} from the list. We will have to wait again.",
                            version);
                    else
                        logger.LogTrace("Not proceeding for some reason or another");
                }
            }
        }
 
        public async Task StartAsync(CancellationToken cancellationToken)
        {
            async ValueTask<byte[]?> GetActiveVersion()
            {
                var activeVersionFileExists = await ioManager.FileExists(ActiveVersionFileName, cancellationToken);
                return !activeVersionFileExists ? null : await ioManager.ReadAllBytes(ActiveVersionFileName, cancellationToken);
            }
 
            var activeVersionBytesTask = GetActiveVersion();
 
            await ioManager.CreateDirectory(DefaultIOManager.CurrentDirectory, cancellationToken);
            var directories = await ioManager.GetDirectories(DefaultIOManager.CurrentDirectory, cancellationToken);
 
            var installedVersionPaths = new Dictionary<string, EngineVersion>();
 
            async ValueTask ReadVersion(string path)
            {
                var versionFile = ioManager.ConcatPath(path, VersionFileName);
                if (!await ioManager.FileExists(versionFile, cancellationToken))
                {
                    logger.LogWarning("Cleaning path with no version file: {versionPath}", ioManager.ResolvePath(path));
                    await ioManager.DeleteDirectory(path, cancellationToken); // cleanup
                    return;
                }
 
                var bytes = await ioManager.ReadAllBytes(versionFile, cancellationToken);
                var text = Encoding.UTF8.GetString(bytes);
                EngineVersion version;
                if (!EngineVersion.TryParse(text, out var versionNullable))
                {
                    logger.LogWarning("Cleaning path with unparsable version file: {versionPath}", ioManager.ResolvePath(path));
                    await ioManager.DeleteDirectory(path, cancellationToken); // cleanup
                    return;
                }
                else
                    version = versionNullable!;
 
                try
                {
                    AddInstallationContainer(version, path, Task.CompletedTask);
                    logger.LogDebug("Added detected BYOND version {versionKey}...", version);
                }
                catch (Exception ex)
                {
                    logger.LogWarning(
                        ex,
                        "It seems that there are multiple directories that say they contain BYOND version {version}. We're ignoring and cleaning the duplicate: {duplicatePath}",
                        version,
                        ioManager.ResolvePath(path));
                    await ioManager.DeleteDirectory(path, cancellationToken);
                    return;
                }
 
                lock (installedVersionPaths)
                    installedVersionPaths.Add(ioManager.ResolvePath(version.ToString()), version);
            }
 
            await ValueTaskExtensions.WhenAll(
                directories
                    .Select(ReadVersion));
 
            logger.LogTrace("Upgrading BYOND installations...");
            await ValueTaskExtensions.WhenAll(
                installedVersionPaths
                    .Select(kvp => engineInstaller.UpgradeInstallation(kvp.Value, kvp.Key, cancellationToken)));
 
            var activeVersionBytes = await activeVersionBytesTask;
            if (activeVersionBytes != null)
            {
                var activeVersionString = Encoding.UTF8.GetString(activeVersionBytes);
 
                EngineVersion? activeVersion;
                bool hasRequestedActiveVersion;
                lock (installedVersions)
                    hasRequestedActiveVersion = EngineVersion.TryParse(activeVersionString, out activeVersion)
                        && installedVersions.ContainsKey(activeVersion!);
 
                if (hasRequestedActiveVersion)
                    ActiveVersion = activeVersion; // not setting TCS because there's no need during init
                else
                {
                    logger.LogWarning("Failed to load saved active version {activeVersion}!", activeVersionString);
                    await ioManager.DeleteFile(ActiveVersionFileName, cancellationToken);
                }
            }
        }
 
        public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
 
        async ValueTask<EngineExecutableLock> AssertAndLockVersion(
            JobProgressReporter? progressReporter,
            EngineVersion version,
            Stream? customVersionStream,
            bool neededForLock,
            bool allowInstallation,
            CancellationToken cancellationToken)
        {
            var ourTcs = new TaskCompletionSource();
            IEngineInstallation installation;
            EngineExecutableLock installLock;
            bool installedOrInstalling;
            lock (installedVersions)
            {
                if (customVersionStream != null)
                {
                    var customInstallationNumber = 1;
                    do
                    {
                        version.CustomIteration = customInstallationNumber++;
                    }
                    while (installedVersions.ContainsKey(version));
                }
 
                installedOrInstalling = installedVersions.TryGetValue(version, out var installationContainerNullable);
                ReferenceCountingContainer<IEngineInstallation, EngineExecutableLock> installationContainer;
                if (!installedOrInstalling)
                {
                    if (!allowInstallation)
                        throw new InvalidOperationException($"Engine version {version} not installed!");
 
                    installationContainer = AddInstallationContainer(
                        version,
                        ioManager.ResolvePath(version.ToString()),
                        ourTcs.Task);
                }
                else
                    installationContainer = installationContainerNullable!;
 
                installation = installationContainer.Instance;
                installLock = installationContainer.AddReference();
            }
 
            try
            {
                if (installedOrInstalling)
                {
                    if (progressReporter != null)
                        progressReporter.StageName = "Waiting for existing installation job...";
 
                    if (neededForLock && !installation.InstallationTask.IsCompleted)
                        logger.LogWarning("The required engine version ({version}) is not readily available! We will have to wait for it to install.", version);
 
                    await installation.InstallationTask.WaitAsync(cancellationToken);
                    return installLock;
                }
 
                // okay up to us to install it then
                try
                {
                    if (customVersionStream != null)
                        logger.LogInformation("Installing custom engine version as {version}...", version);
                    else if (neededForLock)
                    {
                        if (version.CustomIteration.HasValue)
                            throw new JobException(ErrorCode.EngineNonExistentCustomVersion);
 
                        logger.LogWarning("The required engine version ({version}) is not readily available! We will have to install it.", version);
                    }
                    else
                        logger.LogDebug("Requested engine version {version} not currently installed. Doing so now...", version);
 
                    if (progressReporter != null)
                        progressReporter.StageName = "Running event";
 
                    var versionString = version.ToString();
                    await eventConsumer.HandleEvent(EventType.EngineInstallStart, new List<string> { versionString }, false, cancellationToken);
 
                    await InstallVersionFiles(progressReporter, version, customVersionStream, cancellationToken);
 
                    ourTcs.SetResult();
 
                    await eventConsumer.HandleEvent(EventType.EngineInstallComplete, new List<string> { versionString }, false, cancellationToken);
                }
                catch (Exception ex)
                {
                    if (ex is not OperationCanceledException)
                        await eventConsumer.HandleEvent(EventType.EngineInstallFail, new List<string> { ex.Message }, false, cancellationToken);
 
                    lock (installedVersions)
                        installedVersions.Remove(version);
 
                    ourTcs.SetException(ex);
                    throw;
                }
 
                return installLock;
            }
            catch
            {
                installLock.Dispose();
                throw;
            }
        }
 
        async ValueTask InstallVersionFiles(JobProgressReporter? progressReporter, EngineVersion version, Stream? customVersionStream, CancellationToken cancellationToken)
        {
            var installFullPath = ioManager.ResolvePath(version.ToString());
            async ValueTask DirectoryCleanup()
            {
                await ioManager.DeleteDirectory(installFullPath, cancellationToken);
                await ioManager.CreateDirectory(installFullPath, cancellationToken);
            }
 
            var directoryCleanupTask = DirectoryCleanup();
            try
            {
                IEngineInstallationData engineInstallationData;
                if (customVersionStream == null)
                {
                    if (progressReporter != null)
                        progressReporter.StageName = "Downloading version";
 
                    engineInstallationData = await engineInstaller.DownloadVersion(version, progressReporter, cancellationToken);
 
                    progressReporter?.ReportProgress(null);
                }
                else
#pragma warning disable CA2000 // Dispose objects before losing scope, false positive
                    engineInstallationData = new ZipStreamEngineInstallationData(
                        ioManager,
                        customVersionStream);
#pragma warning restore CA2000 // Dispose objects before losing scope
 
                await using (engineInstallationData)
                {
                    if (progressReporter != null)
                        progressReporter.StageName = "Cleaning target directory";
 
                    await directoryCleanupTask;
 
                    if (progressReporter != null)
                        progressReporter.StageName = "Extracting data";
 
                    logger.LogTrace("Extracting engine to {extractPath}...", installFullPath);
                    await engineInstallationData.ExtractToPath(installFullPath, cancellationToken);
                }
 
                if (progressReporter != null)
                    progressReporter.StageName = "Running installation actions";
 
                await engineInstaller.Install(version, installFullPath, cancellationToken);
 
                if (progressReporter != null)
                    progressReporter.StageName = "Writing version file";
 
                // make sure to do this last because this is what tells us we have a valid version in the future
                await ioManager.WriteAllBytes(
                    ioManager.ConcatPath(installFullPath, VersionFileName),
                    Encoding.UTF8.GetBytes(version.ToString()),
                    cancellationToken);
            }
            catch (HttpRequestException ex)
            {
                // since the user can easily provide non-exitent version numbers, we'll turn this into a JobException
                throw new JobException(ErrorCode.EngineDownloadFail, ex);
            }
            catch (OperationCanceledException)
            {
                throw;
            }
            catch
            {
                await ioManager.DeleteDirectory(installFullPath, cancellationToken);
                throw;
            }
        }
 
        ReferenceCountingContainer<IEngineInstallation, EngineExecutableLock> AddInstallationContainer(EngineVersion version, string installPath, Task installationTask)
        {
            var installation = engineInstaller.CreateInstallation(version, installPath, installationTask);
 
            var installationContainer = new ReferenceCountingContainer<IEngineInstallation, EngineExecutableLock>(installation);
 
            lock (installedVersions)
                installedVersions.Add(version, installationContainer);
 
            return installationContainer;
        }
    }
}