GitProcessHandler.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Azure.Sdk.Tools.TestProxy.Common;
using Azure.Sdk.Tools.TestProxy.Common.Exceptions;

namespace Azure.Sdk.Tools.TestProxy.Store
{

    public class CommandResult
    {
        public int ExitCode;
        public string StdErr;
        public string StdOut;
        public string Arguments;
        public Exception CommandException;
    }


    /// <summary>
    /// This class offers an easy wrapper abstraction for shelling out to git.
    /// </summary>
    public class GitProcessHandler
    {
        public const int RETRY_INTERMITTENT_FAILURE_COUNT = 3;
        /// <summary>
        /// Internal class to hold the minimum supported version of git. If that
        /// version changes we only need to change it here.
        /// </summary>
        class GitMinVersion
        {
            // As per https://github.com/Azure/azure-sdk-tools/issues/4146, the min version of git
            // that supports what we need is 2.25.0.
            public static int Major = 2;
            public static int Minor = 25;
            public static int Patch = 0;
            public static string minVersionString = $"{Major}.{Minor}.{Patch}";
        }

        /// <summary>
        /// This dictionary is used to ensure that each git directory will only ever have a SINGLE git command running it at a time.
        /// </summary>
        private ConcurrentDictionary<string, TaskQueue> AssetTasks = new ConcurrentDictionary<string, TaskQueue>();

        /// <summary>
        /// Create a ProcessStartInfo that's exclusively used for execution of git commands
        /// </summary>
        /// <param name="workingDirectory">The directory where the commands are to be executed. For normal processing
        /// through GitStore, this will end up being GitAssetsConfiguration's AssetsRepoLocation.</param>
        /// <returns></returns>
        public virtual ProcessStartInfo CreateGitProcessInfo(string workingDirectory)
        {
            var startInfo = new ProcessStartInfo("git")
            {
                UseShellExecute = false,
                RedirectStandardOutput = true,
                RedirectStandardError = true,
                CreateNoWindow = true,
                WorkingDirectory = workingDirectory,
            };

            startInfo.EnvironmentVariables["PATH"] = Environment.GetEnvironmentVariable("PATH");

            return startInfo;
        }

        /// <summary>
        /// Invokes a git command. If it fails in any way, throws GitProcessException. Otherwise returns the result of the git invocation.
        /// </summary>
        /// <param name="config"></param>
        /// <param name="inputCommands"></param>
        /// <returns>A list of command results. One can assume success in all of them unless an exception has been thrown</returns>
        /// <exception cref="GitProcessException">Throws GitProcessException on returnCode != 0 OR if an unexpected exception is thrown during invocation.</exception>
        public virtual IEnumerable<CommandResult> Run(GitAssetsConfiguration config, params string[] inputCommands)
        {
            List<CommandResult> results = new List<CommandResult>();

            foreach (var inputCommand in inputCommands)
            {
                results.Add(Run(inputCommand, config));
            }

            return results;
        }

        /// <summary>
        /// Invokes a git command. If it fails in any way, throws GitProcessException. Otherwise returns the result of the git invocation.
        /// </summary>
        /// <param name="arguments">git command line arguments</param>
        /// <param name="config">GitAssetsConfiguration</param>
        /// <returns></returns>
        /// <exception cref="GitProcessException">Throws GitProcessException on returnCode != 0 OR if an unexpected exception is thrown during invocation.</exception>
        public virtual CommandResult Run(string arguments, GitAssetsConfiguration config)
        {
            return Run(arguments, config.AssetsRepoLocation.ToString());
        }

        /// <summary>
        /// Invokes a git command. If it fails in any way, throws GitProcessException. Otherwise returns the result of the git invocation.
        /// </summary>
        /// <param name="arguments">git command line arguments</param>
        /// <param name="workingDirectory">effectively the AssetsRepoLocation</param>
        /// <returns></returns>
        /// <exception cref="GitProcessException">Throws GitProcessException on returnCode != 0 OR if an unexpected exception is thrown during invocation.</exception>
        public virtual CommandResult Run(string arguments, string workingDirectory)
        {
            // Surface an easy to understand error when we shoot ourselves in the foot
            if (arguments.StartsWith("git"))
            {
                throw new Exception("GitProcessHandler commands should not start with 'git'");
            }

            ProcessStartInfo processStartInfo = CreateGitProcessInfo(workingDirectory);
            processStartInfo.Arguments = arguments;

            CommandResult result = new CommandResult()
            {
                Arguments = arguments
            };

            var queue = AssetTasks.GetOrAdd(workingDirectory, new TaskQueue());

            queue.Enqueue(() =>
            {
                try
                {
                    int attempts = 1;
                    while (attempts <= RETRY_INTERMITTENT_FAILURE_COUNT)
                    {
                        DebugLogger.LogInformation($"git {arguments}");

                        var output = new List<string>();
                        var error = new List<string>();

                        using (var process = new Process())
                        {
                            process.StartInfo = processStartInfo;

                            process.OutputDataReceived += (s, e) =>
                            {
                                lock (output)
                                {
                                    output.Add(e.Data);
                                }
                            };

                            process.ErrorDataReceived += (s, e) =>
                            {
                                lock (error)
                                {
                                    error.Add(e.Data);
                                }
                            };

                            process.Start();
                            process.BeginErrorReadLine();
                            process.BeginOutputReadLine();
                            process.WaitForExit();

                            int returnCode = process.ExitCode;
                            var stdOut = string.Join(Environment.NewLine, output);
                            var stdError = string.Join(Environment.NewLine, error);

                            DebugLogger.LogDebug($"StdOut: {stdOut}");
                            DebugLogger.LogDebug($"StdErr: {stdError}");
                            DebugLogger.LogDebug($"ExitCode: {process.ExitCode}");

                            result.ExitCode = process.ExitCode;
                            result.StdErr = string.Join(Environment.NewLine, stdError);
                            result.StdOut = string.Join(Environment.NewLine, stdOut);

                            if (result.ExitCode == 0)
                            {
                                break;
                            }
                            var continueToAttempt = IsRetriableGitError(result);

                            if (!continueToAttempt)
                            {
                                throw new GitProcessException(result);
                            }

                            attempts++;

                            if (continueToAttempt && attempts < RETRY_INTERMITTENT_FAILURE_COUNT)
                            {
                                Task.Delay(attempts * 2 * 1000).Wait();
                            }
                        }
                    }
                }
                // exceptions caught here will be to do with inability to start the git process
                // otherwise all "error" states should be handled by the output to stdErr and non-zero exitcode.
                catch (Exception e)
                {
                    DebugLogger.LogDebug(e.Message);

                    result.ExitCode = -1;
                    result.CommandException = e;

                    throw new GitProcessException(result);
                }
            });

            return result;
        }

        /// <summary>
        /// This function evaluates a git command invocation result. The result of "yes you should retry this" only occurs
        /// when the necessary data is available. Otherwise we default to NOT retry.
        ///
        /// Check Azure/azure-sdk-tools#5660 for additional detail on occurrence.
        /// </summary>
        /// <param name="result"></param>
        /// <returns></returns>
        public bool IsRetriableGitError(CommandResult result)
        {
            if (result.ExitCode != 0) {
                // we cannot evaluate an empty stderr to see if it is retriable
                if (string.IsNullOrEmpty(result.StdErr))
                {
                    return false;
                }

                // fatal: unable to access 'https://github.com/Azure/azure-sdk-assets/': The requested URL returned error: 429
                if (result.StdErr.Contains("The requested URL returned error: 429"))
                {
                    return true;
                }

                // fatal: unable to access 'https://github.com/Azure/azure-sdk-assets/': Failed to connect to github.com port 443: Connection timed out
                if (result.StdErr.Contains("Failed to connect to github.com port 443: Connection timed out"))
                {
                    return true;
                }

                // fatal: unable to access 'https://github.com/Azure/azure-sdk-assets/': Failed to connect to github.com port 443: Operation timed out
                if (result.StdErr.Contains("Failed to connect to github.com port 443: Operation timed out"))
                {
                    return true;
                }

                // fatal: unable to access 'https://github.com/Azure/azure-sdk-assets/': Failed to connect to github.com port 443 after 21019 ms: Couldn't connect to server
                var regex = new Regex(@"Failed to connect to github.com port 443 after [\d]+ ms: Couldn't connect to server");
                if (regex.IsMatch(result.StdErr))
                {
                    return true;
                }

                // fatal: unable to access 'https://github.com/Azure/azure-sdk-assets/': Recv failure: Operation timed out
                if (result.StdErr.Contains("Recv failure: Operation timed out"))
                {
                    return true;
                }
            }

            return false;
        }

        /// <summary>
        /// Invokes git binary against a GitAssetsConfiguration.
        /// </summary>
        /// <param name="arguments"></param>
        /// <param name="workingDirectory"></param>
        /// <param name="result"></param>
        /// <returns></returns>
        public virtual bool TryRun(string arguments, string workingDirectory, out CommandResult result)
        {
            // Surface an easy to understand error when we shoot ourselves in the foot
            if (arguments.StartsWith("git"))
            {
                throw new Exception("GitProcessHandler commands should not start with 'git'");
            }

            ProcessStartInfo processStartInfo = CreateGitProcessInfo(workingDirectory);
            processStartInfo.Arguments = arguments;
            var commandResult = new CommandResult();

            var queue = AssetTasks.GetOrAdd(workingDirectory, new TaskQueue());

            queue.Enqueue(() =>
            {
                try
                {
                    int attempts = 1;
                    bool continueToAttempt = true;
                    while (continueToAttempt && attempts <= RETRY_INTERMITTENT_FAILURE_COUNT)
                    {
                        DebugLogger.LogInformation($"git {arguments}");
                        var output = new List<string>();
                        var error = new List<string>();

                        using (var process = new Process())
                        {
                            process.StartInfo = processStartInfo;

                            process.OutputDataReceived += (s, e) =>
                            {
                                lock (output)
                                {
                                    output.Add(e.Data);
                                }
                            };

                            process.ErrorDataReceived += (s, e) =>
                            {
                                lock (error)
                                {
                                    error.Add(e.Data);
                                }
                            };

                            process.Start();
                            process.BeginErrorReadLine();
                            process.BeginOutputReadLine();
                            process.WaitForExit();

                            int returnCode = process.ExitCode;
                            var stdOut = string.Join(Environment.NewLine, output);
                            var stdError = string.Join(Environment.NewLine, error);

                            DebugLogger.LogDebug($"StdOut: {stdOut}");
                            DebugLogger.LogDebug($"StdErr: {stdError}");
                            DebugLogger.LogDebug($"ExitCode: {process.ExitCode}");

                            commandResult = new CommandResult()
                            {
                                ExitCode = process.ExitCode,
                                StdErr = stdError,
                                StdOut = stdOut,
                                Arguments = arguments
                            };

                            if (commandResult.ExitCode == 0)
                            {
                                break;
                            }
                            continueToAttempt = IsRetriableGitError(commandResult);

                            attempts++;
                            if (continueToAttempt && attempts < RETRY_INTERMITTENT_FAILURE_COUNT)
                            {
                                Task.Delay(attempts * 2 * 1000).Wait();
                            }
                        }
                    }
                }
                // exceptions caught here will be to do with inability to start the git process
                // otherwise all "error" states should be handled by the output to stdErr and non-zero exitcode.
                catch (Exception e)
                {
                    DebugLogger.LogDebug(e.Message);

                    commandResult = new CommandResult()
                    {
                        ExitCode = -1,
                        CommandException = e
                    };
                }
            });

            result = commandResult;

            if (result.ExitCode != 0)
            {
                return false;
            }

            return true;
        }

        /// <summary>
        /// Verify that the version of git running on the machine is greater equal the git minimum version.
        /// This is more for the people running the CLI/TestProxy locally than for lab machines which seem
        /// to be running on the latest, released versions. The reason is that any git version less than
        /// 2.37.0 won't have the cone/no-cone options used by sparse-checkout.
        /// </summary>
        /// <exception cref="GitProcessException">Thrown by the internal call to Run.</exception>
        /// <exception cref="GitVersionException">Thrown if the version doesn't meet the min or if we can't determine it.</exception>
        public void VerifyGitMinVersion(string testVersion=null)
        {
            string localGitVersion = testVersion;
            if (String.IsNullOrEmpty(testVersion))
            {
                // We need to run git --version to get the current version. The directory in which
                // the process executes is irrelevant.
                CommandResult result = Run("--version", Directory.GetCurrentDirectory());
                localGitVersion = result.StdOut.Trim();
            }
            // Sample git versions from the various platforms:
            // Windows: git version 2.37.2.windows.2
            // Mac: git version 2.32.1 (Apple Git-133)
            // Linux: git version 2.25.1
            // Regex to scrape major, minor and patch versions from the git version string
            Regex rx = new Regex(@"git version (?<Major>\d*)\.(?<Minor>\d*)(\.(?<Patch>\d*)?)?", RegexOptions.Compiled);
            Match match = rx.Match(localGitVersion);

            if (match.Success)
            {
                string gitVersionExceptionMessage = $"{localGitVersion} is less than the minimum supported Git version {GitMinVersion.minVersionString}";
                // match.Groups["Major"].Value, match.Groups["Minor"].Value, match.Groups["Patch"].Value
                int major = int.Parse(match.Groups["Major"].Value);
                int minor = int.Parse(match.Groups["Minor"].Value);
                int patch = int.Parse(match.Groups["Patch"].Value);
                if (major < GitMinVersion.Major)
                {
                    throw new GitVersionException(gitVersionExceptionMessage);
                }
                else if (major == GitMinVersion.Major)
                {
                    if (minor < GitMinVersion.Minor)
                    {
                        throw new GitVersionException(gitVersionExceptionMessage);
                    }
                    else if (minor == GitMinVersion.Minor)
                    {
                        if (patch < GitMinVersion.Patch)
                        {
                            throw new GitVersionException(gitVersionExceptionMessage);
                        }
                    }
                }
            }
            else
            {
                // In theory we shouldn't get here. If git isn't installed or on the path, the Run command should throw.
                throw new GitVersionException($"Unable to determine the local git version from the returned version string '{localGitVersion}'. Please ensure that git is installed on the machine and has been added to the PATH.");
            }
        }
    }
}