/// <summary>
/// AcquireAsync the lock, waiting as long as it takes or until the configured timeout.
/// </summary>
public async Task <LockAcquisitionResult> AcquireAsync(Context context, TimeSpan waitTimeout)
{
_tracer.Info(context, $"Acquiring lock file=[{_lockFilePath}]");
_fileSystem.CreateDirectory(_lockFilePath.GetParent());
DateTime timeOutTime = DateTime.UtcNow + waitTimeout;
Exception?lastException = null;
int? lastCompetingProcessId = null;
while (DateTime.UtcNow < timeOutTime)
{
try
{
// Anything other than FileShare.None is effectively ignored in Unix
FileShare fileShare = BuildXL.Utilities.OperatingSystemHelper.IsUnixOS ? FileShare.None : FileShare.Read;
_lockFile = await _fileSystem.OpenSafeAsync(
_lockFilePath, FileAccess.Write, FileMode.OpenOrCreate, fileShare);
using (var writer = new StreamWriter(_lockFile, UTF8WithoutBom, bufferSize: 4096, leaveOpen: true))
{
await writer.WriteLineAsync(
$"Lock acquired at {DateTime.UtcNow:O} by computer [{Environment.MachineName}] running command line [{Environment.CommandLine}] with process id [{Process.GetCurrentProcess().Id}]"
);
}
_tracer.Info(context, $"Acquired lock file=[{_lockFilePath}]");
await _lockFile.FlushAsync();
return(LockAcquisitionResult.Acquired());
}
catch (IOException ioException)
{
lastException = ioException;
}
catch (UnauthorizedAccessException accessException)
{
lastException = accessException;
}
try
{
string?contents = await _fileSystem.TryReadFileAsync(_lockFilePath);
if (contents != null)
{
_tracer.Diagnostic(context, $"Lock file=[{_lockFilePath}] contains [{contents}]");
lastCompetingProcessId = TryExtractProcessIdFromLockFilesContent(contents);
}
}
catch (Exception readLockFileException)
{
string message = readLockFileException is UnauthorizedAccessException ae ? ae.Message : readLockFileException.ToString();
// This is just extra cautious. We shouldn't fail hard being unable to get this diagnostic information.
_tracer.Info(
context,
$"Unable to read contents of lock file=[{_lockFilePath}] because [{message}]");
}
await Task.Delay(_pollingInterval);
}
string lastProcessIdText = lastCompetingProcessId == null ? string.Empty : " Competing process Id: " + lastCompetingProcessId;
_tracer.Info(
context,
$"Timed out trying to acquire lock file=[{_lockFilePath}].{lastProcessIdText} Last exception was=[{lastException}]");
return(LockAcquisitionResult.Failed(waitTimeout, lastCompetingProcessId, TryGetProcessName(lastCompetingProcessId), lastException));
}