// Note: calls to ConfigureAwait(false) aren't strictly required here,
// as this method is only ever called in Task.Run, so there won't be a synchronization
// context, but it's simple and harmless to make it "obviously okay".
private async Task RunUploader(CancellationToken cancellationToken)
{
TimeSpan errorDelay = _serverErrorRetrySettings.InitialBackoff;
while (true)
{
List <LogEntryExtra> entries;
// Wait/loop until there are some log entries that need uploading.
while (true)
{
var peek = await _logQ.PeekAsync(_maxUploadBatchSize, cancellationToken).ConfigureAwait(false);
var logEntriesLost = peek.Lost;
entries = peek.Entries;
if (logEntriesLost != null)
{
var lostEntryExtra = new LogEntryExtra(-1, MakeLostEntry(logEntriesLost));
entries = (new[] { lostEntryExtra }).Concat(entries ?? Enumerable.Empty <LogEntryExtra>()).ToList();
}
if (entries != null && entries.Count() > 0)
{
// There are log entries that need uploading, so do that now.
break;
}
await _uploadReadyEvent.WaitAsync(cancellationToken).ConfigureAwait(false);
}
// Upload entries to the Cloud Logging server
try
{
await _client.WriteLogEntriesAsync((LogName)null, null, s_emptyLabels, entries.Select(x => x.Entry), cancellationToken).ConfigureAwait(false);
await _logQ.RemoveUntilAsync(entries.Last().Id, cancellationToken).ConfigureAwait(false);
lock (_lock)
{
_maxConfirmedSentId = entries.Last().Id;
}
_uploadCompleteEvent.Set();
errorDelay = _serverErrorRetrySettings.InitialBackoff;
}
catch (Exception e)
{
// Always retry, regardless of error, as there's nothing much else to be done.
await _scheduler.Delay(errorDelay, cancellationToken).ConfigureAwait(false);
// TODO: Try to use RetryAttempt for this.
errorDelay = _serverErrorRetrySettings.NextBackoff(errorDelay);
// Use log4net internal logging to warn user of upload error.
// Internal logging can be enabled as described in the "Troubleshooting" section of the log4net FAQ.
log4net.Util.LogLog.Warn(typeof(LogUploader), "Error uploading log messages to server.", e);
}
}
}
public void NextBackoff(double current, double expectedNext)
{
var settings = new RetrySettings(
maxAttempts: 5,
initialBackoff: TimeSpan.FromSeconds(1.0),
maxBackoff: TimeSpan.FromSeconds(5.0),
backoffMultiplier: 2.0,
e => true,
RetrySettings.NoJitter);
var expected = TimeSpan.FromSeconds(expectedNext);
var actual = settings.NextBackoff(TimeSpan.FromSeconds(current));
Assert.Equal(expected, actual);
}