/// <summary>
/// Converts a string from lowercase to uppercase, taking an extra long time.
/// During that time, it periodically calls testCancel so that the caller can
/// abort the operation if it's taking too long.
/// </summary>
/// <returns>An uppercase string.</returns>
private string ShoutString(string text, ThrowIfAborted throwIfAborted)
{
string upperText = text.ToUpper();
// Pretend like we're working hard and taking time. Time is a function of
// the number of letters in the word.
var workDeadline = DateTime.UtcNow + TimeSpan.FromSeconds(
upperText.Length * (int)Math.Log(upperText.Length));
var oneSecond = TimeSpan.FromSeconds(1);
while (workDeadline > DateTime.UtcNow)
{
throwIfAborted();
System.Threading.Thread.Sleep(oneSecond);
}
// Simulate different kinds of errors depending on text.
if (upperText.Contains("CHICKEN"))
{
// Simulate a fatal error that cannot possible be handled.
throw new FatalException("Oh no! Not chickens!");
}
if (upperText.Contains("CORN"))
{
// Simulate a flaky error that happens sometimes, but not always.
if (_init.Random.Next(3) > 0)
{
throw new CornException();
}
}
if (upperText.Contains("COW"))
{
// Simulate an error that eventually times out with error.
throw new CowException();
}
return(upperText);
}
/// <summary>
/// Converts a string from lowercase to uppercase, taking an extra long time.
/// During that time, it periodically calls testCancel so that the caller can
/// abort the operation if it's taking too long.
/// </summary>
/// <returns>An uppercase string.</returns>
private string ShoutString(string text, ThrowIfAborted throwIfAborted)
{
string upperText = text.ToUpper();
// Pretend like we're working hard and taking time. Time is a function of
// the number of letters in the word.
var workDeadline = DateTime.UtcNow + TimeSpan.FromSeconds(
upperText.Length * (int)Math.Log(upperText.Length));
var oneSecond = TimeSpan.FromSeconds(1);
while (workDeadline > DateTime.UtcNow)
{
throwIfAborted();
System.Threading.Thread.Sleep(oneSecond);
}
// Simulate different kinds of errors depending on text.
if (upperText.Contains("CHICKEN"))
{
// Simulate a fatal error that cannot possible be handled.
throw new FatalException("Oh no! Not chickens!");
}
if (upperText.Contains("CORN"))
{
// Simulate a flaky error that happens sometimes, but not always.
if (_init.Random.Next(3) > 0)
throw new CornException();
}
if (upperText.Contains("COW"))
{
// Simulate an error that eventually times out with error.
throw new CowException();
}
return upperText;
}
/// <summary>
/// Waits for a shout request message to arrive in the Pub/Sub
/// subscription. Converts the text to uppercase and posts the results
/// back to the website.
/// </summary>
/// <returns>
/// The number of messages pulled from the subscription,
/// or -1 if an expected error occurred.
/// </returns>
public int ShoutOrThrow(System.Threading.CancellationToken cancellationToken)
{
// Pull a shout request message from the subscription.
string subscriptionPath = MakeSubscriptionPath(_init.SubscriptionName);
WriteLog("Pulling shout request messages from " + subscriptionPath + "...",
TraceEventType.Verbose);
var pullRequest = _init.PubsubService.Projects.Subscriptions.Pull(
new PullRequest()
{
MaxMessages = 1,
ReturnImmediately = false
}, subscriptionPath).ExecuteAsync();
Task.WaitAny(new Task[] { pullRequest }, cancellationToken);
var pullResponse = pullRequest.Result;
int messageCount = pullResponse.ReceivedMessages == null ? 0
: pullResponse.ReceivedMessages.Count;
WriteLog("Received " + messageCount + " messages.",
TraceEventType.Information);
if (messageCount < 1)
{
return(0); // Nothing pulled. Nothing to do.
}
// Examine the received message.
var shoutRequestMessage = pullResponse.ReceivedMessages[0];
var attributes = shoutRequestMessage.Message.Attributes;
string postStatusUrl;
string postStatusToken;
DateTime requestDeadline;
try
{
postStatusUrl = attributes["postStatusUrl"];
postStatusToken = attributes["postStatusToken"];
long unixDeadline = Convert.ToInt64(attributes["deadline"]);
requestDeadline = FromUnixTime(unixDeadline);
}
catch (Exception e)
{
WriteLog("Bad shout request message attributes.\n" + e.ToString(),
TraceEventType.Warning);
Acknowledge(shoutRequestMessage.AckId);
return(-1);
}
// Tell the world we are shouting this request.
PublishStatus(postStatusUrl, postStatusToken, "shouting");
WriteLog("Shouting " + postStatusUrl, TraceEventType.Verbose);
try
{
// Decode the payload, the string we want to shout.
byte[] data = Convert.FromBase64String(shoutRequestMessage.Message.Data);
string decodedString = Encoding.UTF8.GetString(data);
// Watch the clock and cancellation token as we work. We need to extend the
// ack deadline if the request takes a while.
var tenSeconds = TimeSpan.FromSeconds(10);
DateTime ackDeadline = DateTime.UtcNow + tenSeconds;
ThrowIfAborted throwIfAborted = () =>
{
cancellationToken.ThrowIfCancellationRequested();
var now = DateTime.UtcNow;
if (requestDeadline < now)
{
throw new FatalException("Request timed out.");
}
if (ackDeadline < now)
{
// Tell the subscription we need more time:
WriteLog("Need more time...", TraceEventType.Verbose);
_init.PubsubService.Projects.Subscriptions.ModifyAckDeadline(
new ModifyAckDeadlineRequest
{
AckIds = new string[] { shoutRequestMessage.AckId },
AckDeadlineSeconds = 15,
}, MakeSubscriptionPath(_init.SubscriptionName)).Execute();
ackDeadline = now + tenSeconds;
}
};
// Shout it.
string upperText = ShoutString(decodedString, throwIfAborted);
// Publish the result.
PublishStatus(postStatusUrl, postStatusToken, "success", upperText);
Acknowledge(shoutRequestMessage.AckId);
return(1);
}
catch (OperationCanceledException)
{
return(1); // Service stopped. Nothing to report.
}
catch (FatalException e)
{
WriteLog("Fatal exception while shouting:\n" + e.Message, TraceEventType.Error);
Acknowledge(shoutRequestMessage.AckId);
PublishStatus(postStatusUrl, postStatusToken, "fatal", e.Message);
return(-1);
}
catch (Exception e)
{
// Something went wrong while shouting. Report the error.
WriteLog("Exception while shouting:\n" + e.Message, TraceEventType.Error);
PublishStatus(postStatusUrl, postStatusToken, "error", e.Message);
return(-1);
}
}
