/// <summary>
/// If activation already exists, use it
/// Otherwise, create an activation of an existing grain by reading its state.
/// Return immediately using a dummy that will queue messages.
/// Concurrently start creating and initializing the real activation and replace it when it is ready.
/// </summary>
/// <param name="address">Grain's activation address</param>
/// <param name="requestContextData">Request context data.</param>
/// <returns></returns>
public IGrainContext GetOrCreateActivation(
GrainAddress address,
Dictionary <string, object> requestContextData)
{
if (TryGetGrainContext(address.GrainId, out var result))
{
return(result);
}
// Lock over all activations to try to prevent multiple instances of the same activation being created concurrently.
lock (activations)
{
if (TryGetGrainContext(address.GrainId, out result))
{
return(result);
}
if (!SiloStatusOracle.CurrentStatus.IsTerminating())
{
result = this.grainActivator.CreateInstance(address);
RegisterMessageTarget(result);
}
} // End lock
if (result is null)
{
// Did not find and did not start placing new
if (logger.IsEnabled(LogLevel.Debug))
{
logger.LogDebug((int)ErrorCode.CatalogNonExistingActivation2, "Non-existent activation {Activation}", address.ToFullString());
}
CounterStatistic.FindOrCreate(StatisticNames.CATALOG_ACTIVATION_NON_EXISTENT_ACTIVATIONS).Increment();
this.directory.InvalidateCacheEntry(address);
// Unregister the target activation so we don't keep getting spurious messages.
// The time delay (one minute, as of this writing) is to handle the unlikely but possible race where
// this request snuck ahead of another request, with new placement requested, for the same activation.
// If the activation registration request from the new placement somehow sneaks ahead of this unregistration,
// we want to make sure that we don't unregister the activation we just created.
_ = this.UnregisterNonExistentActivation(address);
return(null);
}
else
{
// Initialize the new activation asynchronously.
var cancellation = new CancellationTokenSource(collectionOptions.Value.ActivationTimeout);
result.Activate(requestContextData, cancellation.Token);
return(result);
}
}
