public void ProcessHostStarted(HostStartedMessage message)
{
if (message == null)
{
throw new ArgumentNullException("message");
}
string hostId = message.SharedQueueName;
DateTimeOffset hostVersion = message.EnqueuedOn;
DateTime hostVersionUtc = hostVersion.UtcDateTime;
IEnumerable <FunctionDescriptor> messageFunctions = message.Functions ?? Enumerable.Empty <FunctionDescriptor>();
HostSnapshot newSnapshot = new HostSnapshot
{
HostVersion = hostVersion,
FunctionIds = CreateFunctionIds(messageFunctions)
};
if (_hostIndexManager.UpdateOrCreateIfLatest(hostId, newSnapshot))
{
IEnumerable <VersionedMetadata> existingFunctions = _functionIndexManager.List(hostId);
IEnumerable <VersionedMetadata> removedFunctions = existingFunctions
.Where((f) => !newSnapshot.FunctionIds.Any(i => f.Id == i));
foreach (VersionedMetadata removedFunction in removedFunctions)
{
// Remove all functions no longer in our list (unless they exist with a later host version than
// ours).
string fullId = new FunctionIdentifier(hostId, removedFunction.Id).ToString();
_functionIndexManager.DeleteIfLatest(fullId, hostVersion, removedFunction.ETag,
removedFunction.Version);
}
HeartbeatDescriptor heartbeat = message.Heartbeat;
IEnumerable <FunctionDescriptor> addedFunctions = messageFunctions
.Where((d) => !existingFunctions.Any(f => d.Id == f.Id));
foreach (FunctionDescriptor addedFunction in addedFunctions)
{
// Create any functions just appearing in our list (or update existing ones if they're earlier than
// ours).
FunctionSnapshot snapshot = CreateFunctionSnapshot(hostId, heartbeat, addedFunction, hostVersion);
_functionIndexManager.CreateOrUpdateIfLatest(snapshot);
}
// Update any functions appearing in both lists provided they're still earlier than ours (or create them
// if they've since been deleted).
var possiblyUpdatedFunctions = existingFunctions
.Join(messageFunctions, (f) => f.Id, (d) => d.Id, (f, d) => new
{
Descriptor = d,
HostVersion = f.Version,
ETag = f.ETag
});
foreach (var possiblyUpdatedFunction in possiblyUpdatedFunctions)
{
FunctionSnapshot snapshot = CreateFunctionSnapshot(hostId, heartbeat,
possiblyUpdatedFunction.Descriptor, hostVersion);
_functionIndexManager.UpdateOrCreateIfLatest(snapshot, possiblyUpdatedFunction.ETag,
possiblyUpdatedFunction.HostVersion);
}
}
// Delete any functions we may have added or updated that are no longer in the index.
// The create and update calls above may have occured after another instance started processing a later
// version of this host. If that instance had already read the existing function list before we added the
// function, it would think the function had already been deleted. In the end, we can't leave a function
// around unless it's still in the host index after we've added or updated it.
HostSnapshot finalSnapshot = _hostIndexManager.Read(hostId);
IEnumerable <FunctionDescriptor> functionsRemovedAfterThisHostVersion;
if (finalSnapshot == null)
{
functionsRemovedAfterThisHostVersion = messageFunctions;
}
else if (finalSnapshot.HostVersion.UtcDateTime > hostVersionUtc)
{
// Note that we base the list of functions to delete on what's in the HostStartedMessage, not what's in
// the addedFunctions and possibleUpdatedFunctions variables, as this instance could have been aborted
// and resumed and could lose state like those local variables.
functionsRemovedAfterThisHostVersion = messageFunctions.Where(
f => !finalSnapshot.FunctionIds.Any((i) => f.Id == i));
}
else
{
functionsRemovedAfterThisHostVersion = Enumerable.Empty <FunctionDescriptor>();
}
foreach (FunctionDescriptor functionNoLongerInSnapshot in functionsRemovedAfterThisHostVersion)
{
string fullId = new FunctionIdentifier(hostId, functionNoLongerInSnapshot.Id).ToString();
_functionIndexManager.DeleteIfLatest(fullId, hostVersionUtc);
}
_functionIndexVersionManager.UpdateOrCreateIfLatest(newSnapshot.HostVersion);
}
