public bool OnStart()
{
_listener.Listen(
new KeyValuePair <Type, Action <object, CancellationToken, IMessageAcknowledge> >(typeof(WakeWorkflowJob), WakeWorkflow),
new KeyValuePair <Type, Action <object, CancellationToken, IMessageAcknowledge> >(typeof(WorkflowCreate), NewWorkflowInstance),
new KeyValuePair <Type, Action <object, CancellationToken, IMessageAcknowledge> >(typeof(WorkflowStateMachineRetry), FireRetryMsg),
new KeyValuePair <Type, Action <object, CancellationToken, IMessageAcknowledge> >(typeof(FireWorkflowTriggerJob), FireTriggerJobMsg));
_broadcastListener.Listen(new KeyValuePair <Type, Action <object, CancellationToken, IMessageAcknowledge> >(typeof(WorkflowTrigger), DistributeWorkflowTriggers));
var hostEnvironment = Catalog.Factory.Resolve <IHostEnvironment>();
var hostId = hostEnvironment.GetCurrentHostIdentifier(HostEnvironmentConstants.DefaultHostScope);
var instancesQuery = new QuerySpecification
{
BookMark = new GenericPageBookmark {
PageSize = 100
},
Where = new Filter
{
Rules = new Comparison[]
{
new Comparison
{
Data = WorkflowStatus.Complete.ToString(),
Field = "Status",
Test = Test.NotEqual
}
}
}
};
Task.Factory.StartNew(() =>
{
// get this host's chunk of workflow instances to run.
Random rnd = GoodSeedRandom.Create();
bool done = false;
bool first = true;
DateTime lastException = DateTime.MinValue;
while (!done)
{
try
{
int acquired = 0;
IEnumerable <WorkflowInstanceInfo> instances = Enumerable.Empty <WorkflowInstanceInfo>();
instancesQuery.BookMark = new GenericPageBookmark {
PageSize = 100
};
while (instancesQuery.BookMark.More)
{
var qr = _instanceData.Query(instancesQuery);
if (qr.Items.Any())
{
instances = instances.Concat(qr.Items);
}
}
instances = instances.ToArray();
IEnumerable <WorkflowInstanceInfo> tryInstances;
// first pass, pick out existing workflows in a pattern less
// likely to interfere with other workflow hosts trying to acquire
if (first)
{
int startAt;
startAt = rnd.Next(3) * 3;
if (startAt > instances.Count())
{
startAt = rnd.Next(instances.Count() / 3);
}
tryInstances = instances.TakeEvery(startAt, 3);
first = false;
}
else
{
// subsequent passes, be greedy
tryInstances = instances;
}
int waitDur;
foreach (var inst in tryInstances)
{
if (TryAcquireWorkflow(inst.Id) != null)
{
acquired++;
_log.InfoFormat("Host {0} acquired workflow instance {1} ...",
hostId, inst.Id);
// give other hosts a little space to take some.
waitDur = rnd.Next(160);
Thread.Sleep(waitDur);
}
else
{
_log.InfoFormat(
"Host {0} could not acquire workflow instance {1} ...", hostId,
inst.Id);
}
}
if (!first && acquired == 0)
{
done = true;
}
waitDur = rnd.Next(7654);
_log.InfoFormat(
"Host {0} acquired {1} pre-existing workflows, waiting {2} milliseconds to try to attain more.",
hostId, acquired, waitDur);
Thread.Sleep(waitDur);
}
catch (Exception ex)
{
var es = string.Format("exception running workflow host {0}",
ex.TraceInformation());
_dblog.Error(es);
if (DateTime.UtcNow - lastException > TimeSpan.FromMinutes(1.0))
{
_log.TraceException(ex);
var alert = Catalog.Factory.Resolve <IApplicationAlert>();
alert.RaiseAlert(ApplicationAlertKind.System, es);
}
}
}
});
return(true);
}