I've implemented an app that subscribes to MS Graph events. One problem that I have is that sometimes I get Updated events before the corresponding Created events. I've also seen events for mail messages where the response to a message comes before the actual message. This makes is pretty hard to process all events robustly.
Is there a way to control the order of events in MS Graph Subscriptions? How do I ensure that events that depend/reference other events arrive in order?
Thanks!
I think your best solution is likely to not solely rely on the Notifications that you are getting from the webhook but to combine this with the Delta Query functionality.
There's a tutorial on this approach: https://learn.microsoft.com/en-us/graph/tutorials/change-notifications
Related
I'm interested in using MassTransit as the event bus to help me bust a cache, but I'm not sure how to properly throttle the service.
The situation
I have a .Net service that has a refreshCache(itemId) API which recomputes the cache for itemId. I want to call this whenever code in my organization modifies any data related to itemId.
However, due to legacy code, I may have 10 events for a given itemId emitted within the same second. Since the refreshCache(itemId) call is expensive, I'd prefer to only call it once every second or so per itemId.
For instance, imagine that I have 10 events emitted for item1 and then 1 event emitted for item2. I'd like refreshCache to be called twice, once with item1 and once with item2.
Trouble with MassTransit
I could send event messages that essentially are just itemId over SNS/SQS, and the .Net service could use a MassTransit consumer to listen to that SQS queue and call refreshCache for each message. Ideally, I can also throttle either in SNS/SQS or MassTransit.
I've read these docs: https://masstransit-project.com/advanced/middleware/rate-limiter.html and have tried to find the middleware in the code but wasn't able to locate it.
They seem to suggest that the rate-limiting just delays the delivery of messages, which means that my refreshCache would get called 10 times with item1 before getting called with item2. Instead, I'd prefer it get called once per item, ideally both immediately.
Similarly, it seems as if SNS and SQS can either rate-limit in-order delivery or throttle based on the queue but not based on the contents of that queue. It would not be feasible for me to have separate queues per itemId, as there will be 100,000+ distinct itemIds.
The Ask
Is what I'm trying to do possible in MassTransit? If not, is it possible via SQS? I'm also able to be creative with using RabbitMQ or adding in Lambdas, but would prefer to keep it simple.
If you want to have several subscribers to a publisher and you want all of them to receive the published item, you should use a ConnectableFlux.
However, when you use a normal Flux and several subscribers subscribe, only one of them will receive the published item. The normal Flux was likely designed to have a single subscriber.
It has happened to me that several subscribers have subscribed by accident. Is there a way to detect or prevent more than one subscriber to a given Flux or Mono?
Im building a Calendar app, where you can schedule events, and you get Notified by UserNotification.
The Problem is that i recently read that you can only have 64 scheduled events. But what if the user has more than 64 events? I know repeated notifications are counted as one.
Does this limit count for all notification types (Timer,Calendar,Loacation)?
How would u solve this issue? Since i don't use a server, i cant make push/remote notifications.
Looking forward to ur answers!
Thanks in advance!
After the 64th event, you can try to save the ones after that and schedule them once the number of current scheduled event is less than 64. You should take into account the event's schedule time to avoid missing event with sooner start date.
EDIT
Since your app allows user to schedule future events, it makes sense to use CoreData to persist data. For each event they created, you can create an entity with following attributes:
event name
event start date
isScheduled boolean
This should be fairly simple. After that, whenever the app starts, you can fetch the events and schedule the ones with closest start date. This way, you don't have to schedule an event too far ahead.
If you want to check the number of scheduled events, you can do
UIApplicaiton.shared.scheduledLocalNotifications?.count
This method works but it is deprecated so you might want to use
UNUserNotificationCenter.getPendingNotificationRequests
I'm building an online calendar in Ruby on Rails that needs to send out email notifications whenever a user-created event is about to start/finish (i.e you get a reminder when a meeting is 5 minutes away). What's the best way of figuring out when an event is about to start? Would there be a cron task that checks through all events to find out which ones are starting within a certain threshold (i.e 5 minutes) ? A cron task seems inefficient to me, so I'm wondering what might be a better solution. My events are stored in a mySQL database. There must be a design pattern for this... I'm just at a loss for what to search for.
Any help would be greatly appreciated. Thanks.
In all likelihood you will probably implement some background queuing mechanism to actually deliver the notifications - at least you certain should be considering this approach.
Assuming this, why not create your delayed notification jobs at event creation time to be delivered when the associated event is starting or finishing. The background queue, which is already waking up periodically to look for work, will pick these up and run them.
However adopting this approach requires you to consider the following (at least):
Removing queued notification job if the associated event is removed
Amending the notification job if the associated event is amended (say a new time)
Ensuring that the polling resolution of the queuing system does not allow notifications to be delivered so late as to be useless.
If you haven't picked a queuing solution for your application you should consider these options
I'm designing a .net interface for sending and receiving a HL7 message and noticed on this forum theres a few people with this experience.
My question is.... Would anyone be able to share their experience on how long it could take to get a message response back from a hospital HL7 server. (Particularly when requesting patient demographics) - seconds / minutes / Hours?
My dilemma is do I design my application to make the user wait for the message to come back.
(Sorry if this is a little off topic, it’s still kinda programming related? – I searched the web for HL7 forums but got stuck so again if anyone knows of any please let me know )
cheers,
Jason
In my experience, you should receive an ACK or NAK back within a few seconds. The receiving application shouldn't do something like making you wait while it performs operations on the message. We have timeouts set to 30 seconds, and we almost never wait that long for a response.
This is quite dependent on the kind of HL7 message sent, typically messages like ADT's are sent as essentially updates to the server, and are acknowledged almost immediately if the hospital system is behaving well. This will result in a protocol level acknowledgement, which indicates that the peer has received the message but not necessarily processed it yet.
Typically, most systems will employ a broker or message queue in their integration engines so you get your ack almost immediately.
Other messages like lab request messages may actually send another non-ack message back which contains the information requested. These requests can take longer.
You can check with the peer you're communicating with to see what integration engine they are using, and if a queue sits on that end which would help ensure the response times are short.
In the HL7 integration tool I work on, we use queues for inbound data so we can responde immediately. And for our outbound connections, 10s timeouts are default, and seem to work fine for most of our customers.
When sending a Query type event in HL7, it could take a number of seconds to get the proper response back. You also need to code for the possibility that you will never get a response back, and the possibility that connected systems "don't do" queries.
Most HL7 nets that I have worked on, assume that all interested systems are listening for demographic updates at all times. Usually, receiving systems process these updates into a patient database that documents both the Person and Encounter (Stay) information on the fly.
In my location, my system usually gets about 10-20 thousand messages a day, most of which are patient demographic updates.
It depends if the response is generated automatically by a system or if the response is generated after an user does something on the system. For an automatic response it might take less than a second, depending of course on the processing that is done by the system and the current work load of that system. If the system is not too busy and processing is just a couple of queries and verification of some conditions, considering network delays, response time should be a few seconds or less.