Here's my scenario: I need to make three or four calls to different WCF services before completing the transaction - what are my options, if any?
ServiceA.SaveWork(work1);
ServiceB.SaveWork(work2);
ServiceC.SaveWork(work3);
ServiceD.SendNotification(notification);
If one call fails, all fail... Note that these services may not be in the same domain.
Cheers!
You should be able to wrap those into a System.Transctions.TransactionScope to achieve this:
using(TransactionScope scope = new TransactionScope())
{
ServiceA.SaveWork(work1);
ServiceB.SaveWork(work2);
ServiceC.SaveWork(work3);
ServiceD.SendNotification(notification);
scope.Complete();
}
Of course, you need to make sure your WCF services don't explicitly prevent being part of a transaction! (check out the TransactionFlow attribute - avoid the TransactionFlow.NotAllowed setting!)
If these services are all on different machines etc, using two phase commit will lead to lots of real world problems.
Therefore I don’t think transactions are a good solution....
I think you need to make all your services so you can undo the work if needed to recover from an error. Undoing a item of work can be very complex in the real world.
E.g If you need to book a car and a hotel and then the hotel burns down, you can’t expect to be able to un-book the car without losing some money.
However if all the services sit on top of the same database, then transactions may work well for you.
Related
This is not a code/case specific question.
I am new to Apex, and I'm trying to test methods that do Callouts to external APIs. I understand that in order to test this method, I have to create a class that implements HttpCalloutMock and use it in my test.
However, I want to know: in the Test, when I call the actual method I'm testing, does a call go out to the API behind the scenes? Or is the data I'm putting in the mock the only data that gets passed around?
(I'm asking because, if the latter, wouldn't that mean these tests are extremely counterproductive and unnecessary?)
The dummy data you provided in the mock class will be dutifully returned. And yes, it's annoying, double work.
But how else could it be done? Really calling an external API might have bad consequences (sending "My Awesome Test Order!!!1one!eleven" to production fulfilment system would be a disaster, especially if you do it few times because deployment kept failing). And when such API would be down and you really, really need to deploy something to production - you shouldn't be a hostage of 3rd party server, even test one.
Instead of grumbling try to embrace it. Yes, it's rubbish. But this is your opportunity to test how your code handles different outputs. How it reacts when the API response is "HTTP 500 Internal Server Error", HTML instead of JSON or even there's no response, just timeout. The more solid you make it, the more confident you'll be.
Is it really that hard? Capture couple real messages & errors, remove sensitive data, implement some switch statement "if account number = 123 return this else return that" and you're done.
And yes, it essentially means implementing 3rd party's logic yourself. But well, with test-driven development you ideally would start with a dummy representation of their service anyway, something that's close enough to the API "contract" you have. And as a bonus - you get to shout at them when something suddenly breaks and you can prove it wasn't a change on your end.
In the end it's not too different from splitting work with another SF developer. "OK, I'll do the UI bit, you do the apex bit, here's the data interface we promise to use, see you in 1 week's time". How far can you trust the guy, eh? ;)
I'm trying to let my API clients make a POST request that bulk modifies objects that the client doesn't have their IDs.
I'm thinking of implementing this design but I don't feel good about it, are there any better solutions than this?
POST url/objects/modify?name=foo
This request will modify all objects with the name foo
This can be a tricky thing to do with an API because it doesn't age very well.
By that I mean that over time, you might introduce more criteria for the data stored on resources (e.g., you can only set this field to "archived" if the create_time field is older than 6 months). When that happens, your bulk updates will start to only work on some resources and now you have to communicate that back to the person calling the API.
For example, for any failures you need to explain that the update worked for some resources (and list them out) but failed on others (and list them out) and the reason why for each failure (and remember you might have different failure conditions for different resources).
If you're set on going down this path, the closest thing I can think of is the "criteria-based delete" method shown here: https://google.aip.dev/165.
I have an operation contract, on a windows service and it has an attribute
[OperationBehavior(TransactionScopeRequired = true)]
I would like to get rid of this attribute. Reason :
containerize the service.
and Containerized apps do not support MSDTC , that's the purpose of the attribute!
What are the implications of doing this?
I can confirm the code within the operation contract inserts into a single database.
No events triggered, however I am unsure of whether there is a transaction where the service is consumed.
Can I get some advice on this?
Your service is requiring a transaction.
Only you can know whether this is necessary, we cannot check your service and database to check.
Please be aware that this enables not only local transactions, but -depending on binding- also enables distributed transactions. See here for details.
You new system does not seem to support this (MSDTC is the Distributed Transaction Controller from MS). Again, whether this is a problem when you move over to this system is nothing we could find out. You will have to have a look at the system architecture and see whether this is something that was included "just because" and can be deleted without replacement, or if it's a key feature of your system that you need to keep.
I am studying interface design.
Here is what I curious about.
Some of open API support 2 different interfaces to implement toggling. i.e. instagram like interface. It separates like interface(like, cancel like)
What is the advantage of separate those two.(separating into two interfaces makes end-user more complicated in my view)
I question this, since it could be implemented with toggle.
i.e. user send item_id and user_id. server check database(this item is already liked or not), and update.
Thanks for answer!
The real benefit to having two interfaces for toggling is that it doesn't require the user to know the current state of the thing they are attempting to change (i.e. it doesn't require me to first query for the state).
If I am a consumer of an API, typically I will want to perform actions such as like-ing something. Very rarely can I think of a case where I would want to perform the action of do the opposite of what I did previously (unless I'm feeling like flip-flopping). If you didn't have two endpoints for like and unlike then you'd first have to poll the API to get the current status, and then perform the toggle that you're talking about if needed.
This situation introduces more logic into your code, requires that you make 1-2 calls to the API, and assumes that the state didn't change between calls; whereas having two endpoints reduces the logic, limits your API calls to 1 per action, and you don't have to worry about the state changing unexpectedly.
In the case where you try to like something that the user has already liked, then the API would simply return a successful result and not alter the underlying data.
One reason to prefer an interface where you specify the desired state explicitly is that it will be idempotent. That is, the resulting state is the same even if the request is made multiple times.
This is a pretty contrived example, but if two different people sharing the same account tried to like the same thing within a small enough window, you could end up with it being un-liked instead.
I'd like to write a Minecraft mod which adds a new type of mob. Is that possible? I see that, in Bukkit, EntityType is a predefined enum, which leads me to believe there may not be a way to add a new type of entity. I'm hoping that's wrong.
Yes, you can!
I'd direct you to some tutorials on the Bukkit forums. Specifically:
Creating a Meteor Entity
Modifying the Behavior of a Mob or Entity
Disclaimer: the first is written by me.
You cannot truly add an entirely new mob just via Bukkit. You'd have to use Spout to give it a different skin. However, in the case you simply want a mob, and are content with sharing a skin of another entity, then it can be done.
The idea is injecting the EntityType values via Java's Reflection API. It would look something like this:
public static void load() {
try {
Method a = EntityTypes.class.getDeclaredMethod("a", Class.class, String.class, int.class);
a.setAccessible(true);
a.invoke(a, YourEntityClass.class, "Your identifier, can be anything", id_map);
} catch (Exception e) {
//Insert handling code here
}
}
I think the above is fairly straightforward. We get a handle to the private method, make it public, and invoke its registration method.id_map contains the entity id to map your entity to. 12 is that of a fireball. The mapping can be found in EntityType.class. Note that these ids should not be confused with their packet designations. The two are completely different.
Lastly, you actually need to spawn your entity. MC will continue spawning the default entity, since we haven't removed it from the map. But its just a matter of calling the net.minecraft.server.spawnEntity(your_entity, SpawnReason.CUSTOM).
If you need a skin, I suggest you look into SpoutPlugin. It does require running the Spout client to join to such a server, but the possibilities at that point are literally infinite.
It would only be possible with client-side mods as well, sadly. You could look into Spout, (http://www.spout.org/) which is a client mod which provides an API for server-side plugins to do more on the client, but without doing something client side, this is impossible.
It's not possible to add new entities, but it is possible to edit entity behaviors for example one time, I made it so that you could tame iron golems and they followed you around.
Also you can sort of achieve custom looking human entities by accessing player entities and tweaking network packets
It's expensive as you need to create a player account to achieve this that then gets used to act as a mob. You then spawn a named entity and give it the same behaviour AI as you would with an existing mob. Keep in mind however you will need to write the AI yourself (you could borrow code straight from craftbukkit/bukkit) and you will need to push the movement and events of this mob to players within sight .. As technically speaking all your doing is pushing packets to the client from the serve on what's actually happening but if your outside that push list nothing will happen as other players will see you being knocked around by invisible something :) it's a bit of a mental leap :)
I'm using this concept to create Npc that act as friendly and factional armies. I've also used mobs themselves as friendly entities (if you belong to a dark faction)
I'd like to personally see future server API that can push model instructions to the client for server specific cache as well as the ability to tell a client where to download mob skins ..
It's doable today but I'd have to create a plugin for the client to achieve this which is then back to a game of annoyance especially when mojang push out a new release and all the plugins take forever to rise with its tide
In all honesty this entire ecosystem could be managed more strategically but right now I think it's just really ad hoc product management (speaking as a former product manager of .net I'd love to work on this strategy it would be such a fun gig)