This has happend to me more than once, thought someone can give some insight.
I have worked on multiple projects where my project depends on external service. When I have to run the application locally, i would need that service to be up. But sometimes I would be coding to the next version of their service which may not be ready.
So the question is, is there already a way that can have a mock service up and running that i could configure with some request and responses?
For example, lets say that I have a local application that needs to make a rest call to some other service outside to obtain some data. E.g, say, for given a user, i need to find all pending shipments which would come from other service. But I dont have access to that service.
In order to run my application, i need a working external service but I dont have access to it in my environment. Is there a better way rather than having to create a fake service?
You should separate the communications concerns from your business logic (something I call "Edge Component" see here and here).
For one it will let you test the business logic by itself. It will also give you the opportunity to rethink the temporal coupling you currently have. e.g. you may want the layer that handle communications to pre-fetch, cache etc. data from other services so that you will also have more resilient services at run time
Related
We have (roughly) following architecture:
Application service does the infrastructure job - fetches data from repositories which are hidden behind interfaces.
Object graph is created and passed to appropriate domain service.
Domain service does it thing and raises appropriate events.
Events are handled in different application services which perform some persistent operations (altering repositories, sending e-mails etc).
However. Domain service (3) has become so complex that it requires data from different external APIs only if particular conditions are satisfied. For example - if Product X is of type Car, we need to know price of that car model from some external CatalogService (example invented) hidden behind ICatalogService. This operation is potentially expensive one (REST call).
How do we go about this?
A. Do we pre-fetch all data in Application Service listed as (1) even we might not need it? Do we inject interface ICatalogService into given Domain Service and fetch data only when needed? The latter solution might create performance issues if, some other client of Domain Service, calls this Domain Service repeatedly without knowing there is a REST call hidden inside it.
Or did we simply get the domain model wrong?
This question is related to Domain Driven Design.
How do we go about this?
There are two common patterns.
One is to pass the capability to make the query into the domain model, allowing the model to fetch the information itself when it is needed. What this will usually look like is defining an interface / a contract that will be consumed by the domain model, but implemented in the application/infrastructure layers.
The other is to extend the protocol between the domain model and the application, so that we can signal to the application layer what information is needed, and then the application code can decide how to provide it. You end up with something like a state machine for the processes, with the application code coordinating the exchange of information between the external api and the domain model.
If you use a bit of imagination, you've already got a state machine something like this; as your application code is already coordinating the movement of inputs to the repository and the domain model. The difference, of course, is that the existing "state machine" is simple and linear enough that it may not be obvious that there is a state machine present at all.
how exactly would you signal application layer?
Simple queries; which is to say, the application code pulls the information it needs out of the domain model and uses that information to compute the next action. When the action is completed, the application code pushes information to the domain model.
There isn't enough information to give you targeted good advice. I suspect you need to refactor your domains into further subdomains. It sounds like your domain service has way more than 1 responsibility. Keep the service simple.
In addition, If you have a long running task like a service call that takes a long time, then you need to architect it away. The most supple design will not keep the consumer waiting. It'll return immediately with some sort of result to the user even if it's simply a periodic status update.
I need to write test for some JAX RS web service that asserts that certain value is cached in the session from disk on the first request in the session.
The testing process does not have access to the tested process. The use case involves using REST API to invoke services.
I can think of several options to proceed with:
Create a REST endpoint just for testing, and query there the needed session value.
Write and then read a log message.
I am aware that I am trying to test an implementation detail via an external API which does not provide contract for this detail, but currently I'm a bit constrained about which processes may be run by the testing infrastructure.
Are there any additional seams to exploit for testing, and what general good practice exists for this scenario?
I just came up with the idea of changing the cached resource and using the change in the behavior.
I'd like to develop a bunch of SaaS-Applications in Java and I'm not sure wat is the best way to go.
Each Application will have a WAR containing the Webservice and will have at least one Worker-WAR, which is a Thread waiting for new Tasks in the DB to come up and then working off this task. This worker contains the intelligence of the application and uses a lot of cpu. The Webservice gives Users the possibility to add new tasks and other stuff ...
Resource Limitations
The infrastructure must ensure the following:
The Webservice must always get a certain amount of cpu time to be able to respond to the user. So the hungry Worker must not get all cpu time for its working.
Each Tenant has its own worker and they must not interfere with each other as it must be not possible to block the whole system (and all tenants) with a single task.
Resource Sharing
It would be nice to be able to share the resources but always ensure that in extreme situations every worker and webservice gets the required minimum.
Versioning
As new Versions of a application are released each tenant must have the possibility to initiate a update on its own when he adapted to the API-Changes. Furthermore a tenant must be able to keep more than one application-endpoint (lets call them channels) to have a production channel and a beta-channel. In the Beta-Channel the tenant can test againts new versions and when he feels comfortable with the new version he can update his production channel.
User-Management
All applications of a tenant must share a user-Database and have the same way to authenticate.
Environment
I want to use Java EE 7. I would enjoy using Wildfly.
Question
What is the best infrastructure to approach these aims? I want to host this on my own servers.
What I already found
I understand that you cannot limit CPU-usage in a jvm. So the Workers must have their own jvms.
I looked at PaaS-Providers like OpenShift Origin, but it seems that they encourage you to run a application-server per tenant, per application which sounds to me as a resource-eater.
Is there no way to have one Wildfly running and limit the amount cpu-usage per tenant and app?
Thank You
Lukas
I am nearing the release of an iOS app that syncs and otherwise interacts with a server. I am struggling with a testing procedure that can cover most/all possible situations. I don't have any experience with automated testing so I have been doing everything manually so far with the iPhone simulator and a physical device.
How would I start designing automated tests that can help me get better coverage of possible situations and also serve me well in the future as I make changes and add new features?
You probably need to be more specific in your question. ie. outline how you communicate with your server, what technology is being employed etc.
But as a general approach the first thing I would be doing is looking to find a way to get reproducable results from the server. For example if I send a message asking for a record with an id of 'x' then the server will alwasy return the same record with the same data. There are severa ways to do this, one would be to load a set of test data into your server. Another would be to create a local test server and talk to that instead. Another option is to avoid the server all together in your automaticed tests and mock out the communication classes in your app. It totally depends on what you are trying to test and how.
Once you have your back end dealt with you can then look into automating the tests. This very much depends on how you have dealt with the server. For example, if you are performing an integration style test where you actually talk to a server, then the test might take the form:
Reset or clear the server data.
Load it with predictable data.
Run the iOS app using some testing framework and verify any data sent from the server.
Access the server and verify any changes made there.
I'm writing a mock of a third-party web service to allow us to develop and test our application.
I have a requirement to emulate functionality that allows the user to submit data, and then at some point in the future retrieve the results of processing on the service. What I need to do is persist the submitted data somewhere, and retrieve it later (not in the same session). What I'd like to do is persist the data to a database (simplest solution), but the environment that will host the mock service doesn't allow for that.
I tried using IsolatedStorage (application-scoped), but this doesn't seem to work in my instance. (I'm using the following to get the store...
IsolatedStorageFile.GetStore(IsolatedStorageScope.Application |
IsolatedStorageScope.Assembly, null, null);
I guess my question is (bearing in mind the fact that I understand the limitations of IsolatedStorage) how would I go about getting this to work? If there is no consistent way to do it, I guess I'll have to fall back to persisting to a specific file location on the filesystem, and all the pain of permission setting that entails in our environment.
Self-answer.
For the pruposes of dev and test, I realised it would be easiest to limit the lifetime of the persisted objects, and use
HttpRuntime.Cache
to store the objects. This has just enough flexibility to cope with my situation.