In my test case, I perform the http().receive() action for each expected request to the citrus http server.
Now I'd like to verify that there weren't any more requests after the expected ones. How do I accomplish that?
You can use the receiveTimeout() test action that expects that no messages are received on a given endpoint:
receiveTimeout(httpServer)
.timeout(5000);
This will make sure that no requests are received from 'httpServer' endpoint for 5000 ms. The action fails in case a message arrives at this endpoint in that time.
Related
Can one http request have multiple responses? (Response codes out of range 1XX)
Is such functionality supported by clients/servers?
client ----request-----------> server
client <---response1 (402)---- server
client <---responsen2 (202)--- server
...
client <---responseN (200)---- server
No. In HTTP, one request gets one response. The client must send a second request to get a second response.
An HTTP request can have multiple "header responses", but the responses all have status codes in the 1xx range, such as 102 Processing. However, these responses are only headers, never bodies. Sending a response unsolicited is not allowed.
We have 2 Windows services (same machine) that communicate on top of HTTP Protocol.
On specific machine we see the HTTP POST being sent from the client (Windows service) and arrives to the server (Windows service listening to REST CALLs) - 2 times, meaning i get 2 exact HTTP Post request on the service, but we see on client it was executed only 1 time.
Before going to wireshark/analyze the HTTP protocol, I wish to understand what explain this behavior.
When going to https://www.rfc-editor.org/rfc/rfc7231#section-4.3.3
"the origin server SHOULD send a 201 (Created) response containing a Location header
field that provides an identifier for the primary resource created"
I guess we should look in wireshark for 201 response? And if no response? Does the HTTP or network framework for my C# application is retrying the POST on the server side? because we dont see 2 requests sent from client code.
POST reply behavior
While true, more often than not the server replies with a 200-ok status code and some extra information.
Whether this is by mistake or to avoid chatty apis or some other architecture/design consideration, only the developer can tell.
So in theory you get a 201 with an identifier and then make a GET request with said identifier to retrieve details.
In practice a lot of times this does not occur. So it is not safe to assume this behavior.
Your problem
I highly doubt that there is a built in mechanism that retries post. There are plenty of reasons for that:
Duplicating entries. Imagine creating a PayPal payment. If the network has an error and you just did not receive the answer, the built in mechanism will charge you twice.
There are libraries that do that only when you are sure that the request is idempotent, that is the post contained some sort of identifier and the second request will fail.
First, the calls are HTTP GET (not POST).
We define the URL with hostname/FQDN, the solution to avoid duplicated calls was to work with ip address instead of hostname when sending the Rest API.
This is the long explanation of the problem, no root cause yet.
Used both Wireshark/Process Monitor to diag, not sure for the root cause.
Process Monitor: Filtering to display network calls
Wireshark: Filter to show only HTTP
The Client send a single HTTP Get request to:
/DLEManagement/API/Engine/RunLearningPeriod
The call was executed at 11:08:16.931906
We can see 2nd call at 11:08:54.511909 - We did not trigger.
HTTP Get executed from *Server.exe (in red) and the Server is at *Management.Webservice.exe (in red).
We see that a *Client.exe (Antivirus process, in blue) is sending TCPCopy packets in the window between we sent and received.
Also, we can see that the first request was made with APIPA IPv6 and the 2nd call is IPv4, We checked the network interface and it was disabled.
Wireshark screenshot:
Process Monitor screenshot:
Network configuration:
I have an API that charges for an order. It accepts the orderId and the amount as inputs. Then it makes a '/charge' call to the downstream, which returns a 202. Immediately after this call, it calls a '/verify' endpoint to make sure that the previous charge was successful.
Now it may happen that the charge was declined. One of the reasons for this can be that the user used an expired card. What should be the error code in this scenario?
As I see it, I can't send a 4xx as the request was correct for my API perspective. A bad request is something that the user can correct - In this case, he can't correct anything since the API just accepts the 'orderId' and the total amount to charge.
If I am sending a 5XX, then 500 does not make sense as this was not an 'unexpected condition' on my server. I can neither send a 503 as my server was not overloaded or down for maintenance.
Currently, I am sending back a 503 with an app code that maps to: Payment verification failed.
The response of the server must always be in the context of the domain responsibility of the service
If the service "accepts" the request and that is all the requester (client) is expected to know, with the domain operation being performed asynchronously behind the scenes, it should return a 202
If the interaction is synchronous, you must surely respond with an error, since the request was unsuccessful.
The response code depends on the domain remits.
As per your service, if the api accepts an identifier in the request, that led to the failed payment and it was the responsibility of the client to pass the right identifier, then you must respond with a 400 - BAD REQUEST.
If however, the api is just an intimation from the client to request you to perform some domain actions, and one of the domain actions failed; then there is nothing the client can do about it, and you must return a 5XX, since it is a service failure
500 is generally used for ungraceful error scenarios as a rule of thumb. But if you are ok to term this a server error, then return a 500
502 - is a BAD GATEWAY, wherein your domain services acting as a proxy for your downstream services failed to perform a domain action.
Please choose what fits
How is possible to handle timeouts in time consuming operations in a REST API. Let's say we have the following scenario as example:
A client service sends a request to insert a resource through a REST API.
Timeout elapses. The client thinks the insertion failed.
REST API keep working and finishes the insertion.
Client do not notify the resource insertion and it status is "Failed".
I can think I a solution with a message broker to send orders to a queue and wait until they are solved.
Any other workaround?
EDIT 1:
POST-PUT Pattern as has been suggested in this thread.
A Message Broker (add more complexity to the system)
Callback or webhook. Pass in the request a return url that the server API can call to let the client know that the work is completed.
HTTP offers a set of properties for invoking certain methods. These are primarily safetiness, idempotency and cacheability. While the first one guarantees a client that no data is modified, the 2nd one gives a promise whether a request can be reissued in regards to connection issues and the client not knowing whether the initial request succeeded or not and only the response got lost mid way. PUT i.e. does provide such a property, i.e.
A simple POST request to "insert" some data does not have any of these properties. A server receiving a POST request furthermore processes the payload according to its own semantics. The client does not know beforehand whether a resource will be created or if the server just ignores the request. In case the server created a resource the server will inform the client via the Location HTTP response header pointing to the actual location the client can retrieve information from.
PUT is usually used only to "update" a resource, though according to the spec it can also be used in order to create a new resource if it does not yet exist. As with POST on a successful resource creation the PUT response should include such a Location HTTP response header to inform the client that a resource was created.
The POST-PUT-Creation pattern separates the creation of the URI from the actual persistence of the representation by first firing off POST requests to the server until a response is received containing a Location HTTP response header. This header is used in a PUT request to actually send the payload to the server. As PUT is idempotent the server simply can reissue the request until it receives a valid response from the server.
On sending the initial POST request to the server, a client can't be sure whether the request reached the server and only the response got lost, or the initial request didn't make it to the server. As the request is only used to create a new URI (without any content yet) the client may simply reissue the request and in worst case just create a new URI that points to nothing. The server may have a cleanup routine that frees unused URIs after a certain amount of time.
Once the client receives the URI, it simply can use PUT to reliably send data to the server. As long as the client didn't receive a valid response, it can just reissue the request over and over until it receives a response.
I therefore do not see the need to use a message-oriented middleware (MOM) using brokers and queues in order to guarantee reliable messaging.
You could also cache the data after a successful insertion with a previously exchanged request_id or something of that sort. But I believe message broker with some asynchronous task runner is a much better way to deal with the problem especially if your request thread is a scarce resource. What I mean by that is. If you are receiving a good amount of requests all the time. Then it is a good idea to keep your responses as quickly as possible so the workers will be available for any requests to come.
Suppose client call server using GET API, is it possible that server send a response but client misses that response??
If yes how to handle such situation, as I want to make sure that client receives the data. For now I am using second REST call by client as ack of first.
It is certainly possible. For example if you are using a site with a REST API and a request is just sent to the API and your internet connection dies when the answer is supposed to arrive, then it is quite possible that the server has received your request, successfully handled it, even sent the response, but your computer did not receive it. It could be an issue on a server responsible for transmitting the request as well. The solution to this kind of issue is to have a timeout and if a request timed out, then resend it until it is no longer timed out.