At client startup - Interface not found fInterfaces.FindHashed(aUri)

larand54 · 2023-05-09 08:45:18

Suddenly my testclient crashed at start with an access violation in this call: "HttpClient.Services[DHS_LOCAL_CONTRACT].Get(fDHS_LocalService);"
Debugging showed that the function "fInterfaces.FindHashed(aUri)" returns -1.

I've just added a method to the interface, recompile both the server and client and then this happened. I also removed those changes but still the same problem.
Something else must have been changed but I can't imagine what it could be.

I need some idea of where to start looking.

ab · 2023-05-09 09:04:47

The fact that the problem remains after removing the interface seems to show that the problem is not the interface name hashing, but something else.

What does fInterfaces.Count return ?
Is aUri (DHS_LOCAL_CONTRACT) part of the fInterface[] array ?

Can you try to reproduce with a RawUtf8 list of interface names, without any service process?
I doubt it is a TDynArrayHashed bug... but we have to be sure of that.

Verify that TServiceContainerClientAbstract.AddInterface is properly called in your code, before the Get(DHS_LOCAL_CONTRACT) call.

larand54 · 2023-05-09 10:51:41

To make a simple test client I added the following code:

procedure TForm4.FormCreate(Sender: TObject);
begin
  Model := TOrmModel.Create([],SYSTEMLocalROOT);
  HttpClient := TRestHttpClient.Create(IP_Local, HTTP_PORT, Model);
  HttpClient.ServiceDefine([IDHSLocalService], sicShared, DHS_LOCAL_CONTRACT);
  HttpClient.Services[DHS_LOCAL_CONTRACT].Get(fDHS_LocalService);
end;

In the function "TServiceContainerClientAbstract" the parameter aInterfaces contains one interface "IDHSLocalService" which is correct here. I' only use one interface so far.

The call "fHash.FindOrNew(fHash.HashOne(@Item), @Item, nil);" with Item as 'DHS_LOCAL_CONTRACT' returns -161.
This lead to that he interface pointer will be nil.
I'm not sure how to reproduce with a RawUTF8 list of interface. Where should I put the call?

ab · 2023-05-09 12:04:52

You are making a confusion with the contract and the interface name.

It is the interface name, not the contract value, i.e. you should wreite Services['IDHSLocalServer].
But don't mess with the service name.
Just use Services.Resolve(IDHSLocalService).

larand54 · 2023-05-09 12:05:29

Sorry, I found the problem. It's of course my mistake. I misunderstood the usage of the parameter "ContractExpected". It looks like it should have the same name as the service without the leading 'T'. I got the impression of that this parameter is used to make it possible of same version control of the interface. So if you add a new or changed a method you could change this parameter and in that way you get a signal if you have different versions between client and server.

Strange is that I'm sure I had a different name for this parameter from the beginning without any problem.

Sorry I bothered you with this.
Best regards
Lars-G.

Last edited by larand54 (2023-05-09 12:11:37)

larand54 · 2023-05-09 12:26:22

Oh, I got your answer while I was writing.

Yea, I can see now!

Maybe I was not completely wrong about the parameter..?
I took the code from an example just to get a kickstart for testing.
I should be more careful.

Thank's a lot!

mORMot Open Source

#1 2023-05-09 08:45:18

At client startup - Interface not found fInterfaces.FindHashed(aUri)

#2 2023-05-09 09:04:47

Re: At client startup - Interface not found fInterfaces.FindHashed(aUri)

#3 2023-05-09 10:51:41

Re: At client startup - Interface not found fInterfaces.FindHashed(aUri)

#4 2023-05-09 12:04:52

Re: At client startup - Interface not found fInterfaces.FindHashed(aUri)

#5 2023-05-09 12:05:29

Re: At client startup - Interface not found fInterfaces.FindHashed(aUri)

#6 2023-05-09 12:26:22

Re: At client startup - Interface not found fInterfaces.FindHashed(aUri)

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