Frequent problems encountered in Netweaver Gateway Service development

Here is a list of commonly encountered errors and pointers to resolve them. These are compiled from my experiences as well as experiences in answering questions in SCN.

Let me start with two important Transaction codes which will give more information on most errors.

1. /IWFND/ERROR_LOG: This provides error log in the hub system. From here you can navigate to a Gateway specific Application log or directly launch it using /IWFND/APPS_LOG.
2. /IWBEP/ERROR_LOG: This provides the error log in your BEP/Backend system. Again you can navigate to Gateway specific Application Log by going to /IWBEP/VIEW_LOG.

The error messages mentioned in this blog refer to the ones received in the Error Logs, Application Logs or at the Client level. Now let us look at the various problems.

       1. Error Message at Client: While calling a service operation through REST client, you encounter RFC call ended with "System Failure" exception”

Error Analysis: This is a very common error while using the RFC tool in Service Builder. There can be many reasons for this error and error can be pin pointed by looking at the back-end error log. One other option is to go to your Data Provider Class (DPC) and find the place where RFC is called and put a external breakpoint and debug.

Common problems: Mandatory parameters are not supplied to RFC, Problem with RFC destination, Problem with the RFC itself (interface changed, not active etc.).

     2. Error Message at Client: In the context of Data Services an unknown internal server error occurred

Error Analysis: This is a generic error at client side and there can be multiple reasons for it. This error is from the hub system and only way to check this error is to look into error log and application log in hub system.

Common Problems: property type errors (date, decimal/precision etc.)

     3. Error Scenario: You have made changes to the data model. I.e. you have added and entity or added a new Function Import, but do not see in           metadata.

Error Analysis: Metadata can be cached at Backend and also in the Hub system (can be deactivated as well, but not recommended). Once you make any change to the metadata, clear both caches using transaction code /IWFND/CACHE_CLEANUP and /IWBEP/CACHE_CLEANUP.

     4. Error Message at client: The specified HTTP method is not allowed for the resource identified by the Data Service Request URI

Error Analysis: For each http method you need to be aware of the right URI convention.

Common Problems: For a ‘POST’ method URI should point to a Collection.

Example:  …../sap/opu/odata/<NameSpace>/<ServiceName>/<CollectionName>

For a ‘PUT’ and ‘DELETE’ methods URI should point to an Entry.

Example: …../sap/opu/odata/<NameSpace>/<ServiceName>/<CollectionName>(<keys and values>)

     5. Error Scenario: You are querying an OData service and you see that $orderby on query is not behaving as expected

Error Analysis: $orderby is not handled by Gateway framework; instead you need to handle it in your data provider class (DPC). Go to method iwbep/if_mgw_appl_srv_runtime~get_entityset in your DPC and read importing parameter IT_ORDERS and pass this info to your application.

     6. Problem Scenario: I want to create/POST more than one entry at a time, but I get an error message when I try it.

Problem Analysis: OData does not allow you to POST more than one entry at a time, however there are alternatives. You can do a Batch update. See http://scn.sap.com/docs/DOC-29682 for more details. If you want to POST a parent and it children (example: Sales order and its line items, you can do a ‘Deep Insert’. See http://scn.sap.com/docs/DOC-22305 for details.

     7. Problem Scenario:  Within Service Builder, Service Maintenance node is empty. You want to register your recently developed Gateway service           into the Hub system, but see that Service Maintenance Screen node is empty and you do not see any Hub system there.

Problem Analysis: To do Service Registration on a Hub system, you can directly login to hub system and navigate to transaction /IWFND/MAINT_SERVICE. But if you want to do it from your backend system using the Service Maintenance node, then you need to maintain your Hub systems in configure backend through                    SPRO  SAP NetWeaver  Gateway Service Enablement  Backend OData Channel  Connection Settings to SAP NetWeaver Gateway  SAP NetWeaver Gateway Settings in the Gateway hub system

     8. Problem Scenario: External Debugger not reached while debugging a Gateway Service

Problem Analysis:  Ensure that you have set the breakpoint in the right backend system. Check your system alias of the gateway service to identify the right backend system. See below options if it you are sure about it.

1. Clear your browser cache and try again.If this does not solve your problem see below point.
2. Clear your metadata cache in hub and backend and try again. If this does not solve your problem see point.
3. External debugger points are user specific. When you set an external debugging point check the message you get at bottom of the screen. That indicates the user for which the breakpoint was set. Now any call coming to this place in backend with this user, the breakpoint will be hit. If this does not solve your problem see below point
4. Sometimes in development scenarios it is possible that you have a fixed RFC user set in the RFC destination’s logon options. In such a case the call to the backend will be through this RFC user, and not with the user with which you authenticated the Gateway service. In such a case, go to Utilities -> Settings -> ABAP Editor -> Debugging and set this RFC user here.

     9. Error Message: While executing a query/read, encountered In the context of Data services and unknown error occurred

Error Analysis: This is usually problem with the properties involving Date, Time, UoM etc. There seems to be problem with RFC model importer in Service Builder.

Common problems: If your RFC/model has a date property, check that it is of type Edm.DateTime and Precision is 0. Service Builder usually gives a Precision as 8. After changing it to 0, generate the runtime artifacts again, clear the cache and run the operation.

     10. Problem Scenario:

You want to copy an existing Netweaver Gateway Service or

You want to copy an existing Project in Service Builder or

You want to Copy/Rename an existing Project in Service Builder

Problem Analysis: All these functionalities are not yet supported in Service Builder as of SP7, and as I understand they are in pipeline in future releases.

     11. Error Message:Syntax error in program /IWCOR/CL_REST_HTTP_HANDLER===CP

   Error Analysis: This is usually solved by upgrading Basis to SP09. Also look at SAP notes 1551982, 1567128, 1560585 and 816861

     12. Error Scenario:  NW Gateway Service hitting a wrong client. You want the service to hit client 200, but it is hitting client 100, even though               you had registered the service from client 200

     Error Analysis: Unless specified explicitly, service will hit the default client, and in your case 100 seems to be the default client.

     Solution: There are two ways to solve this problem.

1. An SAP specific parameter ‘sap-client’ can be used. Example: https://<host>:<port>/sap/opu/odata/IWBEP/RMTSAMPLEFLIGHT_2/$metadata?sap-client=200
2. Navigate to your service in Transaction SICF. Under Logon Data tab mention your client. Select “Alternative Logon Procedure” from the drop down and save your node.

If you have faced one of these errors/problems and solved it differently, let me know, I will improve the blog.

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