I have to admin the WS2 BPS (3.6.0) is not very revealing about internal exceptions. There's a small chapter in the documentation about troubleshooting, however this setup logs only messages passed to the endpoints.
Questions:
is there way to see internal exceptions thrown during the BPEL execution) wether handled or unhandled? (such as errors in the expressions or scripts). Maybe on the Apache-ODE level?
is there any way to access the fault caught by the "catchAll" fault handler?
Thank you all for any hint
1) One way troubleshoot is, enable BPEL Runtime debug logs, where you can see the execution flow.
log4j.logger.org.apache.ode.bpel.runtime=DEBUG
If you need further information, you can enable debug logs for ODE engine as well.
log4j.logger.org.apache.ode.bpel.engine=DEBUG
2) There is no OTB way to achieve this. This is a limitation in BPEL 2.0 spec. In BPEL 2.0, you can catch only faults that are defined in the partner service WSDL. Additionally, you can assign a variable for the error message. From that, you can access information about the fault.
But CatchAll doesn't associate with a variable. It is a generic fault handler.
I would suggest using flag based solution to handle errors within catchall. (That is what I have seen in most of the solutions.)
Related
I've just successfully implemented a JMS-message-processor in my WSO2-process. However, when logged in as an admin on the ActiveMQ console, I can view the stats of the queue but I cannot access the contents of the pending message. Instead, I see this error:
Cannot display ObjectMessage body. Reason: Failed to build body from content. Serializable class not available to broker. Reason: java.lang.ClassNotFoundException: org.apache.synapse.message.store.impl.commons.StorableMessage
Accessing the contents of a pending message is possible when using the RabbitMQ, so I figured it should also be possible with this message broker.
I've found solutions online, but they don't seem to be working, or perhaps they're out of date. Can somebody point me to the correct answer to solve this? I'm on WSO2 Integration Studio 8.1.0 and am using ActiveMQ 5.17.1.
It appears that WSO2 is using javax.jms.ObjectMessage despite the fact that there's a long list of reasons why doing so is a bad idea, including the issue you're currently facing, but I digress.
The problem here is that the implementation of the javax.jms.ObjectMessage (i.e. org.apache.synapse.message.store.impl.commons.StorableMessage in this case) must be on the classpath of any application which wants to deserialize that message. This class is not, in fact, on the classpath of ActiveMQ therefore the ActiveMQ web console cannot deserialize the message and display its contents (assuming those contents are human-readable in the first place). That's why a ClassNotFoundException is thrown.
You may be able to resolve the issue by putting org.apache.synapse.message.store.impl.commons.StorableMessage on ActiveMQ's classpath. Aside from that there's really nothing to be done.
I assume this is different for RabbitMQ because in that case WSO2 doesn't use the JMS API and uses the AMQP protocol which is not Java-centric like JMS.
Justin has explained the cause of the issue and as suggested you can try adding the class to ActiveMQ runtime and see whether it resolves the issue. This class is located in the Synapse-Core(synapse-core_2.x.x.wso2vXXX.jar). But remember although this may resolve the ActiveMQ UI issue, this message is not consumable by other systems unless they know how to deserialize it.
Let me add more details on why the message is serialized. Message serialization happens when you use the Store mediator, and when you store a message with Store Mediator it is intended to be only read by a Message Processor. Simply the serialized message can only be consumed by WSO2 Message Processors. In other words, Store Mediator and the Message processors are tightly coupled.
If message serialization is an issue for you. For example, if other systems are consuming the messages that WSO2 publishes you can try using the JMS transport to produce and to consume messages from ActiveMQ. Other than that you can also consider using JMS Inbound Endpoint to consume messages, which all use standard media types when storing the message.
It is best practice to handle such API errors by try and catch or the API response suppose to be like Google, Facebook and Microsoft API call
Google API call example
Facebook API call example
Microsoft API call example
As a general rule, there isn't such a thing as a standard API, so there also isn't a best practice as such either. If you are dealing with multiple APIs within your app, you'll end up having at least a handful of variations in what you check for and how you adapt.
Depending on how terminal the failure is, and where it happens in their processing stack, the HTTP status may be set, and you may also get an HTML, JSON or XML body with more detail (no matter what you thought you might get).
APIs also fail randomly with transient errors, so for your code to work reliably, you probably need a retry loop somewhere.
They also throttle, so some kind of detect/backoff/retry handler would help (details vary per API, as ever).
Psuedocode:
retry loop {
request
check connection (network errors)
check HTTP status code
check body
parse body if valid and extract errors
if terminal failure exit (authentication/authorisation etc)
if throttling backoff
}
When I use the try tool of WSO2 Data Services in link:
.../services/User_DataService?tryit
The exceptions generated for the data service are accessible just in the log file, within the sever (.../repository/log/wso2carbon.log).
Is possible receive the full exception in the "Reponse" block when I use the try tool?
Normally you are getting a SOAP fault message with proper reasoning in Data Services when an exception occurs. You will not be getting the complete error log as it is but a meaningful to understand it.
I need to launch the on error sequence o generate a internal error when I receive a soap fault response in my orchestration. Something like throw an exception in Java.
An easy way is to set a filter in each sequence so that, when a fault tag is received, the onError sequence is launched. I guess there must be better ways to do this.
How can I make soap fault responses are treated like an error so that the on error sequence is launched?
This was not straight-forward until WSO2 ESB 4.5.0 (which is the latest release). There is new property introduced "FORCE_ERROR_ON_SOAP_FAULT" to get this done. See this post for a sample configuration.
In your proxy configuration, define the fault sequence..
I have a legacy VB6 application that needs to make asynchronous calls to a web service. The web service provides a search method allows end-users to query a central database and view the results from within the application. I'm using the MSXML2.XMLHTTP to make the requests, and have written a SearchWebService class that encapsulates the web service call and code to handle the response asychronously.
Currently, the SearchWebService raises one of two events to the caller: SearchCompleted and SearchFailed. A SearchCompleted event is raised that contains the search results in a parameter to the event if the call completes successfully. A SearchFailed is raised when any type of failure is detected, which can be anything from an improperly-formatted URL (this is possible because the URL is user-configurable), to low-level network errors such as "Host not found", to HTTP errors such as internal server errors. It returns a error message string to the end-user (which is extracted from the web service response body, if present, or from the HTTP status code text if the response has no body, or translated from the network error code if a network error occurs).
Because of various security requirements, the calling application does not access the web service directly, but instead accesses it through a proxy web server running at the customer site, which in turn accesses the actual web service through via a VPN. However, the SearchWebService doesn't know that the calling application is accessing the web service through a proxy: it's just given a URL and told to make the request. The existence of the proxy is a application-level requirement.
The problem is that from an end-user perspective, it's important that the calling application be able to distinguish between low-level network errors versus HTTP errors from the web service, and to distinguish proxy errors from remote web server errors. For example, the application needs to know if a request failed because the proxy server is down, or because the remote web service that the proxy is accessing is down. An application-specific message needs to be presented to the end-user in each case, such as "Search web service proxy server appears to be down. The proxy server may need to be restarted" versus "The proxy is currently running but the remote web server appears to be unavailable. Please contact (name of person in charge of the remote web server)." I could handle this directly in the SearchWebService class, but it seems wrong to generate these application-specific error messages from such a generic class (and the class might be used in environments that don't require a proxy, where the error messages would no longer make sense).
This distinction is important for troubleshooting: a proxy server problem can usually be resolved by the customer, but a remote web server error has to handled by a third party.
I was thinking one way to handle this would be to have the SearchWebService class detect different types of errors and raise different events in each case. For example, instead of a single SearchFailed event, I could have a NetworkError event for low-level network errors (which would indicate a problem accessing the proxy server), a ConfigurationError event for invalid properties on the SearchWebService class (such as passing an improperly-formatted URL), and a ServiceError for errors that occur on the remote web server (implying that the proxy is working properly but the remote server returned an error).
Now that I think about it, there is also an additional error scenario: it could be possible that the proxy server is running properly, but the remote web server is down, or the proxy server has been misconfigured.
Is the approach of using multiple error events to classify different classes of error a reasonable solution to this problem? For the last scenario (the proxy is running but the remote server cannot be reached), I'm guessing I may have to set up the proxy to return a specific HTTP error code so that client can detect this situation (i.e. something more specific than a 500 response).
Originally I kept the single SearchFailed event and simply added an additional errorCode parameter to the event, but that got messy quickly, especially in cases where there wasn't a logical error code to use (such as if the VB6 raises a "real" error, i.e. if the XMLHTTP class isn't registered).
I think that some ideas I've used with Java exceptions may apply here.
Having a large number of different Exceptions gets pretty messy, yet we need to give enough detail to the user so we don't want to lose information.
Hence I have a small number of specific Exceptions, which I guess would correspond to your Events:
InvalidRequestEvent: Used when the user specifies bad information
TransientErrorEvent: used when there's infrastructure issues when a retry might work.
I tend to work in environments where we have clusters of servers so if a user request hits a dying server then if he resubmits he'll probably get a good one, hence from his perspective a simple retry often works. However sometimes the error is with a service such as the Network or Database and in which case the user needs diagnostic information to report to the helpdesk. Hence we need to decide on the extra information to put into the exception. This is (if I understand you correctly) your question.
In the case of InvalidRequestException we would bet giving some information about the problems with the input. It could be on the lines of "Mismatched parenthese" or "Unknown column CUTSOMER in table ORDER". In the case of TransientErrorException it could be "Proxy server is down".
Now depending upon your exact requirments you may not actually choose to put that text in the Exception, but rather an error number which the presentation layer converts to a locale-specific string (English, French ...).
So either Exception might contain something like this (sorry for that Java syntax, but I hope the idea is clear):
BaseException {
String ErrorText; // the error text itself
// OR if you want to allow for internationaliation
int ErrorCode; // my application specific code, corresponds to text held by the UI
String[] params; // specific parameters to be substitued in the error text
// CUTSOMER and ORDER in my example above
int SystemErrorCode; // If you have an underlying error code it goes here
String SystemErrorText; // any further diagnoistic you might need to give to
// the user so that they can report the problem to the
// help desk.
// OR instead of the text (this is something I've seen done)
int SystemErrorTag; // A unique id for this particular error problem.
// This server systems will label their message in the
// server logs. Users just tell the help desk this number
// they don't need to read detailed server error text.
}