Http 500 error when navigating to Swagger UI

[sameer-coder]

Hello,

We have deployed imposter on AWS lambda using the imposter-awslambda.zip package. We are using the Open API plugin to serve content from a bunch of open API 3.0.1 specs. Everything works great except when we navigate to the Swagger UI, it throws a 500 error. This is only happening with the imposter instance deployed on AWS Lambda. Locally, running with imposter.jar it is working fine.

Any help would be appreciated.

Stack trace

2023-09-15 13:59:48 9d51be98-cc0e-482c-9bdb-a4bb57f854f5 ERROR i.g.i.s.ResourceServiceImpl - Unhandled routing exception for request: GET http://esmdev.lambda-url.us-west-2.on.aws/_spec
java.lang.RuntimeException: Route failed: HttpRoute(path=null, regex=/_spec$, method=GET)
	at io.gatehill.imposter.awslambda.impl.LambdaServer.dispatch(LambdaServer.kt:99) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.HandlerV2.handleRequest(HandlerV2.kt:68) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.HandlerV2.handleRequest(HandlerV2.kt:57) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at lambdainternal.EventHandlerLoader$PojoHandlerAsStreamHandler.handleRequest(EventHandlerLoader.java:205) ~[aws-lambda-java-runtime-0.2.0.jar:?]
	at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:905) ~[aws-lambda-java-runtime-0.2.0.jar:?]
	at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:261) ~[aws-lambda-java-runtime-0.2.0.jar:?]
	at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:200) ~[aws-lambda-java-runtime-0.2.0.jar:?]
	at lambdainternal.AWSLambda.main(AWSLambda.java:194) ~[aws-lambda-java-runtime-0.2.0.jar:?]
Caused by: java.lang.RuntimeException: Unhandled exception processing request [3b7a0973-11c3-43e0-9dab-d758e57f860b] GET http://esmdev.lambda-url.us-west-2.on.aws/_spec
	at io.gatehill.imposter.service.ResourceServiceImpl.handleFailure(ResourceServiceImpl.kt:337) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl.access$handleFailure(ResourceServiceImpl.kt:84) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl$handleRoute$1.invoke(ResourceServiceImpl.kt:141) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl$handleRoute$1.invoke(ResourceServiceImpl.kt:137) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.impl.LambdaServer.dispatch(LambdaServer.kt:93) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	... 7 more
Caused by: java.lang.NullPointerException
	at io.gatehill.imposter.http.HttpRoute$parsedPathParams$2.invoke(HttpRoute.kt:67) ~[imposter-http-3.29.0.jar:?]
	at io.gatehill.imposter.http.HttpRoute$parsedPathParams$2.invoke(HttpRoute.kt:64) ~[imposter-http-3.29.0.jar:?]
	at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74) ~[kotlin-stdlib-1.8.22.jar:1.8.22-release-407(1.8.22)]
	at io.gatehill.imposter.http.HttpRoute.getParsedPathParams(HttpRoute.kt:64) ~[imposter-http-3.29.0.jar:?]
	at io.gatehill.imposter.http.HttpRoute.extractPathParams(HttpRoute.kt:115) ~[imposter-http-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.impl.model.LambdaHttpRequestV2$pathParameters$2.invoke(LambdaHttpRequestV2.kt:66) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.impl.model.LambdaHttpRequestV2$pathParameters$2.invoke(LambdaHttpRequestV2.kt:65) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74) ~[kotlin-stdlib-1.8.22.jar:1.8.22-release-407(1.8.22)]
	at io.gatehill.imposter.awslambda.impl.model.LambdaHttpRequestV2.getPathParameters(LambdaHttpRequestV2.kt:65) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.impl.model.LambdaHttpRequestV2.getPathParams(LambdaHttpRequestV2.kt:94) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	at io.gatehill.imposter.http.SingletonResourceMatcher.matchRequest(SingletonResourceMatcher.kt:74) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.http.AbstractResourceMatcher.filterResourceConfigs(AbstractResourceMatcher.kt:131) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.http.AbstractResourceMatcher.matchResourceConfig(AbstractResourceMatcher.kt:79) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl.handleResource(ResourceServiceImpl.kt:292) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl.access$handleResource(ResourceServiceImpl.kt:84) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl$handleRoute$1.invoke(ResourceServiceImpl.kt:139) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.service.ResourceServiceImpl$handleRoute$1.invoke(ResourceServiceImpl.kt:137) ~[imposter-engine-3.29.0.jar:?]
	at io.gatehill.imposter.awslambda.impl.LambdaServer.dispatch(LambdaServer.kt:93) ~[imposter-adapter-awslambda-3.29.0.jar:?]
	... 7 more

[outofcoffee]

Hi @sameer-coder, thank you for reporting this.

There is improved handling of regex routes in Lambda in v3.31.1. Please could you let us know if this resolves the issue?

[outofcoffee]

Hi @sameer-coder, there were some further fixes required to static asset handling in Lambda to get this working.

These are released in v3.31.2.

[sameer-coder]

Thanks @outofcoffee

I will deploy again and report back on the issue

[sameer-coder]

Hello,

Thanks for the update. I no longer get a 500 error but now I am facing the same problem mentioned in this open issue

At the moment, Imposter serves the swagger UI at https://domain.com/_spec. But this path is unreachable because of the way routing is setup in API Gateway. The API Gateway only forwards requests to imposter which match a pattern (example- https://domain.com/api/v1)

The endpoints in the OpenAPI spec still work fine because I can specify /api/v1 as the basePath in the imposter config as well as the OpenAPI spec. Imposter handles this perfectly.

Probably we could add an env var to set a basePath for Swagger UI so that the url becomes https://domain.com/<basePath>/_spec

Thanks for the help!

[outofcoffee]

Hi @sameer-coder, from v3.32.0 you can set the environment variable IMPOSTER_OPENAPI_SPEC_PATH_PREFIX, to override the default /_spec prefix.

For example:

IMPOSTER_OPENAPI_SPEC_PATH_PREFIX="/api/core-mock/v1/_spec"

...will make the spec UI accessible at http://localhost:8080/api/core-mock/v1/_spec/

[sameer-coder]

Amazing! Thank you 🙏