fix(awslambda): attributes should persist between exchanges for the same request/response pair.

Author: outofcoffee

adapter/awslambda/src/main/java/io/gatehill/imposter/awslambda/impl/LambdaServer.kt

@@ -76,6 +76,8 @@ abstract class LambdaServer<Request, Response>(
 
     fun dispatch(event: Request): Response {
         val response = LambdaHttpResponse()
+        val attributes = mutableMapOf<String, Any>()
+
         var failureCause: Throwable? = null
         try {
             val matched = matchRoutes(event)
@@ -87,7 +89,7 @@ abstract class LambdaServer<Request, Response>(
             } else {
                 matched.forEach { route ->
                     val request = buildRequest(event, route)
-                    val exchange = LambdaHttpExchange(router, route, request, response)
+                    val exchange = LambdaHttpExchange(router, route, request, response, attributes)
                     val handler = route.handler ?: throw IllegalStateException("No route handler set for: $route")
                     try {
                         handler(exchange).get()
@@ -111,12 +113,12 @@ abstract class LambdaServer<Request, Response>(
         when (val statusCode = response.statusCode) {
             in 400..499 -> {
                 errorHandlers[statusCode]?.let { errorHandler ->
-                    failExchange(event, response, statusCode, null, errorHandler)
+                    failExchange(event, response, attributes, statusCode, null, errorHandler)
                 } ?: logger.warn("Unhandled client error for: ${describeRequestShort(event)} [status code: $statusCode]")
             }
             in 500..599 -> {
                 errorHandlers[statusCode]?.let { errorHandler ->
-                    failExchange(event, response, statusCode, failureCause, errorHandler)
+                    failExchange(event, response, attributes, statusCode, failureCause, errorHandler)
                 } ?: logger.error("Unhandled server error for: ${describeRequestShort(event)} [status code: $statusCode]", failureCause)
             }
         }
@@ -127,12 +129,13 @@ abstract class LambdaServer<Request, Response>(
     private fun failExchange(
         event: Request,
         response: LambdaHttpResponse,
+        attributes: MutableMap<String, Any>,
         statusCode: Int,
         failureCause: Throwable?,
         errorHandler: (HttpExchange) -> Unit,
     ) {
         val request = buildRequest(event, null)
-        val exchange = LambdaHttpExchange(router, null, request, response)
+        val exchange = LambdaHttpExchange(router, null, request, response, attributes)
         exchange.fail(statusCode, failureCause)
         errorHandler(exchange)
     }

adapter/awslambda/src/main/java/io/gatehill/imposter/awslambda/impl/model/LambdaHttpExchange.kt

@@ -44,12 +44,7 @@
 package io.gatehill.imposter.awslambda.impl.model
 
 import com.google.common.base.Strings
-import io.gatehill.imposter.http.ExchangePhase
-import io.gatehill.imposter.http.HttpExchange
-import io.gatehill.imposter.http.HttpRequest
-import io.gatehill.imposter.http.HttpResponse
-import io.gatehill.imposter.http.HttpRoute
-import io.gatehill.imposter.http.HttpRouter
+import io.gatehill.imposter.http.*
 import io.gatehill.imposter.util.HttpUtil
 import io.vertx.core.buffer.Buffer
 
@@ -61,9 +56,14 @@ class LambdaHttpExchange(
     override val currentRoute: HttpRoute?,
     override val request: HttpRequest,
     response: HttpResponse,
+
+    /**
+     * Externally manage the lifecycle of attributes so they persist between exchange
+     * instances for the same request/response pair.
+     */
+    private val attributes : MutableMap<String, Any>,
 ) : HttpExchange {
     override var phase = ExchangePhase.REQUEST_RECEIVED
-    private val attributes = mutableMapOf<String, Any>()
 
     override var failureCause: Throwable? = null
         private set

core/engine/src/main/java/io/gatehill/imposter/service/HandlerServiceImpl.kt

@@ -46,13 +46,7 @@ import com.google.common.collect.Lists
 import io.gatehill.imposter.ImposterConfig
 import io.gatehill.imposter.config.ResolvedResourceConfig
 import io.gatehill.imposter.config.util.EnvVars
-import io.gatehill.imposter.http.ExchangePhase
-import io.gatehill.imposter.http.HttpExchange
-import io.gatehill.imposter.http.HttpExchangeFutureHandler
-import io.gatehill.imposter.http.HttpExchangeHandler
-import io.gatehill.imposter.http.HttpMethod
-import io.gatehill.imposter.http.HttpRouter
-import io.gatehill.imposter.http.ResourceMatcher
+import io.gatehill.imposter.http.*
 import io.gatehill.imposter.lifecycle.SecurityLifecycleHooks
 import io.gatehill.imposter.lifecycle.SecurityLifecycleListener
 import io.gatehill.imposter.plugin.config.InterceptorsHolder
@@ -73,7 +67,7 @@ import kotlinx.coroutines.future.future
 import org.apache.logging.log4j.Level
 import org.apache.logging.log4j.LogManager
 import java.io.File
-import java.util.UUID
+import java.util.*
 import java.util.concurrent.CompletableFuture
 import java.util.regex.Pattern
 import javax.inject.Inject
@@ -155,6 +149,8 @@ class HandlerServiceImpl @Inject constructor(
             httpExchange.get<Boolean>(ResourceUtil.RC_SEND_NOT_FOUND_RESPONSE) == true
         ) {
             // only override response processing if the 404 did not originate from the mock engine
+            // otherwise this will attempt to send a duplicate response to an already completed
+            // exchange, resulting in an IllegalStateException
             logAppropriatelyForPath(httpExchange, "File not found")
             responseService.sendNotFoundResponse(httpExchange)
         }