Merge pull request #9 from iDanielBot/feat/5xx-error-codes

feat: 502 / 504 error codes

Author: iDanielBot

src/lambda-invoker.test.ts

@@ -16,21 +16,21 @@ describe('Lambda invoker', () => {
       StatusCode: 200,
       Payload: Uint8ArrayBlobAdapter.fromString(JSON.stringify({
         statusCode: 404,
-        body: {
+        body: JSON.stringify({
           message: 'User not found',
-        },
+        }),
       }))
     })
 
     // then
     const resp = await invokeLambda({ payload: '', functionName: 'test' })
     expect(resp.statusCode).toEqual(404)
-    expect(resp.body).toEqual({
+    expect(resp.body).toEqual(JSON.stringify({
       message: 'User not found',
-    })
+    }))
   })
 
-  it('process 200 response with timeout error returned', async () => {
+  it('converts 200 responses with timeout to 504 Gateway Timeout error', async () => {
     // given
     mockLambda.on(InvokeCommand).resolves({
       StatusCode: 200,
@@ -41,10 +41,18 @@ describe('Lambda invoker', () => {
     })
 
     // then
-    await expect(invokeLambda({ payload: '', functionName: 'test' })).rejects.toThrow()
+    const resp = await invokeLambda({ payload: '', functionName: 'test' })
+    expect(resp.statusCode).toEqual(504)
+    expect(resp.body).toEqual(
+      JSON.stringify({
+        "message": "Service timed out.",
+        "functionName": "test", "error": "Unhandled",
+        "payload": JSON.stringify({ "errorMessage": "2023-01-09T10:48:53.262Z 873b04e4-991b-4d5f-b7ca-b99df84bfd66 Task timed out after 1.00 seconds" })
+      })
+    )
   })
 
-  it('process 200 response with non APIGatewayProxyStructuredResultV2 payload', async () => {
+  it('converts 200 response with non APIGatewayProxyStructuredResultV2 payload to 502 Bad Gateway error', async () => {
     // given
     mockLambda.on(InvokeCommand).resolves({
       StatusCode: 200,
@@ -54,6 +62,19 @@ describe('Lambda invoker', () => {
     })
 
     // then
-    await expect(invokeLambda({ payload: '', functionName: 'test' })).rejects.toThrow()
+    const resp = await invokeLambda({ payload: '', functionName: 'test' })
+    expect(resp.statusCode).toEqual(502)
+    expect(resp.body).toEqual(
+      JSON.stringify({
+        "message": "Service returned a wrongly formatted response.",
+        "functionName": "test",
+        "payload": JSON.stringify({
+          username: 'this should fail'
+        }),
+        "payloadJson": {
+          username: 'this should fail'
+        }
+      })
+    )
   })
 })

src/lambda-invoker.ts

@@ -2,6 +2,10 @@ import { APIGatewayProxyStructuredResultV2 } from 'aws-lambda'
 import { InvocationResponse, Lambda } from '@aws-sdk/client-lambda'
 import { safeParseJson } from './util'
 
+import createDebug from 'debug'
+
+const debug = createDebug('openapi-lambda-adapter')
+
 let lambdaClient: Lambda
 const getLambdaClient = () => {
   if (!lambdaClient) {
@@ -23,21 +27,37 @@ export const invokeLambda = async (params: { payload: string, functionName: stri
       Payload: Buffer.from(payload)
     })
 
+  debug('Lambda invocation response', res)
+
   if (!isSuccess(res.StatusCode)) {
-    throw new Error(`Failed to invoke lambda ${params.functionName} synchronously`)
+    return toApiGwResp({
+      statusCode: 502,
+      body: { message: `Failed to invoke lambda ${params.functionName} synchronously. Check your IAM setup.` }
+    })
   }
 
   const safePayload = Buffer.from(res.Payload).toString('utf-8')
 
   if (hasTimeout(res, safePayload)) {
-    throw new Error(safePayload)
+    return toApiGwResp({
+      statusCode: 504,
+      body: { message: 'Service timed out.', functionName: params.functionName, error: res.FunctionError, payload: safePayload }
+    })
   }
 
   const response = safeParseJson(safePayload)
 
   // response is not in JSON format
   if (!isApiGwStructuredResp(response)) {
-    throw new Error('Received a response which is not in APIGatewayProxyStructuredResultV2 format')
+    return toApiGwResp({
+      statusCode: 502,
+      body: {
+        message: 'Service returned a wrongly formatted response.',
+        functionName: params.functionName,
+        payload: safePayload,
+        payloadJson: response
+      }
+    })
   }
 
   return response
@@ -58,3 +78,13 @@ const isApiGwStructuredResp = (resp: unknown): resp is APIGatewayProxyStructured
 }
 
 const hasTimeout = (res: InvocationResponse, safePayload: string) => 'FunctionError' in res && safePayload?.includes('Task timed out')
+
+const toApiGwResp = (params: { statusCode: number, body: Record<string, unknown> }) => {
+  return {
+    statusCode: params.statusCode,
+    headers: {
+      'Content-Type': 'application/json'
+    },
+    body: JSON.stringify(params.body)
+  }
+}