Fixed issue with exception injection not throwing the exception

README.md

@@ -22,7 +22,7 @@ exports.handler = failureLambda(async (event, context) => {
 ```
 4. Create a parameter in SSM Parameter Store.
 ```json
-{"isEnabled": false, "failureMode": "latency", "rate": 1, "minLatency": 100, "maxLatency": 400, "exceptionMsg": "Exception message!", "statusCode": 404, "diskSpace": 100}
+{"isEnabled": false, "failureMode": "latency", "rate": 1, "catchException": false, "minLatency": 100, "maxLatency": 400, "exceptionMsg": "Exception message!", "statusCode": 404, "diskSpace": 100}
 ```
 ```bash
 aws ssm put-parameter --region eu-north-1 --name failureLambdaConfig --type String --overwrite --value "{\"isEnabled\": false, \"failureMode\": \"latency\", \"rate\": 1, \"minLatency\": 100, \"maxLatency\": 400, \"exceptionMsg\": \"Exception message!\", \"statusCode\": 404, \"diskSpace\": 100}"
@@ -38,6 +38,7 @@ Edit the values of your parameter in SSM Parameter Store to use the failure inje
 * `isEnabled: false` means that the failure injection module is disabled and no failure is injected.
 * `failureMode` selects which failure you want to inject. The options are `latency`, `exception` or `statuscode` as explained below.
 * `rate` controls the rate of failure. 1 means that failure is injected on all invocations and 0.5 that failure is injected on about half of all invocations.
+* `catchException` specifies whether to catch any thrown exceptions or to pass them through to Lambda (**default** is false)
 * `minLatency` and `maxLatency` is the span of latency in milliseconds injected into your function when `failureMode` is set to `latency`.
 * `exceptionMsg` is the message thrown with the exception created when `failureMode` is set to `exception`.
 * `statusCode` is the status code returned by your function when `failureMode` is set to `statuscode`.
@@ -57,6 +58,10 @@ Inspired by Yan Cui's articles on latency injection for AWS Lambda (https://hack
 
 ## Changelog
 
+### 2020-02-08 v0.1.1
+
+* Added a flag to determine whether to catch or release errors before they reach AWS Lambda
+
 ### 2019-12-30 v0.1.0
 
 * Added disk space failure.
@@ -68,4 +73,4 @@ Inspired by Yan Cui's articles on latency injection for AWS Lambda (https://hack
 
 ## Authors
 
-**Gunnar Grosch** - [GitHub](https://github.com/gunnargrosch) | [Twitter](https://twitter.com/gunnargrosch) | [LinkedIn](https://www.linkedin.com/in/gunnargrosch/)
+**Gunnar Grosch** - [GitHub](https://github.com/gunnargrosch) | [Twitter](https://twitter.com/gunnargrosch) | [LinkedIn](https://www.linkedin.com/in/gunnargrosch/)

lib/failure.js

@@ -3,7 +3,7 @@ const aws = require('aws-sdk')
 const ssm = new aws.SSM()
 const childProcess = require('child_process')
 
-async function getConfig () {
+async function getConfig() {
   try {
     let params = {
       Name: process.env.FAILURE_INJECTION_PARAM
@@ -17,10 +17,13 @@ async function getConfig () {
 }
 var injectFailure = function (fn) {
   return async function () {
+    var catchFlag = true
+
     try {
       let configResponse = await getConfig()
       let config = JSON.parse(configResponse)
       if (config.isEnabled === true && Math.random() < config.rate) {
+        catchFlag = config.catchException
         if (config.failureMode === 'latency') {
           let latencyRange = config.maxLatency - config.minLatency
           let setLatency = Math.floor(config.minLatency + Math.random() * latencyRange)
@@ -41,8 +44,10 @@ var injectFailure = function (fn) {
       return fn.apply(this, arguments)
     } catch (ex) {
       console.log(ex)
+      if (! catchFlag) {
+        throw ex
+      }
     }
   }
 }
-
 module.exports = injectFailure