Mockoon Serverless ERROR Uncaught Exception

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Introduction

Mockoon is a popular tool for mocking APIs and testing serverless applications. However, when attempting to stand up a Mockoon serverless deployment on AWS Lambda, users may encounter an uncaught exception error. In this article, we will delve into the details of this error, explore the expected behavior, and provide a step-by-step guide to reproduce the issue.

Where it Happened

The error occurred when attempting to stand up a Mockoon serverless deployment on AWS Lambda with the following configuration:

  • Runtime Version: nodejs:22.v35
  • Mockingbird Version: {version} mockoon-lambda@1.0.0
  • Deployment Environment: AWS Lambda

The error was triggered when injecting a test event from the Lambda console.

Expected Behavior

The expected behavior when injecting a test event into the Mockoon serverless deployment is to process the event with an error or a mock response. This would allow developers to test and debug their serverless applications.

Current Behavior

However, the current behavior is that the Mockoon serverless deployment fails with an uncaught exception error. The error message is as follows:

2025-03-10T23:09:46.793Z undefined ERROR Uncaught Exception "errorType" "TypeError", "errorMessage": "Cannot read properties of undefined (reading 'length')", "stack": [ "TypeError: Cannot read properties of undefined (reading 'length')", " at MockoonServer.generateDatabuckets (/var/task/node_modules/@mockoon/commons-server/dist/cjs/libs/server/server.js:1436:30)", " at MockoonServer.createRequestListener (/var/task/node_modules/@mockoon/commons-server/dist/cjs/libs/server/server.js:261:14)", " at MockoonServerless.requestListener (/var/task/node_modules/@mockoon/serverless/dist/cjs/libs/serverless.js:44:23)", " at MockoonServerless.awsHandler (/var/task/node_modules/@mockoon/serverless/dist/cjs/libs/serverless.js:52:52)", " at Object. (/var/task/index.js:8:44)", " at Module._compile (node:internal/modules/cjs/loader:1554:14)", " at Object..js (node:internal/modules/cjs/loader:1706:10)", " at Module.load (node:internal/modules/cjs/loader:1289:32)", " at Function._load (node:internal/modules/cjs/loader:1108:12)", " at TracingChannel.traceSync (node:diagnostics_channel:322:14)" ]

Steps to Reproduce

To reproduce this issue, follow these steps:

Step 1: Create Serverless Deployment

  1. Initialize a new npm project using npm init -y.
  2. Install the Mockoon serverless package globally using npm install -g @mockoon/serverless.
  3. Create an index.js file with the created environment and upload the deployment-package.zip file.

Step 2: Create a Lambda Test Event

  1. Create a new Lambda test event with the following configuration:
{
  "httpMethod": "GET",
  "path": "/v1/test/1234",
  "headers": {
    "Content-Type": "application/json"
  },
  "queryStringParameters": {
    "param1": "value1"
  }
}

Step 3: Inject Test Event and Observe Logs

  1. Inject the test event into the Mockoon serverless deployment.
  2. Observe the logs to inspect the error.

Conclusion

Q: What is the cause of the Mockoon serverless ERROR: Uncaught Exception error?

A: The cause of the Mockoon serverless ERROR: Uncaught Exception error is a TypeError that occurs when trying to read the length property of an undefined object. This error is typically triggered by a misconfiguration or a bug in the Mockoon serverless deployment.

Q: What is the expected behavior when injecting a test event into the Mockoon serverless deployment?

A: The expected behavior when injecting a test event into the Mockoon serverless deployment is to process the event with an error or a mock response. This would allow developers to test and debug their serverless applications.

Q: What is the current behavior when injecting a test event into the Mockoon serverless deployment?

A: The current behavior when injecting a test event into the Mockoon serverless deployment is that the deployment fails with an uncaught exception error.

Q: What is the error message that is displayed when the Mockoon serverless deployment fails?

A: The error message that is displayed when the Mockoon serverless deployment fails is a TypeError that indicates that it cannot read the length property of an undefined object.

Q: How can I reproduce the Mockoon serverless ERROR: Uncaught Exception error?

A: To reproduce the Mockoon serverless ERROR: Uncaught Exception error, follow these steps:

  1. Initialize a new npm project using npm init -y.
  2. Install the Mockoon serverless package globally using npm install -g @mockoon/serverless.
  3. Create an index.js file with the created environment and upload the deployment-package.zip file.
  4. Create a new Lambda test event with the following configuration:
{
  "httpMethod": "GET",
  "path": "/v1/test/1234",
  "headers": {
    "Content-Type": "application/json"
  },
  "queryStringParameters": {
    "param1": "value1"
  }
}
  1. Inject the test event into the Mockoon serverless deployment.
  2. Observe the logs to inspect the error.

Q: How can I resolve the Mockoon serverless ERROR: Uncaught Exception error?

A: To resolve the Mockoon serverless ERROR: Uncaught Exception error, you will need to identify and fix the underlying cause of the error. This may involve reviewing the Mockoon serverless deployment configuration, checking for any misconfigurations or bugs, and updating the deployment accordingly.

Q: What are some common causes of the Mockoon serverless ERROR: Uncaught Exception error?

A: Some common causes of the Mockoon serverless ERROR: Uncaught Exception error include:

  • Misconfigured deployment settings
  • Bugs in the Mockoon serverless code
  • Incompatible dependencies
  • Incorrectly formatted test events

Q: How can I prevent the Mockoon serverless ERROR: Uncaught Exception error from occurring in the future?

A: To prevent the Mockoon serverless ERROR: Uncaught Exception error from occurring in the future, you can take the following steps:

  • Review and update the Mockoon serverless deployment configuration regularly
  • Test and debug the deployment thoroughly before deploying it to production
  • Use version control to track changes to the deployment configuration and code
  • Monitor the deployment logs for any errors or issues

Conclusion

In conclusion, the Mockoon serverless ERROR: Uncaught Exception error is a complex issue that requires a thorough understanding of the Mockoon serverless deployment configuration and the AWS Lambda environment. By following the steps outlined in this article, developers can reproduce the issue and work towards resolving it. We hope that this article has provided valuable insights and guidance for developers struggling with this error.