Solving the Node.js Service: Why Your API Doesn't Return Anything

Discover solutions to the common problem of a `Node.js` service that hangs without returning data, and learn about effective polling strategies to manage long-running requests.
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This video is based on the question https://stackoverflow.com/q/61182850/ asked by the user 'Sonali Singh' ( https://stackoverflow.com/u/12811342/ ) and on the answer https://stackoverflow.com/a/63936393/ provided by the user 'Sonali Singh' ( https://stackoverflow.com/u/12811342/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: Node.js Service Hangs

When working with Node.js, you might encounter a frustrating situation where your API endpoint appears to be running but simply doesn’t return any response. This can happen, for instance, in your case when waiting for an extensive operation, such as executing tests, where the service just seems to hang without sending back any feedback. Here is a brief overview of your code and the challenges faced:

You are trying to set up an endpoint that waits for 10 minutes (600,000 milliseconds) before responding.

Despite using req.setTimeout(9000000) and server.setTimeout(5000000), your API remains unresponsive with no errors.

Let's dig deeper into why this occurs and how to address it.

Why Does This Happen?

Upon experimentation, it becomes evident that HTTP clients often close the connection after a certain idle period. In your situation, it appears that the client does not wait long enough for the request to complete, particularly after roughly 4 minutes of waiting. This can stem from various factors, including:

Default timeout settings of HTTP client libraries

Idle connection handling by intermediary servers or infrastructure

Proposed Solution: Implement Polling

To effectively manage long-lasting processes in Node.js, we can implement a workaround through polling. Polling allows the client to periodically check if a desired outcome is ready instead of maintaining an open connection indefinitely.

Here are the steps to address your issue:

1. Update the Server Logic

Instead of making the client wait for the completion of the task, change the logic of the endpoint to start the process and return an ID to the client that can be used for polling. This is how you can implement it:

Launch the background process for your task (e.g., executing tests).

Return a response immediately stating the task has started and include a unique ID or token.

[[See Video to Reveal this Text or Code Snippet]]

2. Create a Polling Endpoint

Next, create a separate endpoint that the client can hit to check the status of the long-running task:

[[See Video to Reveal this Text or Code Snippet]]

3. Client-Side Polling Logic

On the client side, implement a polling mechanism that checks the status of the task periodically until it is completed:

[[See Video to Reveal this Text or Code Snippet]]

Summary

By shifting from a blocking endpoint to a non-blocking approach using polling, you can effectively manage long-running processes in Node.js. This not only prevents your service from hanging but also provides a better user experience by allowing clients to check the progress of their requests without facing long wait times.

In conclusion, long tasks can challenge how HTTP protocols handle requests, but with clever designs like polling, you transform how users interact with your Node.js applications. Try implementing these strategies in your project and enjoy smoother API interactions!