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Golang: Streaming Large API Responses in Chunks to a File

Adam Szpilewicz 63

Golang: Streaming Large API Responses in Chunks to a File

Adam Szpilewicz
Level Up Coding
Published in
6 min read23 hours ago


Photo by Toa Heftiba on Unsplash

When working with APIs, especially ones that provide massive amounts of data, efficiently handling the data is crucial. In cases where the API response is extremely large, streaming the response and processing it in chunks can be a lifesaver. It ensures that you don’t consume a lot of memory by trying to hold the entire response in memory. In this article, we’ll explore how you can stream a large API response into a file in chunks using the Go programming language.

The Challenge:

Imagine you’re using the Mixpanel API, which provides a large dataset. Instead of loading the entire response into memory (which could lead to your application crashing or slowing down due to high memory usage), you decide to process and save the data in smaller chunks.

The Solution:

Using Go’s built-in packages, you can easily stream an HTTP response and write the data in chunks to a file. Here’s how you can achieve this:

Step 1: Making the API Request

Start by defining a function to make the API request. In this example, we’re fetching data from the Mixpanel API:

// getMixpanelData retrieves the Mixpanel data.
func getMixpanelData() (*http.Response, error) {
baseURL := "https://data.mixpanel.com/api/2.0/export"
params := prepareParams()
urlWithParams := baseURL + "?" + params.Encode()
req, err := http.NewRequest("GET", urlWithParams, nil)
if err != nil {
return nil, err
req.Header.Add("Authorization", "Basic XXX") // replace XXX with your base64 encoded "username:password"
client := &http.Client{}
return client.Do(req)

Step 2: Preparing the Query Parameters

You can abstract the preparation of query parameters into its function:

// prepareParams prepares the query params.
func prepareParams() url.Values {
params := url.Values{}
params.Add("from_date", "2023-09-25")
params.Add("to_date", "2023-09-25")
return params

Step 3: Streaming the Response in Chunks