Compression in HTTP

Compression is a technique used to reduce the size of the data that is being transferred between the server and the client. This is done by compressing the data before sending it and then decompressing it on the client side. This can help reduce the amount of data that needs to be transferred, which can improve the performance of your website.

Content-Encoding and Accept-Encoding HTTP headers are used for this behavior. The Content-Encoding header is used to specify the compression algorithm that was used to compress the data, while the Accept-Encoding header is used to specify the compression algorithms that the client supports.

Learn more about compression in HTTP

Hive Gateway is capable of handling compressions in the following directions. We can selectively enable or disable compression in each direction.

From the gateway to the client

When the client sends a request to the gateway, it can specify the compression algorithm that it supports using the Accept-Encoding header. Then the gateway can compress the response using the specified algorithm before sending it back to the client with the Content-Encoding header, so that the client can decompress it.

In the following example, we say that the client supports the gzip algorithm for compression. Then the gateway compresses the response using the gzip algorithm before sending it back to the client. So the client can decompress the response using the gzip algorithm.

const res = await fetch('http://localhost:4000/graphql', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Accept-Encoding': 'gzip'
  },
  body: JSON.stringify({
    query: `
      query {
        hello
      }
    `
  })
})
console.assert(res.headers.get('Content-Encoding') === 'gzip', 'Response is compressed')

You need to configure the gateway for this feature. See here

From the client to the gateway

When the client sends a request to the gateway, it can compress the request using the specified algorithm before sending it to the gateway. Then the gateway can decompress the request before processing it.

In the following example, we compress the request using the gzip algorithm before sending it to the gateway. Then the gateway decompresses the request before processing it.

const res = await fetch('http://localhost:4000/graphql', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'Content-Encoding': 'gzip'
  },
  // Compress the request body
  body: gzip(
    JSON.stringify({
      query: `
      query {
        hello
      }
    `
    })
  )
})

Here we are using the gzip function to compress the request body before sending it to the gateway. We assume that the gzip function is a function that compresses the data using the gzip algorithm.

Configuration on Gateway

In your gateway configuration, you need to enable the compression for the gateway.

import { defineConfig } from '@graphql-hive/gateway'
 
export const gatewayConfig = defineConfig({
  contentEncoding: true
})

Now gateway will respect the Accept-Encoding header from the client and compress the response accordingly.

From the subgraph to the gateway

When the subgraph sends a response to the gateway, it can compress the response using the specified algorithm before sending it to the gateway. Then the gateway can decompress the response before sending it to the client.

It has the same principle as the previous example, but here the gateway is acting like a client against a subgraph.

Configuration on Subgraph

You should configure your subgraph to respect the Accept-Encoding header and compress the response accordingly. For example if you have a GraphQL subgraph using GraphQL Yoga server you can use useContentEncoding plugin to enable this;

npm i @whatwg-node/server

import { createYoga } from 'graphql-yoga'
import { useContentEncoding } from '@whatwg-node/server'
 
const server = createYoga({
  schema,
  plugins: [useContentEncoding()]
})

From the gateway to the subgraph

When the gateway sends a request to the subgraph, it can compress the request using the specified algorithm before sending it to the subgraph. Then the subgraph can decompress the request before processing it.

In this case, gateway will always send a compressed request to the defined subgraphs with Content-Encoding header.

Configuration on Gateway

In your gateway configuration, you need to enable the compression.

import { defineConfig } from '@graphql-hive/gateway'
 
export const gatewayConfig = defineConfig({
  contentEncoding: {
    subgraphs: ['*'] // Enable compression for all subgraphs
    // subgraphs: ['subgraph1', 'subgraph2'] // Enable compression for specific subgraphs
  }
})