Compression

---

Overview

This module improves the performance of your web applications by compressing HTTP response bodies returned by your upstream application.

If an HTTP request includes an Accept-Encoding header, HTTP responses will be automatically compressed and a Content-Encoding response header will be added. If the response was already compressed by your upstream application, ngrok takes no action.

Quickstart

Agent CLI

ngrok http 80 --compression

Agent Configuration File

tunnels:
  example:
    proto: http
    addr: 80
    compression: true

SSH

ssh -R 443:localhost:80 connect.ngrok-agent.com http --compression

Go SDK

import (
    "context"
    "net"

    "golang.ngrok.com/ngrok"
    "golang.ngrok.com/ngrok/config"
)

func listenCompressed(ctx context.Context) net.Listener {
    listener, _ := ngrok.Listen(ctx,
        config.HTTPEndpoint(
            config.WithCompression(),
        ),
        ngrok.WithAuthtokenFromEnv(),
    )

    return listener
}

Rust SDK

use ngrok::prelude::*;

async fn start_tunnel() -> anyhow::Result<impl Tunnel> {
    let sess = ngrok::Session::builder()
        .authtoken_from_env()
        .connect()
        .await?;

    let tun = sess
        .http_endpoint()
        .compression()
        .listen()
        .await?;

    println!("Listening on URL: {:?}", tun.url());

    Ok(tun)
}

Kubernetes Ingress Controller

kind: NgrokModuleSet
apiVersion: ingress.k8s.ngrok.com/v1alpha1
metadata:
  name: ngrok-module-set
modules:
  compression:
    enabled: true
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    k8s.ngrok.com/modules: ngrok-module-set
spec:
  ingressClassName: ngrok
  rules:
    - host: your-domain.ngrok.app
      http:
        paths:
          - path: /
            pathType: Prefix
            backend:
              service:
                name: example-service
                port:
                  number: 80

Edges

Compression is a supported Edge module. Unlike most edge modules, Compression has no configuration parameters. It is either enabled or disabled.

• Compression Edge Module API Resource

Behavior

Streaming Compression

When ngrok performs compression, the response body is not buffered; the response body is compressed as it is streamed through the ngrok edge.

Algorithm Choice

If a request specifies Accept-Encoding but no requested values are supported, ngrok takes no action and the upstream response is returned without modification.

ngrok negotiates the encoding type as defined by the RFC for Accept-Encoding. It respects q-values and chooses the Accept-Encoding supported algorithm with the highest q-value.

ngrok supports the following compression algorithms in the Accept-Encoding header.

Algorithm	Supported
br	no
compress	no
deflate	yes
gzip	yes

Response Headers

When ngrok performs compression, the following changes are made to the HTTP response header:

• The Content-Length header is removed
• A Content-Encoding header is added with the negotiated algorithm
• A Vary: Accept-Encoding header is added

Compression Level

The compression level is a value which indicates whether the compression algorithm should prefer to save more space at the expense of being slower and using more compute. This value is not currently configurable. ngrok automatically chooses a value that provides a reasonable tradeoff.

Reference

Configuration

This module does not support any configuration. It is either enabled or disabled.

Upstream Headers

This module does not add any upstream headers.

Errors

This module does not return any errors.

Events

When this module is enabled, it populates the following fields in http_request_complete.v0 events.

Fields
compression.algorithm
compression.bytes_saved

Limits

This module is available on all plans.

Try it out

For testing purposes, create a directory with a file in it and then enter that directory.

mkdir test-dir
cd test-dir
echo "hello world" > t.txt

ngrok can serve files from any directory (just like Python's Simple HTTP Server) by forwarding to a file:// URL. We're going to use that capability for our compression testing.

First let's see what this looks like without using compression by running the following in your test-dir directory:

ngrok http file://`pwd` --domain your-domain.ngrok.app

Then in another terminal while ngrok is still running:

curl --compressed -D - https://your-domain.ngrok.app/

• --compressed instructs curl to set the Accept-Encoding header to request compressed content
• -D - instructs curl to show the HTTP response headers

You should get a response that looks like:

HTTP/2 200
content-type: text/html; charset=utf-8
date: Tue, 18 Jul 2023 09:52:49 GMT
last-modified: Tue, 18 Jul 2023 09:52:34 GMT
ngrok-agent-ips: 71.227.75.230
ngrok-trace-id: 24e925dd0f348c1040d7ff62b06606cd
content-length: 39

<pre>
<a href="t.txt">t.txt</a>
</pre>

Now let's try it again with compression. Stop your ngrok agent and restart it by changing the command to:

ngrok http file://`pwd` --domain your-domain.ngrok.app --compression

Rerun the same curl command:

curl --compressed -D - https://your-domain.ngrok.app/

This time you should see that HTTP response headers include content-encoding: deflate indicating that the response was compressed.

HTTP/2 200
content-encoding: deflate
content-type: text/html; charset=utf-8
date: Tue, 18 Jul 2023 10:03:22 GMT
last-modified: Tue, 18 Jul 2023 09:52:34 GMT
ngrok-agent-ips: 71.227.75.230
ngrok-trace-id: b6b6cdce029e94123188ce53c0febee4
vary: Accept-Encoding

<pre>
<a href="t.txt">t.txt</a>
</pre>