Add GZip compression to HAProxy config file

[MartinaeyNL]

Description

Fixes #13

As a simple test, I tried out this HAProxy config locally to experiment if the Manager UI would load properly.
I'm not an expert in HAProxy nor any proxy application, so it was just a simple attempt 😉
I looked at the official documentation, and made adjustments based on that.

It seems to correctly apply the GZip compression, and significantly reduce the download sizes.
For example, the Manager UI bundle went down from 6.5MB to about 2.7MB.

Any feedback on this is welcome 👍

Changelog

• Adds GZip compression to HTML, CSS, JavaScript, JSON, and SVG files from the Manager backend.

[MartinaeyNL]

Maybe we should add a minimum file size as described here in their documentation.
Will do that quickly.

[Copilot]

Pull request overview

This PR adds GZip compression to the HAProxy configuration for the Manager backend to reduce download sizes for web assets. Testing shows the Manager UI bundle size decreased from 6.5MB to approximately 2.7MB. The change adds compression directives to the manager_backend section of the HAProxy configuration.

Changes:

• Adds GZip compression configuration to the manager_backend in HAProxy
• Configures compression for HTML, CSS, JavaScript, JSON, and SVG MIME types
• Sets minimum response size of 1500 bytes for compression eligibility
• Enables compression offload to prevent double compression

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[dominiquekleeven]

Running the proxy image with the updated haproxy.cfg, results in the following error:

[NOTICE]   (20) : haproxy version is 2.9.15-e872a3f
[ALERT]    (20) : config : parsing [/etc/haproxy/haproxy.cfg:148] : 'compression' expects 'algo', 'type' 'direction' or 'offload'
[ALERT]    (20) : config : Error(s) found in configuration file : /etc/haproxy/haproxy.cfg
[ALERT]    (20) : config : Fatal errors found in configuration.
[ERROR][2026-02-03 16:46:47] Cannot start proxy until config file errors are resolved in '/etc/haproxy/haproxy.cfg'

Removing the following line resolves it.

compression minsize-res 1500

minsize-res was added in HAProxy version 3.2, see https://www.haproxy.com/documentation/haproxy-configuration-tutorials/performance/compression/#set-a-minimum-file-size

We are currently using version 2.9. It might be OK to remove the minsize, or maybe try bumping the version to 3.2

[MartinaeyNL]

Good catch!

Maybe we should indeed create an issue for doing the upgrade.
I'll remove that minsize-res line for this PR 👍

[MartinaeyNL]

Thanks for the review @dominiquekleeven , good catch there 👍
Processed the changes, and ready for a review again.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

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[Copilot]

The compression configuration is only applied to the manager_backend but not to the keycloak_backend at line 154. If the Keycloak backend also serves compressible content (HTML, CSS, JavaScript, JSON), it should also benefit from compression. Consider whether compression should be applied consistently across all backends or if there's a specific reason to exclude Keycloak.