Summary

Replace HTTPClient gem with Faraday throughout the codebase to eliminate maintenance burden and improve SSL certificate handling.

Current status: zync uses httpclient directly, oauth2 gem uses faraday + httpclient adapter.

Goal: Get rid of httpclient, use faraday for both zync and oauth2 gem. Use the net-http-persistent adapter, or any other, for both zync and oauth2

Background

Zync currently uses the httpclient gem for all HTTP operations (Keycloak API calls, REST adapter calls, OIDC discovery). This dependency has become problematic:

1. HTTPClient is abandoned - The upstream gem was last released in 2016 and is essentially unmaintained
2. Requires a fork for SSL support - We maintain a fork (3scale/httpclient branch ssl-env-cert) because upstream HTTPClient ignores SSL_CERT_FILE and SSL_CERT_DIR environment variables, which are needed for custom CA certificates in OpenShift/Kubernetes environments
3. Requires faraday-httpclient - Since Faraday 2.x, the httpclient adapter is no longer bundled, requiring an additional faraday-httpclient gem dependency for OAuth2 token requests

Proposed Solution

Migrate all HTTP operations from HTTPClient to Faraday with an appropriate adapter. This would:

• Unify HTTP handling - OAuth2 gem already uses Faraday internally; we could share the same adapter for both OAuth2 token requests and Zync's direct API calls
• Remove forked dependency - Faraday adapters based on Net::HTTP natively respect SSL_CERT_FILE/SSL_CERT_DIR via OpenSSL
• Reduce maintenance burden - No need to maintain a fork of an abandoned gem

Requirements

The replacement solution must provide:

• Connection pooling
• Keep-alive (persistent connections)
• Thread safety
• Native SSL environment variable support (SSL_CERT_FILE/SSL_CERT_DIR)

Suggested Approach

Use Faraday with the net-http-persistent adapter, which provides all the required features. Other adapters could also be evaluated from the Awesome Faraday adapters list.

# Gemfile
gem 'faraday'
gem 'faraday-net_http_persistent'
gem 'net-http-persistent'

This would allow removing:

• httpclient (forked gem)
• faraday-httpclient