使用Faraday Gem发起请求时本地正常、部署至Heroku/Render后出现Faraday::ConnectionFailed错误的排查求助

Hey there, let's dig into why your login flow (backed by the Faraday call to https://subdomain.example.com/authentication) works locally but throws a Faraday::ConnectionFailed execution expired error on Heroku or Render. Since it runs smoothly on your machine, the issue is tied to the hosted environment's network, configuration, or the target server's restrictions. Here are the most likely causes and fixes:

1. Outbound Network Restrictions on Hosted Platforms #

Heroku and Render enforce outbound network rules, and it’s possible the target server (subdomain.example.com) has blocked the IP ranges used by these platforms.

• Debug Step: Use your platform’s console to test direct connectivity. On Heroku, run:

  heroku run curl https://subdomain.example.com/authentication -v
  

  On Render, open the service’s shell and run the same curl command. If you get a timeout or connection refused here, the target server is likely blocking the platform’s IPs.
• Fix: Reach out to the owner of subdomain.example.com to request whitelisting Heroku/Render’s IP ranges, or use a platform-supported proxy service to route your requests through an allowed IP.

2. Insufficient Timeout Configuration #

Your current Faraday setup doesn’t specify timeout values. Heroku/Render’s network latency is often higher than your local machine, so the default timeout (usually 5 seconds) might be too short, leading to an execution expired error.

• Fix: Add explicit timeout settings to your Faraday connection, and move adapter configuration to a global initializer to avoid per-request conflicts:

  # Move this line to config/initializers/faraday.rb (configure once globally)
  # Faraday.default_adapter = :net_http
  
  def login
    conn = Faraday.new(
      url: 'https://subdomain.example.com',
      params: { version: '4.2.1', client: 'ios' },
      headers: { 'Content-Type': 'application/json' },
      request: { timeout: 10, open_timeout: 10 } # 10-second timeouts (adjust as needed)
    )
    response = conn.post('/authentication') do |req|
      req.body = { username: 'username', password: 'password' }.to_json
    end
    render json: { status: response.status, body: response.body }
  end
  

3. DNS Resolution Failures in Hosted Environments #

Your local DNS resolves subdomain.example.com correctly, but Heroku/Render’s DNS servers might not be able to resolve it (e.g., due to DNS propagation delays or misconfigured DNS records on the target domain).

• Debug Step: Run nslookup subdomain.example.com or dig subdomain.example.com in your platform’s console. If the command returns no valid IPs, the domain has DNS issues.
• Fix: Check the target domain’s DNS configuration to ensure it’s properly propagated. As a temporary test, you can replace the domain in your Faraday URL with the target server’s direct IP (note: this will break HTTPS certificate validation, so only use it for debugging).

4. SSL/TLS Certificate Trust Issues #

The target server’s SSL certificate might not be trusted by the CA certificate store used by Heroku/Render’s runtime environment (e.g., if it’s a self-signed certificate or uses a lesser-known CA).

• Debug Step: Temporarily disable SSL verification in your Faraday connection (only for debugging—never use this in production):

  conn = Faraday.new(
    url: 'https://subdomain.example.com',
    params: { version: '4.2.1', client: 'ios' },
    headers: { 'Content-Type': 'application/json' },
    ssl: { verify: false }
  )
  

  If the request works now, the issue is certificate trust.
• Fix: Ensure the target server uses a certificate signed by a public, trusted CA. If you must use a custom CA, add its certificate to your app’s trusted store and configure Faraday to use it.

5. Target Server Rate Limiting or Geo-Restrictions #

It’s possible subdomain.example.com has rate limits or geo-restrictions that block traffic from Heroku/Render’s data centers, but allow your local IP.

• Debug Step: Use a tool to simulate a request from an IP in Heroku/Render’s region. If the request fails, the target server is likely restricting access based on IP location or request volume.
• Fix: Contact the target server’s administrator to adjust their restrictions, or use a geographically proxied service to route your requests from an allowed region.

Start with the network connectivity test (via curl in the platform console)—that will quickly narrow down whether the issue is on the platform side or the target server side.

内容的提问来源于stack exchange，提问作者Amarildo Lucas