Fix Thruster and HTTP/2 configuration for Control Plane deployment

CRITICAL FIX: Change workload protocol from http2 back to http

Root cause identified through live debugging on Control Plane:
- Thruster IS running correctly in the container
- Thruster handles HTTP/2 on the public-facing TLS connection
- Control Plane's load balancer expects HTTP/1.1 from the container
- Setting protocol: http2 causes 502 "protocol error"

What I discovered:
1. Accessed live QA app: qa-react-webpack-rails-tutorial-687
2. Verified Thruster is running: PID 1 is "thrust bin/rails server"
3. Rails responds correctly on localhost:3000
4. But external requests get 502 with "protocol error"
5. Issue: Protocol mismatch between load balancer and container

The correct architecture:
- End User → HTTPS/HTTP2 → Control Plane Load Balancer
- Load Balancer → HTTP/1.1 → Thruster in Container
- Thruster → HTTP/1.1 → Rails (localhost:3000)

Changes:
1. Update rails.yml: protocol: http2 → protocol: http
2. Add detailed explanation in rails.yml comments
3. Update .controlplane/readme.md with correct configuration
4. Update docs/thruster.md with protocol explanation
5. Add troubleshooting section for 502 protocol errors

Key insight:
Thruster provides HTTP/2 to end users through TLS termination,
but the container must expose HTTP/1.1 to the load balancer.
This is different from running Thruster in production with
direct TLS termination where it would handle HTTP/2 end-to-end.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

.controlplane/readme.md

@@ -147,14 +147,20 @@ CMD ["bundle", "exec", "thrust", "bin/rails", "server"]
 
 #### 2. Workload Port Protocol (`.controlplane/templates/rails.yml`)
 
-The workload port must be configured for HTTP/2:
+The workload port should remain as HTTP/1.1:
 
 ```yaml
 ports:
   - number: 3000
-    protocol: http2  # Must be http2, not http
+    protocol: http  # Keep as http, not http2
 ```
 
+**Important:** This may seem counter-intuitive, but here's why:
+- **Thruster handles HTTP/2** on the public-facing TLS connection
+- **Control Plane's load balancer** communicates with the container via HTTP/1.1
+- Setting `protocol: http2` causes a protocol mismatch and 502 errors
+- Thruster automatically provides HTTP/2 to end users through its TLS termination
+
 ### Important: Dockerfile vs Procfile
 
 **On Heroku:** The `Procfile` defines how dynos start:
@@ -204,14 +210,18 @@ After deployment, verify HTTP/2 is working:
 - Incorrect CMD syntax in Dockerfile
 - Port mismatch (ensure Rails listens on 3000)
 
-#### HTTP/2 not working (showing HTTP/1.1)
+#### Getting 502 errors after enabling HTTP/2
+
+**Symptom:** Workload returns 502 Bad Gateway with "protocol error"
 
-**Symptom:** Browser shows protocol as "http/1.1" instead of "h2"
+**Root Cause:** Setting `protocol: http2` in rails.yml causes a protocol mismatch
 
 **Solution:**
-1. Verify `protocol: http2` in `.controlplane/templates/rails.yml`
+1. Change `protocol: http2` back to `protocol: http` in `.controlplane/templates/rails.yml`
 2. Apply the template: `cpflow apply-template rails -a <app-name>`
-3. Redeploy: `cpflow deploy-image -a <app-name>`
+3. The workload will immediately update (no redeploy needed)
+
+**Why:** Thruster provides HTTP/2 to end users, but Control Plane's load balancer communicates with containers via HTTP/1.1. Setting the port protocol to `http2` tells the load balancer to expect HTTP/2 from the container, which Thruster doesn't provide on the backend.
 
 #### Assets not loading or CORS errors
 

.controlplane/templates/rails.yml

@@ -19,7 +19,9 @@ spec:
       memory: 512Mi
       ports:
         - number: 3000
-          protocol: http2
+          protocol: http
+          # Note: Keep as 'http' - Thruster handles HTTP/2 on the TLS frontend,
+          # but the load balancer communicates with the container via HTTP/1.1
   defaultOptions:
     # Start out like this for "test apps"
     autoscaling:

docs/thruster.md

@@ -157,15 +157,20 @@ CMD ["bundle", "exec", "thrust", "bin/rails", "server"]
 
 #### 2. Workload Port Configuration
 
-The workload port must be set to HTTP/2 (`.controlplane/templates/rails.yml`):
+The workload port should remain as HTTP/1.1 (`.controlplane/templates/rails.yml`):
 
 ```yaml
 ports:
   - number: 3000
-    protocol: http2  # Required for HTTP/2
+    protocol: http  # Keep as http, NOT http2
 ```
 
-**Important:** On Control Plane/Kubernetes, the `Dockerfile CMD` determines container startup, NOT the `Procfile`. This differs from Heroku where Procfile is used.
+**Important:** Keep the protocol as `http` (not `http2`) because:
+- Thruster handles HTTP/2 on the public-facing TLS connection
+- Control Plane's load balancer communicates with containers via HTTP/1.1
+- Setting `protocol: http2` causes 502 protocol errors
+
+**Note:** On Control Plane/Kubernetes, the `Dockerfile CMD` determines container startup, NOT the `Procfile`. This differs from Heroku where Procfile is used.
 
 #### Deployment Commands