Decopule using a CTG Interceptor

With External Decoupling, external consumers continue calling CTG (possibly at a new network address), so nothing changes on their side. Behind the scenes, a CTG Interceptor redirects calls to an OpenLegacy Bridge, which invokes the modernized service (e.g., COBOL-to-Java). This preserves stability for consumers while enabling a seamless, step-by-step modernization path.

Why This Matters

• Minimal disruption: External apps still call CTG directly, with no protocol or integration changes.
• Transparent modernization: CTG acts as a stable façade while requests are redirected to modernized services.
• Gradual transition: Programs can be modernized incrementally without breaking consumer connections.
• Future flexibility: Once modernization is complete, external apps can be switched from CTG to direct API calls at the right time.

Flow

1. External App (e.g. Intranet) Continues to call CTG directly, just as before. The only change is that the CTG endpoint may have a different network address (e.g., if CTG is relocated or containerized).
2. CTG Interceptor Intercepts the CTG request. Instead of passing it to the original mainframe program, the interceptor calls an OpenLegacy Bridge over REST.
3. OpenLegacy Bridge Receives the REST call from CTG. Routes it to the modernized application logic (e.g., COBOL refactored into Java on Kubernetes).
4. Modernized App Executes the business logic. Sends the response back through the Bridge → Interceptor → CTG → External App.

Configure External Apps to use the CTG Interceptor

Once the Interceptor is deployed, external applications need to be directed to it. This step is typically seamless: the applications continue calling CTG as before, but the connection is pointed to the Interceptor-enabled CTG instance (usually just a change in the network address). No modifications to the applications themselves are required.

The result: external consumers interact with CTG exactly as they always have, while the Interceptor ensures their calls are routed through the modernization layer behind the scenes.