Architecture

The debugger consists of three parts:

1. The client. This is typically a GUI displays the source code, current stack frame, variables etc, and allows the user to set breakpoints and step throught the code. The client can reside on a different host than the database server.

2. The target backend. This is the backend that runs the code being debugged. The plugin_debugger.so library must be loaded into the target backend.

3. Debugging proxy. This is another backend process that the client is connected to. The API functions, pldbg_* in pldbgapi.so library, are run in this backend.

The client is to connected to the debugging proxy using a regular libpq connection. When a debugging session is active, the proxy is connected to the target via a socket. The protocol between the proxy and the target backend is not visible to others, and is subject to change. The pldbg_* API functions form the public interface to the debugging facility.

debugger client  *------ libpq --------* Proxy backend
  (pgAdmin)                                 *
                                            |
                                  pldebugger socket connection
                                            |
                                            *
application client *----- libpq -------* Target backend