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081a8fd5cf
Added README documentation for each test configuration (sa, cmp, ctx, fe-be, empty, full) describing event coverage, signal usage, instrument tables, span hierarchies and run instructions.
125 lines
4.1 KiB
Plaintext
125 lines
4.1 KiB
Plaintext
Frontend / backend test configuration (fe/ + be/)
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=================================================
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The 'fe-be' test uses two cascaded HAProxy instances to demonstrate
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inter-process trace context propagation via HTTP headers. The frontend instance
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(fe/) creates the root trace and injects span context into the HTTP request
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headers. The backend instance (be/) extracts that context and continues the
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trace as a child of the frontend's span.
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The two instances run as separate processes: the frontend listens on port 10080
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and proxies to the backend on port 11080, which in turn proxies to the origin
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server on port 8000.
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Files
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-----
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fe/otel.cfg OTel filter configuration for the frontend instance
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fe/haproxy.cfg HAProxy configuration for the frontend instance
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be/otel.cfg OTel filter configuration for the backend instance
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be/haproxy.cfg HAProxy configuration for the backend instance
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run-fe-be.sh Convenience script to launch both instances
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Events
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------
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T = Trace (span)
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Both instances produce traces only -- no metrics or log-records.
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Frontend (fe/) events:
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Event Scope T
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--------------------------------------------------------
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on-client-session-start client_session_start x
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on-frontend-tcp-request frontend_tcp_request x
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on-frontend-http-request frontend_http_request x
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on-backend-tcp-request backend_tcp_request x
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on-backend-http-request backend_http_request x
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on-client-session-end client_session_end -
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on-server-session-start server_session_start x
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on-tcp-response tcp_response x
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on-http-response http_response x
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on-server-session-end server_session_end -
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Backend (be/) events:
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Event Scope T
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--------------------------------------------------------
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on-frontend-http-request frontend_http_request x
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on-backend-tcp-request backend_tcp_request x
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on-backend-http-request backend_http_request x
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on-client-session-end client_session_end -
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on-server-session-start server_session_start x
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on-tcp-response tcp_response x
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on-http-response http_response x
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on-server-session-end server_session_end -
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The backend starts its trace at on-frontend-http-request where it extracts
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the span context injected by the frontend. Earlier request events
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(on-client-session-start, on-frontend-tcp-request) are not needed because
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the context is not yet available in the HTTP headers at that point.
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Context propagation
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-------------------
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The frontend injects context into HTTP headers in the backend_http_request
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scope:
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span "HAProxy session"
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inject "otel-ctx" use-headers
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The backend extracts that context in its frontend_http_request scope:
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extract "otel-ctx" use-headers
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span "HAProxy session" parent "otel-ctx" root
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Span hierarchy
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--------------
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Frontend (fe/):
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"HAProxy session" (root)
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+-- "Client session"
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+-- "Frontend TCP request"
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+-- "Frontend HTTP request"
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+-- "Backend TCP request"
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+-- "Backend HTTP request"
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"HAProxy session" (root)
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+-- "Server session"
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+-- "TCP response"
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+-- "HTTP response"
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Backend (be/):
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"HAProxy session" (root, parent: frontend's "HAProxy session")
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+-- "Client session"
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+-- "Frontend HTTP request"
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+-- "Backend TCP request"
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+-- "Backend HTTP request"
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"HAProxy session" (root)
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+-- "Server session"
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+-- "TCP response"
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+-- "HTTP response"
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Running the test
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----------------
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From the test/ directory:
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% ./run-fe-be.sh [/path/to/haproxy] [pidfile]
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If no arguments are given, the script looks for the haproxy binary three
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directories up from the current working directory. The backend origin server
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must be running on 127.0.0.1:8000.
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The script launches both HAProxy instances in the background and waits.
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Press CTRL-C to stop both instances.
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