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YuryShkoda
850695024f
A failed session (e.g. SAS %abort;, or a non-zero JS/PY/R exit) is a normal outcome of running arbitrary user code, not a request-shape or server problem. The #388 fix stopped processProgram() from hanging forever on a failed SAS session, but did so by throwing a SessionExecutionError, which surfaced as an HTTP 400 with a bespoke JSON shape - breaking Studio's log tab, which only renders on 2xx. Align the SAS branch with the pre-existing JS/PY/R behaviour: resolve instead of throwing, and let Execution.ts fold session.failureReason into the log the same way it already does for a debug-mode run. This removes the now-dead SessionExecutionError class and its try/catch wrapper entirely. Update the diagrams in api/docs/diagrams/ to match.
70 lines
4.3 KiB
Markdown
70 lines
4.3 KiB
Markdown
# Request execution flow (end-to-end)
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Full path from an inbound HTTP request to the HTTP response, covering
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session-pool acquisition and the two structurally different runtime
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branches: SAS (reuses a parked long-lived process) vs JS/PY/R (spawns a
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fresh interpreter process per request).
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```mermaid
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flowchart TD
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A["HTTP request<br/>POST /SASjsApi/code/execute<br/>or /SASjsApi/stp/execute"] --> B["Controller<br/>code.ts / stp.ts<br/>try/catch wrapper"]
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B --> C["ExecutionController.executeProgram<br/>or .executeFile<br/>Execution.ts:40-77"]
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C --> D{"session already provided?<br/>(e.g. file-upload flow)"}
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D -- no --> E["getSessionController(runTime).getSession()<br/>Session.ts:59-69"]
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D -- yes --> F["use provided session"]
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E --> G{"pending session<br/>available in pool?"}
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G -- yes --> H["reuse it"]
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G -- no --> I["createSession()<br/>SAS: spawns a real sas process, see<br/>sas-execution-handshake.md<br/>JS/PY/R: cheap - folder + id only"]
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H --> J["pre-warm: if pool has fewer<br/>than 3 pending, fire off more<br/>createSession() calls (not awaited)<br/>Session.ts:66"]
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I --> J
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F --> K
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J --> K["session.state = running<br/>Execution.ts:78"]
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K --> L["write webout.txt (empty),<br/>reqHeaders.txt<br/>Execution.ts:85-89"]
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L --> M["processProgram(...)<br/>Execution.ts:96-107"]
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M --> N{"runTime?"}
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N -- SAS --> O["createSASProgram():<br/>wrap user code with _webout<br/>filename, macro vars, autoexec"]
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O --> P["write code.sas via .bkp + rename<br/>processProgram.ts:48-49"]
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P --> Q["poll: while state !== completed<br/>AND state !== failed<br/>processProgram.ts:58-63"]
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Q --> R["processProgram() resolves either way -<br/>state was set by the session's own<br/>process exit handler in Session.ts,<br/>see sas-execution-handshake.md"]
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N -- "JS / PY / R" --> T["createJSProgram / createPythonProgram /<br/>createRProgram: wrap user code similarly"]
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T --> U["write code file; spawn interpreter<br/>fresh via execFile; pipe stdout/stderr<br/>into a log.log write stream<br/>processProgram.ts:117-124"]
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U -- "exit 0" --> Uc["session.state = completed<br/>processProgram.ts:126"]
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U -- "exit non-zero" --> Uf["session.state = failed<br/>session.failureReason = err.toString()<br/>processProgram.ts:131-133"]
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Uc --> R
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Uf --> R
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R --> V["read log.log, webout.txt,<br/>stpsrv_header.txt<br/>Execution.ts:109-113, 121-125"]
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V --> W["guard: if state !== failed,<br/>set state = completed<br/>(don't overwrite a failed session)<br/>Execution.ts:127-137"]
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W --> X["build httpHeaders + result;<br/>embed log in result if<br/>isDebugOn(vars) or<br/>session.failureReason is set<br/>Execution.ts:139-164"]
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X --> Y["Controller: res.send(result)<br/>HTTP 200<br/>(log embedded if the session failed -<br/>same shape as a successful run)"]
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```
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## Notes
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- **Session pool is per-runtime.** SAS sessions and JS/PY/R sessions live in
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separate controllers/pools (`process.sasSessionController` vs
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`process.sessionController`, `Session.ts:239-253`) - a pending SAS session
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is never handed out for a JS request or vice versa.
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- **The SAS branch and the JS/PY/R branch converge** on the same
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success/failure signal shape: `session.state` becomes `completed` or
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`failed` either way, and both paths flow through the same log/webout
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reading logic in `Execution.ts` afterward. The mechanics of *how* that
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state gets set differ substantially (see `session-lifecycle.md`).
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- **A failed session never throws.** `processProgram()` resolves normally
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whether the session completed or failed - a failed session (e.g. SAS
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`%abort;`, or a non-zero JS/PY/R exit) is a normal outcome of running
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arbitrary user code, not a request-shape/server problem. There is no
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separate error path: the same `Execution.ts:139-164` logic that embeds
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the log for a debug-mode successful run also embeds it when
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`session.failureReason` is set, and the controller always responds 200.
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- **`includePrintOutput`** (SAS only) additionally appends `output.lst`
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content to the result when debug mode is on - omitted above for brevity;
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see `Execution.ts:149-156`.
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- **`triggerProgram`/`triggerCode`** (fire-and-forget variants, not shown)
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call the same `ExecutionController` methods without awaiting them and
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immediately return `{ sessionId }`; the client polls
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`GET /SASjsApi/session/{sessionId}/state` separately.
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