66일차 교안/실습 추가

Last3Mon/66/workflow-lab/src/miniflow/platforms.py

@@ -0,0 +1,117 @@
+"""Run the same business workflow on interchangeable platforms, with failover.
+
+Application code calls `FailoverRunner(["n8n", "miniflow"]).run("request", inputs)`.
+Which platforms exist and how each one runs a workflow is decided by adapters
+and `platforms.json`, so the calling code never changes when a platform is swapped.
+"""
+
+import json
+import os
+import time
+import urllib.error
+import urllib.request
+from pathlib import Path
+from typing import Any, Protocol
+
+from miniflow.engine import WorkflowError, load_workflow, run_workflow
+
+PROJECT_DIR = Path(__file__).resolve().parents[2]
+CONFIG_FILE = PROJECT_DIR / "platforms.json"
+
+
+class PlatformError(RuntimeError):
+    """A platform could not run the workflow (down, timeout, bad answer)."""
+
+
+class WorkflowPlatform(Protocol):
+    name: str
+
+    def run(self, workflow: str, inputs: dict[str, Any]) -> dict[str, Any]: ...
+
+
+def load_config(path: Path = CONFIG_FILE) -> dict[str, Any]:
+    return json.loads(path.read_text(encoding="utf-8"))
+
+
+class N8nPlatform:
+    """Calls an n8n workflow through its production webhook URL."""
+
+    name = "n8n"
+
+    def __init__(self, config: dict[str, Any]):
+        self.workflows = config["workflows"]
+        self.base_url = os.getenv("N8N_BASE_URL", config.get("n8n", {}).get("base_url", "http://localhost:5678"))
+        self.timeout = float(os.getenv("N8N_TIMEOUT", config.get("n8n", {}).get("timeout", 120)))
+
+    def run(self, workflow: str, inputs: dict[str, Any]) -> dict[str, Any]:
+        settings = self.workflows.get(workflow, {}).get("n8n")
+        if not settings:
+            raise PlatformError(f"n8n has no mapping for workflow '{workflow}'")
+        url = f"{self.base_url.rstrip('/')}/webhook/{settings['webhook']}"
+        request = urllib.request.Request(url, data=json.dumps(inputs).encode("utf-8"),
+                                         headers={"Content-Type": "application/json"}, method="POST")
+        try:
+            with urllib.request.urlopen(request, timeout=self.timeout) as response:
+                return json.loads(response.read().decode("utf-8"))
+        except urllib.error.HTTPError as error:
+            raise PlatformError(f"n8n returned HTTP {error.code} for {url}") from error
+        except (urllib.error.URLError, TimeoutError, ConnectionError) as error:
+            raise PlatformError(f"n8n is not reachable at {url} ({error})") from error
+        except json.JSONDecodeError as error:
+            raise PlatformError("n8n answered with something that is not JSON") from error
+
+
+class MiniflowPlatform:
+    """Runs the matching JSON flow with the local miniflow engine."""
+
+    name = "miniflow"
+
+    def __init__(self, config: dict[str, Any]):
+        self.workflows = config["workflows"]
+
+    def run(self, workflow: str, inputs: dict[str, Any]) -> dict[str, Any]:
+        settings = self.workflows.get(workflow, {}).get("miniflow")
+        if not settings:
+            raise PlatformError(f"miniflow has no mapping for workflow '{workflow}'")
+        try:
+            report = run_workflow(load_workflow(PROJECT_DIR / settings["flow"]), inputs, verbose=False)
+        except WorkflowError as error:
+            raise PlatformError(str(error)) from error
+        if report["status"] != "completed":
+            failed = report["trace"][-1]
+            raise PlatformError(f"miniflow failed at node '{failed['id']}': {failed.get('error')}")
+        return report["result"]
+
+
+PLATFORMS: dict[str, type] = {"n8n": N8nPlatform, "miniflow": MiniflowPlatform}
+
+
+def register_platform(name: str, adapter: type) -> None:
+    """Add another platform adapter without touching the calling code."""
+    PLATFORMS[name] = adapter
+
+
+class FailoverRunner:
+    """Try platforms in order; when one raises PlatformError, move on to the next."""
+
+    def __init__(self, order: list[str], config: dict[str, Any] | None = None):
+        config = config or load_config()
+        unknown = [name for name in order if name not in PLATFORMS]
+        if unknown:
+            raise PlatformError(f"Unknown platform(s): {', '.join(unknown)}. Registered: {', '.join(PLATFORMS)}")
+        self.platforms = [PLATFORMS[name](config) for name in order]
+
+    def run(self, workflow: str, inputs: dict[str, Any]) -> dict[str, Any]:
+        attempts = []
+        for platform in self.platforms:
+            started = time.perf_counter()
+            try:
+                result = platform.run(workflow, inputs)
+            except PlatformError as error:
+                attempts.append({"platform": platform.name, "status": "failed", "error": str(error),
+                                 "ms": round((time.perf_counter() - started) * 1000, 1)})
+                continue
+            attempts.append({"platform": platform.name, "status": "ok",
+                             "ms": round((time.perf_counter() - started) * 1000, 1)})
+            return {"workflow": workflow, "served_by": platform.name, "result": result, "attempts": attempts}
+        raise PlatformError("All platforms failed: " + "; ".join(f"{a['platform']}: {a['error']}" for a in attempts))