feat: make mobile issue capture idempotent (#177)

src/main.py

@@ -6,7 +6,7 @@ from contextlib import asynccontextmanager
 from pathlib import Path
 from typing import Any, Literal
 
-from fastapi import FastAPI, HTTPException, Path as PathParam, Query
+from fastapi import FastAPI, Header, HTTPException, Path as PathParam, Query
 from fastapi.responses import JSONResponse
 from fastapi.staticfiles import StaticFiles
 from pydantic import BaseModel, Field, PositiveInt, field_validator, model_validator
@@ -55,6 +55,8 @@ EVENT_STREAM_TIMEOUT_SECONDS = 5.0
 READINESS_TIMEOUT_SECONDS = 5.0
 REVIEW_DETAIL_TIMEOUT_SECONDS = 5.0
 ISSUE_ACTION_TIMEOUT_SECONDS = 5.0
+ISSUE_CREATION_IDEMPOTENCY_TTL_SECONDS = 600.0
+ISSUE_CREATION_IDEMPOTENCY_MAX_ENTRIES = 256
 NOTIFICATION_MUTATION_TIMEOUT_SECONDS = 5.0
 NOTIFICATION_PAGE_TIMEOUT_SECONDS = 5.0
 WORK_PAGE_TIMEOUT_SECONDS = 5.0
@@ -80,6 +82,9 @@ _live_section_retry_at: dict[str, float | None] = {
 }
 _live_snapshot_refreshing_sections: set[str] = set()
 _read_notification_ids: set[int] = set()
+_issue_creation_operations: dict[
+    str, tuple[tuple[Any, ...], asyncio.Task, float]
+] = {}
 
 
 class ContextPayloadError(ValueError):
@@ -952,7 +957,12 @@ async def repository_labels(owner: str, repo: str):
 
 
 @app.post("/api/v1/repos/{owner}/{repo}/issues", status_code=201)
-async def create_assigned_issue(creation: IssueCreation, owner: str, repo: str):
+async def create_assigned_issue(
+    creation: IssueCreation,
+    owner: str,
+    repo: str,
+    idempotency_key: str | None = Header(default=None, max_length=128),
+):
     repository = f"{owner}/{repo}"
 
     async def create_issue():
@@ -980,8 +990,48 @@ async def create_assigned_issue(creation: IssueCreation, owner: str, repo: str):
             repository, creation.title, creation.body, login, creation.label_ids
         )
 
+    operation = create_issue()
+    if idempotency_key:
+        now = time.monotonic()
+        expired = [
+            key for key, (_, task, created_at) in _issue_creation_operations.items()
+            if task.done()
+            and now - created_at >= ISSUE_CREATION_IDEMPOTENCY_TTL_SECONDS
+        ]
+        for key in expired:
+            _issue_creation_operations.pop(key, None)
+        fingerprint = (
+            repository, creation.title, creation.body, tuple(creation.label_ids)
+        )
+        existing = _issue_creation_operations.get(idempotency_key)
+        if existing is not None:
+            operation.close()
+            if existing[0] != fingerprint:
+                raise HTTPException(status_code=409, detail="Idempotency key already used")
+            task = existing[1]
+        else:
+            while len(_issue_creation_operations) >= ISSUE_CREATION_IDEMPOTENCY_MAX_ENTRIES:
+                completed = [
+                    key for key, (_, task, _) in _issue_creation_operations.items()
+                    if task.done()
+                ]
+                if not completed:
+                    operation.close()
+                    raise HTTPException(
+                        status_code=503,
+                        detail="Issue creation is busy; please retry",
+                        headers={"Retry-After": "1"},
+                    )
+                oldest = min(
+                    completed, key=lambda key: _issue_creation_operations[key][2]
+                )
+                _issue_creation_operations.pop(oldest)
+            task = asyncio.create_task(operation)
+            _issue_creation_operations[idempotency_key] = (fingerprint, task, now)
+        operation = asyncio.shield(task)
+
     try:
-        result = await asyncio.wait_for(create_issue(), timeout=ISSUE_ACTION_TIMEOUT_SECONDS)
+        result = await asyncio.wait_for(operation, timeout=ISSUE_ACTION_TIMEOUT_SECONDS)
     except HTTPException:
         raise
     except Exception: