Use lock to avoid kernel address conflicts in nb-tester

.gitignore

@@ -19,3 +19,4 @@ poetry.lock
 /dist/
 /test-results/
 Untitled*.ipynb
+*.lock

scripts/nb-tester/qiskit_docs_notebook_tester/__init__.py

@@ -18,6 +18,8 @@
 import platform
 from datetime import datetime
 
+import nbclient
+
 from .config import get_notebook_jobs, get_parser
 from .execute import execute_notebook, cancel_trailing_jobs
 
@@ -32,7 +34,10 @@ async def _main() -> None:
 
     start_time = datetime.now()
     print("Executing notebooks:")
-    results = await asyncio.gather(*(execute_notebook(job) for job in jobs))
+    setup_kernel_lock = asyncio.Lock()
+    results = await asyncio.gather(
+        *(execute_notebook(job, setup_kernel_lock) for job in jobs)
+    )
 
     if not args.ignore_trailing_jobs:
         print("Checking for trailing jobs...")

scripts/nb-tester/qiskit_docs_notebook_tester/execute.py

@@ -13,6 +13,7 @@
 from __future__ import annotations
 
 
+import asyncio
 import tempfile
 import textwrap
 from dataclasses import dataclass
@@ -65,7 +66,7 @@ def extract_warnings(notebook: nbformat.NotebookNode) -> list[NotebookWarning]:
     return notebook_warnings
 
 
-async def execute_notebook(job: NotebookJob) -> Result:
+async def execute_notebook(job: NotebookJob, kernel_setup_lock: asyncio.Lock) -> Result:
     """
     Wrapper function for `_execute_notebook` to print status and write result
     """
@@ -80,7 +81,7 @@ async def execute_notebook(job: NotebookJob) -> Result:
         nbclient.exceptions.CellTimeoutError,
     )
     try:
-        nb = await _execute_notebook(job, working_directory.name)
+        nb = await _execute_notebook(job, working_directory.name, kernel_setup_lock)
     except execution_exceptions as err:
         print(f"❌ Problem in {job.path}:\n{err}")
         return Result(False, reason="Exception in notebook")
@@ -118,7 +119,7 @@ async def _execute_in_kernel(kernel: AsyncKernelClient, code: str) -> None:
 
 
 async def _execute_notebook(
-    job: NotebookJob, working_directory: str
+    job: NotebookJob, working_directory: str, kernel_setup_lock: asyncio.Lock
 ) -> nbformat.NotebookNode:
     """
     Use nbclient to execute notebook. The steps are:
@@ -130,11 +131,12 @@ async def _execute_notebook(
     """
     nb = nbformat.read(job.path, as_version=4)
 
-    kernel_manager, kernel = await start_new_async_kernel(
-        kernel_name="python3",
-        extra_arguments=["--InlineBackend.figure_format='svg'"],
-        cwd=working_directory,
-    )
+    async with kernel_setup_lock:
+        kernel_manager, kernel = await start_new_async_kernel(
+            kernel_name="python3",
+            extra_arguments=["--InlineBackend.figure_format='svg'"],
+            cwd=working_directory,
+        )
 
     await _execute_in_kernel(kernel, job.pre_execute_code)
     if job.backend_patch: