HTTP2 Stream ID Conflict Occurs with ConnectionPool During Multi-threaded Concurrent Usage

[chenlcme]

When I submit HTTP2 requests concurrently using multiple threads through ConnectionPool, an error occurs. An analysis of the logs reveals that multiple threads are using the same stream ID, leading to an error returned by the server.

example:

import logging
import threading
import time

from httpcore import ConnectionPool

logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s %(levelname)s [%(threadName)s] %(message)s',
)

with ConnectionPool(http1=False, http2=True) as pool:
    thread_count = 3
    done_threads: list[str] = []

    def post_one():
        try:
            response = pool.request(
                "POST",
                "https://httpbin.org/post",
                headers=[(b"content-type", b"application/json")],
                content=b'{"hello": "world"}',
            )
            assert response.status == 200
        except Exception as e:
            logging.exception(e)
        finally:
            done_threads.append(threading.current_thread().name)

    for i in range(thread_count):
        thread = threading.Thread(target=post_one)
        thread.start()

    while len(done_threads) < thread_count:
        time.sleep(1)

    print(done_threads)

the key logs:

the hold log:
log.txt

I reviewed the source code of _sync.http2.HTTP2Connection and h2.connection.H2Connection. H2Connection states that it is not thread-safe, and I found the following code block has concurrency issues。I think the code block for acquiring a new stream ID needs to be locked.