Logging an exception before re-raising it turns a crash into a handled error #8096

# python repro.py <plain|log-then-raise>
import gzip, json, logging, sys, threading
from http.server import BaseHTTPRequestHandler, HTTPServer

import sentry_sdk
from flask import Flask

sessions, events = [], []


class Sink(BaseHTTPRequestHandler):
    def log_message(self, *a):
        pass

    def do_POST(self):
        body = self.rfile.read(int(self.headers["Content-Length"]))
        if self.headers.get("Content-Encoding") == "gzip":
            body = gzip.decompress(body)
        lines = body.split(b"\n")
        for i in range(1, len(lines) - 1, 2):
            try:
                item = json.loads(lines[i])
                payload = json.loads(lines[i + 1])
            except Exception:
                continue
            if item.get("type") == "sessions":
                sessions.extend(payload["aggregates"])
            if item.get("type") == "event":
                values = payload["exception"]["values"]
                events.append(values[-1]["mechanism"]["handled"])
        self.send_response(200)
        self.end_headers()


srv = HTTPServer(("127.0.0.1", 0), Sink)
threading.Thread(target=srv.serve_forever, daemon=True).start()
sentry_sdk.init(dsn="http://k@127.0.0.1:%d/1" % srv.server_port, release="demo@1.0.0")

app = Flask(__name__)
log = logging.getLogger("app")
mode = sys.argv[1]


@app.route("/")
def index():
    try:
        raise ValueError("db down")
    except ValueError:
        if mode == "log-then-raise":
            log.exception("failed to load")
        raise


logging.getLogger("werkzeug").disabled = True
app.logger.disabled = True
app.test_client().get("/")
sentry_sdk.get_client().session_flusher.flush()
sentry_sdk.flush()
totals = {k: sum(a.get(k, 0) for a in sessions) for k in ("exited", "errored", "crashed")}
print(f"{mode:15} events handled={events}  request sessions={totals}")