René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"BufferError with Tornado and asyncio","articleBody":"## Problem\r\n\r\nSince adding the StackImpact agent to a Tornado/asyncio application, we started seeing `BufferError`s like this:\r\n```\r\nBufferError: Existing exports of data: object cannot be re-sized\r\n  File \"tornado/web.py\", line 1513, in _execute\r\n    self.finish()\r\n  File \"tornado/web.py\", line 991, in finish\r\n    self.flush(include_footers=True)\r\n  File \"tornado/web.py\", line 947, in flush\r\n    start_line, self._headers, chunk, callback=callback)\r\n  File \"tornado/http1connection.py\", line 400, in write_headers\r\n    self._pending_write = self.stream.write(data)\r\n  File \"tornado/iostream.py\", line 406, in write\r\n    self._handle_write()\r\n  File \"tornado/iostream.py\", line 872, in _handle_write\r\n    del self._write_buffer[:self._write_buffer_pos]\r\n```\r\n\r\n## Environment\r\n\r\nOur application runs inside a Docker container. We use:\r\n* Python 3.6.1\r\n* `tornado` 4.5.1\r\n* `stackimpact` 1.0.0\r\n\r\nWe start it like this (simplified for brevity):\r\n```python\r\nimport asyncio\r\n\r\nfrom tornado.platform.asyncio import AsyncIOMainLoop\r\nfrom tornado.httpserver import HTTPServer\r\nfrom tornado.web import Application\r\n\r\n\r\nif __name__ == '__main__':\r\n    AsyncIOMainLoop().install()\r\n    loop = asyncio.get_event_loop()\r\n\r\n    app = Application(...)\r\n    server = HTTPServer(app)\r\n    server.listen(8080)\r\n\r\n    internal_app = Application(...)\r\n    internal_server = HTTPServer(app)\r\n    internal_server.listen(8081)\r\n\r\n    loop.run_forever()\r\n```\r\n\r\n## Notes\r\n\r\nCursory googling turned up the same error happening in the same place, as reported in [this comment](https://github.com/tornadoweb/tornado/pull/2008#issuecomment-297975575) on a Tornado pull request. I don't know enough about Tornado's internals to guess at what's going on here but maybe @bdarnell can provide more insight.\r\n\r\nIn any case, I'm happy to provide more details as needed.","author":{"url":"https://github.com/adamrothman","@type":"Person","name":"adamrothman"},"datePublished":"2017-06-28T06:01:04.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/1/stackimpact-python/issues/1"}