The motivation for supporting an alternative to WebSockets is that while all browsers supported by Grist offer native WebSocket support, some networking environments do not allow WebSocket traffic.
Engine.IO is used as the underlying implementation of HTTP long polling. The Grist client will first attempt a regular WebSocket connection, using the same protocol and endpoints as before, but fall back to long polling using Engine.IO if the WebSocket connection fails.
Include these changes:
- CORS websocket requests are now rejected as a stronger security measure. This shouldn’t affect anything in practice; but previously it could be possible to make unauthenticated websocket requests from another origin.
- GRIST_HOST variable no longer affects CORS responses (also should not affect anything in practice, as it wasn't serving a useful purpose)
Summary:
- Node has a strong recommendation to assume bad state and exit promptly on
unhandled exceptions and rejections. We follow it, and only make an effort to
clean up before exiting, and to log the error in a more standard way.
- The only case seen in recent month of an unhandled rejection was for
attempting to write overly large JSON to a Client websocket. Ensure that's
handled, and add a test case that artificially reproduces this scenario.
Test Plan:
Added a test case for failing write to Client, and a test case that unhandled
errors indeed kill the server but with an attempt at cleanup.
Reviewers: georgegevoian
Reviewed By: georgegevoian
Differential Revision: https://phab.getgrist.com/D4124
Summary:
- Implements MemoryPool for waiting on memory reservations.
- Uses MemoryPool to control memory used for stringifying JSON responses in Client.ts
- Limits total size of _missedMessages that may be queued for a particular client.
- Upgrades ws library, which may reduce memory usage, and allows pausing the websocket for testing.
- The upgrade changed subtle behavior corners, requiring various fixes to code and tests.
- dos.ts:
- Includes Paul's fixes and updates to the dos.ts script for manual stress-testing.
- Logging tweaks, to avoid excessive dumps on uncaughtError, and include timestamps.
Test Plan:
- Includes a test that measures heap size, and fails without memory management.
- Includes a unittest for MemoryPool
- Some cleanup and additions to TestServer helper; in particular adds makeUserApi() helper used in multiple tests.
- Some fixes related to ws upgrade.
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D3974
