This project is for reproducing the blocking of the event loop when unsubscribing in meteor.
Run
meteorWait till the subscription is ready, it might take a while, but it never blocks the event loop, the data comes gradually. Once it is ready, click on Unsubscribe.
Check the console
I20180420-12:27:19.629(2)? 1524220039629
I20180420-12:27:19.932(2)? [BLOCKED] Blocked for 226.95668499946595ms, operation started here:
I20180420-12:27:19.932(2)? at Zlib.emitInitNative (internal/async_hooks.js:133:43), at InflateRaw.Zlib (zlib.js:231:18), at new InflateRaw (zlib.js:576:8), at Object.InflateRaw (zlib.js:575:12), at ServerSession.Session._getInflate (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/permessage-deflate/lib/session.js:130:31), at ServerSession.Session.processIncomingMessage (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/permessage-deflate/lib/session.js:26:22), at Functor.call (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/pipeline/functor.js:46:32), at Cell._exec (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/pipeline/cell.js:36:29), at Cell.incoming (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/pipeline/cell.js:22:8), at pipe (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/pipeline/index.js:39:28), at Pipeline._loop (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/pipeline/index.js:44:3), at Pipeline.processIncomingMessage (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/pipeline/index.js:13:8), at Extensions.processIncomingMessage (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-extensions/lib/websocket_extensions.js:133:20), at Hybi._emitMessage (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-driver/lib/websocket/driver/hybi.js:445:22), at Hybi._emitFrame (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-driver/lib/websocket/driver/hybi.js:405:19), at Hybi.parse (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-driver/lib/websocket/driver/hybi.js:141:18), at IO.write (/Users/peterpalkoszta/.meteor/packages/ddp-server/.2.1.2.1xtgy5z.fui7++os+web.browser+web.cordova/npm/node_modules/websocket-driver/lib/websocket/streams.js:80:16), at Socket.ondata (_stream_readable.js:639:20), at emitOne (events.js:121:20), at Socket.emit (events.js:211:7), at addChunk (_stream_readable.js:263:12), at readableAddChunk (_stream_readable.js:250:11), at Socket.Readable.push (_stream_readable.js:208:10), at TCP.onread (net.js:607:20)
I20180420-12:27:19.933(2)? 1524220039932
You can see the error above, for 2000 small documents, it's already blocking the event loop for 200ms+ on a decent computer.
Just to make sure it's not false positive, I also print the current timestamp every 100ms, but as you can see there is nothing printed between 1524220039629 and 1524220039932 (=303ms), so indeed the even loop was really blocked for 200ms+.