leveldown: LevelDown version > `5.0.2` with PouchDB => MacOS crash with MaxListenersExceededWarning (once called more than once)

As reported in PouchDB: https://github.com/pouchdb/pouchdb/issues/7819 https://github.com/pouchdb/pouchdb/issues/7825 https://github.com/pouchdb/pouchdb/issues/7848

I narrowed-down the bug to the leveldown transition from version 5.0.2 to 5.0.3 (ALL other package versions are latest, currently levelup = 4.3.2, pouchdb-adapter-leveldb = 7.1.1, pouchdb-adapter-leveldb = 7.1.1, etc.)

In other words, ONLY leveldown needs to be pinned to version 5.0.2. In my case, the package.json looks like:

  "optionalDependencies": {
    "leveldown": "5.0.2",
    "pouchdb-adapter-leveldb": "^7.1.1"
  },
  "resolutions": {
    "leveldown": "5.0.2"
  }

LevelDown diff between version 5.0.2 and 5.0.3: https://github.com/Level/leveldown/compare/v5.0.2...v5.0.3

Note my app stacktrace:

Uncaught Exception:
Error: once called more than once
    at /project/node_modules/pouchdb-core/node_modules/pouchdb-utils/lib/index.js:88:13
    at /project/node_modules/argsarray/index.js:14:18
    at /project/node_modules/pouchdb-core/lib/index.js:769:14
    at /project/dist/node_modules/pouchdb-adapter-leveldb-core/lib/index.js:350:18
    at /project/dist/node_modules/argsarray/index.js:14:18
    at /project/dist/node_modules/pouchdb-adapter-leveldb-core/lib/index.js:429:16
    at /project/dist/node_modules/sublevel-pouchdb/lib/index.js:243:9
    at /project/dist/node_modules/sublevel-pouchdb/lib/index.js:74:13

So, I am not certain that the problem actually stems from the leveldown implementation, but I thought I’d post this here as well as in the PouchDB issue tracker, just in case somebody here has a clue as to why the leveldown code change introduced in version 5.0.3 trips the PouchDB LevelDB adapter.

I should point out that my app is built with Electron version 6.0.12 (NodeJS 12), but I had the exact same problem with earlier Electron/NodeJS versions. LevelDown is built with npm rebuild --runtime=electron --target=6.0.12 --disturl=https://atom.io/download/atom-shell --build-from-source.

Thank you!

About this issue

Original URL
State: closed
Created 5 years ago
Comments: 35 (24 by maintainers)

Commits related to this issue

hotfix(dev): LevelDown versions in node_modules were only deduped at code level during NPM install, precompiled binaries of NodeJS plugins were loaded several times (Fixes #496 Also see https://github... — committed to edrlab/thorium-reader by danielweck 5 years ago
Produce a unique namespace at compile time Closes #686. — committed to Level/leveldown by vweevers 5 years ago
Try out -fvisibility=hidden for mac Ref #686, #687. — committed to Level/leveldown by vweevers 5 years ago
Hide symbols on mac with -fvisibility=hidden (#688) Ref #686, #687. — committed to Level/leveldown by vweevers 5 years ago

Most upvoted comments

It looks like you are on the right track! 😃

Meanwhile, I have found a better workaround that does not require pinning to version 5.0.2. Instead I can just use the latest version (^5.3.0) but I must make sure to delete the de-duped leveldown NPM package (./node_modules/pouchdb-adapter-leveldb/node_modules/leveldown, which contains build/Release/leveldown.node). It’s that simple 😃 Thanks for putting me on this track!

danielweck on Oct 14, 2019

This works:

#define CONCAT_(a,b) a##b
#define CONCAT(a,b) CONCAT_(a,b)
#define NS CONCAT(NODE_GYP_MODULE_NAME,VERSION)

namespace NS {
  // ..
}

This way symbols get prefixed with a versioned namespace.

Better yet, use random bytes, hex-encoded, so it always produces valid identifiers.

vweevers on Oct 18, 2019

Where do we go from here? Test more versions and combinations? Even if only 5.0.2 turns out to have the problem, it’s a severe problem. If we don’t figure it out, it might bite us later. But I have no idea how to further investigate this.

We sleep on it.

ralphtheninja on Oct 14, 2019

@vweevers There is a pattern between “newer version” vs “older version” above. Note that the version pairs

5.3.0 / 5.0.2 too many 5.0.2 / 5.3.0 not called

behave exactly the same as

5.0.3 / 5.0.2 too many 5.0.2 / 5.0.3 not called

I’m betting you’ll get the same result if you replace 5.3.0 with 5.2.0 or any other version over 5.0.3.

I’m thinking it could be related to different class function memory layout, given that we have changed a bit how some methods are pure virtual, adding DoComplete() we might end up in a weird situation because we’re loading libraries dynamically and maybe messing around with function address space. I’m guessing very hand wavy here.

ralphtheninja on Oct 14, 2019

This “MaxListenersExceededWarning” MacOS-specific definitely needs a minimal repro test-case. I am not sure what triggers this, I was hoping that the stack trace posted at the top of this comment thread would provide some clues.

I suspect that the issue filed here for leveldown can safely be closed, because the problem probably arises from how PouchDB integrates it. However I am very grateful for your replies, which have helped on multiple levels already.

Cheers.

danielweck on Oct 14, 2019