Failing test for PouchDB 7.3.0 race condition

[PaulMest]

This PR contains:

• IMPROVED TESTS

Describe the problem you have without this PR

PouchDB 7.3.0 introduced a race condition where two databases open in memory at the same time could cause hanging conditions. This was initially discovered randomly by 2 tests in the test suite. This PR adds a smaller consolidated view of this race condition.

Simple repro:

$ npm install
$ npm run test:fast:pouchdb

Todos

• Changelog
• Actual fix

[cetsupport]

@PaulMest Looks like there have race condition when close one of multiple database.

When execute db.close, will call pouchdb-adapter-leveldb-core/lib/index.js:
From line 1218:

  api._close = function (callback) {
    /* istanbul ignore if */
    if (db.isClosed()) {
      return callback(pouchdbErrors.createError(pouchdbErrors.NOT_OPEN));
    }
    db.close(function (err) {
      /* istanbul ignore if */
      if (err) {
        callback(err);
      } else {
        dbStore.delete(name);

        var adapterName = pouchdbUtils.functionName(leveldown);
        var adapterStore = dbStores.get(adapterName);
        var keys = [...adapterStore.keys()].filter(k => k.includes("-mrview-"));
        keys.forEach(key => {
          var eventEmitter = adapterStore.get(key);
          eventEmitter.removeAllListeners();
          eventEmitter.close();
          adapterStore.delete(key);
        });

        callback();
      }
    });
  };

The problem happen in below line:

        var keys = [...adapterStore.keys()].filter(k => k.includes("-mrview-"));

So when we close first database, actually will select the second database views... and disconnect it. This cause problem from my point of view.

I will submit a PR to pouchdb.

[pubkey]

I am closing this issue here because there is nothing that can be done on the RxDB side. I will reopen when it is fixed on the pouchdb side.
Related links:
apache/pouchdb#8515
apache/pouchdb#8513

[PaulMest]

apache/pouchdb#8513 has been merged. The fix should be in the next version of PouchDB.