Race condition

[nolanlawson]

I am 99% sure there is a race condition in this module. If you run npm run test-pouchdb in pouchdb-server enough times, you'll see stuff like this:

Possibly unhandled Error: database is closed
    at applyNextDocCountDelta (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/adapters/leveldb.js:120:28)
    at incrementDocCount (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/adapters/leveldb.js:142:5)
    at countDocs (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/adapters/leveldb.js:107:14)
    at PouchAlt.LevelPouch.api._info (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/adapters/leveldb.js:154:5)
    at PouchAlt.<anonymous> (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/adapter.js:666:8)
    at PouchAlt.<anonymous> (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/utils.js:443:21)
    at PouchAlt.<anonymous> (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/node_modules/argsarray/index.js:14:18)
    at /Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/lib/utils.js:405:21
    at tryCatch2 (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/node_modules/bluebird/js/main/util.js:73:19)
    at Promise$_resolveFromResolver [as _resolveFromResolver] (/Users/nolan/workspace/pouchdb-server/node_modules/pouchdb/node_modules/bluebird/js/main/promise.js:595:13)

[gr2m]

despite the issue being old, just want to mention that the problem here is that this module executes asynchronous code in event handlers:

pouchdb-all-dbs/lib/index.js

Lines 57 to 105 in a90d0b1

	Pouch.on('created', function (dbName) {
	dbName = normalize(dbName);
	if (canIgnore(dbName)) {
	return;
	}
	dbName = prefixed(dbName);
	init();
	queue.add(function (callback) {
	pouch.get(dbName).then(function () {
	// db exists, nothing to do
	}).catch(function (err) {
	/* istanbul ignore if */
	if (err.name !== 'not_found') {
	throw err;
	}
	return pouch.put({_id: dbName});
	}).then(function () {
	if (cache) {
	cache[dbName] = true;
	}
	callback();
	}, callback);
	}, log);
	});
	Pouch.on('destroyed', function (dbName) {
	dbName = normalize(dbName);
	if (canIgnore(dbName)) {
	return;
	}
	dbName = prefixed(dbName);
	init();
	queue.add(function (callback) {
	pouch.get(dbName).then(function (doc) {
	return pouch.remove(doc);
	}).catch(/* istanbul ignore next */ function (err) {
	// normally a not_found error; nothing to do
	if (err.name !== 'not_found') {
	throw err;
	}
	}).then(function () {
	/* istanbul ignore else */
	if (cache) {
	delete cache[dbName];
	}
	callback();
	}, callback);
	}, log);
	});

This is what can cause race condition