Description
Referring to issue #107
I have looked through the code and found that the only way that this error can happen
/app/node_modules/neo4j-driver/lib/v1/internal/ch-node.js:214
for (var i = 0; i < pending.length; i++) {
^
TypeError: Cannot read property 'length' of null
at /app/node_modules/neo4j-driver/lib/v1/internal/ch-node.js:214:34
...
is if the trust certificate callback is called twice:
this._handleConnectionError = this._handleConnectionError.bind(this);
-> this._conn = connect(opts, function () {
if (!self._open) {
return;
}
<...>
var pending = self._pending;
self._pending = null;
for (var i = 0; i < pending.length; i++) {
self.write(pending[i]);
}
}, this._handleConnectionError);
because it it setting self._pending to be null.
The trust certificate function can be called twice if the loadFingerprint callback is called twice.
After looking at the known_hosts file
localhost:7687 fabacd62dbd94...
localhost:7687 fabacd62dbd94...
We see that there are duplicate entries, causing this to fire more than once:
require('readline').createInterface({
input: fs.createReadStream(knownHostsPath)
}).on('line', (line) => {
if( line.startsWith( serverId )) {
--> found = true;
--> cb( line.split(" ")[1] );
}
}).on('close', () => {
if(!found) {
cb(null);
}
});
But why are there duplicates?
Under the circumstances that the known_hosts file exists but is empty (manually created by someone) and if the app is calling for two (or more) driver sessions in the same process tick
const session = driver.session();
const session2 = driver.session();
The driver doesn't have time to update the known_hosts file and thus creates two (or more) entries of the same thing.
After that, the next session that is created:
setTimeout(() => {
const session3 = driver.session();
}, 1000);
will throw the error.