Connection and memory leak when pipeline is reloaded

[jakelandis]

Testing against 5.6.4 with 4.3.0 of this plugin.

Everytime a pipeline is reloaded a connection is leaked.

For example a healthy non-reloaded pipeline doing jdbc work:

Then reload the pipeline ~10 times and the open/closed connections gap widens, and the number of noncollectable objects increase too.

Since we only use 1 connection (by default) and as of 4.3.0 open/close connections per statement, the gap between open and close should always be within 1.

The root cause here is that the underlying library does not guarantee a connection in use will actually get disconnected. From the underlying library disconnect method: "This method has the effect of disconnecting from the database, assuming that no connections are currently being used. "

We do not offer any assurances that the pipeline thread during a reload will not try to call disconnect while the connection is use. If that happens the library attempts to disconnect and looses it reference to the connection (thinking it is closed), but when in fact it is still open (since it is in use). Hence the connection leak. All the objects associated with the connection are leaked, hence the memory leak.

This issue will only impact consumers that reload frequently since the connection and memory leak is directly related to the reload frequency.

Note - 4.3.0 did not introduce this issue.

[jakelandis]

Fixed in 4.3.2 of the plugin.