suggester rebuild + setting configuration results in apparent hang

[vladak]

I've just experienced what might be hang. There was indexer running in the background. The indexing was done with opengrok-sync, i.e. per project. This means the suggester for each project was being rebuilt. At the same time I wanted to change a setting in the configuration (rebuildThreadPoolSizeInNcpuPercent in suggesterConfig) so I used opengrok-projadm to retrieve the current configuration from the web app, merge it with the read-only configuration and send it back to the web app using the RESTful API call to set new configuration. At that point the incoming requests to the web app stopped.

Here's the thread dump from that moment: tomcat-suggester-hang.txt