Scenario: A JDK8 Docker container using OJDBC7 to connect to the database. Sounds simple enough, what could go wrong?
Simptoms: Connecting to the database randomly takes several minutes, fails with a weird SqlRecoverableException: no more data to read from socket or just works fine as if there is no problem.
The same Docker image also works fine on some machine but fails consistently on other.
The reason is this. Docker is not good at /dev/random. Probably even more so if you run it in a VM, since it’s double isolated from actual entropy sources (my non scientific observation). For whatever reason, OJDBC defaults to /dev/random and this causes a block when connecting to the database due to high probability of /dev/random depletion.
Simple solution is to just mount /dev/urandom to /dev/random inside the Docker, in docker run command:
So.. if you ever want to use OJDBC inside Docker, remember this flag. It will save lives or at least spare you hours of useless debugging.
I recently installed Fedora 24 XFCE on my brand new Entroware Apollo, a Linux friendly laptop. Here is a list of problems I encountered during my first week of use. While most of these problems had a solution with a bit of googling, non-tech savvy person would have severe problems solving them.
- System completely hangs when I connect a second monitor. Unresolved.
- Could not see any WiFi networks because the interface was not managed. Had to make it managed in NetworkManager.conf manually.
- At some point, XFCE panel would not show up anymore and I got an error message on startup asking me to start the panel. Solved it by deleting .config folder. What the hell?
- No login prompt when laptop comes out of suspend, even though I have both option in power management and session settings turned on. Unresolved.
- Adding programs to favorites in Whiskers menu sometimes does not persist across reboots. I think esepcially when I did a hard reset due to issue #1.
- My Nexus 4 would not automount in Thunar over USB. After an hour of Googling and installing random packages I got it to work, I think?
- Numix theme on XFCE is extremely nice, I love it. There is just one small bug so far in Volume widget, the selection color hides the slider completely.
- My FreeNAS was automatically detected by Thunar while the old Gnome-files setup would not show it and even refuse to mount it sometimes manually. A nice surprise.
- I like how you can fully customize XFCE panels. The only thing I actually couldn’t do is completely hide the panel (there is like a 3px grey bar when the panel is hidden). Other than that it’s super nice.
- Fedy is super nice. Props to it’s maintainers, it all just works.
So basically, everything kinda works now but it was a bumpy road to achieve this. Hopefully I get some feedback on issue #1 in Fedora bug tracker because it’s really severe.