Update: rendering complete (20180826@11:53, 27 hours rendering time), new map is live. Most missing blocks appear. The only anomaly I have noticed thus far is that rail is not oriented properly. Well done, Minecraft Overviewer team!
In response to the apparent overheating problems when running Minecraft Overviewer, I installed software to monitor the CPU core temperature. I found that it was hovering around 40°C at idle. When I ran overviewer, that would climb to the low 90’s, but the system never shut down (which happens at around 127°C, I believe). So I enabled the nightly cron job to update the map, and all went well for a few days. Last night, the server shut down again.
The initial run of overviewer seemed to work well. Yesterday, I re-enabled the cron job to update the map every day at midnight. When I got up this morning, I discovered that the server had died at 00:16.
I restarted the server and tried updating the map by running overviewer from the command line, and the server switched off abruptly after a few minutes with no error messages.
There’s nothing in the logs, and the server doesn’t just die, it powers off. The most likely cause is that the processor is overheating, but it seems odd that it completed the initial build during several days of triple-digit temperatures with server room temps reaching the mid 80’s, and last night the temp in the server room was in the low 70’s. But CPU fans and cooling paste can fail over time, and perhaps overviewer actually taxes the processor more when most blocks are already up-to-date.
Right now the server is running, but the maps won’t be updated until at least the weekend when I have a few moments to troubleshoot.
Some amazing volunteers have been updating Minecraft Overviewer to work with the new 1.13 file format. I am running a test version now. It estimated sixty hours (!) to render the new map from scratch, but it’s going a bit faster than that.
UPDATE: The rendering is finished (in just under 30 hours) and the new map is installed. As expected, there are blocks that don’t render but overall it looks good. Check it out!