Potential Nginx Configuration Issues After Updating to Plesk Obsidian 18.0.72 Update 2 on Specific Virtualized Setups

Symptoms

• After updating Plesk to Obsidian 18.0.72 Update 2, all domains nginx configuration files are broken.

• The following error message appears on the Home page in Plesk:

  PLESK_ERROR: New configuration files for the Apache web server were not created due to the errors in configuration templates: nginx: [emerg] could not build map_hash, you should increase map_hash_bucket_size: 32 nginx: configuration file /etc/nginx/nginx.conf test failed

• Domains show a http 404 error.
• IPv6 addresses are used on the server.
• The CPU with 32-bit cache size or QEMU Virtual CPU is used.

Cause

This behavior was identified as bug PPPM-15110. In some virtualization setups that use QEMU-based virtual CPUs, Nginx can incorrectly detect the CPU cache line size. This misdetection often results in a default map_hash_bucket_size of 34, which may lead to configuration issues, particularly when processing long IPv6 addresses.

Resolution

Until the bug is fixed, refer to the following workaround to increase the map_hash_bucket_size parameter:

1. Connect to the server via SSH.

2. Create a configuration file with the parameter added:

   # echo 'map_hash_bucket_size 64;' >> /etc/nginx/conf.d/fix_hash_bucket.conf

3. Restart nginx:

   # systemctl restart nginx

4. Rebuild the web server configuration:

   # plesk sbin httpdmng --reconfigure-all