log rotation

[cyb3rz3us]

Hello all - I had a few questions re: log rotation:

• When a given log hits a threshold, when is the log rotated? Immediately? At a hard-coded time? Other?
• Do the rotation parameters apply to both the app & query logs?
• Is it possible to config separate rotation parameters for the app & query logs?
• Can a sub-1MB size be cfg'd for the "log_files_max_size" parameter?
• Are the "log_files_max_age" & "log_files_max_backups" parameters complimentary. If so, how is rotation handled; i.e. is the log rotated when the first parameter threshold is crossed?
• Can I take any information gleaned here and post into the docs?

[jedisct1]

Here’s how log rotation currently works in dnscrypt-proxy:

• A rotated log is rolled over when it is opened and already at or above the configured size limit, or when a new write would make it exceed that limit. So rotation is effectively size-triggered, not tied to a fixed time of day.
• The log_files_max_size, log_files_max_age, and log_files_max_backups settings apply to the query/plugin log files, such as query_log, nx_log, and the allow/block name/IP logs.
• These settings do not apply to the main application log_file. The application log uses a separate logging path and is not automatically rotated by dnscrypt-proxy.
• There is no separate built-in configuration to use one rotation policy for the application log and another for the query/plugin logs.
• log_files_max_size is handled as an integer number of megabytes, so values below 1 MB are not supported.
• log_files_max_age and log_files_max_backups are complementary. After a rotation, old files are cleaned up using both rules:
  • files older than log_files_max_age days are removed
  • if more than log_files_max_backups backups remain, the oldest extra ones are removed
• One detail worth noting: the current example comment says that log_files_max_size = 0 means unlimited, but the underlying rotation library does not actually treat 0 that way. In practice, 0 falls back to that library’s default maximum size.

I hope that helps clarify things.