3.5 KiB
Migrating from BIRD 2 to BIRD 3
With proper multithreading, we had to change not only the internal architecture, but also some user-visible behavior, mostly because these changes were needed either for development, or the original features stopped making sense at all with the new internal architecture.
We tried to keep these changes as small as possible but as this major upgrade is a good opportunity to do backwards-incompatible changes, we obviously had to do that to fix some historically inaccurate concepts.
Threads
Number of working threads is now configured by threads <num>; on toplevel.
By default, this is 1, which actually means 2 running threads. The main one and
the worker one. When BFD is configured, you get another one for BFD.
Every instance of BGP, BFD, Pipe and RPKI gets its own loop which is a packed unit transferrable between the working threads.
Logging
Log files have a slightly different format, indicating by [abcd] the actual
thread logging the message. This enables the user to better comprehend what's
actually going on between interleaved messages from different threads,
especially when detailed route tracing is on.
There is also a new logging option, a fixed-size circular logfile. This is handy if you need to switch on detailed tracing but you don't want to overfill your disk. Also this option is by far the fastest one.
Tables
It's now possible to set the debug option to trace events happening directly
inside the table.
Also settle timers were changed; there is a configurable idle-state timeout before any route export is announced after import is done. This helps to coalesce the routes on export and improves BIRD's overall performance.
There is also an explicit back-pressure feature, called cork, to avoid memory bloating with route flaps. This feature basically forces the readers to flush the table journal before more imports are added. Parameters of the cork are configurable.
ROA settle timers were moved into channels.
Channels
ROA settle timers are set separately per-channel now. Also by default, only the possibly affected routes get autoreloaded, contrary to BIRD 2.
Export is now done by blocks which are by default quite large. This may hamper responsiveness of single protocols and therefore cause other issues. With complex export filters, you may want to drop this value from 16K down. But you shouldn't have complex export filters anyway.
Export supports also export in form, allowing to export only subprefixes of
the given prefix. Experimental.
Reload of filters is now done by reload filters command, contrary to just reload in BIRD 2.
Route attributes
All protocol attributes have been renamed in CLI to align with the filter language tokens.
Output of show route all also shows more information, including some internal
data for easier debugging and route tracing.
The onlink route attribute has been temporarily disabled until we find out
how to implement it properly.
The scope route attribute has been removed. Use custom route attributes instead.
Pipe
It's now impossible to check immediately whether the route has entered a pipe
loop. Instead of that, every Pipe pass increases the route's generation
internal attribute, and when it is too high, the route is discarded.
BGP
The export table now shows the state immediately before sending on the wire, thus without custom attributes and after all updates done by BGP. This should help with performance a little, while also being more accurate.