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96 lines
3.8 KiB
Markdown
96 lines
3.8 KiB
Markdown
# Migrating from BIRD 2 to BIRD 3
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With proper multithreading, we had to change not only the internal architecture,
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but also some user-visible behavior, mostly because these changes were needed
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either for development, or the original features stopped making sense at all
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with the new internal architecture.
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We tried to keep these changes as small as possible but as this major upgrade is
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a good opportunity to do backwards-incompatible changes, we obviously had to do
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that to fix some historically inaccurate concepts.
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## Threads
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Number of working threads is now configured by `threads <num>;` on toplevel.
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By default, this is 1, which actually means 2 running threads. The main one and
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the worker one. When BFD is configured, you get another one for BFD.
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Every instance of BGP, BFD, Pipe and RPKI gets its own *loop* which is a packed
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unit transferrable between the working threads.
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## Logging
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Log files have a slightly different format, indicating by `[abcd]` the actual
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thread logging the message. This enables the user to better comprehend what's
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actually going on between interleaved messages from different threads,
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especially when detailed route tracing is on.
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There is also a new logging option, a fixed-size circular logfile. This is handy
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if you need to switch on detailed tracing but you don't want to overfill your disk.
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Also this option is by far the fastest one.
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## Tables
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It's now possible to set the `debug` option to trace events happening directly
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inside the table.
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Also settle timers were changed; there is a configurable idle-state timeout
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before any route export is announced after import is done. This helps to
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coalesce the routes on export and improves BIRD's overall performance.
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There is also an explicit back-pressure feature, called cork, to avoid memory
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bloating with route flaps. This feature basically forces the readers to flush
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the table journal before more imports are added. Parameters of the cork are
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configurable.
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ROA settle timers were moved into channels.
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## Channels
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ROA settle timers are set separately per-channel now. Also by default, only
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the possibly affected routes get autoreloaded, contrary to BIRD 2.
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Export is now done by blocks which are by default quite large. This may hamper
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responsiveness of single protocols and therefore cause other issues. With
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complex export filters, you may want to drop this value from 16K down. But you
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shouldn't have complex export filters anyway.
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Export supports also `export in` form, allowing to export only subprefixes of
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the given prefix. Experimental.
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Reload of filters is now done by `reload filters` command, contrary to just `reload` in BIRD 2.
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## Filters
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We have removed the exception for `case` where multiple commands could be written
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after the case label without braces. This caused unneeded complexity in the parser.
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## Route attributes
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All protocol attributes have been renamed in CLI to align with the filter language tokens.
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Output of `show route all` also shows more information, including some internal
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data for easier debugging and route tracing.
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The `onlink` route attribute has been temporarily disabled until we find out
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how to implement it properly.
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The `scope` route attribute has been removed. Use custom route attributes instead.
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## Protocols common
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There is now a guard against too frequent restarts due to limits, called
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`restart time`, set by default to 5 seconds. To disable, set this to 1 us.
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## Pipe
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It's now impossible to check immediately whether the route has entered a pipe
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loop. Instead of that, every Pipe pass increases the route's `generation`
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internal attribute, and when it is too high, the route is discarded.
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## BGP
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The export table now shows the state immediately before sending on the wire,
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thus without custom attributes and after all updates done by BGP. This should
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help with performance a little, while also being more accurate.
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