bind/doc/notes/notes-9.21.9.rst

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Notes for BIND 9.21.9
---------------------

New Features
~~~~~~~~~~~~

- Add support for zone templates.

  To simplify the configuration of multiple similar zones, BIND now
  supports a zone template mechanism. `template` blocks containing zone
  options can be defined at the top level of the configuration file;
  they can then be referenced in `zone` statements. A zone referencing a
  template will use the options in the specified `template` block as
  defaults. (Options locally defined in the `zone` statement override
  the template.)

  The filename for a zone can now be generated parametrically from a
  format specified in the `file` option. The first occurrences of
  `$name`, `$type` and `$view` in `file` are replaced with the zone
  origin, the zone type (i.e., primary, secondary, etc), and the view
  name, respectively.

  Primary zones can now take an `initial-file` option, specifying the
  path to a generic zone file that will be copied into the zone's `file`
  path when the zone is first loaded, if the `file` does not already
  exist.

  For example, the following template can be used for primary zones: ```
  template primary {                 type primary;                 file
  "$name.db";                 initial-file "generic.db";         }; ```

  With this template in place, a new primary zone could be added using a
  single `rndc addzone` command:

  ```         $ rndc addzone example.com '{ template primary; };' ```

  The zone would be created using the filename `example.com.db`, which
  would be copied into place from `generic.db`. :gl:`#2964`

- Redesign the unreachable primaries cache.

  Previously, the cache for the unreachable primary servers was limited
  to 10 entries (LRU) and a fixed 10 minutes delay for each entry,
  unless removed forcibly by a new entry. The cache is now redesigned to
  remove the 10 entry limitation and to introduce delay values with
  exponential backoff time - initially an unreachable primary server is
  cached as being unreachable for 10 seconds, but each time the cache
  entry is expired and the same server is added again during the
  eligibility period of the next 120 seconds, the delay time is doubled
  up until to the maximum of 640 seconds. :gl:`#3992`

- Implement a new 'notify-defer' configuration option.

  This new option sets a delay (in seconds) to wait before sending a set
  of NOTIFY messages for a zone. Whenever a NOTIFY message is ready to
  be sent, sending will be deferred for this duration. This option is
  not to be confused with the :any:`notify-delay` option. The default is
  0 seconds. :gl:`#5259`

Bug Fixes
~~~~~~~~~

- Fix zone deletion issue.

  A secondary zone could initiate a new zone transfer from the primary
  server after it had been already deleted from the secondary server,
  and before the internal garbage collection was activated to clean it
  up completely. This has been fixed. :gl:`#5291`

- Fix a zone refresh bug.

  A secondary zone could fail to further refresh with new versions of
  the zone from a primary server if named was reconfigured during the
  SOA request step of an ongoing zone transfer. This has been fixed.
  :gl:`#5307`