[kea-dev] Lease File Compression Requirements

Stephen Morris stephen at isc.org
Tue Dec 16 12:22:07 UTC 2014

On 16/12/14 12:02, Marcin Siodelski wrote:

> As a first step towards the implementation of this feature in Kea, 
> I created a page with requirements:
> http://kea.isc.org/wiki/LeaseFileCompressionRequirements
> All input to this document is welcome.
> I am planning on creating an accompanying design document using the
> requirements presented here.
> Again, please share your thoughts.

(Commenting on version 3 of the requirements.)

The requirements look OK, but the only one I question is 2.d "The LFC
must not spread the lease information in multiple lease files. The only
exception is the period before the start and end of LFC." This
requirement seems to introduce extra complexity for little gain.

The emails in the thread:


have suggested a method of LFC compression where the server renames
the current lease file and opens a new one; compression then takes
place asynchronously on the old file.  This would mean that for
virtually all the time the server is operating there are two files -
the current one and the compressed one. (I'm assuming that when LFC
kicks in, it would combine any old files with the one it is processing.)

As the first email in the thread suggests, combining the compressed
lease file with the current one means interrupting processing for a
short while the server appends the latter to the former. I suggest
that most operators are not too concerned about the contents of the
file, so whether the lease information is in one file or split between
two is of no concern to them.  If they do require a single file
containing snapshot of all the leases, it is simple to concatenate the
two files.


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