# Kea 1.7.2, November 27th 2019, Release Notes
Welcome to Kea 1.7.2, a third monthly development release of Kea. This
release is the next step towards having fully multi-threaded DHCP
servers, which will eventually become available as 1.8.0. This is a
development release. Use with caution! Development releases are not
recommended for production use.
Changes introduced in this version:
1. **Multi-threading**. One of the major building blocks of the
multi-threaded solution has been implemented. We now have a thread pool,
which is a mechanism for managing pools. Current Kea DHCPv4 and DHCPv6
daemons each have a single-threaded process that does all tasks
sequentially. The upcoming Kea 1.8.0 will have many threads processing
multiple packets and possibly performing other tasks in parallel. This
code adds the management mechanism to govern threads. It is not used yet
by the code, but it is an essential milestone that the upcoming work
will be based on. The first part of the code that has been updated to
the new threading model is MySQL connection handling. Instead of having
one connection shared by all threads, there is now a connection pool
that will eventually allow each thread to use a separate connection.
Another element is generic support for a critical section. NOTE: The
multi-threading solution is not usable yet. (#883, #960, #970).
2. **Default CA port change**. There were some inconsistencies between
various Kea elements (the default value for the CA itself, the
kea-shell, the example configs, and the ARM) regarding the TCP port the
Control Agent (CA) listens on. The default port is now 8000; it can be
configured to other values if needed (#793).
3. **perfdhcp improvements**. Perfdhcp, our DHCP performance testing
tool, is focused on performance and has always had a very simplified
logic regarding validating response correctness. It used to count any
responses as valid, even those that did not assign any address. This
deficiency has been resolved. We intend to use this new capability for
multi-threaded experiments, but it is a general improvement that can be
helpful in any performance test (#572).
4. **New hook points: cb4_updated and cb6_updated**. Two new hook points
called cb4_updated and cb6_updated have been defined. They are
called every time a configuration update is retrieved from the config
backend (CB). This allows ISC and other developers to implement
additional mechanisms on top of the CB (#596).
5. **Improved support for backup servers in HA configuration**. Kea
1.4.0 introduced High Availability mode with an optional capability to
send lease updates to a third backup server. It was recently discovered
that under special circumstances (initial traffic being serviced by the
primary server, followed by more than 30 seconds of inactivity), the
backup server could close the connection. The primary server would enter
a "confused" state where it believed there was data to be received from
the backup server, but the connection was broken. In effect, the primary
server would enter a busy loop, resulting in 100% CPU utilization and
general unresponsiveness to DHCP traffic and API commands. This bug has
been fixed. This problem affects only users who use HA configuration
with an additional backup server and periods of inactivity. (#964).
## Changes to Release Model
The Kea project has been in development for several years now, and it
has a significant production deployment base with users who are looking
for stability, rather than a constant stream of new "bleeding-edge"
features. At the same time, we want to continue developing the software,
including some new powerful, but difficult-to-implement, features. As a
result, we decided to change the release cycle. Starting from 1.6.0,
there are two series of releases: stable and development.
Stable releases are what you would expect: stable, released
infrequently, without new features or significant changes, very
well-tested. Those can be identified by the middle version number being
even. The current stable release is 1.6.0. If we discover important bugs
that require fixing, we may release 1.6.1, but that will be determined
on a case-by-case basis. The next major stable version will be 1.8.0,
followed by 2.0.0 in the future.
Our team continues development of new features. In particular, we're
tackling the difficult problem of being able to use all available CPU
cores simultaneously. The multi-threading implementation is a complex
task and it is unknown how long it will take before the solution is
stable and ready for production environment. At the same time, we
continue to receive a stream of requests for small features and bug
fixes. We don't want to force users to wait half a year or more for the
fixes and features that are already done. Therefore, we have decided to
start issuing development releases on a monthly basis. Those are
slightly less well-tested and may have features that are not complete; a
good example may be multi-threading. It is possible that one of the next
releases will provide a configuration knob to specify the number of
threads, but the actual code won't be extended yet to spawn those
threads.
The development releases can be easily identified by the middle version
number being odd: for example, 1.7.2 is a development release. In
December 2019 we will release 1.7.3, the next development version. Once
1.8.0 is out, we will continue our development work with 1.9.0, then
1.9.1, and so on.
Our goal is to make the development release available on the last
Wednesday of each month. There may be exceptions (such as during
holidays), but that's the general plan.
We encourage users to test the development releases and report back
their findings.
For more details on the plan, see ISC's Software Support Policy at
https://kb.isc.org/v1/docs/aa-00896.
## Kea overview
Kea is a DHCP implementation developed by Internet Systems Consortium,
Inc. that features fully functional DHCPv4 and DHCPv6 servers, a dynamic
DNS update daemon, a Control Agent (CA) that provides a REST API to
control the DHCP and DNS update servers, an example shell client to
connect to the CA, a daemon that is able to retrieve YANG configuration
and updates from Sysrepo, and a DHCP performance-measurement tool. Both
DHCP servers fully support server discovery, address assignment,
renewal, rebinding, release, decline, information request, DNS updates,
client classification, and host reservations. The DHCPv6 server also
supports prefix delegation. Lease information is stored in a CSV file by
default; it can optionally be stored in a MySQL, PostgreSQL, or
Cassandra database instead. Host reservations can be stored in a
configuration file, or in a MySQL, PostgreSQL, or Cassandra database.
They can also be retrieved from a RADIUS server, although this
functionality is somewhat limited. Kea DHCPv4 and DHCPv6 daemons provide
support for YANG models, which are stored in a Sysrepo datastore and can
be configured via the NETCONF protocol.
This text references issue numbers. For more details, visit the Kea
GitLab page at https://gitlab.isc.org/isc-projects/kea/issues.
## License
This version of Kea is released under the Mozilla Public License,
version 2.0.
https://www.mozilla.org/en-US/MPL/2.0
The premium and subscriber-only hook libraries are provided in source
code form, under the terms of an End User License Agreement (you will
get the source code that you can modify freely, but you are not
permitted to redistribute it).
## Download
Pre-built ISC packages for current versions of the most popular Linux
operating systems are available at:
https://cloudsmith.io/~isc/repos/
The Kea source and PGP signature for this release may be downloaded from:
https://www.isc.org/downloads
The signature was generated with the ISC code signing key which is
available at:
https://www.isc.org/pgpkeys
ISC provides detailed documentation, including installation instructions
and usage tutorials, in the Kea Administrator Reference Manual.
Documentation is included with the installation or via
https://kb.isc.org/docs/kea-administrator-reference-manual in HTML,
plain text, or PDF formats. ISC maintains a public open source code
tree, wiki, issue tracking system, milestone planning, and a roadmap at
https://gitlab.isc.org//isc-projects/kea.
Limitations and known issues with this release can be found at
https://gitlab.isc.org/isc-projects/kea/wikis/known-issues-list.
We ask users of this software to please let us know how it worked for
you and what operating system you tested on. Feel free to share your
feedback on the Kea Users mailing list
(https://lists.isc.org/mailman/listinfo/kea-users). Also we would like
to hear whether the documentation is adequate and accurate. Please open
tickets in the Kea GitLab project for bugs, documentation omissions and
errors, and enhancement requests. We want to hear from you even if
everything worked.
## Support
Professional support for Kea is available from ISC. We encourage all
professional users to consider this option; Kea development and
maintenance are funded with support subscriptions. For more information
on ISC's Kea and DHCP software support see https://www.isc.org/support/.
Free best-effort support is provided by our user community via a mailing
list. Information on all public email lists is available at
https://www.isc.org/community/mailing-list. If you have any comments or
questions about working with Kea, please share them to the Kea Users
List (https://lists.isc.org/mailman/listinfo/kea-users). Bugs and
feature requests may be submitted via GitLab at
https://gitlab.isc.org/isc-projects/kea/issues.
## Changes
The following summarizes changes and important upgrade notes since the
previous release (1.7.1).
1686. [func] razvan
Added a generic ThreadPool class which can be used to process
functor work items in parallel, on multiple threads. It uses
a queue container to manage the work items.
(Gitlab #883)
1685. [build] fdupont
Small build improvement. The fcntl.h header is included in more
portable way. This should make it easier to build on Alpine
systems and possibly other systems.
(Gitlab #765)
1684. [func] fdupont
As a preparation for upcoming multi-threading, the MySQL
connection pool has been implemented. This code is not
usable on its own yet, but it will allow all threads
to have share a pool of connections in the future. This
should improve the overall MySQL lease backend performance.
(Gitlab #960)
1683. [bug] wlodek
Perfdhcp is able to parse incoming packet and determine
if included IA_NA/IA_PD options are correct, counter
of rejected leases is introduced for all DHCP v6 message
exchanges. Perfdhcp will no longer send Request/Renew/Release
message without proper IA_NA/IA_PD included.
(Gitlab #572)
1682. [bug]* tmark
Added logic to core code and HA hook lib to allow HA peers
to detect and handle out of bandwidth socket events. This
corrects a defect introduced in Kea 1.6.0 that can cause
an HA server to become unresponsive when an HA socket has
been closed by a peer. Note that there is a change to the
signature of the external socket callback handler invoked
by IfaceMgr. Custom hook libraries happen register external
sockets with IfaceMgr will require modification and
recompilation.
(Gitlab #964)
Thank you again to everyone who assisted us in making this release
possible.
We look forward to receiving your feedback.