mir/kea
2
0
Fork 0
mirror of https://gitlab.isc.org/isc-projects/kea synced 2025-08-31 22:15:23 +00:00
Code Issues Releases Wiki Activity

Update hooks-ha.xml

Browse Source
This commit is contained in:
Suzanne Goldlust
2019-01-07 15:59:26 -05:00
committed by Tomek Mrugalski
parent 647f5259c3
commit 3fa032744e
1 changed files with 9 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
doc/guide/hooks-ha.xml
View File

@@ -10,7 +10,7 @@
<title>ha: High Availability</title> <title>ha: High Availability</title>
<para> <para>
This section describes the High Availability hooks library, which can be This section describes the High Availability hooks library, which can be
loaded on a pair of DHCPv4 or DHCPv6 servers to increase reliability of loaded on a pair of DHCPv4 or DHCPv6 servers to increase the reliability of
the DHCP service in the event of an outage of one of the servers. This library the DHCP service in the event of an outage of one of the servers. This library
was previously only available to ISC's paid subscribers, but is now part of was previously only available to ISC's paid subscribers, but is now part of
the open source Kea, available to all users. the open source Kea, available to all users.
@@ -31,7 +31,7 @@
significant features are communication between the servers, partner significant features are communication between the servers, partner
failure detection, and lease synchronization between the servers. failure detection, and lease synchronization between the servers.
However, the DHCPv4 failover standardization process was never completed However, the DHCPv4 failover standardization process was never completed
at IETF. The DHCPv6 failover standard (RFC 8156) was published, but it by the IETF. The DHCPv6 failover standard (RFC 8156) was published, but it
is complex, difficult to use, has significant operational constraints, is complex, difficult to use, has significant operational constraints,
and is different than its v4 counterpart. and is different than its v4 counterpart.
Although it may be useful for some users to use a "standard" failover Although it may be useful for some users to use a "standard" failover
@@ -55,7 +55,7 @@
<para>The Kea HA hook library supports two configurations, also known as HA <para>The Kea HA hook library supports two configurations, also known as HA
modes: load balancing and hot standby. In the load-balancing mode, modes: load balancing and hot standby. In the load-balancing mode,
two servers respond to DHCP requests. The load-balancing function two servers respond to DHCP requests. The load-balancing function
is implemented as described in RFC3074, with each server responding to is implemented as described in <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://tools.ietf.org/html/rfc3074">RFC 3074</link>, with each server responding to
half the received DHCP queries. When one of the servers allocates a lease half the received DHCP queries. When one of the servers allocates a lease
for a client, it notifies the partner server over the control channel for a client, it notifies the partner server over the control channel
(RESTful API), so the partner can save the lease information in its (RESTful API), so the partner can save the lease information in its
@@ -570,7 +570,7 @@
into account the specifics of the network in which the DHCP servers are into account the specifics of the network in which the DHCP servers are
operating. Note that the server in question may not respond to some operating. Note that the server in question may not respond to some
DHCP clients because these clients are not to be serviced DHCP clients because these clients are not to be serviced
by this server per administrative policy. The server may also by this server according to administrative policy. The server may also
drop malformed queries from clients. Therefore, selecting too drop malformed queries from clients. Therefore, selecting too
low a value for the <command>max-unacked-clients</command> parameter may low a value for the <command>max-unacked-clients</command> parameter may
result in a transition to the <command>partner-down</command> result in a transition to the <command>partner-down</command>
@@ -897,7 +897,7 @@
and/or database synchronization between the active servers, if the and/or database synchronization between the active servers, if the
exchange of information about the allocated leases is performed exchange of information about the allocated leases is performed
using some other mechanism. Kea supports various database types using some other mechanism. Kea supports various database types
to be used as storage for leases, including MySQL, Postgres, and Cassandra. that can be used to store leases, including MySQL, Postgres, and Cassandra.
Those databases include built-in solutions for data replication which Those databases include built-in solutions for data replication which
are often used by Kea administrators to provide redundancy.</para> are often used by Kea administrators to provide redundancy.</para>
@@ -979,14 +979,14 @@
Increasing the page size decreases the number of lease queries sent to Increasing the page size decreases the number of lease queries sent to
the partner server, but it causes the partner server to generate the partner server, but it causes the partner server to generate
larger responses, which lengthens transmission time as well as larger responses, which lengthens transmission time as well as
memory and CPU utilization on both servers. Decreasing the increases memory and CPU utilization on both servers. Decreasing the
page size helps to decrease resource utilization, but requires page size helps to decrease resource utilization, but requires
more lease queries to be issued to fetch the entire lease more lease queries to be issued to fetch the entire lease
database.</para> database.</para>
<para>The default value of the <command>sync-page-limit</command> command <para>The default value of the <command>sync-page-limit</command> command
controlling the page size is 10000. This means that the entire controlling the page size is 10000. This means that the entire
lease database can be fetched with a single command if the lease database can be fetched with a single command if the
size of the database is equal to or lower than 10000 lines. size of the database is equal to or less than 10000 lines.
</para> </para>
</section> </section>
@@ -1059,7 +1059,7 @@
<para> <para>
It is important to note that extending this <command>sync-timeout</command> value may sometimes It is important to note that extending this <command>sync-timeout</command> value may sometimes
be insufficient to prevent issues with timeouts during be insufficient to prevent issues with timeouts during
lease-database synchronization. The control commands travel via lease-database synchronization. The control commands travel via the
Control Agent, which also monitors incoming (with a synchronizing Control Agent, which also monitors incoming (with a synchronizing
server) and outgoing (with a DHCP server) connections for timeouts. server) and outgoing (with a DHCP server) connections for timeouts.
The DHCP server also monitors the connection from the Control The DHCP server also monitors the connection from the Control
@@ -1347,7 +1347,7 @@
</para> </para>
<para> <para>
When the server receives this command, it first disables the When the server receives this command it first disables the
DHCP service of the server from which it will be fetching leases, by DHCP service of the server from which it will be fetching leases, by
sending the <command>dhcp-disable</command> command to that server. sending the <command>dhcp-disable</command> command to that server.
The <command>max-period</command> parameter specifies the maximum The <command>max-period</command> parameter specifies the maximum