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Problem(Abstract) |
The steps listed in the administration guide to configure
high availability are incorrectly ordered. |
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Cause |
When the configuration is saved, Load Balancer (also known
as Network Dispatcher in earlier releases) places the commands in the
correct order; however, if you write your own configurations, follow these
updated steps to avoid problems with ServerUp ServerDown scripts and
possible problems with ownership of the clusters that can lead to
forwarding problems. |
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Resolving the
problem |
The following are the correct steps for configuring high
availability for the Dispatcher component:
Note: For Network Dispatcher 4.0 (Edge Server 2.0), substitute the
use of dscontrol with ndcontrol.
- Create alias script files on each of the 2 Dispatcher machines.
- Start the server on both Dispatcher server machines.
- Start the executor on both machines.
- Ensure that the nonforwarding address (NFA) of each Dispatcher machine
is configured, and is a valid IP address for the subnet of the Dispatcher
machines.
Windows® platform: For Network Dispatcher versions 4.x and Load Balancer
5.x only:
In addition, configure each nonforwarding address using the dsconfig
command.
For example:
dsconfig en0 nfa_addr netmask
netmask
- Add the heartbeat information on both machines:
dscontrol highavailability heartbeat add
sourceaddress destinationaddress
Note: sourceaddress and destinationaddress are
the IP addresses (either DNS names or dotted-decimal addresses) of the
Dispatcher machines.
The values are reversed on each machine.
For example:
Primary - highavailability heartbeat add 9.67.111.3 9.67.186.8
Backup - highavailability heartbeat add 9.67.186.8 9.67.111.3
At least one heartbeat pair must have the NFAs on the pair as the source
and destination address.
If possible, it is recommended that a least one of the heartbeat pairs be
across a different subnet than the regular cluster traffic. Keeping the
heartbeat traffic distinct helps prevent false takeovers during very heavy
network loads and also improves complete recovery times after a failover.
Note: This is unique for Load Balancer 5.1.1 and higher levels:
Set the number of seconds that the executor uses to timeout high
availability heartbeats.
For example:
dscontrol executor set hatimeout 3
The default is 2 seconds.
- On both machines, configure the list of IP addresses that the
Dispatcher must be able to reach to ensure full service, using the reach
add command.
For example:
dscontrol highavailability reach add 9.67.125.18
Reach targets are recommended but not required.
- Add the backup information to each machine.
- For the primary machine:
dscontrol highavailability backup add primary [auto|manual] port
- For the backup machine:
dscontrol highavailability backup add backup [auto|manual] port
- For mutual high availability each Dispatcher has both
primary and backup roles:
dscontrol highavailability backup add both [auto|manual] port
Note: Select an unused port on your machines as the port. Your two
machines will communicate over this port.
- Check the high availability status on each machine:
dscontrol highavailability status
The machines must each have the correct role (backup, primary, or both),
states, and substates. The primary must be active and synchronized; the
backup must be in a standby mode and must be synchronized within a short
time. The strategies must be the same.
- Set up the cluster, port, and server information on both machines.
- Start the manager and advisors on both machines.
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Cross Reference information |
Segment |
Product |
Component |
Platform |
Version |
Edition |
Application Servers |
Network Dispatcher |
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Multi-Platform |
4.0 |
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Application Servers |
Runtimes for Java Technology |
Java SDK |
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