This section focuses on administering production environments
and realistic test environments.
- Enabling advisors to manage load balancing
- Tuning is a critical part of getting the best performance from
your Web site, but tuning involves analyzing performance data and
determining the optimal server configuration. This determination requires
considerable knowledge about the various components in the application
server and their performance characteristics. The performance advisors
encapsulate this knowledge, analyze the performance data and provide
configuration recommendations to improve the application server performance.
Therefore, the performance advisors provide a starting point to the
application server tuning process and help you without requiring that
you become an expert.
- Configuring high availability
- The high availability feature involves the use of a second Dispatcher
machine. The first Dispatcher machine performs load balancing for
all the client traffic as it does in a single Dispatcher configuration.
The second Dispatcher machine monitors the "health" of the first,
and takes over the task of load balancing if it detects that the first
Dispatcher machine has failed.
- Use encapsulation forwarding to forward traffic across network segments
- Use encapsulation forwarding when the back-end server is not located
on the same network segment or if you are using virtualization technology
and need to forward packets that are otherwise unable to be forwarded.
- Quiesce servers for server maintenance windows
- To remove a server from the Load Balancer configuration for any
reason (updates, upgrades, service, etc.), you can use the dscontrol
manager quiesce command.
- Optimize connections with client-to-server affinity
- The Load Balancer affinity feature maps a client IP address to
a back-end server. Affinity is established once a packet's destination
IP address matches the cluster, the destination port matches the Load
Balancer port, and the source IP address matches.
- Restricting incoming traffic with ipchains and iptables
- Built into the Linux kernel is a firewall facility called ipchains.
When Load Balancer and ipchains run concurrently, Load Balancer sees
packets first, followed by ipchains. This allows the use of ipchains
to harden a Linux Load Balancer machine, which could be, for example,
a Load Balancer machine that is used to load balance firewalls.
- Logging with Load Balancer
- Load Balancer posts entries to a server log, a manager log, a
metric monitor log (logging communications with Metric Server agents),
and a log for each advisor you use.
- Support for ICMP forwarding and messaging
- Load Balancer now supports forwarding and processing ICMP messages
to improve the robustness of connection protocols and permit Load
Balancer to receive ICMP fragmentation messages.
- Configure rules to manage traffic to busy or unavailable servers
- Use rules-based load balancing to fine tune when and why packets
are sent to which servers. Load Balancer reviews any rules you add
from first priority to last priority, stopping on the first rule that
it finds to be true, then load balancing the traffic between any servers
associated with the rule. It already balances the load based on the
destination and port, but using rules expands your ability to distribute
connections.
- Sample scripts to generate alerts and record server failure
- Load Balancer provides user exits that trigger scripts that you
can customize. You can create the scripts to perform automated actions,
such as alerting an Administrator when servers are marked down by
the manager or simply record the event of the failure.