Specifications

Chapter 6: Administering Virtual Clusters
94 Equalizer Installation and Administration Guide
Setting Maximum Connections per Server
A new feature has been added for the HTTP, HTTPS, and L4 TCP cluster types that allows you to
set a hard upper limit on the number of active connections per server. When a server in the cluster
reaches the maximum connections limit, requests will not be routed to that server until the number
of active connections falls below the limit.
Typical reasons to set a maximum number of connections include:
• implementing a connection limit that is required due to software limitations, such as an
application that can service a limited number of concurrent requests
• implementing license restrictions that are not enforced by software; such as limiting the
number of active connections to an application that is licensed for a limited number of
concurrent connections
• setting a threshold that will limit resource utilization on the cluster
The max_conn limit can be set on a cluster or on individual servers in a cluster, and behaves as
described below:
• Setting max_conn when you create a cluster sets the maximum number of connections for all
subsequently created servers in the cluster.
• Setting (or changing) max_conn when modifying an existing cluster does not set (or change)
max_conn on any of the existing servers in the cluster. If you want the new max_conn limit
to apply to existing servers, you will need to set (or change) max_conn on each existing
server.
• Setting max_conn when you create or modify a server overrides the max_conn setting for
the cluster.
• The max_conn limit may be ignored on Layer 7 clusters with persist enabled. The persist
option tells Equalizer to insert a session cookie into all responses back to the client. When
Equalizer gets another request containing the cookie, and the max_conn limit has already
been reached, it accepts the request anyway. However, if a hot spare is defined for the cluster,
it sends the request to the hot spare instead. If persist is not enabled, max_conn is always
enforced.
• The max_conn limit may be ignored on L4 TCP clusters with a non-zero sticky time. The
sticky time option tells Equalizer to keep a “sticky record” so an L4 connection can be
persistent. When Equalizer gets another request on a connection that already has a sticky
record, and the max_conn limit has already been reached, it accepts the request anyway.
However, if a hot spare is defined for the cluster, it sends the request to the hot spare instead.
If no sticky time is set, max_conn is always enforced.
• A new flag, dont persist, has been introduced. It is intended to be used to override persistent
connections for a hot spare in an L4 or L7 cluster that has a maximum connection limit. See
the section “Using a Hot Spare in a Cluster with a Maximum Connections Limit” on page 96.
Setting Maximum Connections on a Cluster:
1. Log into the Equalizer Administration Interface in Edit mode.
2. Do one of the following: