Server Health Check Probes and Timeouts
Equalizer Installation and Administration Guide
265
Note that there are also some kernel variables associated with Secure Socket Layer (ssl) client connections, such as
when someone logs into Equalizer over an SSH connection. These variables are
not
incremented by HTTPS
connections:
eq.l7lb.ssl.total_clients
eq.l7lb.ssl.current_clients
eq.l7lb.ssl.max_clients
eq.l7lb.ssl.requests
Server Health Check Probes and Timeouts
There are four levels of server health check probes supported by Equalizer:
•
ICMP probes; all cluster types, enabled by default
•
High Level TCP Probes; all cluster types, enabled by default
•
High Level ACV (Active Content Verification) Probes; all cluster types except Layer 4 UDP clusters,
disabled by default
•
Server Agent Probes; all cluster types, disabled by default
ICMP Probes
By default, Equalizer sends an Internet Control Message Protocol (ICMP) echo request (commonly called a “ping”)
to the IP address of every server in every cluster.
The delay between successive ping requests to the same server is determined internally, but can be as short as one
second on a server that is not responding to ICMP requests. On a lightly loaded Equalizer it may be 5 seconds or
longer.
If a server does not respond to an ICMP echo request, Equalizer continues to issue any other probes (TCP, ACV,
server agent) configured for the cluster. This means, for example, that if TCP and ICMP probes are both configured
(the default), then a server can fail any number of ICMP probes and will still be marked
up
as long as it continues to
respond to TCP probes.
If a server does not respond to an ICMP echo request and no other probes are configured, the server is marked
down
,
and Equalizer continues to send ICMP requests to the server’s IP address. If an ICMP echo response is subsequently
received, the server is marked
up
again.
ICMP probing can be turned off by disabling the
ICMP probe
flag in the global parameters. This turns ICMP echo
requests off for all clusters. (ICMP probes do not use any of the timeouts and parameters defined in the following
section for High Level Probes.)
High Level TCP and ACV Probes
Equalizer sends High Level Probes to every server at the interval specified by
probe delay
(default: 10 seconds). By
default, TCP probes are enabled for all servers, and ACV probes can be enabled for individual clusters. Both probes
must complete within the same
probe timeout
period, and are controlled by the same set of parameters, as
summarized in the following figure.
Note –
Responding to ICMP echo requests is an option on most server platforms. If ICMP echo reply is disabled
on one or more of the servers your configuration, then you may want to disable ICMP echo requests on Equalizer
to reduce traffic between Equalizer and the servers, and rely solely on the other probing mechanisms.
Содержание E350GX
Страница 18: ...Chapter Preface 18 Equalizer Installation and Administration Guide ...
Страница 38: ...Chapter 1 Equalizer Overview 38 Equalizer Installation and Administration Guide ...
Страница 50: ...Chapter 2 Installing and Configuring Equalizer Hardware 50 Equalizer Installation and Administration Guide ...
Страница 62: ...Chapter 3 Using the Administration Interface 62 Equalizer Installation and Administration Guide ...
Страница 80: ...Chapter 4 Equalizer Network Configuration 80 Equalizer Installation and Administration Guide ...
Страница 110: ...Chapter 5 Configuring Equalizer Operation 110 Equalizer Installation and Administration Guide ...
Страница 208: ...Chapter 7 Monitoring Equalizer Operation 208 Equalizer Installation and Administration Guide ...
Страница 240: ...Chapter 8 Using Match Rules 238 Equalizer Installation and Administration Guide ...
Страница 258: ...Chapter 9 Administering GeoClusters 254 Equalizer Installation and Administration Guide Envoy Configuration Worksheet ...
Страница 262: ...Appendix A Server Agent Probes 258 Equalizer Installation and Administration Guide ...
Страница 274: ...Appendix B Timeout Configuration 270 Equalizer Installation and Administration Guide ...
Страница 280: ...Appendix D Regular Expression Format 276 Equalizer Installation and Administration Guide ...
Страница 296: ...Appendix E Using Certificates in HTTPS Clusters 292 Equalizer Installation and Administration Guide ...
Страница 310: ...Appendix F Equalizer VLB 306 Equalizer Installation and Administration Guide ...
Страница 318: ...Appendix G Troubleshooting 314 Equalizer Installation and Administration Guide ...