Netra Proxy Cache Server User's Manual

Test and Load Objects

Test and load objects are pieces of software that run in the context of the Netra Proxy Cache array daemon, communicating the health of a service/host instantiation to the monitor object (cache_monitor or dns_monitor) in that daemon. The monitor object is responsible for monitoring a service on a given array host.

The format of the values returned by test and load objects are:

From a test object, a monitor object expects a boolean value, indicating, for example, whether an interface is up or whether a service is available.

From a load object, a monitor object expects two integers, one for current load, the other for current capacity.

The return values for test and load objects can be applied to a wide variety of resources. For example, a memory-intensive service might call for a load object to measure the availability of swap space.

In the current release of the Netra Proxy Cache product, all array members have the same set of test and load objects. These objects are selected for their appropriateness for a proxy cache service and an array DNS.

The array daemon configuration file, scalrd.conf, contains parameter settings for each test and load object. The file scalrd.conf is stored in /etc/opt/SUNWscalr. If you have a serial connection to an array host, you can use the scalrcontrol (1) utility, stored in /opt/SUNWscalr/bin, to obtain the output from the test and load objects.

There is a man page for each test object type, in /opt/SUNWscalr/man/man5. These man pages describe the parameters for each test object instance below. There is also a man page for scalrcontrol, in /opt/SUNWscalr/man/man1.

In the following object descriptions, parameters are taken from scalrd.conf. Values for these parameters are the default values.

Test Objects

The test objects listed below are shipped with the Netra Proxy Cache product. Their output is displayed in the Host Status page that you invoke from the Array Status page.

cache_connect_test

An object of type ConnectTest (5). Tests the TCP port used by the proxy cache service (8080). Also tests the service address(es) and control address used by the proxy cache service. The test object instance is configured to test persistent TCP connections. The parameters for this test object are as follows:

ConnectTest cache_connect_test
port=8080
check_addr=0.0.0.0
interval=10
retries=3
retry_interval=2
reset_min_interval=60
monitor_object=cache_monitor
max_connect=99999999
check_control=true
persistent_connection=true
connection_test_object=cache_http_test

cache_process_test

An object of type ProcessTest (5). Tests for the presence of the process associated with the proxy cache service. The parameters for this test object are as follows:

ProcessTest cache_process_test
process_id_script="/etc/init.d/scalr.cache getpid"
interval=2
retries=3
retry_interval=2
reset_min_interval=60

cache_test

An object of type AndTest (5). Combines the outputs from cache_connect_test, cache_process_test, and service_interface_test. Reports failure to the monitor object (cache_monitor) if any of these "child" test objects returns failure. The parameters for this test object are as follows:

AndTest cache_test
test_objects=cache_connect_test,cache_process_test
reset_script="/etc/init.d/scalr.cache restart"
reset_min_interval=60
monitor_object=cache_monitor

control_interface_test

An object of type PingTest (5). Tests the integrity of the control interface. The parameters for this test object are as follows:

PingTest control_interface_test
ping_addr=192.168.89.255
min_replies=1
exclude_same_host=true
interval=600
ping_timeout=5
retries=3
retry_interval=2

dns_connect_test

An object of type ConnectTest (5). Tests the TCP port used by the array DNS (53). Also tests the service address(es) and control address used by the DNS. The parameters for this test object are as follows:

ConnectTest dns_connect_test
port=53
check_addr=0.0.0.0
interval=10
retries=3
retry_interval=2
reset_min_interval=60
monitor_object=dns_monitor
max_connect=99999999
check_control=true
persistent_connection=false

dns_process_test

An object of type ProcessTest (5). Tests for the presence of the process associated with the array DNS. The parameters for this test object are as follows:

ProcessTest dns_process_test
process_id_script="/opt/SUNWscalr/scripts/dns.getpid"
interval=2
retries=3
retry_interval=2
reset_min_interval=60

dns_test

An object of type AndTest (5). Combines the outputs from dns_connect_test, dns_udp_test, dns_process_test, and service_interface_test. Reports failure to the monitor object (dns_monitor) if any of these "child" test objects returns failure. The parameters for this test object are as follows:

AndTest dns_test
test_objects=dns_connect_test,dns_process_test,dns_udp_test
reset_script="/opt/SUNWscalr/scripts/dns.reset"
reset_min_interval=30
monitor_object=dns_monitor

dns_udp_test

An object of type DNSTest (5). Tests the ability of the array DNS to resolve the name of a domain. By default the name localhost is used. The parameters for this test object are as follows:

DNSTest dns_udp_test
domain_name=localhost
port=53
check_addr=0.0.0.0
interval=10
timeout=5
retries=3
retry_interval=2
reset_min_interval=60
monitor_object=dns_monitor
max_check=99999999
check_control=true

service_interface_test

An object of type PingTest (5). Tests the integrity of the service interface used by a monitor object. The parameters for this test object are as follows:

PingTest service_interface_test
ping_addr=129.144.91.255
min_replies=1
exclude_same_host=true
interval=60
ping_timeout=5
retries=3
retry_interval=2

Load Objects

The load objects listed below are shipped with the Netra Proxy Cache product. Their output is displayed in the Host Status page that you invoke from the Array Status page.

There is a man page for each load object type, in /opt/SUNWscalr/man/man5. These man pages describe the parameters for each load object instance below.

cache_adjust_load

An object of type AdjustLoad (5). Adjusts the output from the cpu_load object to account for special conditions, such as startup and shutdown. The parameters for this load object are as follows:

AdjustLoad cache_adjust_load
interval=10
adjust_load_file=/tmp/.proxyload.adjust
max_adjust=100
load_object=cpu_load

cpu_load

An object of type CPULoad (5). Returns the CPU utilization on a host. The parameters for this test object are as follows:

CPULoad cpu_load
interval=30
divide_by_cpus=false
divide_by_cpu_clocks=false

Relationships Among Objects

The relationship among monitor, test, and load objects is illustrated in Figure 17-2.

Figure 17-2 Relationships Among Objects

The significance of the relationships illustrated in Figure 17-2 is as follows:

For test objects, a failure of a lowest-level object (indicated by a not-OK status in the Host Status page) causes the parent object (cache_test and dns_test, both of type AndTest) to fail. The failure of such a parent object, in turn, causes the monitor object return failure status. This failure is also reflected in the Host Status page. When a service on a host fails, the monitor object removes the service address associated with that service from the array's DNS zone and moves the service address to the least loaded host in the array.

For load objects, the lowest-level object (cpu_load) returns its load and capacity figures to its parent (cache_adjust_load, of type AdjustLoad). Using our example, the cache_adjust_load object performs any adjustments required and returns "final" load and capacity figures to the monitor object, cache_monitor. The monitor object compares figures obtained from cache_adjust_load to high- and low-water marks that it maintains for the service and takes action if one of these thresholds is crossed. If a monitor object determines that a service is overloaded, it removes its service address from the array's DNS zone. If the monitor object determines that a formerly overloaded service is now in its normal range, it reintroduces the service address for that service in the DNS zone.