Load Balancing Service Test

A service is a ADC entity that represents applications on a server. While services are normally combined with virtual servers, in the absence of a virtual server, a service can still manage application-specific traffic.

This test reports the current state of the virtual server for each service and also reports the load on each service along with critical metrics that provide detailed information on the connections handled by each service and the data transfer happening on each service.

Target of the test : An ADC VPX/MPX

Agent deploying the test : A remote agent

Outputs of the test : One set of results for each service in each service group configured on the ADC appliance being monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which the test is being configured.

NetScaler Username and NetScaler Password

To monitor a ADC device, the eG agent should be configured with the credentials of a user with read-only privileges to the target ADC device. Specify the credentials of such a user in the NetScaler Username and NetScaler Password text boxes.

Confirm Password

Confirm the ADC Password by retyping it here.

SSL

The eG agent collects performance metrics by invoking NITRO (ADC Interface Through Restful interfaces and Objects) APIs on the target ADC device. Typically, the NITRO APIs can be invoked through the HTTP or the HTTPS mode. By default, the eG agent invokes the NITRO APIs using the HTTPS mode. This is why, the SSL flag is set to Yes by default. If the target ADC device is not SSL-enabled, then the NITRO APIs can be accessed through the HTTP mode only. In this case, set the SSL flag to No.

Show Up Server Only

The default setting of this flag is No; this indicates that this test, by default, monitors all the services configured in a ADC device. If you want the test to monitor only those services that are up and running currently, then set this value to Yes.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Server state

Indicates the current state of the virtual server bound to this service in the ADC device.

 

The values that this measure can report and their numeric equivalents are listed in the table below:

Measure Value Numeric Value
Up 0
Down 1
Out of service 2
Transition out of service 3
Down when going out of service 4
Unknown -1

Note:

By default, this measure reports the above-mentioned Measure Values to indicate the state of the virtual server. However, in the graph of this measure the virtual server state will be represented using the corresponding numeric equivalents only.

The detailed diagnosis of this measure shows the Service Type, Primary Port, the Primary IP address of the virtual server and the Traffic Domain.

Server connections

Indicates the number of current connections to the actual servers behind the virtual server bound to this service.

Number

These measures serve as good indicators of the current workload of a service.

Client connections

Indicates the number of current client connections to this service.

Number

Active connections

Indicates the number of active transactions (including those in the surge queue) handled by this service.

Number

Load on service

Indicates the load on this service.

Number

ADC uses a special type of monitor known as a Load Monitor to calculate the load on each service in the network. Load calculation enables the ADC Load Balancing engine to make load balancing decisions and distribute the traffic appropriately between the services.

This measure reports the service load as calculated by the Load Monitor. By comparing the value of this measure across services, you can quickly determine whether/not the load is balanced across services, isolate the overloaded services, and initiate measures to fix the load-balancing irregularities.

Requests in idle queue/reuse pool

Indicates the number of requests in the idle queue or the reuse pool.

Number

Ideally, the value of this measure should be low. A very high value indicates that too many idle connections have been placed in the idle queue/reuse pool and have not been reused yet. Such requests drain resources unnecessarily. To avoid this, you can limit the number of connections that can be added to the connection reuse pool of the appliance. You can add an HTTP profile and attach it at a virtual server (VServer) or a service level. You can use this profile to limit the number of connections that can be added to the connection reuse pool.

Avg TTFB between ADC and server

Indicates the average response Time to First Byte (TTFB) to the ADC device from the server.

Milliseconds

Time to First Byte is a metric used to measure response time, calculated based on the time it takes to send a GET Request and receive a GET Response back from a server. A high value is a clear indication of network congestion or connection failure.

Maximum open connections allowed:

Indicates the maximum number of open connections that are allowed on this service.

Number

 

Surge queue:

Indicates the number of requests in the surge queue of this service.

Number

The ADC device can be used to limit the number of simultaneous requests that are passed on to a server. When a request is completed, additional requests are forwarded to the server. If a request arrives and the server is handling the maximum configured number of requests, the ADC device places the new request in a surge queue, where the request waits for its turn to be sent to the server for processing. The surge queue allows a server to run at peak capacity without the risk of having it spiral out of control because of a surge of incoming requests. If the surge queue is consistently greater than 0, this indicates that the server is not able to keep up with the workload and additional server capacity is required. On the other hand, a periodic surge is not a cause for concern.

When a surge in client requests overloads a server, server response becomes slow, and the server is unable to respond to new requests. The Surge Protection feature ensures that connections to the server occur at a rate that the server can handle. The response rate depends on how surge protection is configured. The ADC appliance also tracks the number of connections to the server, and uses that information to adjust the rate at which it opens new server connections.

Server connections in established state:

Indicates the number of connections to the virtual server bound to this service that are currently in ESTABLISHED state.

Number

 

Request data received:

Indicates the amount of data received as requests on this service or virtual server during the last measurement period.

MB

 

Response data received:

Indicates the amount of data received as responses on this service or virtual server during the last measurement period.

MB

 

Requests received:

Indicates the number of requests received on this service or virtual server during the last measurement period.

Number

 

Responses received:

Indicates the number of responses received on this service or virtual server during the last measurement period.

Number

 

Packets received:

Indicates the number of packets received on this service or virtual server during the last measurement period.

Number

 

Packets sent:

Indicates the number of packets sent from this service or virtual server during the last measurement period.

Number

 

Throughput:

Indicates the rate at which the data is received from and sent by this service or virtual server during the last measurement period.

Mbps

Comparing the throughput across services will enable you to instantly isolate the service that is consuming bandwidth excessively.

Service hits:

Indicates the number of times this service has been requested during the last measurement period.

Number