eG Monitoring
 

Measures reported by A10VserverTest

The A10 Application Delivery Controller consists of a virtual server (also referred to as a virtual cluster, virtual IP or VIP) which, in turn, consists of an IP address and port. This virtual server is bound to a number of physical servers a.k.a real servers within a server farm. On the A10 Application Delivery Controller, a virtual server (VIP) is typically a publicly facing IP address which responds to user requests. Typically, load balancing, content switching and persistence rules and methods are assigned on a per-VIP basis. A virtual server is capable of performing the following:

  • Distribute client requests across multiple servers to balance server load;

  • Apply various behavioral settings to a specific type of traffic;

  • Enable persistence for a specific type of traffic;

  • Direct traffic according to user-written iRules®

In addition, virtual servers can also be used in the following ways:

  • Directing traffic to a load balancing pool;

  • Sharing an IP address with a VLAN node;

  • Forwarding traffic to a specific destination IP address;

  • Increasing the speed of processing HTTP traffic;

  • Increasing the speed of processing Layer 4 traffic;

  • Relaying DHCP traffic

Since the virtual servers are able to manage the traffic and divert client requests to servers that are managing fewer requests, poor performance and outages can be avoided. Irregularities in load balancing can cause significant delay in request processing thus affecting the user experience with the A10 Application Delivery Controller.To avoid this, you can configure the periodic execution of the A10VserverTest test. For each virtual server configured on the A10 Application Delivery Controller, this test continuously monitors the load on the load-balancing virtual servers and reveals how well each server processes client requests. In addition, this test detects inconsistencies in load-balancing early on and warns administrators of possible deviations proactively.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Health_status Indicates current health of this virtual server.   The values of this measure and their corresponding numeric values are listed below:

Measure Value Numeric Value
Disabled 0
Up 1
Down 2

Note:

By default, this measure reports one of the Measure Values listed in the table above to indicate status of this virtual server. In the graph of this measure however, the current health will be represented using the numeric equivalents.
Data_transmitted Indicates the rate at which data was transmitted from this virtual server during the last measurement period. MB/Sec Compare the value of these measures across the virtual servers to identify the server that is experiencing the maximum traffic.
Data_received Indicates the rate at which data was received by this virtual server during the last measurement period. MB/Sec
Packets_transmitted Indicates the rate at which the packets were transmitted from this virtual server during the last measurement period. Packets/Sec Compare the value of these measures across the virtual servers to identify the server that is experiencing the maximum traffic.
Packets_received Indicates the rate at which packets were received by this virtual server during the last measurement period. Packets/Sec
Curr_connections Indicates the number of connections that are currently active on this virtual server. Number This measure is a good indicator of the load on the virtual server.
Tot_connections Indicates the total number of connections established on this virtual server since the start of the A10 Application Delivery Controller. Number  
Connection_rate Indicates the rate at which the connections were established on this virtual server during the last measurement period. Conns/Sec A sudden increase in the value of this measure indicates an increase in the load on the virtual server.
Conn_usage Indicates the percentage of connections used by this virtual server. Percent A value close to 100% indicates that this virtual server is currently overloaded.
Persistent_conns Indicates the number of connections that were persistent on this virtual server. Number TCP connections that are kept open after transactions complete are called persistent connections. Persistent connections stay open across transactions, until either the client or the server decides to close them. These connections when reused can significantly reduce the overload on the new connections to the virtual server.
Peak_conns Indicates the maximum number of connections that were established on this virtual server since the start of the A10 Application Delivery Controller. Number  
Curr_L7_requests Indicates the number of L7 requests currently processed by this virtual server. Number Both these measures serve as effective pointers to the L7 requests processing in the A10 Application Delivery Controller.

Layer-7 load balancing, also known as application-level load balancing, is to parse L7 requests in application layer and distribute L7 requests to the servers based on different types of request content, so that it can provide quality of service requirements for different types of content and improve overall performance of the A10 Application Delivery Controller.
Tot_L7_requests Indicates the total number of L7 requests processed by this virtual server during the last measurement period. Requests/Sec
Succ_L7_requests Indicates the number of L7 requests that were processed successfully by this virtual server. Number Ideally, value of this measure should be high.