eG Monitoring
 

Measures reported by CtxNSCSVServerTest

Content Switching enables the NetScaler appliance to direct requests sent to the same Web host to different servers with different content. A typical content switching configuration consists of a content switching virtual server, a load balancing setup consisting of load balancing virtual servers and services, and content switching policies. To configure content switching, administrators must configure a content switching virtual server and associate it with policies and load balancing virtual servers. This process creates a content group - a group of all virtual servers and policies involved in a particular content switching configuration. When a request reaches the content switching virtual server, the virtual server applies the associated content switching policies to that request. After evaluating the policies, the content switching virtual server routes the requests to the load balancing virtual servers, which send them to the appropriate services. This result in reduced overheads to process the client requests on the appliance. Irregularities in content switching can hence cause significant delays in request processing and lead to poor performance and outages, thus adversely impacting the user experience. To avoid this, adminisrtators should continuously monitor the state and the request processing capability of the content switching server. This can be easily done by periodically running the CtxNSCSVServerTest test!

This test auto-discovers the virtual servers that are available on the NetScaler appliance for content switching, and reports state of each virtual server. Additionally, this test reveals the load on the virtual servers, how well each server processes client requests and how quickly the server receives responses. In the process, this test detects the discrepancies and notifies to the administrators at the earliest.

Outputs of the test : One set of results for each content switching virtual server configured on the NetScaler appliance being monitored.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Server_state Indicates the current state of this virtual server.   The values reported by this measure and their numeric equivalents are as shown in the table:

Measure Value Numeric Value
Up 100
Out of Service 75
Transition Out of Service 50
Down when going Out of Service 30
Down 10
unknown 0

Note:

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

The detailed diagnosis of this measure shows the Service Type, Primary Port and the Primary IP address of the virtual server.
Cur_clt_conn Indicates the current number of client connections to this virtual server. Number This is a good indicator of the load on the virtual server. Compare the values of this measure across virtual servers to determine which virtual server is heavily loaded currently.
Cur_srvr_conn Indicates the number of current connections to the load-balanced application servers behind this virtual server. Number  
Established_conn Indicates the number of client connections that were in the ESTABLISHED state during the last measurement period. Number  
Tot_resp_bytes Indicates the amount of request data received on this service or virtual server during the last measurement period. MB These measures serve as effective indicators of data/packet load on a virtual server.
Tot_requ_bytes Indicates the amount of response data transmitted by this service or virtual server during the last measurement period. MB
Total_pkts_recvd Indicates the number of packets received on this service or virtual server during the last measurement period. Number
Tot_pkts_sent Indicates the number of packets sent by this service or virtual server during the last measurement period. Number
Tot_requests Indicates the number of requests received on this service or virtual server during the last measurement period. NUmber If the number of Tot_requests is a lot higher than the Tot_responses for a virtual server, it indicates that many requests are still pending processing on the virtual server; one of the reasons for latencies in request processing is an inefficient load-balancing algorithm.
Tot_responses Indicates the amount of responses received by this service or virtual server during the last measurement period. Number
So_threshold Indicates the spillover threshold that was set on the virtual server during the last measurement period. Number Spillover is a means to divert new connections to a vserver to a backup vserver when the number of connections to the vserver exceeds the threshold value. Spillover can either be connection-based or dynamic.
Tot_spill_overs Indicates the number of times the spill over threshold was exceeded by this virtual server during the last measurement period. Number A connection overload can cause a spillover. A high value of this measure indicates that the virtual server was often overloaded with connections. This can in turn be caused by inefficient load-balancing by the virtual server.
Deferred_req Indicates the number of deferred requests received on this virtual server during the last measurement period. Number  
Labelled_conn Indicates the number of client connections to this virtual server that were labeled during the last measurement period. Number The NetScaler Web 2.0 push feature enables the server to label a client connection and subsequently identify and send data over that labeled connection. With NetScaler Web 2.0 push enabled, the client first establishes a TCP/IP connection and connects to the NetScaler appliance. The appliance uses the configured load balancing method or content switching policy to select a Web server (referred to as a notification server) to which the request is to be forwarded. The appliance then initiates the labeling protocol with the Web server. This protocol enables the Web server to label the connection and defer the response. The protocol also enables the server to process other requests without invoking push processing.

Upon receipt of the deferred response from the Web server, the appliance starts waiting for updates from the Web server. When updates become available, the Web server uses the message push protocol to push the updates/messages to a push virtual server. A push virtual server is a load balancing virtual server with service type PUSH or SSL_PUSH. The appliance then processes updates/messages and uses the label to 'push' the updates to the client. This way, the NetScaler Web 2.0 push feature helps reduce the frequent polling of the Web server for updates, and thus minimizes the load on the server.

From a load-balancing perspective therefore, a large number of Labelled connections and Push labels are desired.
Push_label Indicates the number of labels for this push virtual server during the last measurement period. Number
Tot_hits Indicates the number of virtual server hits during the last measurement period. Number  
Avg_ttlb Indicates the percentage of time that the client takes to receive last byte from this virtual server. Percentage  
Clt_resp_time_apdex Indicates the apdex index of this virtual server based on client response times. Seconds Apdex (Application Performance Index) is an open standard developed by an alliance of companies. It defines a standard method for reporting and comparing the performance of software applications in computing. Its purpose is to convert measurements into insights about user satisfaction, by specifying a uniform way to analyze and report on the degree to which measured performance meets user expectations. Here, the apdex index is calculated based on how quickly the clint responds to the virtual server.
Cur_mptcp_sess Indicates the number of multipath TCP sessions that are currently active on this virtual server. Number This measure is a good indicatior of load on the virtual server.
Cur_subflow_conn Indicates the total number of sub-flows established for the multipath TCP sessions on this virtual server. Number  
Frustrating_ttlb_trans Indicates the number of frustrating TTLB transactions based on the APDEX index. Number Ideally, the value of this measure should be 0. A higher value of this measure is a cause for concern, as it implies that the experience of users has been less than satisfactory.
Invalid_requ_resp Indicates the number of invalid requests/responses that were received on this virtual server during the last measurement period. Number Ideally, the value of this measure should be very low. A sudden/gradual increase in the value of this measure could be a cause for concern.
Invalid_requ_resp_drop Indicates the number of invalid requests/responses that were dropped on this virtual server during the last measurement period. Number  
Tolerating_ttlb_trans Indicates the number of frustrating TTLB transactions based on the APDEX index. Number Ideally, the value of this measure should be 0. A higher value of this measure is a cause for concern, as it implies that the experience of users has been less than satisfactory.
Tot_clt_ttlb_trans Indicates the total number of TTLB transactions performed on this virtual server during the last measurement period. Number  
Tot_vserver_dbHits Indicates the number of times that the traffic was diverted to the backup virtual server since this virtual server was down. Number