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Manual Chapter: Investigating Server Latency Issues
Manual Chapter
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Overview: Investigating server latency issues

This implementation describes how to investigate server latency on the BIG-IP system. You can investigate server latency issues on the Analytics charts when Application Visibility and Reporting (AVR) is provisioned.

Investigating the server latency of applications

Before you can investigate server latency, you need to have created an Analytics profile that is logging statistics internally on the BIG-IP system. The Analytics profile must be associated with one or more virtual servers, or an iApps application service.
Note:

Newer browsers (Internet Explorer 9 or later, Firefox 3.6 or later, or Chrome 14 or later) support viewing Analytics charts with no additional plug-in. If using older browsers (Internet Explorer 8 or earlier, Firefox 3.5 or earlier, or Chrome 13 or earlier), Adobe Flash Player (version 8 or later) must be installed on the computer where you plan to view Analytics charts.

You can review statistics concerning server latency on the Analytics charts. Server latency is how long it takes (in milliseconds ) from the time a request reaches the BIG-IP system, for it to proceed to the web application server, and return a response to the BIG-IP system.
  1. On the Main tab, click Statistics > Analytics > HTTP. The Overview screen opens.
  2. From the Latency menu, choose Server Latency. A chart shows the server latency for all applications and virtual servers associated with all Analytics profiles.
  3. To view server latency for a specific application, in the Details table, select only that application. The charts show latency only for the selected application.
  4. To view server latency for a specific virtual server:
    1. In the View By list, select Virtual Servers. The charts show latency for all virtual servers.
    2. In the Details list near the charts, click the virtual server you are interested in. The charts show latency only for the selected virtual server.
  5. If further investigation is needed, in the View By setting, select other entities to view charts that show latency for other collected entities included in the Analytics profile, for example, specific pool members, URLs, countries, or client IP addresses.
Tip: If you are concerned about server latency, you can configure the Analytics profile so that it sends an alert when the average server latency exceeds a number of milliseconds for some period of time.

Getting an alert when server latency is high

Before you can configure the system to send alerts concerning server latency, you need to have created an Analytics profile to collect application statistics locally (Statistics Logging Type must have Internal selected). To set up email alerts, the default analytics profile must specify an SMTP configuration.
You can configure the BIG-IP system to send an alert when server latency is high.
  1. On the Main tab, click Local Traffic > Profiles > Analytics.
    Tip: If Analytics is not listed, you need to provision Application Visibility and Reporting (AVR) first.
    The Profiles: Analytics screen opens.
  2. Click the name of a previously created Analytics profile, or create a new one.
  3. Select the Custom check box.
  4. For the Statistics Logging Type setting, verify that Internal is selected. If it is not, select it. Selecting Internal causes the system to store statistics locally, and you can view the charts on the system by starting at the Main tab, and clicking Statistics > Analytics > HTTP.
  5. To send email alerts, specify an SMTP Configuration (this can only be done on the default analytics profile). If you created a new profile, configure SMTP later.
  6. For the Notification Type setting, select how you want the system to send alerts and notifications.
    Option Description
    Syslog Select Syslog if you want the system to send notification and alert messages to the local log system. You can view the messages on the System > Logs > Local Traffic screen.
    SNMP Select SNMP if you want the system to send notification and alert messages as SNMP traps. You can create the trap by clicking Configuration can be found here (System > SNMP > Traps > Destination). Enabling SNMP automatically sets up Syslog notifications, too.
    E-mail Select E-mail if you want the system to send notification and alert messages to email addresses. Type each email address in the Notification E-Mails field, and click Add to create the list. This option requires that the parent analytics profile includes an SMTP configuration.
    When you select a notification type, the screen displays the Alerts and Notifications Configuration area, where you can indicate the criteria for alerts and notifications.
  7. In the Alerts and Notifications Configuration area, for the Add New Rule setting, define the rule that determines when the system sends an alert about server latency.
    1. For Alert when, select Average Server Latency.
    2. Select above, and then type the number of milliseconds (the threshold) that is too high for your application. For example, type 100 if you want to receive an alert when latency is above 100 for 300 seconds. It is a good idea for you to get familiar with the typical average server latency of your application so you can recognize high server latency.
    3. Select Application as the granularity level to which the threshold applies.
    4. Click Add. The rule is added to the list of Active Rules.
  8. Click Update.
  9. If you need to configure SMTP (if sending alerts by email), click the default analytics profile on the Profiles: Analytics screen.
    1. For SMTP Configuration, select an existing configuration.
    2. If no SMTP configurations are listed, click the here link to create one. When you are done, you need to select the configuration you created in the default analytics profile.
The system sends an alert when the average server latency of an application exceeds 100 ms for 300 seconds. Another alert is sent when server latency changes back to under 100 ms for 300 seconds.
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