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Manual Chapter: Investigating Server Latency Issues
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Investigating Server Latency Issues

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 HTTP Analytics profile that is logging statistics internally on the BIG-IP system. The HTTP Analytics profile must be associated with one or more virtual servers, or with an iApps application service.
You can review statistics concerning server latency on the HTTP Overview chart. 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 and displays current HTTP statistics averaged over the last hour. On the screen, you can see time controls on the top, charts on the left, and a list of dimensions on the right.
  2. Scroll down to the Avg Server Latency chart.
    The 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, from the dimensions on the right, expand Applications and select only that application.
    The chart shows latency only for the selected application.
  4. To see more detailed latency statistics for any expanded dimensions, click the handle at the top of the dimensions column,
    Tables containing detailed statistics for the items in the dimensions are displayed.
  5. In the table, hover over the headings to see the full names of the columns, and view the data.
    • Avg Server Latency (ms) shows the average server latency in milliseconds.
    • Min Server Latency (ms) shows the minimum server latency in milliseconds.
    • Max Server Latency (ms) shows the maximum server latency in milliseconds.
  6. To view the graphic charts and dimensions again, click the handle on the top left of the table.
  7. To view server latency for a specific virtual server, from the dimensions on the right, expand Virtual Servers and select only that virtual server.
  8. You can clear all filter selections or those for a dimension.
    • To clear a single selection, click the selected object.
    • To clear all selections, click the gear icon at the top of the column and select Clear All.
    • To clear selections for a dimension, click the options icon (three horizontal lines to the left of the title), and select Clear Selection.
      Tip: You can click the numbered icon at the top right-hand corner of the dimension to clear all selections for a dimension.
  9. If further investigation is needed, select other dimensions to show latency for other entities, for example, specific pool members, URLs, countries, or client IP addresses.
Tip: If you are concerned about server latency, you can configure the HTTP Analytics profile so that it sends an alert when the average server latency exceeds a number of milliseconds for some period of time. See Getting an alert when server latency is high.

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 HTTP 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 > HTTP Analytics .
    Tip: To have the Analytics 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 .
  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 default 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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