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Manual Chapter: Troubleshooting Applications by Capturing Traffic
Manual Chapter
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Overview: Troubleshooting applications by capturing traffic

This implementation describes how to set up the BIG-IP® system to collect application traffic so that you can troubleshoot problems that have become apparent by monitoring application statistics. For example, by examining captured requests and responses, you can investigate issues with latency, throughput, or reduced transactions per second to understand what is affecting application performance.

When Application Visibility and Reporting (AVR) is provisioned, you can create an Analytics profile that includes traffic capturing instructions. The system can collect application traffic locally, remotely, or both. If the system is already monitoring applications, you can also update an existing Analytics profile to make it so that it captures traffic.

If logging locally, the system logs the first 1000 transactions and displays charts based on the analysis of those transactions. If logging remotely, the system logs information on that system; log size is limited only by any constraints of the remote logging system. To see updated application statistics, you can clear the existing data to display the current statistics.

Task Summary

Prerequisites for capturing application traffic

After you finish a basic networking configuration of the BIG-IP® system, you must complete the following tasks as prerequisites for setting up application statistics collection:

  • Provision Application Visibility and Reporting (AVR): System > Resource Provisioning
  • Create an iApps™ application service (go to iApp > Application Services ), or configure at least one virtual server with a pool pointing to one or more application servers.
  • The Traffic Sampling Ratio must be set to all in the default Analytics profile.

You can set up the system for capturing traffic locally or remotely (or both).

Tip: Before setting up traffic capturing, it is a good idea to clear the captured transaction log. On the Captured Transactions screen, click Clear All to clear all previously captured data records.

Capturing traffic for troubleshooting

To set up traffic capturing, the Transaction Sampling Ratio of the default analytics profile must be set to all.
You can configure the BIG-IP® system to capture application traffic and store the information locally or remotely (on syslog servers or SIEM devices, such as Splunk). To do this, you create an Analytics profile designed for capturing traffic. The profile instructs the BIG-IP system to collect a portion of application traffic using the Application Visibility and Reporting module.
Note: You typically use traffic capturing if you notice an application issue, such as trouble with throughput or latency, discovered when examining application statistics, and want to troubleshoot the system by examining actual transactions.
  1. On the Main tab, click Local Traffic > Profiles > Analytics .
    Tip: If Analytics is not listed, this indicates that Application Visibility and Reporting (AVR) is not provisioned, or you do not have rights to create profiles.
    The Analytics screen opens and lists all Analytics profiles that are on the system, including a default profile called analytics.
  2. Click Create. The New Analytics Profile screen opens. By default, the settings are initially the same as in the default analytics profile.
  3. In the Profile Name field, type a name for the Analytics profile.
  4. To the right of the General Configuration area, click the Custom check box. The settings in the area become available for modification.
  5. For Traffic Capturing Logging Type, specify where to store captured traffic.
    • To store traffic locally, click Internal. You can view details on the Statistics: Captured Transactions screen. This option is selected by default.
    • To store traffic on a remote logging server, click External and type the Remote Server IP Address and Remote Server Port number.
      Tip: If you specify remote logging for multiple applications, you can use the Remote Server Facility filter to sort the data for each.
  6. In the Included Objects area, specify the virtual servers for which to capture application statistics:
    1. For the Virtual Servers setting, click Add. A popup lists the virtual servers that you can assign to the Analytics profile.
    2. From the Select Virtual Server popup list, select the virtual servers to include and click Done.
    Note: You need to have previously configured the virtual servers (with an HTTP profile) for them to appear in the list. Also, you can assign only one Analytics profile to a virtual server so the list shows only virtual servers that have not been assigned an Analytics profile.
    Special considerations apply if using Analytics on a BIG-IP system with both Application Security Manager™ and Access Policy Manager™, where security settings (in Portal Access webtop or an iRule) redirect traffic from one virtual server to a second one. In this case, you need to attach the Analytics profile to the second virtual server to ensure that the charts show accurate statistics.
  7. In the Statistics Gathering Configuration, for Collected Metrics, select the statistics you want the system to collect:
    Option Description
    Server Latency Tracks how long it takes to get data from the application server to the BIG-IP system (selected by default).
    Page Load Time Tracks how long it takes an application user to get a complete response from the application, including network latency and completed page processing.
    Note: End user response times and latencies can vary significantly based on geography and connection types.
    Throughput Saves information about HTTP request and response throughput (selected by default).
    User Sessions Stores the number of unique user sessions. For Timeout, type the number of minutes of user non-activity to allow before the system considers the session to be over. If using transaction sampling, this option is not available.
  8. For Collected Entities, select the entities for which you want the system to collect statistics:
    Option Description
    URLs Collects the requested URLs.
    Countries Saves the name of the country where the request came from based on the client IP address.
    Client IP Addresses Saves the IP address where the request originated. The address saved also depends on whether the request has an XFF (X-forwarded-for) header and whether Trust XFF is selected.
    Response Codes Saves HTTP response codes that the server returned to requesters (selected by default).
    User Agents Saves information about browsers used when making the request.
    Methods Saves HTTP methods in requests (selected by default).
  9. In the Capture Filter area, from the Capture Requests and Capture Responses lists, select the options that indicate the part of the traffic to capture.
    Option Description
    None Specifies that the system does not capture request (or response) data.
    Headers Specifies that the system captures request (or response) header data only.
    Body Specifies that the system captures the body of requests (or responses) only.
    All Specifies that the system captures all request (or response) data.
  10. Depending on the application, customize the remaining filter settings to capture the portion of traffic to that you need for troubleshooting.
    Tip: By focusing in on the data and limiting the type of information that is captured, you can troubleshoot particular areas of an application more quickly. For example, capture only requests or responses, specific status codes or methods, or headers containing a specific string.
  11. Click Finished.
The BIG-IP system captures the application traffic described by the Analytics profile for 1000 transactions locally (or until system limits are reached). If logging remotely, the system logs information on that system; log size is limited only by constraints of the remote logging system.
Note: System performance is affected when traffic is being captured.

Reviewing captured traffic

Before you can review captured traffic details on the BIG-IP® system, you need to have created an Analytics profile that is capturing application traffic locally. The settings you enable in the Capture Filter area of the profile determine what information the system captures. You need to associate the Analytics profile with one or more virtual servers, or with an iApps™ application service.
The system starts capturing application traffic as soon as you enable it on the Analytics profile. You can review the captured transactions locally on the BIG-IP system. The system logs the first 1000 transactions.
  1. On the Main tab, click System > Logs > Captured Transactions . The Captured Transactions screen opens and lists all of the captured transactions.
  2. Optionally, use the time period and filter settings to limit which transactions are listed.
  3. In the Captured Traffic area, click any transaction that you want to examine. Details of the request display on the screen.
  4. Review the general details of the request.
    Tip: The general details, such as the response code or the size of the request and response, help with troubleshooting.
  5. For more information, click Request or Response to view the contents of the actual transaction. Review the data for anything unexpected, and other details that will help with troubleshooting the application.
  6. On the Captured Transactions screen, click Clear All to clear all previously captured data records (including those not displayed on the screen) and start collecting transactions again. The system captures up to 1000 transactions locally and displays them on the screen. Captured transactions are visible a few seconds after they occur.
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