Monitoring tasks are assigned to Private Agents according to the monitoring device settings. Private Agent can reject to run a monitoring session or fail to return monitoring results to the server due to various reasons.

Possible reasons for failures in monitoring sessions include the following:

  1. Session limitations on the Private Agent.
  2. Server resources limitations.
  3. Connectivity issues.
  4. Other issues. Contact technical support for more details.

Put another way, the ratio represents the number of monitoring sessions that were rejected from monitoring by the agent or never returned monitoring results. Failed Ratio is the proportion of Private Agent failed sessions and all sessions that had to be executed on the Private AgentFailed Ratio is provided for each Private Agent on the Private Agents manager page (Configure > Private Agents).

Sessions with monitoring errors (including device errors) are considered successful in terms of Failed Ratio calculations if the monitoring results are received by Dotcom-Monitor.

Failed Ratio values vary between monitoring sessions. Generally, the ratio under 10% is considered acceptable. However, the ratio value over 10% points to issues on the corresponding Private Agent and should be examined.

Session Limitations

In the case of ServerView/WebView monitoring devices, there are no limitations put by Dotcom-Monitor on the number of sessions that can be executed in parallel by a Private Agent. However, the capacity of the server where a Private Agent is running and the type of monitoring device should be taken into account upon configuring monitoring. For example, the execution of Streaming Media monitoring sessions requires more resources than would be used to run HTTP monitoring sessions in parallel on the same Private Agent. On average, a Private Agent installed on an 8-core server can execute up to 50 devices in parallel without overloading the server.

For BrowserView/UserView monitoring devices, the Private Agent services by default support the execution of four monitoring devices on a Private Agent in parallel. Thus, four browser sessions can be executed in parallel by one Private Agent.

If a Private Agent is installed on a server with high capacity, you can adjust the number of BrowserView/UserView monitoring devices that can be run on a Private Agent in parallel in the Private Agent settings. Note that it is necessary to restart the Private Agent after any changes in its configuration.

When all the services are in use, and one more session is scheduled to be started, the session limit will be reached and the Private Agent will fail to execute the session. In this case, the failure will be reflected by the Failed Ratio value.

To prevent Private Agent failures, consider the monitoring frequency and device execution duration, as well as the number of devices that must be executed on the Private Agent. To calculate the number of Private Agents for your monitoring requirements, see How many Private Agents will be required.

Server Resources Limitation

During monitoring execution, the server resources limit (CPU, memory, etc.) can be hit on the Private Agent server. To avoid overload situations, consider CPU requirements during Private Agent installation.

Connectivity Issues

If network connection issues occur during the monitoring session, the Private Agent results will not received by Dotcom-Monitor.  Such sessions are considered failed and are presented in the Failed Ratio value.