Before we move forward with the Dotcom-Monitor monitoring algorithm, let’s define the differences between a monitoring session and a monitoring cycle.

  • Monitoring session is an operation when the system initiates monitoring at a single location.
  • Monitoring cycle includes all monitoring sessions at all selected locations.

The monitoring algorithm is based on a cyclical procedure that differs depending on the type of the cycling mode set for a monitoring device. There are two cycling modes that can be applied to the monitoring procedure:

    • Allow Simultaneous Checks: Yes
    • Allow Simultaneous Checks: No

For HTTP-based monitoring (ServerView Platform and WebView Platform), the Allow Simultaneous Checks option is set to Yes by default. To change the cycling mode, go to the device edit page > Monitoring > Advanced Configuration.

For browser-based monitoring (BrowserView / UserView Platforms), the Allow Simultaneous Checks option is always set to No and can’t be changed.

How it works

Allow Simultaneous Checks: Yes

Once a device has been set up Dotcom-Monitor initiates monitoring sessions from all configured (activated during device configuration) monitoring locations. A counter, equal to the monitoring frequency duration, starts after each most recently received monitoring response. As a result, a new session of monitoring starts exactly as specified by the monitoring frequency.

There can be two possible flows for the monitoring algorithm depending on the monitoring results of the initial monitoring session. The system follows the “Single-mode” flow when all monitoring locations report the same state (i.e. each monitoring session returns a “success” state, or an “error” state). In this case, Dotcom-Monitor initiates a single monitoring session from a single monitoring location. Subsequently, the device cycles through each location, triggering task execution at the specified frequency.

The second “Mixed-mode” flow of the web monitoring algorithm is applied when at least one monitoring location returns a state different from the states received from the other monitoring locations. In this situation, Dotcom-Monitor initiates monitoring sessions from all available monitoring agents simultaneously. For example, when there are five active monitoring agents, four of them report a “success” state, and one fails and reports back an “error” state.

The following applies to both “Single-mode” and “Mixed-mode” monitoring flows:

Monitoring agents (locations) may become unavailable (enter a “disabled” state) for various reasons, or they could still be processing the previous monitoring session (in an “in process” state). Agents in either the “disabled” or “in process” states are disregarded during monitoring.

Each monitoring session sends back its state (so-called keep-alive messages) during the process of monitoring. The status of each monitoring session is tracked by the Dotcom-Monitor system. Dotcom-Monitor “marks” an agent (location) when more than five minutes (current value for “session in process timeout”) have passed since the last keep-alive message. If there is a marked agent at the moment when a new session should be initiated, then both agents will initiate a monitoring session.

Allow Simultaneous Checks: No

Once a device has been set up, Dotcom-Monitor initiates monitoring sessions from the first configured (activated during device configuration) monitoring location. During the initial monitoring cycle (the first cycle after the device has been created or re-started), new sessions are created immediately after receiving the completion of the previous ones. In the online report, you will see the start time of the session. To see the time of its completion, expand the response and scroll down to the end.

In order to provide continuous monitoring, despite possible monitoring agent issues, when it may go offline, a counter, equal to 5 minutes, starts on each new session. This counter specifies a time point when the next session should be initiated (in case the previous session hangs up at some stage).

If there is still any unfinished monitoring session at the moment when the time is up, session initiation delays on the same principle (current time + 5 min). After the initial monitoring cycle is completed (each selected monitoring agent returned the response, or its downstate was confirmed) Dotcom-Monitor waits for a time that equals to the monitoring frequency duration and then analyzes the group of responses.

Similar to the Allow Simultaneous Checks: Yes mode, there can be two possible flows for the monitoring algorithm depending on the monitoring results of the initial monitoring session. When all monitoring agents report the same state, Dotcom-Monitor continues to initiate new monitoring sessions one by one at regular intervals which are equal to the monitoring frequency. In the second case, the system switches to the session-by-session monitoring, excluding monitoring frequency value, like during the initial monitoring cycle.