Dotcom-Monitor supports adding multiple targets under the same device (see the Adding Multiple Targets within a Single Device article for more details). However, unless targets are closely related and depend on each other (for example, monitoring of website transactions or web API that requires authentication), we recommend you create one target per device.
All alerting, reporting, and dashboards are created at the device level. For example, the alerts are triggered on a device error state, but not on an error detected upon executing an individual task. In contrast, a monitoring device with a single task can be configured to generate an alert notification immediately every time the system detects an error while executing the task and provides you with detailed element-by-element report data.
When you have several monitoring targets set up as separate tasks under the same monitoring device, in the case of an error, you will get an alert notification that will identify Device Name and the failed Task Name. It seems enough, yet a task usually returns results from a number of dependent web elements. So, we have three actual levels of inheritance, but only two levels (the Device and Task Name levels) presented in an alert notification. In the case when some of the web elements respond with errors, you will see only the Task Name, but not the details on the web element that caused an error.
One more item to mention is that tasks in a device are executed sequentially. For example, let’s assume you have three HTTP requests set up as a separate tasks within the same device. Additionally, each task has a 120-second completion timeout. The system will run the tasks in the order they are set up in the device. If the first target service stops responding, an alert notification will be sent only after six minutes from the error detection. In the case of setting up each HTTP request under a separate device, the same alert will be generated after two minutes in the event the related device reports an error.
Getting an element-by-element report is also challenging in the case of multi-target devices. Since our Uptime, Performance, SLA reports, and Online Dashboards run on the device level, you will not get any visibility into monitoring tasks. For example, if one of the target URLs of your multi-target device generates an error, the device will be marked as DOWN in the reports regardless the state of other tasks in the device. So, at a glance, you will not have full information about the actual performance of each individual target within your multi-target device. However, you still can find individual target performance by tasks in the related Online Report.
Increase in Execution Time
Another consideration is related to the sequential order Dotcom-Monitor runs tasks in a monitoring device. For example, if you have your device set up to monitor every minute, but the first monitoring task is timing out, then the following task from the device may not be run for another 5-10 minutes.