Configuring Filters

You can access Filters from the Manage menu in the left sidebar. From here, you can create a new filter or edit or delete an existing one.

Adding a New Filter

To add a filter, on the Filters page, click New Filter.

In the upper-left corner, enter a filter name. Use a clear, descriptive name so you can easily identify the filter later in dropdown lists. You can also add a description explaining the filter’s purpose.

When configuring a filter, you can define rules to ignore specific errors or to ignore errors only when certain conditions are met. You can also assign the filter to one or multiple devices directly from the edit screen.

How to Filter Errors by Specific Conditions

In the Ignore an Error if the Following Conditions Apply section, you can specify multiple filters to help eliminate false positives and excessive alerts:

• Error is reported for less than (X) minutes – filters problems based on the frequency of an occurrence. For example, a five-minute setting filters out any problems that last for less than five minutes. Additionally, this option might be used for a brief rebooting of a web server when no alerts are desired.
• Error is not confirmed by at least (X) monitoring locations – filters errors based on the number of monitoring stations reporting the error. For example, a single monitoring station might not connect to a specific URL, but other stations do connect, which signals that the problem lies with a backbone provider for that single station. Dotcom-Monitor recommends setting this filter value to two or higher to help filter out problems that are occurring on a specific backbone.
• Error is detected in less than (X) tasks – filter alerts based on the number of task errors occurring in a monitored device. For example, a monitoring device might consist of tasks that access three web servers in a server farm. If one server fails, the device will still work as set up using only the remaining servers. By default, Dotcom-Monitor will send an alert because one server is unavailable. If the filter is set at 2, an alert is sent only when two tasks in the device fail.

How to Ignore Errors of Specific Types and Codes

You can create filters to ignore specific errors that may occur but are not relevant to the purpose of a particular device. When an error matches a configured filter, the system will not generate alerts for that response. For example, DNS-related errors can be ignored if DNS server availability is managed by a third party.

Tips

• To ignore a range of error codes, use a dash (for example, 500–504).
• To ignore several error codes in a specific category, list the codes separated by commas or semicolons (for example, 404;504).

You can find a comprehensive list of supported error codes in the HTTP Status Codes List | HTTP Error Codes Explained article of this wiki.

For example, if 404 errors are expected or not relevant for a specific device, you can filter them out to avoid receiving alerts when those errors occur. The error details will still be available for review in the device reports.

Assigning a Filter to Devices

To assign a filter to one or several monitoring devices, go to the Assigned Devices section and select the device(s) from the list. The filter will be applied automatically to the selected devices. However, you can always set a corresponding filter for a device while configuring the Up&Down Filter settings for the device.