Configuring Filters

You can access Filters under the Manage menu from the left-side menu bar. 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 left upper corner, specify a filter name. Be sure to specify a descriptive filter name so that you can identify the filter later in a drop-down list of other filters. Add additional explanations for what this filter is intended to accomplish.

While configuring a filter, you can set rules to ignore errors if specific conditions were met or ignore specific types of errors. You can also assign the filter to one or multiple devices at once from within 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 which 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 with Specific Types and Codes

You can create filters that will ignore specific errors that you know may occur and are not relevant to the goal of a specific device. The system will not generate alerts on responses with error codes that match the filters. For example, DNS errors could be filtered out based on who is responsible for DNS server operations. In addition, you can configure the system to ignore a range of error codes using a dash, or multiple error codes using semicolons as a separator.

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

For example, if you do not care about 404 errors on one particular device, you can filter them out so that you do not receive alerts when they the errors are detected. The error details will 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 automatically applied 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.