The Site Failover Property Manager behavior lets you define what logic to execute in the event that an EdgeWorkers function fails.

Detect an EdgeWorkers failure

These steps describe how to use a Property Manager match condition to detect an EdgeWorkers failover. You can then define which Failover action to take when the rule detects a failure.

By default a match condition detects errors that occur when executing onClientRequest, onClientResponse, onOriginRequest, and onOriginResponse. It does not currently detect errors from responseProvider.

The following Property Manager logic detects errors from all event handlers.

1. Create a rule with a match condition that enables the PMUSER_RP_STATUS variable when the Metadata Stage is client-response.

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The Site Failover rules need to appear after the EdgeWorkers behavior. If you add them before the EdgeWorkers behavior the Site Failover logic will not execute.

2. Create a child rule to the Is client-response rule.
3. Add a match condition that enables the PMUSER_RP_ERROR variable when the PMUSER_RP_STATUS is not empty AND is not *success* or *unimplementedHandler*.

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You can also add *unknownEdgeWorker* to the list of variable values. This prevents Site Failover from triggering when your configuration includes a deactivated EdgeWorker ID.

For more information about the variable values you can use in a match condition, refer to the Execution status report description.

4. You also need to enable wildcards for this rule. To do this, click the gear icon in the match condition and select the Wildcards in value check box from the Additional Options window and uncheck the case-sensitive value check box.

If you don't see the gear icon, hover your mouse over the match condition.

5. Add another child rule to the Is client-response rule. Add a match condition that enables the Site Failover behavior when the EdgeWorkers Execution status is Failure OR the PMUSER_RP_ERROR is true.

Invoke failover

You can define the appropriate logic to execute when an EdgeWorkers failure is detected. This section documents three common failover options. For more information refer to the Site Failover Property Manager behavior documentation.

Retry the request

The example in the previous section shows how to use Site Failover to retry the request to the original host and path.

This will re-execute the request and invoke the EdgeWorkers function again. Retrying the request can be useful when you are experiencing occasional EdgeWorkers errors due to resource limits. Often, a retry will be successful even though the first attempt exceeded a CPU limit, memory limit, or timeout.

Failover to static content

When an EdgeWorkers function fails you can serve alternate content from NetStorage.

In some cases, existing failover logic may also detect EdgeWorkers errors and interfere with attempts to implement EdgeWorkers-specific failover. In particular, the match condition for Origin Timeout errors is known to match on some types of EdgeWorkers errors.

Failover to a different location

You can also forward the request to an alternate location to execute the origin logic when an EdgeWorkers failure occurs.