You should use the Site Failover Property Manager behavior to define what logic to execute in the event that an EdgeWorkers function fails.

Programming errors, unexpected input from end-users, changes in documents returned from htmlRequest(), and timeouts can cause an EdgeWorkers function to fail. You can intercept these errors and any others by using one of these supported failover actions:

• Redirect to a different location by specifying a redirect action. This action sends the end user to alternate content with an end user facing Location change - this is best suited for full HTML page requests.

• Use an alternate origin and path so the end user remains on the original URL.

• Display a 500 error to the end user.

• Use EdgeWorkers Execution Status in a match condition.

• Retry the failed EdgeWorkers request and continue processing the delivery property metadata.

• By-pass the failed EdgeWorkers function and serve the same URL. Support is required to implement this Failover action. Contact your account team or send an email to edgeworkers@akamai.com for more information.

👍

EdgeWorkers failures caused by a coding issue throw a JavaScript error. Where possible, catch errors in your JavaScript code and execute alternative logic.

📘

When testing Site Failover you need to remove the akamai-x-ew-debug-rp Pragma header. For more information refer to the known issue.

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.

👍

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*.

📘

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.