Failure Management
| IOTREL 5. How does your IoT application withstand failure? |
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Because IoT is an event-driven workload, your application code must be resilient to handling known and unknown errors that can occur as events are permeated through your application. A well-architected IoT application has the ability to log and retry errors in data processing. An IoT application will archive all data in its raw format. By archiving all data, valid and invalid, an architecture can more accurately restore data to a given point in time.
With the IoT rules engine, an application can enable an IoT error action. If a problem occurs when invoking an action, the rules engine will invoke the error action. This allows you to capture, monitor, alert, and eventually retry messages that could not be delivered to their primary IoT action. We recommend that an IoT error action is configured with a different AWS service from the primary action. Use durable storage for error actions such as Amazon SQS or Amazon Kinesis.
Beginning with the rules engine, your application logic should initially process messages from a queue and validate that the schema of that message is correct. Your application logic should catch and log any known errors and optionally move those messages to their own DLQ for further analysis. Have a catch-all IoT rule that uses Amazon Kinesis Data Firehose and AWS IoT Analytics channels to transfer all raw and unformatted messages into long-term storage in Amazon S3, AWS IoT Analytics data stores, and Amazon Redshift for data warehousing.
| IOTREL 6. How do you verify different levels of hardware failure modes for your physical assets? |
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IoT implementations must allow for multiple types of failure at the device level. Failures can be due to hardware, software, connectivity, or unexpected adverse conditions. One way to plan for thing failure is to deploy devices in pairs, if possible, or to deploy dual sensors across a fleet of devices deployed over the same coverage area (meshing).
Regardless of the underlying cause for device failures, if the device can communicate to your cloud application, it should send diagnostic information about the hardware failure to AWS IoT Core using a diagnostics topic. If the device loses connectivity because of the hardware failure, use Fleet Indexing with connectivity status to track the change in connectivity status. If the device is offline for extended periods of time, trigger an alert that the device may require remediation.
