16. Discarded Discovery Events
Date: 2024-10-15
Context
The discovery workflow allows Trento Agent instances to publish their
host system’s information to the Trento Web’s collect API operation.
Once accepted, the event results in one or more commands that are
dispatched to the ES/CQRS system. Responsibilities are separated between
the publisher (Trento Agent) and the collector (Trento Web): Trento
Agent’s job is done once the payload has been received and stored.
There are cases in which a discovery sent from a Trento Agent is not processed; they can be categorized as:
-
The Trento Agent fails to connect to the Trento Web instance (network issues);
-
The Trento Agent fails to authenticate with the Trento Web instance (authentication issues);
-
The request payload does not match the expected shape, thus it cannot be mapped to a command (API contract issues);
-
The discovery is rejected because of the current state in Trento.
Currently all these scenarios result in an error being returned by the
collect endpoint and subsequent log in trento agent.
Decision
Failures that depend on the current Trento data (4) are not reported as errors to the publishing Trento Agent; instead, it will receive a success status code indicating that the event has been correctly ingested by Trento Web, even if it won’t be processed. This is legitimated by the periodicity of the discoveries that would lead Trento to eventually converge to a consistent state.
Such events, alongside the ones that fall into (3), are traced into the
discarded_discovery_events database table for inspection and
troubleshooting.
The decision of whether API contract issues (3) should be treated the same way, has been postponed.