Define events for the vector source

[binarylogic]

As part of finishing https://github.com/timberio/vector-product/issues/14, we need to define internal events for the vector source.

Special Note

To my knowledge, this source wraps the socket source. I'm curious how we should approach defining events in this case, since we do not emit duplicate events (ex: *EventReceived events).

Defining events

• If you have not already, please read RFC 2064.
  • Be sure to read the Guide-level Proposal section and the implementation details that affect performance.
• You can also look at the currently defined events for precedence.
• Events should be named properly: <ComponentName><Noun><Verb>. For example, the syslog source defines the SyslogEventReceived struct.

Requirements

• Add a VectorEventReceived event.
  • Derive a events_processed metric via the emit_metrics method. (example)
  • If possible, derive a bytes_processed metric via the emit_metrics method. (example)
• Audit and add events for all possible errors. (example)
• Audit and add events for all component-specific behavior. (example)
• Ensure that logs in the hot path are rate limited via the rate_limit_secs parameter. (example).
• Ensure that all log messages start with a lowercase letter and end with a .. (example)

[ktff]

Was done in #1953

[ktff]

this source wraps the socket source. I'm curious how we should approach defining events in this case

@binarylogic it was wrapping socket source, now the shared code is separated. For vector source, that is tcp code which only emits a generic TcpConnectionError that covers all errors that get propagated to it, and it's own. While vector source emits it's own VectorEventReceived.