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Optional event id #422

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Optional event id #422

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f038a41
Issue #331: Clarify scope of source and id uniqueness
alanconway Feb 20, 2019
79000b9
Issue #331: Explanatory text/examples for scope of URI uniqueness.
alanconway Feb 26, 2019
ee72a4f
Issue #331: Clarify producer/application responsibilities.
alanconway Mar 1, 2019
d37c6eb
Issue #331: Fix typo in spec.md
deissnerk Mar 25, 2019
1d10f72
Issue #331: Tighten up the text
alanconway Apr 17, 2019
9e00070
Issue #326: Make event-id an optional field.
alanconway Apr 24, 2019
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44 changes: 30 additions & 14 deletions spec.md
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Original file line number Diff line number Diff line change
Expand Up @@ -190,18 +190,28 @@ within the same JSON object.
### source

- Type: `URI-reference`
- Description: This describes the event producer. Often this will include
information such as the type of the event source, the organization publishing
the event, the process that produced the event, and some unique identifiers.
The exact syntax and semantics behind the data encoded in the URI is event
producer defined.
- Description: Identifies the event producer. Often this will include
information such as the type of the event source, the organization
publishing the event, the process that produced the event, and some unique
identifiers. The exact syntax and semantics behind the data encoded in the URI
is event producer defined.

An application MUST assign a distinct `source` to each distinct producer.
The application MAY use UUIDs, URNs, DNS authorities or an application-specific
scheme to create unique identifiers.

- Constraints:
- REQUIRED
- Examples
- https://github.com/cloudevents/spec/pull
- /cloudevents/spec/pull
- urn:event:from:myapi/resource
- mailto:cncf-wg-serverless@lists.cncf.io
- Internet-wide unique URI with a DNS authority.
- https://github.com/cloudevents/spec/pull/123
- mailto:cncf-wg-serverless@lists.cncf.io
- Universally-unique URN with a UUID:
- urn:uuid:6e8bc430-9c3a-11d9-9669-0800200c9a66
- Application-specific identifiers
- /cloudevents/spec/pull/123
- /sensors/tn-1234567/alerts
- 1-555-123-4567

### subject

Expand Down Expand Up @@ -236,14 +246,20 @@ within the same JSON object.
### id

- Type: `String`
- Description: ID of the event. The semantics of this string are explicitly
undefined to ease the implementation of producers. Enables deduplication.
- Description: Optionally identifies an event for de-duplication.
Absent if de-duplication is not required.
If present, the `source` and `id` attributes together uniquely identify the event.
- Examples:
- An event counter maintained by the producer
- A database commit ID
- A UUID
- Constraints:
- REQUIRED
- MUST be a non-empty string
- MUST be unique within the scope of the producer
- OPTIONAL
- Producers MAY omit `id` if de-duplication is not required.
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The Design Goal section states:

CloudEvents are typically used in a distributed system to allow for services to be loosely coupled during development, deployed independently, and later can be connected to create new applications.

In a loosely coupled system, a producer can't tell if de-duplication is not required (otherwise they're strongly coupled), and even if it could - can the producer tell that if it is later connected to create a new application, de-duplication won't be required in the future?

- Consumers MUST process events lacking `id` as non-duplicate events.
- If present, MUST be a non-empty string.
- Producers MUST ensure each distinct event from the same `source` has a unique `id` If a duplicate event is re-sent due to a network error, it MAY have the same `id`.
- Consumers MAY assume that events with matching `source` and `id` are duplicates.

### time

Expand Down