Re-Introducing Protocol Buffer Representation

.gitignore

@@ -1,4 +1,5 @@
 .idea/
 gen/
 .vscode/
+gen/
 .DS_Store

README.md

@@ -37,6 +37,7 @@ The following documents are available:
 | Kafka Protocol Binding        | [v1.0](https://github.com/cloudevents/spec/blob/v1.0/kafka-protocol-binding.md) | [master](https://github.com/cloudevents/spec/blob/master/kafka-protocol-binding.md) |
 | MQTT Protocol Binding         | [v1.0](https://github.com/cloudevents/spec/blob/v1.0/mqtt-protocol-binding.md) | [master](https://github.com/cloudevents/spec/blob/master/mqtt-protocol-binding.md)  |
 | NATS Protocol Binding         | [v1.0](https://github.com/cloudevents/spec/blob/v1.0/nats-protocol-binding.md) | [master](https://github.com/cloudevents/spec/blob/master/nats-protocol-binding.md)  |
+| Protobuf Event Format | | [master][proto-working] |
 | Web hook                      |     [v1.0](https://github.com/cloudevents/spec/blob/v1.0/http-webhook.md)      |      [master](https://github.com/cloudevents/spec/blob/master/http-webhook.md)      |
 |                               |
 | **Additional Documentation:** |
@@ -153,3 +154,6 @@ Periodically, the group may have in-person meetings that coincide with a major
 conference. Please see the
 [meeting minutes](https://docs.google.com/document/d/1OVF68rpuPK5shIHILK9JOqlZBbfe91RNzQ7u_P7YCDE/edit#)
 for any future plans.
+
+[proto-working]: ./protobuf-format.md
+[proto-latest]: ./protobuf-format.md

protobuf-format.md

@@ -0,0 +1,227 @@
+# Protobuf Event Format for CloudEvents - Version 1.0
+
+## Abstract
+
+[Protocol Buffers][proto-home] is a mechanism for marshalling structured data,
+this document defines how CloudEvents are represented using [version 3][proto-3]
+of that specification.
+
+In this document the terms *Protocol Buffers*, *protobuf*, and *proto* are used
+interchangeably.
+
+## Status of this document
+
+This document is a working draft.
+
+## Table of Contents
+
+1. [Introduction](#1-introduction)
+2. [Attributes](#2-attributes)
+3. [Data](#3-data)
+4. [Transport](#4-transport)
+5. [Examples](#5-examples)
+
+## 1. Introduction
+
+[CloudEvents][ce] is a standardized and protocol-agnostic definition of the
+structure and metadata description of events. This specification defines how the
+elements defined in the CloudEvents specification are are represented using
+a protobuf schema.
+
+The [Attributes](#2-attributes) section describes the naming conventions and
+data type mappings for CloudEvents attributes for use as protobuf message
+properties.
+
+The [Data](#3-data) section describes how the event payload is carried.
+
+### 1.1. Conformance
+
+The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",
+"SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
+interpreted as described in [RFC2119][rfc2119].
+
+### 1.2 Content-Type
+
+There is no official IANA *media-type* designation for protobuf, as such this
+specification uses 'application/protobuf' to identify such content.
+
+## 2. Attributes
+
+This section defines how CloudEvents attributes are represented in the protobuf
+[schema][proto-schema].
+
+## 2.1 Type System
+
+The CloudEvents type system is mapped to protobuf as follows :
+
+| CloudEvents   | protobuf |
+| ------------- | ---------------------------------------------------------------------- |
+| Boolean       | [boolean][proto-scalars] |
+| Integer       | [sint32][proto-scalars] |
+| String        | [string][proto-scalars] |
+| Binary        | [bytes][proto-scalars] |
+| URI           | [string][proto-scalars] following [RFC 3986 §4.3][rfc3986-section43]|
+| URI-reference | [string][proto-scalars] following [RFC 3986 §4.1][rfc3986-section41] |
+| Timestamp     | [Timestamp][proto-timestamp]  |
+
+## 2.3 Required Attributes
+
+Required attributes are represented explicitly as protobuf fields.
+
+## 2.4 Optional Attributes & Extensions
+
+Optional and extension attributes are represented using a map construct enabling
+direct support of the CloudEvent [type system][ce-types].
+
+```proto
+map<string, CloudEventAttribute> attribute = 1;
+
+message CloudEventAttribute {
+
+    oneof attr_oneof {
+      bool ce_boolean = 1;
+      sfixed32 ce_integer = 2;
+      string ce_string = 3;
+      bytes ce_binary = 4;
+      string ce_uri = 5;
+      string ce_uri_reference = 6;
+      google.protobuf.Timestamp ce_timestamp = 7;
+    }
+}
+```
+
+In this model an attribute's name is used as the map *key* and is
+associated with its *value* stored in the appropriately typed property.
+
+This approach allows for attributes to be represented and transported
+with no loss of *type* information.
+
+## 3. Data
+
+The specification allows for data payloads of the following types to be explicitly represented:
+
+* string
+* bytes
+* protobuf object/message
+
+```proto
+oneof data_oneof {
+
+    // Binary data
+    bytes binary_data = 2;
+
+    // String data
+    string text_data = 3;
+
+    // Protobuf Message data
+    google.protobuf.Any proto_data = 4;
+}
+```
+
+* Where the data is a protobuf message it MUST be stored in the `proto_data` property.
+  * `datacontenttype` MAY be populated with `application/protobuf`
+  * `dataschema` SHOULD be populated with the type URL of the protobuf data message.
+
+* When the type of the data is text, the value MUST be stored in the `text_data` property.
+  * `datacontenttype` SHOULD be popuplated with the appropriate media-type.
+
+* When the type of the data is binary the value MUST be stored in the `binary_data` property.
+  * `datacontenttype` SHOULD be populated with the appropriate media-type.
+
+
+
+## 4. Transport
+
+Transports that support content identification MUST use the following designation:
+
+```text
+   application/cloudevents+protobuf
+```
+
+## 5. Examples
+
+The following code-snippets shows how proto representations might be constucted asuming the availability of some convenience methods ...
+
+### 5.1 Plain Text event data
+
+```java
+public static Spec.CloudEvent plainTextExample() {
+  Spec.CloudEvent.Builder ceBuilder = Spec.CloudEvent.newBuilder();
+
+  ceBuilder
+    //-- Required Attributes.
+    .setId(UUID.randomUUID().toString())
+    .setSpecVersion("1.0")
+    .setType("io.cloudevent.example")
+    .setSource("producer-1")
+
+    //-- Data.
+    .setTextData("This is a plain text message");
+
+    //-- Optional Attributes
+    withCurrentTime(ceBuilder, "time");
+    withAttribute(ceBuilder, "datacontenttype", "text/plain");
+
+    // Build it.
+    return ceBuilder.build();
+}
+
+```
+
+### 5.2 Proto message as event data
+
+Where the event data payload is itself a protobuf message (with its own schema)
+a protocol buffer idiomatic method can be used to carry the data.
+
+```java
+private static Spec.CloudEvent protoExample() {
+
+  //-- Build an event data protobuf object.
+  Test.SomeData.Builder dataBuilder = Test.SomeData.newBuilder();
+
+  dataBuilder
+    .setSomeText("this is an important message")
+    .setIsImportant(true);
+
+  //-- Build the CloudEvent.
+  Spec.CloudEvent.Builder ceBuilder = Spec.CloudEvent.newBuilder();
+
+  ceBuilder
+    .setId(UUID.randomUUID().toString())
+    .setSpecVersion("1.0")
+    .setType("io.cloudevent.example")
+    .setSource("producer-2")
+
+    // Add the proto data into the CloudEvent envelope.
+    .setProtoData(Any.pack(dataBuilder.build()));
+
+    // Add the protto type URL
+    withAttribute(ceBuilder, "dataschema", ceBuilder.getProtoData().getTypeUrl());
+
+    // Set Content-Type (Optional)
+    withAttribute(ceBuilder, "datacontenttype", "application/protobuf");
+
+    //-- Done.
+    return ceBuilder.build();
+
+}
+```
+
+## References
+
+* [Protocol Buffer 3 Specification][proto-3]
+* [CloudEvents Protocol Buffers format schema][proto-schema]
+
+[Proto-3]: https://developers.google.com/protocol-buffers/docs/reference/proto3-spec
+[proto-home]: https://developers.google.com/protocol-buffers
+[proto-scalars]: https://developers.google.com/protocol-buffers/docs/proto3#scalar
+[proto-wellknown]: https://developers.google.com/protocol-buffers/docs/reference/google.protobuf
+[proto-timestamp]: https://developers.google.com/protocol-buffers/docs/reference/google.protobuf#google.protobuf.Timestamp
+[proto-schema]: ./spec.proto
+[json-format]: ./json-format.md
+[ce]: ./spec.md
+[ce-types]: ./spec.md#type-system
+[rfc2119]: https://tools.ietf.org/html/rfc2119
+[rfc3986-section41]: https://tools.ietf.org/html/rfc3986#section-4.1
+[rfc3986-section43]: https://tools.ietf.org/html/rfc3986#section-4.3
+[rfc3339]: https://tools.ietf.org/html/rfc3339

spec.proto

@@ -0,0 +1,55 @@
+/**
+ * CloudEvent Protobuf Format
+ *
+ * - Required context attributes are explicity represented.
+ * - Optional and Extension context attributes are carried in a map structure.
+ * - Data may be represented as binary, text, or protobuf messages.
+ */
+
+syntax = "proto3";
+
+package io.cloudevents.v1;
+
+import "google/protobuf/any.proto";
+import "google/protobuf/timestamp.proto";
+
+option java_package = "io.cloudevents.v1.proto";
+
+message CloudEvent {
+
+  // -- CloudEvent Context Attributes
+
+  // Required Attributes
+  string id = 1;
+  string source = 2; // URI-reference
+  string spec_version = 3;
+  string type = 4;
+
+  // Optional & Extension Attributes
+  map<string, CloudEventAttribute> attribute = 5;
+
+  // -- CloudEvent Data (Bytes, Text, or Proto)
+  oneof data_oneof {
+    bytes binary_data = 6;
+    string text_data = 7;
+    google.protobuf.Any proto_data = 8;
+  }
+
+  /**
+   * The CloudEvent specification defines
+   * seven atrribute types...
+   */
+
+  message CloudEventAttribute {
+
+    oneof attr_oneof {
+      bool ce_boolean = 1;
+      int32 ce_integer = 2;
+      string ce_string = 3;
+      bytes ce_bytes = 4;
+      string ce_uri = 5;
+      string ce_uri_ref = 6;
+      google.protobuf.Timestamp ce_timestamp = 7;
+    }
+  }
+}