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Protobuf Schemas

The datahub-protobuf module is designed to be used with the Java Emitter, the input is a compiled protobuf binary *.protoc files and optionally the corresponding *.proto source code. In addition, you can supply the root message in cases where a single protobuf source file includes multiple non-nested messages.

Supported Features

The following protobuf features are supported and are translated into descriptions, tags, properties and terms on a dataset.

* C++/C style code comments on Messages and Fields
* Nested Types
* Scalar Values
* Well Known Type Wrappers (i.e. DoubleValue, FloatValue, StringValue)
* Enumerations
* Oneof
* Maps
* Extensions
* Web links
* Parsing of GitHub team names and slack channel references

Usage

Protobuf Compile Options

In order to support parsing comments the following option flags should be used during protoc compilation.

protoc --include_imports --include_source_info --descriptor_set_out=MyProto.protoc MyProto.proto

Code Example

Given an input stream of the protoc binary and the emitter the minimal code is shown below.

import com.linkedin.common.FabricType;
import com.linkedin.common.AuditStamp;
import com.linkedin.common.urn.CorpuserUrn;
import datahub.client.rest.RestEmitter;
import datahub.protobuf.ProtobufDataset;

RestEmitter emitter;
InputStream protocInputStream;

AuditStamp auditStamp = new AuditStamp()
.setTime(System.currentTimeMillis())
.setActor(new CorpuserUrn("datahub"));

ProtobufDataset dataset = ProtobufDataset.builder()
.setDataPlatformUrn(new DataPlatformUrn("kafka"))
.setProtocIn(protocInputStream)
.setAuditStamp(auditStamp)
.setFabricType(FabricType.DEV)
.build();

dataset.getAllMetadataChangeProposals().flatMap(Collection::stream).forEach(mcpw -> emitter.emit(mcpw, null).get());

Additionally, the raw protobuf source can be included as well as information to allow parsing of additional references to GitHub and Slack in the source code comments.

ProtobufDataset dataset = ProtobufDataset.builder()
.setDataPlatformUrn(new DataPlatformUrn("kafka"))
.setSchema(" my raw protobuf schema ")
.setProtocIn(protocInputStream)
.setAuditStamp(auditStamp)
.setFabricType(FabricType.DEV)
.setGithubOrganization("myOrg")
.setSlackTeamId("SLACK123")
.build();

Protobuf Extensions

In order to extract even more metadata from the protobuf schema we can extend the FieldOptions and MessageOptions to be able to annotate Messages and Fields with arbitrary information. This information can then be emitted as DataHub primary key information, tags, glossary terms or properties on the dataset.

An annotated protobuf schema would look like the following, except for the is_primary_key all annotations are configurable for individual needs.

Note: Extending FieldOptions and MessageOptions does not change the messages themselves. The metadata is not included in messages being sent over the wire.

syntax = "proto3";
import "meta.proto";

message Department {
int32 id = 1 [(meta.fld.is_primary_key) = true];
string name = 2;
}

message Person {
option(meta.msg.type) = ENTITY;
option(meta.msg.classification_enum) = HighlyConfidential;
option(meta.msg.team) = "TeamB";
option(meta.msg.bool_feature) = true;
option(meta.msg.alert_channel) = "#alerts";

string name = 1 [(meta.fld.classification) = "Classification.HighlyConfidential"];

int32 id = 2
[(meta.fld.is_primary_key) = true];

string email = 3
[(meta.fld.classification_enum) = Confidential];

Department dept = 4;

string test_coverage = 5
[(meta.fld.product_type_bool) = true, (meta.fld.product_type) = "my type", (meta.fld.product_type_enum) = EVENT];
}

meta.proto

In order to use the annotations above, create a proto file called meta.proto. Feel free to customize the kinds of metadata and how it is emitted to DataHub for your use cases.

syntax = "proto3";
package meta;

import "google/protobuf/descriptor.proto";

/*
This is assigned to metadata fields. It describes how the metadata field should be represented
in DataHub. This enum must be used in the `meta` package. Multiple can be used for the same
metadata annotation. This allows a single piece of information to be captured in DataHub
as a property, tag and/or term.

Tags can be strings, enums, or booleans
Terms can be strings or enums
Properties should be strings

*/
enum DataHubMetadataType {
PROPERTY = 0; // Datahub Custom Property
TAG = 1; // Datahub Tag
TAG_LIST = 2; // Datahub Tags from comma delimited string
TERM = 3; // Datahub Term
OWNER = 4; // Datahub Owner
DOMAIN = 5; // Datahub Domain
DEPRECATION = 6; // Datahub Deprecation
}

/*
Example below: The following is not required for annotation processing. This is an example
of creating an annotation using an enum.
*/

enum MetaEnumExample {
UNKNOWN = 0;
ENTITY = 1;
EVENT = 2;
}

// Assuming Glossary Term defined from bootstrap example
enum Classification {
HighlyConfidential = 0;
Confidential = 1;
Sensitive = 2;
}

FieldOptions

Define possible annotations on fields and how they are exported to DataHub.


message fld {
extend google.protobuf.FieldOptions {
// Required: Mark option field with how to export to DataHub in one or more places.
repeated meta.DataHubMetadataType type = 6000;

/*
Examples below: The following is not required for annotation processing.
*/

// Set true if the field is a primary key. This works for any boolean with `primary_key` in it.
bool is_primary_key = 6010;

// Extract classification field option as a Term, either works
string classification = 6001 [(meta.fld.type) = TERM];
meta.Classification classification_enum = 6002 [(meta.fld.type) = TERM];

// Expose this option as a tag on the field.
string product_type = 70004 [(meta.fld.type) = TAG];
bool product_type_bool = 70005 [(meta.fld.type) = TAG];
meta.MetaEnumExample product_type_enum = 70006 [(meta.fld.type) = TAG];
}
}

MessageOptions

Define possible annotations on messages and how they are exported to DataHub.


message msg {
extend google.protobuf.MessageOptions {
/*
Examples below: The following is not required for annotation processing.
*/

// Place the classification term at the Message/Dataset level, either string or enum is supported
string classification = 4000 [(meta.fld.type) = TERM, (meta.fld.type) = PROPERTY];
meta.Classification classification_enum = 4001 [(meta.fld.type) = TERM, (meta.fld.type) = PROPERTY];

// Attach these Message/Dataset options as a tag and property.
string product = 5001 [(meta.fld.type) = TAG, (meta.fld.type) = PROPERTY];
string project = 5002 [(meta.fld.type) = TAG, (meta.fld.type) = PROPERTY];
string team = 5003 [(meta.fld.type) = OWNER, (meta.fld.type) = PROPERTY];

string domain = 60003 [(meta.fld.type) = DOMAIN, (meta.fld.type) = PROPERTY];
meta.MetaEnumExample type = 60004 [(meta.fld.type) = TAG, (meta.fld.type) = PROPERTY];
bool bool_feature = 60005 [(meta.fld.type) = TAG];
string alert_channel = 60007 [(meta.fld.type) = PROPERTY];

repeated string deprecation_note = 60008 [(meta.fld.type) = DEPRECATION, (meta.fld.type) = PROPERTY];
uint64 deprecation_time = 60009 [(meta.fld.type) = DEPRECATION, (meta.fld.type) = PROPERTY];
}
}

DataHubMetadataType

DataHubMetadataTypeStringBoolEnumRepeatedUint64
PROPERTYXXXX
TAGXXX
TAG_LISTX
TERMXX
OWNERXX
DOMAINXX
DEPRECATIONX (notes)X (notes)X (time)
PROPERTY

Custom properties can be captured as key/value pairs where the protobuf option name is the key and the option value is the option's value.

For example, generating a custom property with key prop1 and value value1.

   message msg {
extend google.protobuf.MessageOptions {
string prop1 = 5000 [(meta.fld.type) = PROPERTY];
}
}

message Message {
option(meta.msg.prop1) = "value1";
}

Booleans are converted to a value of either true or false.

   message msg {
extend google.protobuf.MessageOptions {
bool prop1 = 5000 [(meta.fld.type) = PROPERTY];
}
}

message Message {
option(meta.msg.prop1) = true;
}

Enum values are similarly converted to their string representation.

   enum MetaEnumExample {
UNKNOWN = 0;
ENTITY = 1;
EVENT = 2;
}

message msg {
extend google.protobuf.MessageOptions {
MetaEnumExample prop1 = 5000 [(meta.fld.type) = PROPERTY];
}
}

message Message {
option(meta.msg.prop1) = ENTITY;
}

Repeated values will be collected and the value will be stored as a serialized json array. The following example would result in the value of ["a","b","c"].

   message msg {
extend google.protobuf.MessageOptions {
repeated string prop1 = 5000 [(meta.fld.type) = PROPERTY];
}
}

message Message {
option(meta.msg.prop1) = "a";
option(meta.msg.prop1) = "b";
option(meta.msg.prop1) = "c";
}
TAG & TAG_LIST

The tag list assumes a string that contains the comma delimited values of the tags. In the example below, tags would be added as a, b, c.

   message msg {
extend google.protobuf.MessageOptions {
string tags = 5000 [(meta.fld.type) = TAG_LIST];
}
}

message Message {
option(meta.msg.tags) = "a, b, c";
}

Tags could also be represented as separate boolean options. Only the true options result in tags. In this example, a single tag of tagA would be added to the dataset.

   message msg {
extend google.protobuf.MessageOptions {
bool tagA = 5000 [(meta.fld.type) = TAG];
bool tagB = 5001 [(meta.fld.type) = TAG];
}
}

message Message {
option(meta.msg.tagA) = true;
option(meta.msg.tagB) = false;
}

Alternatively, tags can be separated into different fields with the option name as a dot delimited prefix. The following would produce two tags with values of tagA.a and tagB.a.

   message msg {
extend google.protobuf.MessageOptions {
string tagA = 5000 [(meta.fld.type) = TAG];
string tagB = 5001 [(meta.fld.type) = TAG];
}
}

message Message {
option(meta.msg.tagA) = "a";
option(meta.msg.tagB) = "a";
}

The dot delimited prefix also works with enum types where the prefix is the enum type name. In this example two tags are created, MetaEnumExample.ENTITY.

  enum MetaEnumExample {
UNKNOWN = 0;
ENTITY = 1;
EVENT = 2;
}

message msg {
extend google.protobuf.MessageOptions {
MetaEnumExample tag = 5000 [(meta.fld.type) = TAG];
}
}

message Message {
option(meta.msg.tag) = ENTITY;
}

In addition, tags can be added to fields as well as messages. The following is a consolidated example for all the possible tag options on fields.

  enum MetaEnumExample {
UNKNOWN = 0;
ENTITY = 1;
EVENT = 2;
}

message fld {
extend google.protobuf.FieldOptions {
string tags = 6000 [(meta.fld.type) = TAG_LIST];
string tagString = 6001 [(meta.fld.type) = TAG];
bool tagBool = 6002 [(meta.fld.type) = TAG];
MetaEnumExample tagEnum = 6003 [(meta.fld.type) = TAG];
}
}

message Message {
uint32 my_field = 1
[(meta.fld.tags) = "a, b, c",
(meta.fld.tagString) = "myTag",
(meta.fld.tagBool) = true,
(meta.fld.tagEnum) = ENTITY];
}
TERM

Terms are specified by either a fully qualified string value or an enum where the enum type's name is the first element in the fully qualified term name.

The following example shows both methods, either of which would result in the term Classification.HighlyConfidential being applied.

   enum Classification {
HighlyConfidential = 0;
Confidential = 1;
Sensitive = 2;
}

message msg {
extend google.protobuf.MessageOptions {
Classification term = 5000 [(meta.fld.type) = TERM];
string class = 5001 [(meta.fld.type) = TERM];
}
}

message Message {
option(meta.msg.term) = HighlyConfidential;
option(meta.msg.class) = "Classification.HighlyConfidential";
}

The following is a consolidated example for the possible field level term options.

   enum Classification {
HighlyConfidential = 0;
Confidential = 1;
Sensitive = 2;
}

message fld {
extend google.protobuf.FieldOptions {
Classification term = 5000 [(meta.fld.type) = TERM];
string class = 5001 [(meta.fld.type) = TERM];
}
}

message Message {
uint32 my_field = 1
[(meta.fld.term) = HighlyConfidential,
(meta.fld.class) = "Classification.HighlyConfidential"];
}
OWNER

One or more owners can be specified and can be any combination of corpUser and corpGroup entities. The default entity type is corpGroup. By default, the ownership type is set to producer, see the second example for setting the ownership type.

The following example assigns the ownership to a group of myGroup and a user called myName.

   message msg {
extend google.protobuf.MessageOptions {
repeated string owner = 5000 [(meta.fld.type) = OWNER];
}
}

message Message {
option(meta.msg.owner) = "corpUser:myName";
option(meta.msg.owner) = "myGroup";
}

In this example, the option name determines the ownership type. User myName is assigned as the Technical Owner and myGroup as the Data Steward.

   message msg {
extend google.protobuf.MessageOptions {
repeated string technical_owner = 5000 [(meta.fld.type) = OWNER];
repeated string data_steward = 5001 [(meta.fld.type) = OWNER];
}
}

message Message {
option(meta.msg.technical_owner) = "corpUser:myName";
option(meta.msg.data_steward) = "myGroup";
}
DOMAIN

Set the domain id for the dataset. The domain should exist already. Note that the id of the domain is the value. If not specified during domain creation it is likely a random string.

   message msg {
extend google.protobuf.MessageOptions {
string domain = 5000 [(meta.fld.type) = DOMAIN];
}
}

message Message {
option(meta.msg.domain) = "engineering";
}
DEPRECATION

Deprecation of fields and messages are natively supported by protobuf options. The standard "Deprecation" aspect is used for a dataset generated from a protobuf message. Field deprecation adds a tag with the following urn urn:li:tag:deprecated (red, #FF000).

   message msg {
extend google.protobuf.MessageOptions {
repeated string deprecation_note = 5620 [(meta.fld.type) = DEPRECATION];
uint64 deprecation_time = 5621 [(meta.fld.type) = DEPRECATION];
}
}

message Message {
option deprecated = true;
option (meta.msg.deprecation_note) = "Deprecated for this other message.";
option (meta.msg.deprecation_note) = "Drop in replacement.";
option (meta.msg.deprecation_time) = 1649689387;
}

The field deprecation tag works without definition in meta.proto using the native protobuf option.

message Message {
uint32 my_field = 1 [deprecated = true];
}

Gradle Integration

An example application is included which works with the protobuf-gradle-plugin, see the standalone example project.

Usage

Using the

export DATAHUB_API=...
export DATAHUB_TOKEN=...

# Optional parameters
# export DATAHUB_ENV=PROD
# export DATAHUB_GITHUBORG=datahub-project
# export DATAHUB_SLACKID=

./gradlew publishSchema