List schema revisions for a topic

This document shows you how to list the revisions of a schema for Pub/Sub topics.

Before you begin

Required roles and permissions

To get the permissions that you need to list schema revisions and manage them, ask your administrator to grant you the Pub/Sub Editor (roles/pubsub.editor) IAM role on your project. For more information about granting roles, see Manage access to projects, folders, and organizations.

This predefined role contains the permissions required to list schema revisions and manage them. To see the exact permissions that are required, expand the Required permissions section:

Required permissions

The following permissions are required to list schema revisions and manage them:

  • Create schema: pubsub.schemas.create
  • Attach schema to topic: pubsub.schemas.attach
  • Commit a schema revision: pubsub.schemas.commit
  • Delete a schema or a schema revision: pubsub.schemas.delete
  • Get a schema or schema revisions: pubsub.schemas.get
  • List schemas: pubsub.schemas.list
  • List schema revisions: pubsub.schemas.listRevisions
  • Rollback a schema: pubsub.schemas.rollback
  • Validate a message: pubsub.schemas.validate
  • Get the IAM policy for a schema: pubsub.schemas.getIamPolicy
  • Configure the IAM policy for a schema: pubsub.schemas.setIamPolicy

You might also be able to get these permissions with custom roles or other predefined roles.

You can grant roles and permissions to principals such as users, groups, domains, or service accounts. You can create a schema in one project and attach it to a topic located in a different project. Ensure that you have the required permissions for each project.

List the revisions of a schema

You can list the revisions of a schema in a Google Cloud project using the Google Cloud console, the gcloud CLI, the Pub/Sub API, or the Cloud Client Libraries.

Console

  1. In the Google Cloud console, go to the Pub/Sub schemas page.

    Go to Schemas

    The list of schemas is displayed.

  2. Click the name of the schema that you want to view.

    The Schema details page for the schema opens.

    In the Revisions section, you can see the list of available revisions for the schema.

gcloud

To view the latest revision for a schema:

gcloud pubsub schemas list-revisions SCHEMA_ID

Use the gcloud pubsub schemas list-revisions <var>SCHEMA_ID</var> --view=FULL command to see the definitions for the schema revisions.

REST

To list the schemas revisions for a schema, send a GET request like the following:

GET https://pubsub.googleapis.com/v1/projects/SCHEMA_NAME:listRevisions

If successful, the response body contains a JSON object containing all schema revisions for the schema.

C++

Before trying this sample, follow the C++ setup instructions in Quickstart: Using Client Libraries. For more information, see the Pub/Sub C++ API reference documentation. 

namespace pubsub = ::google::cloud::pubsub;
[](pubsub::SchemaServiceClient client, std::string const& project_id,
   std::string const& schema_id) {
  auto const parent = pubsub::Schema(project_id, schema_id).FullName();
  for (auto& s : client.ListSchemaRevisions(parent)) {
    if (!s) throw std::move(s).status();
    std::cout << "Schema revision: " << s->DebugString() << "\n";
  }
}

Go

Before trying this sample, follow the Go setup instructions in Quickstart: Using Client Libraries. For more information, see the Pub/Sub Go API reference documentation. 

import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/pubsub"
	"google.golang.org/api/iterator"
)

func listSchemaRevisions(w io.Writer, projectID, schemaID string) ([]*pubsub.SchemaConfig, error) {
	// projectID := "my-project-id"
	// schemaID := "my-schema-id"
	ctx := context.Background()
	client, err := pubsub.NewSchemaClient(ctx, projectID)
	if err != nil {
		return nil, fmt.Errorf("pubsub.NewSchemaClient: %w", err)
	}
	defer client.Close()

	var schemas []*pubsub.SchemaConfig

	schemaIter := client.ListSchemaRevisions(ctx, schemaID, pubsub.SchemaViewFull)
	for {
		sc, err := schemaIter.Next()
		if err == iterator.Done {
			break
		}
		if err != nil {
			return nil, fmt.Errorf("schemaIter.Next: %w", err)
		}
		fmt.Fprintf(w, "Got schema revision: %#v\n", sc)
		schemas = append(schemas, sc)
	}

	fmt.Fprintf(w, "Got %d schema revisions", len(schemas))
	return schemas, nil
}

Java

Before trying this sample, follow the Java setup instructions in Quickstart: Using Client Libraries. For more information, see the Pub/Sub Java API reference documentation. 

import com.google.cloud.pubsub.v1.SchemaServiceClient;
import com.google.pubsub.v1.Schema;
import com.google.pubsub.v1.SchemaName;
import java.io.IOException;

public class ListSchemaRevisionsExample {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String schemaId = "your-schema-id";

    listSchemaRevisionsExample(projectId, schemaId);
  }

  public static void listSchemaRevisionsExample(String projectId, String schemaId)
      throws IOException {
    SchemaName schemaName = SchemaName.of(projectId, schemaId);

    try (SchemaServiceClient schemaServiceClient = SchemaServiceClient.create()) {
      for (Schema schema : schemaServiceClient.listSchemaRevisions(schemaName).iterateAll()) {
        System.out.println(schema);
      }
      System.out.println("Listed schema revisions.");
    }
  }
}

Python

Before trying this sample, follow the Python setup instructions in Quickstart: Using Client Libraries. For more information, see the Pub/Sub Python API reference documentation. 

from google.cloud.pubsub import SchemaServiceClient

# TODO(developer): Replace these variables before running the sample.
# project_id = "your-project-id"
# schema_id = "your-schema-id"

schema_client = SchemaServiceClient()
schema_path = schema_client.schema_path(project_id, schema_id)

for schema in schema_client.list_schema_revisions(request={"name": schema_path}):
    print(schema)

print("Listed schema revisions.")

Node.js

Before trying this sample, follow the Node.js setup instructions in Quickstart: Using Client Libraries. For more information, see the Pub/Sub Node.js API reference documentation. 

/**
 * TODO(developer): Uncomment this variable before running the sample.
 */
// const schemaNameOrId = 'YOUR_SCHEMA_NAME_OR_ID';

// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function listSchemaRevisions(schemaNameOrId) {
  // Get the fully qualified schema name.
  const schema = pubSubClient.schema(schemaNameOrId);
  const name = await schema.getName();

  // Use the gapic client to list the schema revisions.
  const schemaClient = await pubSubClient.getSchemaClient();
  const [results] = await schemaClient.listSchemaRevisions({
    name,
  });
  for (const rev of results) {
    console.log(rev.revisionId, rev.revisionCreateTime);
  }
  console.log(`Listed revisions of schema ${name}.`);
}

Node.js

Before trying this sample, follow the Node.js setup instructions in Quickstart: Using Client Libraries. For more information, see the Pub/Sub Node.js API reference documentation. 

/**
 * TODO(developer): Uncomment this variable before running the sample.
 */
// const schemaNameOrId = 'YOUR_SCHEMA_NAME_OR_ID';

// Imports the Google Cloud client library
import {PubSub} from '@google-cloud/pubsub';

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function listSchemaRevisions(schemaNameOrId: string) {
  // Get the fully qualified schema name.
  const schema = pubSubClient.schema(schemaNameOrId);
  const name = await schema.getName();

  // Use the gapic client to list the schema revisions.
  const schemaClient = await pubSubClient.getSchemaClient();
  const [results] = await schemaClient.listSchemaRevisions({
    name,
  });
  for (const rev of results) {
    console.log(rev.revisionId, rev.revisionCreateTime);
  }
  console.log(`Listed revisions of schema ${name}.`);
}

What's next