rpc-priority-read.js

// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// sample-metadata:
//  title: Read data with RPC Priority
//  usage: node rpc-priority-read.js <INSTANCE_ID> <DATABASE_ID> <PROJECT_ID>

'use strict';

async function main(instanceId, databaseId, projectId) {
  // [START spanner_rpc_priority_read]
  // Imports the Google Cloud client library.
  const {Spanner, protos} = require('@google-cloud/spanner');
  const Priority = protos.google.spanner.v1.RequestOptions.Priority;

  /**
   * TODO(developer): Uncomment the following lines before running the sample.
   */
  // const projectId = 'my-project-id';
  // const instanceId = 'my-instance';
  // const databaseId = 'my-database';

  // Creates a client
  const spanner = new Spanner({
    projectId: projectId,
  });

  async function readDataWithRpcPriority(instanceId, databaseId) {
    // Gets a reference to a Cloud Spanner instance and database
    const instance = spanner.instance(instanceId);
    const database = instance.database(databaseId);

    const albumsTable = database.table('Albums');

    const query = {
      columns: ['SingerId', 'AlbumId', 'AlbumTitle'],
      keySet: {
        all: true,
      },
      requestOptions: {
        priority: Priority.PRIORITY_LOW,
      },
    };

    // Reads the Albums table using an index
    try {
      const [rows] = await albumsTable.read(query);

      console.log(
        `Successfully fetched ${rows.length} rows using low RPC priority.`
      );

      rows.forEach(row => {
        const json = row.toJSON();
        console.log(
          `SingerId: ${json.SingerId}, AlbumId: ${json.AlbumId}, AlbumTitle: ${json.AlbumTitle}`
        );
      });
    } catch (err) {
      console.error('ERROR:', err);
    } finally {
      // Close the database when finished.
      database.close();
    }
  }
  readDataWithRpcPriority(instanceId, databaseId);
  // [END spanner_rpc_priority_read]
}

process.on('unhandledRejection', err => {
  console.error(err.message);
  process.exitCode = 1;
});
main(...process.argv.slice(2));