common/lib/driver_connection_provider.ts

/*
  Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 
  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.
*/

import { ConnectionProvider } from "./connection_provider";
import { HostRole } from "./host_role";
import { HostInfo } from "./host_info";
import { HostSelector } from "./host_selector";
import { RandomHostSelector } from "./random_host_selector";
import { UnsupportedStrategyError } from "./utils/errors";
import { WrapperProperties } from "./wrapper_property";
import { Messages } from "./utils/messages";
import { RdsUtils } from "./utils/rds_utils";
import { promisify } from "util";
import { lookup } from "dns";
import { PluginService } from "./plugin_service";
import { logger } from "../logutils";
import { maskProperties } from "./utils/utils";
import { ClientWrapper } from "./client_wrapper";
import { RoundRobinHostSelector } from "./round_robin_host_selector";
import { DriverDialect } from "./driver_dialect/driver_dialect";

export class DriverConnectionProvider implements ConnectionProvider {
  private static readonly acceptedStrategies: Map<string, HostSelector> = new Map([
    [RandomHostSelector.STRATEGY_NAME, new RandomHostSelector()],
    [RoundRobinHostSelector.STRATEGY_NAME, new RoundRobinHostSelector()]
  ]);
  private readonly rdsUtils: RdsUtils = new RdsUtils();

  acceptsStrategy(role: HostRole, strategy: string): boolean {
    return DriverConnectionProvider.acceptedStrategies.has(strategy);
  }

  acceptsUrl(hostInfo: HostInfo, props: Map<string, any>): boolean {
    return true;
  }

  async connect(hostInfo: HostInfo, pluginService: PluginService, props: Map<string, any>): Promise<ClientWrapper> {
    let resultTargetClient;
    const resultProps = new Map(props);
    resultProps.set(WrapperProperties.HOST.name, hostInfo.host);
    if (hostInfo.isPortSpecified()) {
      resultProps.set(WrapperProperties.PORT.name, hostInfo.port);
    }
    const driverDialect: DriverDialect = pluginService.getDriverDialect();
    try {
      resultTargetClient = await driverDialect.connect(hostInfo, resultProps);
    } catch (e: any) {
      if (!WrapperProperties.ENABLE_GREEN_HOST_REPLACEMENT.get(props)) {
        throw e;
      }

      if (!e.message.includes("Error: getaddrinfo ENOTFOUND")) {
        throw e;
      }

      if (!this.rdsUtils.isRdsDns(hostInfo.host) || !this.rdsUtils.isGreenInstance(hostInfo.host)) {
        throw e;
      }

      // check DNS for green host name
      let resolvedAddress;
      try {
        resolvedAddress = await promisify(lookup)(hostInfo.host, {});
      } catch (tmp) {
        // do nothing
      }

      if (resolvedAddress) {
        // Green node DNS exists
        throw e;
      }

      // Green instance DNS doesn't exist. Try to replace it with corresponding node name and connect again.
      const originalHost: string = hostInfo.host;
      const fixedHost: string = this.rdsUtils.removeGreenInstancePrefix(hostInfo.host);
      resultProps.set(WrapperProperties.HOST.name, fixedHost);

      logger.info(
        "Connecting to " +
          fixedHost +
          " after correcting the hostname from " +
          originalHost +
          "\nwith properties: \n" +
          JSON.stringify(Object.fromEntries(maskProperties(resultProps)))
      );

      resultTargetClient = driverDialect.connect(hostInfo, resultProps);
    }
    pluginService.attachErrorListener(resultTargetClient);
    return resultTargetClient;
  }

  getHostInfoByStrategy(hosts: HostInfo[], role: HostRole, strategy: string, props?: Map<string, any>): HostInfo {
    const acceptedStrategy = DriverConnectionProvider.acceptedStrategies.get(strategy);
    if (!acceptedStrategy) {
      throw new UnsupportedStrategyError(Messages.get("ConnectionProvider.unsupportedHostSelectorStrategy", strategy, "DriverConnectionProvider"));
    }
    return acceptedStrategy.getHost(hosts, role, props);
  }
}