Step 2: Test connectivity to the ledger

Important

End of support notice: Existing customers will be able to use Amazon QLDB until end of support on 07/31/2025. For more details, see Migrate an Amazon QLDB Ledger to Amazon Aurora PostgreSQL.

In this step, you verify that you can connect to the vehicle-registration ledger in Amazon QLDB using the transactional data API endpoint.

To test connectivity to the ledger

Use the following program (ConnectToLedger.ts) to create a data session connection to the vehicle-registration ledger.

2.x


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

import { QldbDriver, RetryConfig  } from "amazon-qldb-driver-nodejs";
import { ClientConfiguration } from "aws-sdk/clients/qldbsession";

import { LEDGER_NAME } from "./qldb/Constants";
import { error, log } from "./qldb/LogUtil";

const qldbDriver: QldbDriver = createQldbDriver();

/**
 * Create a driver for creating sessions.
 * @param ledgerName The name of the ledger to create the driver on.
 * @param serviceConfigurationOptions The configurations for the AWS SDK client that the driver uses.
 * @returns The driver for creating sessions.
 */
export function createQldbDriver(
    ledgerName: string = LEDGER_NAME,
    serviceConfigurationOptions: ClientConfiguration = {}
): QldbDriver {
    const retryLimit = 4;
    const maxConcurrentTransactions = 10;
    //Use driver's default backoff function (and hence, no second parameter provided to RetryConfig)
    const retryConfig: RetryConfig = new RetryConfig(retryLimit);
    const qldbDriver: QldbDriver = new QldbDriver(ledgerName, serviceConfigurationOptions, maxConcurrentTransactions, retryConfig);
    return qldbDriver;
}

export function getQldbDriver(): QldbDriver {
    return qldbDriver;
}

/**
 * Connect to a session for a given ledger using default settings.
 * @returns Promise which fulfills with void.
 */
const main = async function(): Promise<void> {
    try {
        log("Listing table names...");
        const tableNames: string[] = await qldbDriver.getTableNames();
        tableNames.forEach((tableName: string): void => {
            log(tableName);
        });
    } catch (e) {
        error(`Unable to create session: ${e}`);
    }
}

if (require.main === module) {
    main();
}

1.x


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

import { QldbDriver  } from "amazon-qldb-driver-nodejs";
import { ClientConfiguration } from "aws-sdk/clients/qldbsession";

import { LEDGER_NAME } from "./qldb/Constants";
import { error, log } from "./qldb/LogUtil";

const qldbDriver: QldbDriver = createQldbDriver();

/**
 * Create a driver for creating sessions.
 * @param ledgerName The name of the ledger to create the driver on.
 * @param serviceConfigurationOptions The configurations for the AWS SDK client that the driver uses.
 * @returns The driver for creating sessions.
 */
export function createQldbDriver(
    ledgerName: string = LEDGER_NAME,
    serviceConfigurationOptions: ClientConfiguration = {}
): QldbDriver {
    const qldbDriver: QldbDriver = new QldbDriver(ledgerName, serviceConfigurationOptions);
    return qldbDriver;
}

export function getQldbDriver(): QldbDriver {
    return qldbDriver;
}

/**
 * Connect to a session for a given ledger using default settings.
 * @returns Promise which fulfills with void.
 */
var main = async function(): Promise<void> {
    try {
        log("Listing table names...");
        const tableNames: string[] = await qldbDriver.getTableNames();
        tableNames.forEach((tableName: string): void => {
            log(tableName);
        });
    } catch (e) {
        error(`Unable to create session: ${e}`);
    } 
}

if (require.main === module) {
    main();
}

Note

To run data transactions on your ledger, you must create a QLDB driver object to connect to a specified ledger. This is a different client object than the qldbClient object that you used in the previous step to create the ledger. That previous client is only used to run the management API operations listed in the Amazon QLDB API reference.

To run the transpiled program, enter the following command.
```
node dist/ConnectToLedger.js
```

To create tables in the vehicle-registration ledger, proceed to Step 3: Create tables, indexes, and sample data.

Warning Javascript is disabled or is unavailable in your browser.

To use the Amazon Web Services Documentation, Javascript must be enabled. Please refer to your browser's Help pages for instructions.

Document Conventions

Step 1: Create a new ledger

Step 3: Create tables, indexes, and sample data