# Node.js 和 DAX
<a name="DAX.client.run-application-nodejs"></a>

执行这些步骤可在 Amazon EC2 实例上运行 Node.js 示例应用程序。

**运行 DAX 的 Node.js 示例**

1. 在 Amazon EC2 实例上设置 Node.js，如下所示：

   1. 安装节点版本管理器 (`nvm`)。

      ```
      curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
      ```

   1. 使用 nvm 安装 Node.js。

      ```
      nvm install 12.16.3
      ```

   1. 测试 Node.js 已安装且运行正常。

      ```
      node -e "console.log('Running Node.js ' + process.version)"
      ```

      这应该显示以下消息。

      `Running Node.js v12.16.3`

1. 使用节点程序包管理器 (`npm`) 安装 DAX Node.js 客户端。

   ```
   npm install amazon-dax-client
   ```

1. 下载示例程序源代码（`.zip` 文件）。

   ```
   wget http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/samples/TryDax.zip
   ```

   下载完成后，解压缩源文件。

   ```
   unzip TryDax.zip
   ```

1. 运行以下 Node.js 程序。第一个程序创建一个名为 `TryDaxTable` 的 Amazon DynamoDB 表。第二个程序向表中写入数据。

   ```
   node 01-create-table.js
   node 02-write-data.js
   ```

1. 运行以下 Node.js 程序。

   ```
   node 03-getitem-test.js
   node 04-query-test.js
   node 05-scan-test.js
   ```

    记下计时信息—`GetItem`、`Query` 和 `Scan` 测试所需的时间（以毫秒为单位）。

1. 在上一步中，您已针对 DynamoDB 端点运行程序。重新运行这些程序，但此次，`GetItem`、`Query` 和 `Scan` 操作将由 DAX 集群处理。

   要确定 DAX 集群的端点，请选择下列选项之一：
   + **使用 DynamoDB 控制台**—选择 DAX 集群。集群端点显示在控制台中，如下面的示例所示。

     ```
     dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com
     ```
   + **使用 AWS CLI**—输入以下命令。

     ```
     aws dax describe-clusters --query "Clusters[*].ClusterDiscoveryEndpoint"
     ```

     集群端点显示在输出中，如下面的示例所示。

     ```
     {
         "Address": "my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com",
         "Port": 8111,
         "URL": "dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com"
     }
     ```

   现在再次运行这些程序，但这次将集群端点指定为命令行参数。

   ```
   node 03-getitem-test.js dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com
   node 04-query-test.js dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com
   node 05-scan-test.js dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com
   ```

   查看输出的其余内容，并记下计时信息。与 DynamoDB 相比，使用 DAX 时，`GetItem`、`Query` 和 `Scan` 的运行时间应明显更短。

1. 运行以下 Node.js 程序删除 `TryDaxTable`。

   ```
   node 06-delete-table
   ```

有关这些程序的更多信息，请参见以下各部分：
+ [01-create-table.js](DAX.client.run-application-nodejs.01-create-table.md)
+ [02-write-data.js](DAX.client.run-application-nodejs.02-write-data.md)
+ [03-getitem-test.js](DAX.client.run-application-nodejs.03-getitem-test.md)
+ [04-query-test.js](DAX.client.run-application-nodejs.04-query-test.md)
+ [05-scan-test.js](DAX.client.run-application-nodejs.05-scan-test.md)
+ [06-delete-table.js](DAX.client.run-application-nodejs.06-delete-table.md)

# 01-create-table.js
<a name="DAX.client.run-application-nodejs.01-create-table"></a>

`01-create-table.js` 程序创建一个表 (`TryDaxTable`)。本部分的其他 Node.js 程序都将依赖此表。

```
const AmazonDaxClient = require("amazon-dax-client");
var AWS = require("aws-sdk");

var region = "us-west-2";

AWS.config.update({
  region: region,
});

var dynamodb = new AWS.DynamoDB(); //low-level client

var tableName = "TryDaxTable";

var params = {
  TableName: tableName,
  KeySchema: [
    { AttributeName: "pk", KeyType: "HASH" }, //Partition key
    { AttributeName: "sk", KeyType: "RANGE" }, //Sort key
  ],
  AttributeDefinitions: [
    { AttributeName: "pk", AttributeType: "N" },
    { AttributeName: "sk", AttributeType: "N" },
  ],
  ProvisionedThroughput: {
    ReadCapacityUnits: 10,
    WriteCapacityUnits: 10,
  },
};

dynamodb.createTable(params, function (err, data) {
  if (err) {
    console.error(
      "Unable to create table. Error JSON:",
      JSON.stringify(err, null, 2)
    );
  } else {
    console.log(
      "Created table. Table description JSON:",
      JSON.stringify(data, null, 2)
    );
  }
});
```

# 02-write-data.js
<a name="DAX.client.run-application-nodejs.02-write-data"></a>

`02-write-data.js` 程序向 `TryDaxTable` 中写入测试数据。

```
const AmazonDaxClient = require("amazon-dax-client");
var AWS = require("aws-sdk");

var region = "us-west-2";

AWS.config.update({
  region: region,
});

var ddbClient = new AWS.DynamoDB.DocumentClient();

var tableName = "TryDaxTable";

var someData = "X".repeat(1000);
var pkmax = 10;
var skmax = 10;

for (var ipk = 1; ipk <= pkmax; ipk++) {
  for (var isk = 1; isk <= skmax; isk++) {
    var params = {
      TableName: tableName,
      Item: {
        pk: ipk,
        sk: isk,
        someData: someData,
      },
    };

    //
    //put item

    ddbClient.put(params, function (err, data) {
      if (err) {
        console.error("Unable to write data: ", JSON.stringify(err, null, 2));
      } else {
        console.log("PutItem succeeded");
      }
    });
  }
}
```

# 03-getitem-test.js
<a name="DAX.client.run-application-nodejs.03-getitem-test"></a>

`03-getitem-test.js` 程序在 `GetItem` 上执行 `TryDaxTable` 操作。

```
const AmazonDaxClient = require("amazon-dax-client");
var AWS = require("aws-sdk");

var region = "us-west-2";

AWS.config.update({
  region: region,
});

var ddbClient = new AWS.DynamoDB.DocumentClient();
var daxClient = null;

if (process.argv.length > 2) {
  var dax = new AmazonDaxClient({
    endpoints: [process.argv[2]],
    region: region,
  });
  daxClient = new AWS.DynamoDB.DocumentClient({ service: dax });
}

var client = daxClient != null ? daxClient : ddbClient;
var tableName = "TryDaxTable";

var pk = 1;
var sk = 10;
var iterations = 5;

for (var i = 0; i < iterations; i++) {
  var startTime = new Date().getTime();

  for (var ipk = 1; ipk <= pk; ipk++) {
    for (var isk = 1; isk <= sk; isk++) {
      var params = {
        TableName: tableName,
        Key: {
          pk: ipk,
          sk: isk,
        },
      };

      client.get(params, function (err, data) {
        if (err) {
          console.error(
            "Unable to read item. Error JSON:",
            JSON.stringify(err, null, 2)
          );
        } else {
          // GetItem succeeded
        }
      });
    }
  }

  var endTime = new Date().getTime();
  console.log(
    "\tTotal time: ",
    endTime - startTime,
    "ms - Avg time: ",
    (endTime - startTime) / iterations,
    "ms"
  );
}
```

# 04-query-test.js
<a name="DAX.client.run-application-nodejs.04-query-test"></a>

`04-query-test.js` 程序在 `Query` 上执行 `TryDaxTable` 操作。

```
const AmazonDaxClient = require("amazon-dax-client");
var AWS = require("aws-sdk");

var region = "us-west-2";

AWS.config.update({
  region: region,
});

var ddbClient = new AWS.DynamoDB.DocumentClient();
var daxClient = null;

if (process.argv.length > 2) {
  var dax = new AmazonDaxClient({
    endpoints: [process.argv[2]],
    region: region,
  });
  daxClient = new AWS.DynamoDB.DocumentClient({ service: dax });
}

var client = daxClient != null ? daxClient : ddbClient;
var tableName = "TryDaxTable";

var pk = 5;
var sk1 = 2;
var sk2 = 9;
var iterations = 5;

var params = {
  TableName: tableName,
  KeyConditionExpression: "pk = :pkval and sk between :skval1 and :skval2",
  ExpressionAttributeValues: {
    ":pkval": pk,
    ":skval1": sk1,
    ":skval2": sk2,
  },
};

for (var i = 0; i < iterations; i++) {
  var startTime = new Date().getTime();

  client.query(params, function (err, data) {
    if (err) {
      console.error(
        "Unable to read item. Error JSON:",
        JSON.stringify(err, null, 2)
      );
    } else {
      // Query succeeded
    }
  });

  var endTime = new Date().getTime();
  console.log(
    "\tTotal time: ",
    endTime - startTime,
    "ms - Avg time: ",
    (endTime - startTime) / iterations,
    "ms"
  );
}
```

# 05-scan-test.js
<a name="DAX.client.run-application-nodejs.05-scan-test"></a>

`05-scan-test.js` 程序在 `Scan` 上执行 `TryDaxTable` 操作。

```
const AmazonDaxClient = require("amazon-dax-client");
var AWS = require("aws-sdk");

var region = "us-west-2";

AWS.config.update({
  region: region,
});

var ddbClient = new AWS.DynamoDB.DocumentClient();
var daxClient = null;

if (process.argv.length > 2) {
  var dax = new AmazonDaxClient({
    endpoints: [process.argv[2]],
    region: region,
  });
  daxClient = new AWS.DynamoDB.DocumentClient({ service: dax });
}

var client = daxClient != null ? daxClient : ddbClient;
var tableName = "TryDaxTable";

var iterations = 5;

var params = {
  TableName: tableName,
};
var startTime = new Date().getTime();
for (var i = 0; i < iterations; i++) {
  client.scan(params, function (err, data) {
    if (err) {
      console.error(
        "Unable to read item. Error JSON:",
        JSON.stringify(err, null, 2)
      );
    } else {
      // Scan succeeded
    }
  });
}

var endTime = new Date().getTime();
console.log(
  "\tTotal time: ",
  endTime - startTime,
  "ms - Avg time: ",
  (endTime - startTime) / iterations,
  "ms"
);
```

# 06-delete-table.js
<a name="DAX.client.run-application-nodejs.06-delete-table"></a>

`06-delete-table.js` 程序删除 `TryDaxTable`。完成测试后运行此程序。

```
const AmazonDaxClient = require("amazon-dax-client");
var AWS = require("aws-sdk");

var region = "us-west-2";

AWS.config.update({
  region: region,
});

var dynamodb = new AWS.DynamoDB(); //low-level client

var tableName = "TryDaxTable";

var params = {
  TableName: tableName,
};

dynamodb.deleteTable(params, function (err, data) {
  if (err) {
    console.error(
      "Unable to delete table. Error JSON:",
      JSON.stringify(err, null, 2)
    );
  } else {
    console.log(
      "Deleted table. Table description JSON:",
      JSON.stringify(data, null, 2)
    );
  }
});
```