本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

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

請按照此程序操作，在 Amazon EC2 執行個體上執行 Node.js 範例應用程式。

**執行 DAX 的 Node.js 範例**

1. 在您的 Amazon EC2 執行個體上設定 Node.js，如下所示：

   1. 安裝節點版本管理工具 (`nvm`)。

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

   1. 使用 nvm 安裝 Node.js。

      ```
      nvm install 12.16.3
      ```

   1. 測試 Node.js 已安裝且正常運作。

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

      這應該會顯示以下訊息。

      `Running Node.js v12.16.3`

1. 使用節點套件管理工具 (`npm`) 安裝 DAX Node.js 用戶端。

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

1. 下載範例程式來源碼 (`.zip` 檔案)。

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

   下載完成後，解壓縮來源檔案。

   ```
   unzip TryDax.zip
   ```

1. 執行下列 Node.js 程式。第一個程式會建立名為 `TryDaxTable` 的 Amazon DynamoDB 資料表。第二個程式會將資料寫入資料表。

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

1. 執行下列 Node.js 程式。

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

    記下計時資訊：`GetItem`、`Query` 和 `Scan` 測試所需要的毫秒數。

1. 在先前的步驟中，您已針對 DynamoDB 端點執行程式。請再次執行程式，但這一次 `GetItem`、`Query` 和 `Scan` 操作會由您的 DAX 叢集處理。

   若要判斷您 DAX 叢集的端點，請選擇下列其中一個項目：
   + **使用 DynamoDB 主控台**：選擇您的 DAX 叢集。叢集端點會在主控台上顯示，如以下範例。

     ```
     dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com
     ```
   + **使用 AWS CLI**- 輸入下列命令。

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

     如下列範例所示，叢集端點會在輸出上顯示。

     ```
     {
         "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"
     }
     ```

   現在重新執行程式，但這一次，請將叢集端點做為命令列參數指定。

   ```
   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
   ```

   查看輸出的剩餘部分，並記下計時資訊。使用 DAX 的 `GetItem`、`Query` 和 `Scan` 已耗用時間應遠低於使用 DynamoDB 的已耗用時間。

1. 執行以下 Node.js 程式，刪除 `TryDaxTable`。

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

如需這些程式的詳細資訊，請參閱下列各節：
+ [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` 程式會建立資料表 (`TryDaxTable`)。本節剩餘的 Node.js 程式會依存此資料表。

```
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` 程式會將測試資料寫入 `TryDaxTable`。

```
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` 程式會在 `GetItem` 上執行 `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` 程式會在 `Query` 上執行 `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` 程式會在 `TryDaxTable` 上執行 `Scan` 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` 程式會刪除 `TryDaxTable`。請在完成測試之後執行此程式。

```
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)
    );
  }
});
```