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
DAX SDK for Node.js v3.x 相容於 [AWS SDK for Node.js v3.x](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/introduction/)。DAX SDK for Node.js v3.x 支援使用[彙總](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/introduction/#high-level-concepts)用戶端。請注意，DAX 不支援建立裸機用戶端。如需不支援功能的詳細資訊，請參閱 [功能與 AWS SDK V3 不相同](#DAX.client.run-application-nodejs-3-not-in-parity)。
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/v0.40.1/install.sh | bash
```
1. 使用 nvm 安裝 Node.js。
```
nvm install 18
```
1. 使用 nvm 來使用 Node 18
```
nvm use 18
```
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 v18.x.x`
1. 使用節點套件管理工具 (`npm`) 安裝 DaxDocument Node.js 用戶端。
```
npm install @amazon-dax-sdk/lib-dax
```
## TryDax 範本程式碼
若要評估 DynamoDB Accelerator (DAX) 的效能優勢，請依照下列步驟執行範例測試，以比較標準 DynamoDB 和 DAX 叢集之間的讀取操作時間。
1. 在設定工作空間並將 `lib-dax` 安裝為依存項目之後，請將 [TryDax.js](DAX.client.tutorial-TryDax.md) 複製到您的專案中。
1. 針對 DAX 叢集執行程式。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"
}
```
1. 現在請將叢集端點指定為命令列參數以執行程式。
```
node TryDax.js dax://my-cluster.l6fzcv.dax-clusters.us-east-1.amazonaws.com
```
您應該會看到類似下列的輸出：
```
Attempting to create table; please wait...
Successfully created table. Table status: ACTIVE
Writing data to the table...
Writing 20 items for partition key: 1
Writing 20 items for partition key: 2
Writing 20 items for partition key: 3
...
Running GetItem Test
Total time: 153555.10 µs - Avg time: 383.89 µs
Total time: 44679.96 µs - Avg time: 111.70 µs
Total time: 36885.86 µs - Avg time: 92.21 µs
Total time: 32467.25 µs - Avg time: 81.17 µs
Total time: 32202.60 µs - Avg time: 80.51 µs
Running Query Test
Total time: 14869.25 µs - Avg time: 2973.85 µs
Total time: 3036.31 µs - Avg time: 607.26 µs
Total time: 2468.92 µs - Avg time: 493.78 µs
Total time: 2062.53 µs - Avg time: 412.51 µs
Total time: 2178.22 µs - Avg time: 435.64 µs
Running Scan Test
Total time: 2395.88 µs - Avg time: 479.18 µs
Total time: 2207.16 µs - Avg time: 441.43 µs
Total time: 2443.14 µs - Avg time: 488.63 µs
Total time: 2038.24 µs - Avg time: 407.65 µs
Total time: 1972.17 µs - Avg time: 394.43 µs
Running Pagination Test
Scan Pagination
[
{ pk: 1, sk: 1, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 2, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 3, someData: 'XXXXXXXXXX' }
]
[
{ pk: 1, sk: 4, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 5, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 6, someData: 'XXXXXXXXXX' }
]
...
Query Pagination
[
{ pk: 1, sk: 1, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 2, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 3, someData: 'XXXXXXXXXX' }
]
[
{ pk: 1, sk: 4, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 5, someData: 'XXXXXXXXXX' },
{ pk: 1, sk: 6, someData: 'XXXXXXXXXX' }
]
...
Attempting to delete table; please wait...
Successfully deleted table.
```
請記下計時資訊。`GetItem`、`Query`、`Scan` 測試所需的微秒數。
1. 在此情況下，您會針對 DAX 叢集執行程式。現在您將再次執行該程式，但此次針對的是 DynamoDB。
1. 現在重新執行程式，但這一次叢集端點 URL 並沒有作為命令列參數。
```
node TryDax.js
```
查看輸出，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。
## 功能與 AWS SDK V3 不相同
+ [裸機](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/introduction/#high-level-concepts)用戶端：Dax Node.js V3 不支援裸機用戶端。
```
const dynamoDBClient = new DynamoDBClient({ region: 'us-west-2' });
const regularParams = {
TableName: 'TryDaxTable',
Key: {
pk: 1,
sk: 1
}
};
// The DynamoDB client supports the send operation.
const dynamoResult = await dynamoDBClient.send(new GetCommand(regularParams));
// However, the DaxDocument client does not support the send operation.
const daxClient = new DaxDocument({
endpoints: ['your-dax-endpoint'],
region: 'us-west-2',
});
const params = {
TableName: 'TryDaxTable',
Key: {
pk: 1,
sk: 1
}
};
// This will throw an error - send operation is not supported for DAX. Please refer to documentation.
const result = await daxClient.send(new GetCommand(params));
console.log(result);
```
+ [中介軟體堆疊](https://aws.amazon.com/blogs/developer/middleware-stack-modular-aws-sdk-js/)：Dax Node.js V3 不支援使用中介軟體函式。
```
const dynamoDBClient = new DynamoDBClient({ region: 'us-west-2' });
// The DynamoDB client supports the middlewareStack.
dynamoDBClient.middlewareStack.add(
(next, context) =>> async (args) => {
console.log("Before operation:", args);
const result = await next(args);
console.log("After operation:", result);
return result;
},
{
step: "initialize", // or "build", "finalizeRequest", "deserialize"
name: "loggingMiddleware",
}
);
// However, the DaxDocument client does not support the middlewareStack.
const daxClient = new DaxDocument({
endpoints: ['your-dax-endpoint'],
region: 'us-west-2',
});
// This will throw an error - custom middleware and middlewareStacks are not supported for DAX. Please refer to documentation.
daxClient.middlewareStack.add(
(next, context) => async (args) => {
console.log("Before operation:", args);
const result = await next(args);
console.log("After operation:", result);
return result;
},
{
step: "initialize", // or "build", "finalizeRequest", "deserialize"
name: "loggingMiddleware",
}
);
```