### Start Mock Server

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

Navigate to the test directory and run the mock server script. It uses non-privileged ports and automatically generates a self-signed certificate on first run. Press Ctrl+C to stop.

```bash
cd AlicloudHttpDNSTests/Network
python3 mock_server.py
```

--------------------------------

### Example: Combined Global and Service-Level Logging with Custom Handler

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

This comprehensive example demonstrates enabling global logging with HttpdnsLog and setting a custom logger for a specific HttpDnsService instance, all within the DEBUG build configuration. It initializes the service and configures logging for both levels.

```objc
@interface AppDelegate () 
@property (nonatomic, strong) HttpDnsService *httpdnsService;
@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application 
    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    
    // 初始化HTTPDNS
    self.httpdnsService = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                         secretKey:@"secret"];
    
    // 只在DEBUG模式启用日志
#ifdef DEBUG
    [HttpdnsLog enableLog];  // 启用全局日志
    
    // 同时设置自定义logger用于服务实例
    [self.httpdnsService setLogHandler:[[CustomLogger alloc] init]];
    [self.httpdnsService setLogEnabled:YES];
#endif
    
    return YES;
}

@end
```

--------------------------------

### Example: Runtime Log Toggle with UI Switch

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

This example shows how to implement a UI switch in a view controller to dynamically enable or disable both global HTTPDNS logging and service-level logging at runtime. It updates the switch's state based on the current logging status.

```objc
@interface DebugViewController : UITableViewController
@property (nonatomic, strong) HttpDnsService *service;
@end

@implementation DebugViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 添加日志开关控制
    UISwitch *logSwitch = [[UISwitch alloc] init];
    [logSwitch addTarget:self action:@selector(toggleLog:) forControlEvents:UIControlEventValueChanged];
    logSwitch.on = [HttpdnsLog isEnabled];
    
    UIBarButtonItem *item = [[UIBarButtonItem alloc] initWithCustomView:logSwitch];
    self.navigationItem.rightBarButtonItem = item;
}

- (void)toggleLog:(UISwitch *)sender {
    if (sender.on) {
        [HttpdnsLog enableLog];
        [self.service setLogEnabled:YES];
    } else {
        [HttpdnsLog disableLog];
        [self.service setLogEnabled:NO];
    }
}

@end
```

--------------------------------

### Example: Enable and Use SDK Logging

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Demonstrates enabling global SDK logging using HttpdnsLog, then initializing HttpDnsService and performing a resolution. Logs will be output during the resolution process. Finally, it shows how to disable logging.

```objc
// 启用SDK日志
[HttpdnsLog enableLog];

// SDK此后输出日志到默认位置（Xcode控制台或系统日志）
HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                          secretKey:@"secret"];
HttpdnsResult *result = [service resolveHostSync:@"www.aliyun.com" 
                                       byIpType:HttpdnsQueryIPTypeAuto];
// 此时SDK会输出解析过程中的日志

// 禁用日志
[HttpdnsLog disableLog];
```

--------------------------------

### Install OpenSSL

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

If the 'openssl' command is not found, install it using your system's package manager.

```bash
# macOS (通常已预装)
brew install openssl

# Ubuntu/Debian
sudo apt-get install openssl

# CentOS/RHEL
sudo yum install openssl
```

--------------------------------

### Example: Enable Service-Level Logging with Custom Handler

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Shows how to enable logging for a specific HttpDnsService instance and set a custom log handler for its output. Logs will be directed through the custom handler during resolution.

```objc
HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                          secretKey:@"secret"];

// 启用此实例的日志
[service setLogEnabled:YES];

// 使用自定义日志处理器
[service setLogHandler:[[MyLogger alloc] init]];

// 进行解析操作，日志将通过自定义handler输出
HttpdnsResult *result = [service resolveHostSync:@"www.aliyun.com" 
                                       byIpType:HttpdnsQueryIPTypeAuto];

// 禁用此实例的日志
[service setLogEnabled:NO];
```

--------------------------------

### Example: Conditional Logging in Application Launch

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

This snippet demonstrates how to conditionally enable or disable SDK logging based on the build environment (DEBUG vs. Release) during application launch. It also shows the initialization of the HttpDnsService.

```objc
- (BOOL)application:(UIApplication *)application 
    didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    
#ifdef DEBUG
    // 开发调试时启用日志
    [HttpdnsLog enableLog];
#else
    // 生产环境禁用日志
    [HttpdnsLog disableLog];
#endif
    
    // 初始化HTTPDNS服务
    HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                              secretKey:@"secret"];
    
    return YES;
}
```

--------------------------------

### Example: Conditionally Enable Logging Based on User Defaults

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

This example shows how to enable or disable HTTPDNS logging dynamically based on a boolean value stored in NSUserDefaults, allowing for runtime configuration of logging behavior.

```objc
- (void)setupHttpDnsLogging {
    // 根据配置条件启用日志
    BOOL shouldLogHttpdns = [[NSUserDefaults standardUserDefaults] 
                             boolForKey:@"httpdns_debug_log"];
    
    if (shouldLogHttpdns) {
        [HttpdnsLog enableLog];
    } else {
        [HttpdnsLog disableLog];
    }
}
```

--------------------------------

### Enable Logging and Get Session ID

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Enable global logging and retrieve a session ID for a specific HTTPDNS service instance. This session ID is useful for correlating logs with support requests.

```Objective-C
[HttpdnsLog enableLog];

HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                         secretKey:@"secret"];
NSString *sessionId = [service getSessionId];
NSLog(@"HTTPDNS SessionId: %@", sessionId);

HttpdnsResult *result = [service resolveHostSync:@"www.aliyun.com" 
                                       byIpType:HttpdnsQueryIPTypeAuto];
// 使用sessionId和结果联系技术支持
```

--------------------------------

### CREATING to IN_USE Transition

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Handles the transition of a new connection from the CREATING state to the IN_USE state. This occurs when a new connection is created, successfully opened, and added to the pool.

```objc
newConnection.inUse = YES;
newConnection.lastUsedDate = now;
[pool addObject:newConnection];  // 加入池
```

--------------------------------

### 构建脚本基本用法

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/ios-xcframework-build-script/README.md

展示了 Workspace 和 Project 模式下构建脚本的基本调用格式。

```bash
# Workspace 模式
./build.sh framework_id framework_name build_config build_dir [workspace_name]

# Project 模式
./build_proj.sh framework_id framework_name build_config build_dir [project_name]
```

--------------------------------

### 构建脚本使用示例

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/ios-xcframework-build-script/README.md

针对不同场景（如名称相同、名称不同、多 SDK 构建、Project 模式）的脚本调用示例。

```bash
./build.sh MySDK_1.0.0 MySDK Release /Users/developer/output
```

```bash
./build.sh MySDK_1.0.0 MySDK Release /Users/developer/output MyProject
```

```bash
# 构建第一个 SDK
./build.sh SDK1_1.0.0 SDK1 Release /Users/developer/output SharedWorkspace

# 构建第二个 SDK
./build.sh SDK2_1.0.0 SDK2 Release /Users/developer/output SharedWorkspace
```

```bash
./build_proj.sh MySDK_1.0.0 MySDK Release /Users/developer/output MyProject
```

--------------------------------

### 运行 Xcode 测试命令

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/README.md

使用 xcodebuild 命令行工具执行单元测试、集成测试或单个测试用例。

```bash
xcodebuild test \
  -workspace AlicloudHttpDNS.xcworkspace \
  -scheme AlicloudHttpDNSTests \
  -destination 'platform=iOS Simulator,name=iPhone 15' \
  -only-testing:AlicloudHttpDNSTests/HttpdnsNWHTTPClientTests
```

```bash
xcodebuild test \
  -workspace AlicloudHttpDNS.xcworkspace \
  -scheme AlicloudHttpDNSTests \
  -destination 'platform=iOS Simulator,name=iPhone 15' \
  -only-testing:AlicloudHttpDNSTests/HttpdnsNWHTTPClientIntegrationTests
```

```bash
xcodebuild test \
  -workspace AlicloudHttpDNS.xcworkspace \
  -scheme AlicloudHttpDNSTests \
  -destination 'platform=iOS Simulator,name=iPhone 15' \
  -only-testing:AlicloudHttpDNSTests/HttpdnsNWHTTPClientTests/testParseHTTPHeaders_ValidResponse_Success
```

--------------------------------

### IN_USE to IDLE Transition (Normal Return)

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Handles the normal return of a connection from the IN_USE state to the IDLE state. It ensures the connection is not invalidated and is added back to the pool if not already present, followed by pruning the pool.

```objc
if (shouldClose || connection.isInvalidated) {
    // → INVALIDATED (见#4)
} else {
    connection.inUse = NO;
    connection.lastUsedDate = now;
    if (![pool containsObject:connection]) {
        [pool addObject:connection];  // 防止双重添加
    }
    [self pruneConnectionPool:pool referenceDate:now];
}
```

--------------------------------

### 脚本权限设置

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/ios-xcframework-build-script/README.md

解决执行权限问题的命令。

```bash
chmod +x build.sh
```

--------------------------------

### IDLE to IN_USE Transition (Connection Reuse)

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Manages the reuse of an idle connection. It iterates through the pool to find an available and viable connection, marking it as in use and updating its last used date.

```objc
for (HttpdnsNWReusableConnection *candidate in pool) {
    if (!candidate.inUse && [candidate isViable]) {
        candidate.inUse = YES;
        candidate.lastUsedDate = now;
        connection = candidate;
        break;
    }
}
```

--------------------------------

### Trace Network Issues with Logs

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Enable logging and perform a host resolution to observe network-related logs. If resolution fails, check the SDK logs for detailed error messages such as timeouts or DNS failures.

```Objective-C
[HttpdnsLog enableLog];

// 执行解析，观察日志输出
HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                         secretKey:@"secret"];
HttpdnsResult *result = [service resolveHostSync:@"www.aliyun.com" 
                                       byIpType:HttpdnsQueryIPTypeAuto];

if (!result) {
    // 查看日志中的错误信息，如超时、DNS failure等
    NSLog(@"Resolution failed, check logs above for details");
}
```

--------------------------------

### CI/CD 集成示例

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/ios-xcframework-build-script/README.md

将构建脚本集成到 CI/CD 流程中的完整 Bash 脚本示例。

```bash
#!/bin/bash

print_info() {
  echo -e "\033[32m[INFO]\033[0m $1"
}

print_error() {
  echo -e "\033[31m[ERROR]\033[0m $1"
}

# 设置构建参数
FRAMEWORK_ID="MySDK_$(date +%Y%m%d_%H%M%S)"
FRAMEWORK_NAME="MySDK"
BUILD_CONFIG="Release"
BUILD_DIR="/tmp/build"
WORKSPACE_NAME="MyProject"

print_info "开始构建 XCFramework..."

# 清理并创建构建目录
rm -rf Build && mkdir Build

# 执行构建（从项目根目录执行）
sh ios-xcframework-build-script/build.sh $FRAMEWORK_ID $FRAMEWORK_NAME $BUILD_CONFIG $BUILD_DIR $WORKSPACE_NAME

if [[ $? -eq 0 ]]; then
  print_info "$FRAMEWORK_NAME XCFramework 构建完成!"
  print_info "Framework ID: $FRAMEWORK_ID"
  print_info "构建目录: $BUILD_DIR"
else
  print_error "$FRAMEWORK_NAME XCFramework 构建失败!"
  exit 1
fi
```

--------------------------------

### Verify Cache Behavior with Logs

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Enable logging and persistent cache. Observe logs for network requests on the first resolution and cache hits on subsequent resolutions for the same host.

```Objective-C
[HttpdnsLog enableLog];

HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                         secretKey:@"secret"];
[service setPersistentCacheIPEnabled:YES];

// 第一次调用，应该会看到网络请求日志
HttpdnsResult *result1 = [service resolveHostSync:@"www.aliyun.com" 
                                        byIpType:HttpdnsQueryIPTypeAuto];

// 第二次调用，应该看到缓存命中日志
HttpdnsResult *result2 = [service resolveHostSync:@"www.aliyun.com" 
                                        byIpType:HttpdnsQueryIPTypeAuto];
```

--------------------------------

### Run Integration Tests

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

Execute integration tests using xcodebuild. You can run all tests or specify a single test case. Ensure you are in the project's root directory.

```bash
cd ~/Project/iOS/alicloud-ios-sdk-httpdns

xcodebuild test \
  -workspace AlicloudHttpDNS.xcworkspace \
  -scheme AlicloudHttpDNSTests \
  -destination 'platform=iOS Simulator,name=iPhone 15' \
  -only-testing:AlicloudHttpDNSTests/HttpdnsNWHTTPClientIntegrationTests
```

```bash
xcodebuild test \
  -workspace AlicloudHttpDNS.xcworkspace \
  -scheme AlicloudHttpDNSTests \
  -destination 'platform=iOS Simulator,name=iPhone 15' \
  -only-testing:AlicloudHttpDNSTests/HttpdnsNWHTTPClientIntegrationTests/testConcurrency_ParallelRequestsSameHost_AllSucceed
```

--------------------------------

### Enable SDK Logging

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Call this method to enable the SDK's internal log output. Logs will be directed to the Xcode console or system log.

```objc
+ (void)enableLog;
```

--------------------------------

### HttpdnsNWHTTPClientTestHelper 辅助工具

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/README.md

提供用于构造 HTTP 响应、处理 Chunked 编码及生成测试数据的工具方法。

```objc
// 构造标准 HTTP 响应
+ (NSData *)createHTTPResponseWithStatus:(NSInteger)statusCode
                              statusText:(NSString *)statusText
                                 headers:(NSDictionary *)headers
                                    body:(NSData *)body;

// 构造 chunked 响应
+ (NSData *)createChunkedHTTPResponseWithStatus:(NSInteger)statusCode
                                        headers:(NSDictionary *)headers
                                         chunks:(NSArray<NSData *> *)chunks;
```

```objc
+ (NSData *)encodeChunk:(NSData *)data;
+ (NSData *)encodeLastChunk;
```

```objc
+ (NSData *)randomDataWithSize:(NSUInteger)size;
+ (NSData *)jsonBodyWithDictionary:(NSDictionary *)dictionary;
```

--------------------------------

### State Transition Sequence Verification

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Verifies the sequence of state changes from creation to reuse.

```objc
// 验证转换序列
[client resetPoolStatistics];

// CREATING → IN_USE
response1 = [client performRequest...];
XCTAssertEqual(creationCount, 1);

// IN_USE → IDLE
[NSThread sleepForTimeInterval:0.5];
XCTAssertEqual(poolCount, 1);

// IDLE → IN_USE (reuse)
response2 = [client performRequest...];
XCTAssertEqual(reuseCount, 1);
```

--------------------------------

### Enable Debug Logging in Mock Server

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

Uncomment the `log_message` method in `mock_server.py` to enable detailed logging for debugging purposes.

```python
def log_message(self, format, *args):
    print(f"[{self.address_string()}] {format % args}")
```

--------------------------------

### 构建输出目录结构

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/ios-xcframework-build-script/README.md

构建成功后生成的目录结构示意。

```text
build_dir/
├── framework_id.zip                    # 打包的 ZIP 文件
└── framework_id/                       # Framework 目录
    └── framework_name.xcframework/     # XCFramework 文件
        ├── ios-arm64/                  # iOS 设备端
        └── ios-arm64_x86_64-simulator/ # iOS 模拟器端
```

--------------------------------

### enableLog

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Enables the SDK's internal log output. Once enabled, the SDK will output internal log information to the default location (Xcode console or system log).

```APIDOC
## enableLog

### Description
Enables the SDK's internal log output. Once enabled, the SDK will output internal log information.

### Method
`+ (void)enableLog;`

### Parameters
This method takes no parameters.

### Response
This method returns void.

### Example
```objc
[HttpdnsLog enableLog];
```
```

--------------------------------

### Find Process Using Port

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

If a port is already in use, use these commands to find the process ID (PID) and then terminate it using 'sudo kill -9 <PID>'.

```bash
sudo lsof -i :80
sudo lsof -i :443
```

--------------------------------

### Global and Service-Specific Logging Configuration

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Configure logging infrastructure globally using `[HttpdnsLog enableLog]` and then enable/disable logging for a specific `HttpDnsService` instance using `setLogEnabled:`. A custom logger can also be assigned to a service instance.

```Objective-C
// 全局启用日志基础设施
[HttpdnsLog enableLog];

// 为特定service实例配置日志处理
HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                         secretKey:@"secret"];
[service setLogHandler:[[CustomLogger alloc] init]];  // 自定义处理
[service setLogEnabled:YES];  // 启用此实例的日志

// 结果：此service的日志将通过CustomLogger处理
```

--------------------------------

### Return Connection to Pool

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Logic for returning a connection to a specific pool key, noting potential for pool contamination if the key is incorrect.

```objc
- (void)returnConnection:(HttpdnsNWReusableConnection *)connection
                   forKey:(NSString *)key
              shouldClose:(BOOL)shouldClose {
    // ...
    NSMutableArray<HttpdnsNWReusableConnection *> *pool = self.connectionPool[key];
    // 会添加到错误的池!
}
```

--------------------------------

### Direct State Check Verification

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Basic assertions to verify connection state properties and pool counts.

```objc
// 验证状态属性
XCTAssertTrue(connection.inUse);
XCTAssertFalse(connection.isInvalidated);
XCTAssertEqual([poolCount], expectedCount);
```

--------------------------------

### Handling Stale Connections in Pool

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Illustrates the current code's behavior when encountering stale connections in the pool during dequeue operations. It checks `isViable` to reuse only valid connections, otherwise creating a new one. This highlights a potential risk if `isViable` checks are not comprehensive.

```objc
for (HttpdnsNWReusableConnection *candidate in pool) {
    if (!candidate.inUse && [candidate isViable]) {  // ← isViable 检查
        // 只复用有效连接
    }
}
// 如果所有连接都 !isViable，会创建新连接
```

--------------------------------

### Conditional Logging for Debug and Release Builds

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Conditionally enable logging for DEBUG builds and disable it for RELEASE builds to optimize performance in production environments. This is a common best practice for managing SDK logging.

```Objective-C
#ifdef DEBUG
    [HttpdnsLog enableLog];
#else
    [HttpdnsLog disableLog];
#endif
```

--------------------------------

### Add New Endpoint to Mock Server

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

To add a new endpoint, modify the `do_GET` method in `mock_server.py` and implement a handler function for your custom endpoint.

```python
def do_GET(self):
    path = urlparse(self.path).path

    if path == '/your-new-endpoint':
        self._handle_your_endpoint()
    # ... 其他 endpoints

def _handle_your_endpoint(self):
    """处理自定义 endpoint"""
    data = {'custom': 'data'}
    self._send_json(200, data)
```

--------------------------------

### Test Case: Verifying Pool State After Single Timeout

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/TIMEOUT_ANALYSIS.md

This test case initiates a request with a short timeout to simulate a timeout scenario. It then asserts that the timed-out connection is removed from the pool and verifies overall connection counts.

```Objective-C
[client resetPoolStatistics];

// 发起超时请求
NSError *error = nil;
HttpdnsNWHTTPClientResponse *response = [client performRequestWithURLString:@"http://127.0.0.1:11080/delay/10"
                                                                   userAgent:@"TimeoutTest"
                                                                     timeout:1.0
                                                                       error:&error];

XCTAssertNil(response);
XCTAssertNotNil(error);

// 验证池状态
NSString *poolKey = @"127.0.0.1:11080:tcp";
XCTAssertEqual([client connectionPoolCountForKey:poolKey], 0, @"Timed-out connection should be removed");
XCTAssertEqual([client totalConnectionCount], 0, @"No connections should remain");
XCTAssertEqual(client.connectionCreationCount, 1, @"Should have created 1 connection");
XCTAssertEqual(client.connectionReuseCount, 0, @"No reuse for timed-out connection");
```

--------------------------------

### Handle Connection Open Failure

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Invalidates and discards a connection if it fails to open within the timeout period.

```objc
if (![newConnection openWithTimeout:timeout error:error]) {
    [newConnection invalidate];  // ← 立即失效
    return nil;                  // ← 不加入池
}
```

--------------------------------

### IN_USE/IDLE to INVALIDATED Transition

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Handles the invalidation of a connection, moving it to the INVALIDATED state. This is triggered by conditions like `shouldClose` being true or the connection already being marked as invalidated.

```objc
if (shouldClose || connection.isInvalidated) {
    [connection invalidate];
    [pool removeObject:connection];
}
```

--------------------------------

### Modify Mock Server Ports

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/MOCK_SERVER.md

If ports are occupied, you can modify the mock_server.py script to use different ports. Remember to update the test code URLs accordingly.

```python
# 修改端口号（同时需要更新测试代码中的 URL）
run_http_server(port=8080)
run_https_server(port=8443)
```

--------------------------------

### Test Case for Stale Connection Scenario

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

A placeholder for a test case designed to verify the handling of stale connections within the pool. This test aims to ensure that the system correctly skips stale connections and proceeds to create a new one when necessary.

```objc
testStateTransition_StaleConnectionInPool_SkipsAndCreatesNew
```

--------------------------------

### HttpdnsNWHTTPClient.m: Timeout Handling Logic

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/TIMEOUT_ANALYSIS.md

This snippet shows the timeout handling flow within HttpdnsNWHTTPClient.m. If a raw response is not received, the connection is returned to the pool and marked for closure.

```Objective-C
if (!rawResponse) {
    [self returnConnection:connection forKey:poolKey shouldClose:YES];
    // 返回 nil，error 设置
}
```

--------------------------------

### Prevent Double Return of Connections

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Checks if a connection is already in the pool before adding it to prevent duplicate entries.

```objc
if (![pool containsObject:connection]) {
    [pool addObject:connection];  // ← 防止重复添加
}
```

--------------------------------

### Connection State Properties

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Defines the properties that represent the state of a reusable connection within the pool: last used date, in-use status, and invalidated status.

```objc
@property (nonatomic, strong) NSDate *lastUsedDate;  // 最后使用时间
@property (nonatomic, assign) BOOL inUse;            // 是否正在被使用
@property (nonatomic, assign, getter=isInvalidated, readonly) BOOL invalidated;  // 是否已失效
```

--------------------------------

### Custom Log Level Control

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Implement a custom logger to selectively enable or disable logging for different levels (DEBUG, INFO, WARN, ERROR). This allows fine-grained control over log verbosity. The default configuration logs only WARN and ERROR messages.

```Objective-C
@interface SelectiveLogger : NSObject <HttpdnsLoggerProtocol>
@property (nonatomic, assign) BOOL logDebug;
@property (nonatomic, assign) BOOL logInfo;
@property (nonatomic, assign) BOOL logWarn;
@property (nonatomic, assign) BOOL logError;
@end

@implementation SelectiveLogger

- (instancetype)init {
    self = [super init];
    if (self) {
        // 默认只记录WARN和ERROR
        _logDebug = NO;
        _logInfo = NO;
        _logWarn = YES;
        _logError = YES;
    }
    return self;
}

- (void)log:(NSString *)logStr {
    BOOL shouldLog = NO;
    
    if ([logStr containsString:@"[DEBUG]"] && self.logDebug) {
        shouldLog = YES;
    } else if ([logStr containsString:@"[INFO]"] && self.logInfo) {
        shouldLog = YES;
    } else if ([logStr containsString:@"[WARN]"] && self.logWarn) {
        shouldLog = YES;
    } else if ([logStr containsString:@"[ERROR]"] && self.logError) {
        shouldLog = YES;
    }
    
    if (shouldLog) {
        NSLog(@"[HTTPDNS] %@", logStr);
    }
}

@end

// 使用
SelectiveLogger *logger = [[SelectiveLogger alloc] init];
logger.logDebug = YES;
logger.logInfo = YES;
logger.logWarn = YES;
logger.logError = YES;

HttpDnsService *service = [[HttpDnsService alloc] initWithAccountID:1000000 
                                                         secretKey:@"secret"];
[service setLogHandler:logger];
[service setLogEnabled:YES];
```

--------------------------------

### Test Requirement for Error During Use

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Identifier for the test case verifying connection invalidation on error.

```objc
testStateTransition_ErrorDuringUse_Invalidated
```

--------------------------------

### Pool Invariant Verification

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Iterates through all connection pools to ensure they do not exceed the maximum size.

```objc
// 验证池不变式
NSArray *keys = [client allConnectionPoolKeys];
for (NSString *key in keys) {
    NSUInteger count = [client connectionPoolCountForKey:key];
    XCTAssertLessThanOrEqual(count, 4, @"Pool invariant: max 4 connections");
}
```

--------------------------------

### Test Requirement for Open Failure

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Identifier for the test case verifying that failed connections are not added to the pool.

```objc
testStateTransition_OpenFails_NotAddedToPool
```

--------------------------------

### HttpdnsNWHTTPClient.m: returnConnection:forKey:shouldClose: Logic

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/TIMEOUT_ANALYSIS.md

This function handles the return of a connection to the pool. If the connection should be closed or is invalidated, it is invalidated and removed from the pool.

```Objective-C
if (shouldClose || connection.isInvalidated) {
    [connection invalidate];    // 取消底层 nw_connection
    [pool removeObject:connection];  // 从池中移除
}
```

--------------------------------

### Check if Logging is Enabled

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Checks if the SDK's logging feature is currently enabled. Returns YES if enabled, NO otherwise.

```objc
+ (BOOL)isEnabled;
```

--------------------------------

### isEnabled

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Checks if the log functionality is currently enabled. Returns YES if logs are enabled, and NO if they are disabled.

```APIDOC
## isEnabled

### Description
Checks if the log functionality is currently enabled.

### Method
`+ (BOOL)isEnabled;`

### Parameters
This method takes no parameters.

### Response
- **BOOL**: YES if logs are enabled, NO if logs are disabled.

### Example
```objc
BOOL logEnabled = [HttpdnsLog isEnabled];
if (logEnabled) {
    NSLog(@"Log is enabled");
}
```
```

--------------------------------

### Test Requirement for Double Return

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Identifier for the test case verifying idempotent double return behavior.

```objc
testStateTransition_DoubleReturn_Idempotent
```

--------------------------------

### Test Requirement for Wrong Pool Key

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Identifier for the test case verifying isolation when returning to the wrong pool.

```objc
testStateTransition_ReturnToWrongPool_Isolated
```

--------------------------------

### Pruning Connection Pool (EXPIRED to INVALIDATED)

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Implements the logic to prune the connection pool, moving expired connections to the INVALIDATED state. It identifies idle connections exceeding the timeout and removes them, also enforcing a maximum pool size.

```objc
- (void)pruneConnectionPool:(NSMutableArray<HttpdnsNWReusableConnection *> *)pool referenceDate:(NSDate *)referenceDate {
    // ...
    NSMutableArray<HttpdnsNWReusableConnection *> *toRemove = [NSMutableArray array];
    for (HttpdnsNWReusableConnection *conn in pool) {
        if (conn.inUse) continue;  // 跳过使用中的

        NSTimeInterval idle = [referenceDate timeIntervalSinceDate:conn.lastUsedDate];
        if (idle > kHttpdnsNWHTTPClientConnectionIdleTimeout) {  // 30秒
            [toRemove addObject:conn];
        }
    }

    for (HttpdnsNWReusableConnection *conn in toRemove) {
        [conn invalidate];
        [pool removeObject:conn];
    }

    // 限制池大小 ≤ 4
    while (pool.count > kHttpdnsNWHTTPClientMaxIdleConnectionsPerHost) {
        HttpdnsNWReusableConnection *oldest = pool.firstObject;
        [oldest invalidate];
        [pool removeObject:oldest];
    }
}
```

--------------------------------

### Pool Overflow Removal Strategy

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Removes the oldest connection when the pool exceeds the maximum allowed capacity.

```objc
while (pool.count > kHttpdnsNWHTTPClientMaxIdleConnectionsPerHost) {
    HttpdnsNWReusableConnection *oldest = pool.firstObject;  // ← 移除最老的
    [oldest invalidate];
    [pool removeObject:oldest];
}
```

--------------------------------

### disableLog

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Disables the SDK's internal log output. This stops the SDK from logging internal information.

```APIDOC
## disableLog

### Description
Disables the SDK's internal log output.

### Method
`+ (void)disableLog;`

### Parameters
This method takes no parameters.

### Response
This method returns void.

### Example
```objc
[HttpdnsLog disableLog];
```
```

--------------------------------

### Test Requirement for Concurrent Dequeue and Prune

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Identifier for the test case verifying thread safety during pool operations.

```objc
testStateTransition_ConcurrentDequeueAndPrune_NoCorruption
```

--------------------------------

### Prune Connection Pool Concurrency Guard

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Skips connections currently in use during the pool pruning process to avoid race conditions.

```objc
- (void)pruneConnectionPool:... {
    for (HttpdnsNWReusableConnection *conn in pool) {
        if (conn.inUse) continue;  // ← 跳过使用中的
    }
}
```

--------------------------------

### Test Requirement for Pool Overflow

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Identifier for the test case verifying the removal of the oldest connection.

```objc
testStateTransition_PoolOverflow_RemovesOldest
```

--------------------------------

### Disable SDK Logging

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/_autodocs/api-reference/HttpdnsLog.md

Call this method to disable the SDK's internal log output.

```objc
+ (void)disableLog;
```

--------------------------------

### Handle Connection Invalidation During Use

Source: https://github.com/aliyun/alibabacloud-httpdns-ios-sdk/blob/master/AlicloudHttpDNSTests/Network/STATE_MACHINE_ANALYSIS.md

Invalidates a connection if a network error occurs during request transmission.

```objc
NSData *rawResponse = [connection sendRequestData:requestData ...];
if (!rawResponse) {
    [self returnConnection:connection forKey:poolKey shouldClose:YES];  // ← invalidated
}
```

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