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# Client Configuration
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The Fabric8 Kubernetes Client provides flexible configuration options for connecting to Kubernetes clusters. Configuration can be auto-discovered from kubeconfig files, environment variables, or explicitly set through the Config and ConfigBuilder classes.
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## Core Configuration Classes
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### Config Class
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```java { .api }
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public class Config {
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    // Factory methods
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    public static Config empty();
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    public static Config autoConfigure(String context);
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    public static Config fromKubeconfig(String kubeconfigContents);
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    public static Config fromKubeconfig(File kubeconfigFile);
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    public static Config fromKubeconfig(String context, File kubeconfig);
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    public static ConfigBuilder builder();
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    // Connection settings
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    public String getMasterUrl();
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    public String getApiVersion();
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    public String getNamespace();
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    // Authentication
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    public String getUsername();
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    public String getPassword();
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    public String getOauthToken();
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    public String getCaCertFile();
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    public String getCaCertData();
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    public String getClientCertFile();
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    public String getClientCertData();
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    public String getClientKeyFile();
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    public String getClientKeyData();
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    public String getClientKeyAlgo();
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    public String getClientKeyPassphrase();
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    // Timeouts and limits
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    public int getConnectionTimeout();
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    public int getRequestTimeout();
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    public int getUploadRequestTimeout();
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    public int getWatchReconnectInterval();
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    public int getWatchReconnectLimit();
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    public long getWebsocketPingInterval();
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    // Security settings
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    public Boolean isTrustCerts();
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    public Boolean isDisableHostnameVerification();
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    // HTTP settings
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    public String getHttpProxy();
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    public String getHttpsProxy();
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    public String[] getNoProxy();
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    public String getProxyUsername();
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    public String getProxyPassword();
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    // Configuration management
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    public Config refresh();
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    public File getFile();
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    public File getFileWithCluster();
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    public File getFileWithAuthInfo();
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    public List<NamedContext> getContexts();
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    public NamedContext getCurrentContext();
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    public void setCurrentContext(NamedContext context);
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}
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```
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### ConfigBuilder Class
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```java { .api }
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public class ConfigBuilder {
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    // Connection configuration
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    public ConfigBuilder withMasterUrl(String masterUrl);
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    public ConfigBuilder withApiVersion(String apiVersion);
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    public ConfigBuilder withNamespace(String namespace);
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    // Authentication
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    public ConfigBuilder withUsername(String username);
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    public ConfigBuilder withPassword(String password);
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    public ConfigBuilder withOauthToken(String oauthToken);
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    public ConfigBuilder withCaCertFile(String caCertFile);
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    public ConfigBuilder withCaCertData(String caCertData);
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    public ConfigBuilder withClientCertFile(String clientCertFile);
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    public ConfigBuilder withClientCertData(String clientCertData);
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    public ConfigBuilder withClientKeyFile(String clientKeyFile);
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    public ConfigBuilder withClientKeyData(String clientKeyData);
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    public ConfigBuilder withClientKeyAlgo(String clientKeyAlgo);
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    public ConfigBuilder withClientKeyPassphrase(String clientKeyPassphrase);
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    // Timeout configuration
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    public ConfigBuilder withConnectionTimeout(int connectionTimeout);
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    public ConfigBuilder withRequestTimeout(int requestTimeout);
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    public ConfigBuilder withUploadRequestTimeout(int uploadRequestTimeout);
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    public ConfigBuilder withWatchReconnectInterval(int watchReconnectInterval);
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    public ConfigBuilder withWatchReconnectLimit(int watchReconnectLimit);
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    public ConfigBuilder withWebsocketPingInterval(long websocketPingInterval);
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    // Security configuration
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    public ConfigBuilder withTrustCerts(Boolean trustCerts);
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    public ConfigBuilder withDisableHostnameVerification(Boolean disableHostnameVerification);
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    // HTTP proxy configuration
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    public ConfigBuilder withHttpProxy(String httpProxy);
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    public ConfigBuilder withHttpsProxy(String httpsProxy);
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    public ConfigBuilder withNoProxy(String[] noProxy);
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    public ConfigBuilder withProxyUsername(String proxyUsername);
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    public ConfigBuilder withProxyPassword(String proxyPassword);
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    // Build the configuration
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    public Config build();
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}
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```
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## Client Builder
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### KubernetesClientBuilder Class
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```java { .api }
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public class KubernetesClientBuilder {
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    public KubernetesClientBuilder withConfig(Config config);
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    public KubernetesClientBuilder withConfig(String config);
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    public KubernetesClientBuilder withConfig(InputStream config);
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    public KubernetesClientBuilder withHttpClientFactory(HttpClient.Factory factory);
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    public KubernetesClientBuilder withTaskExecutor(Executor executor);
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    public KubernetesClientBuilder withTaskExecutorSupplier(ExecutorSupplier executorSupplier);
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    public KubernetesClientBuilder withHttpClientBuilderConsumer(Consumer<HttpClient.Builder> consumer);
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    public KubernetesClientBuilder withKubernetesSerialization(KubernetesSerialization kubernetesSerialization);
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    public KubernetesClient build();
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}
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```
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## Usage Examples
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### Auto-Configuration
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The simplest way to create a client using auto-discovered configuration:
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```java
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try (KubernetesClient client = new KubernetesClientBuilder().build()) {
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    // Client automatically discovers configuration from:
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    // 1. System properties
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    // 2. Environment variables
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    // 3. ~/.kube/config file
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    // 4. Service account token (when running in cluster)
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    String namespace = client.getConfiguration().getNamespace();
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    System.out.println("Connected to cluster, default namespace: " + namespace);
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}
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```
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### Custom Configuration
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Creating a client with explicit configuration:
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```java
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Config config = new ConfigBuilder()
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    .withMasterUrl("https://kubernetes.example.com:6443")
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    .withNamespace("my-namespace")
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    .withOauthToken("my-token")
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    .withTrustCerts(true)
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    .withConnectionTimeout(10000)
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    .withRequestTimeout(30000)
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    .build();
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try (KubernetesClient client = new KubernetesClientBuilder()
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    .withConfig(config)
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    .build()) {
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    // Use the client with custom configuration
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    PodList pods = client.pods().list();
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}
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```
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### Configuration from Kubeconfig
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Loading configuration from a specific kubeconfig file:
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```java
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Config config = Config.fromKubeconfig("/path/to/kubeconfig");
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try (KubernetesClient client = new KubernetesClientBuilder()
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    .withConfig(config)
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    .build()) {
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    // Client uses the specified kubeconfig
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    NodeList nodes = client.nodes().list();
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}
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```
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### Certificate-Based Authentication
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Configuring client certificate authentication:
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```java
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Config config = new ConfigBuilder()
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    .withMasterUrl("https://kubernetes.example.com:6443")
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    .withCaCertFile("/path/to/ca.crt")
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    .withClientCertFile("/path/to/client.crt")
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    .withClientKeyFile("/path/to/client.key")
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    .withClientKeyPassphrase("key-passphrase")
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    .build();
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try (KubernetesClient client = new KubernetesClientBuilder()
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    .withConfig(config)
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    .build()) {
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    // Client uses certificate authentication
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    ServiceList services = client.services().list();
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}
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```
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### Proxy Configuration
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Configuring HTTP proxy settings:
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```java
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Config config = new ConfigBuilder()
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    .withMasterUrl("https://kubernetes.example.com:6443")
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    .withHttpProxy("http://proxy.example.com:8080")
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    .withHttpsProxy("https://proxy.example.com:8080")
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    .withNoProxy(new String[]{"localhost", "127.0.0.1", "*.local"})
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    .withProxyUsername("proxy-user")
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    .withProxyPassword("proxy-password")
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    .build();
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try (KubernetesClient client = new KubernetesClientBuilder()
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    .withConfig(config)
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    .build()) {
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    // Client uses proxy settings
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    NamespaceList namespaces = client.namespaces().list();
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}
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```
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### Timeout Configuration
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Configuring various timeout settings:
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```java
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Config config = new ConfigBuilder()
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    .withConnectionTimeout(15000)     // 15 seconds to establish connection
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    .withRequestTimeout(60000)        // 60 seconds for regular requests
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    .withUploadRequestTimeout(300000) // 5 minutes for upload requests
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    .withWatchReconnectInterval(1000) // 1 second between watch reconnect attempts
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    .withWatchReconnectLimit(10)      // Maximum 10 reconnect attempts
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    .withWebsocketPingInterval(30000) // 30 seconds between websocket pings
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    .build();
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try (KubernetesClient client = new KubernetesClientBuilder()
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    .withConfig(config)
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    .build()) {
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    // Client uses custom timeout settings
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    ConfigMapList configMaps = client.configMaps().list();
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}
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```
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## Configuration Sources
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The client configuration is auto-discovered from multiple sources in the following order of precedence:
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1. **System Properties**: Java system properties starting with `kubernetes.`
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2. **Environment Variables**: Environment variables like `KUBERNETES_MASTER`, `KUBERNETES_NAMESPACE`, etc.
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3. **Kubeconfig File**: Default location `~/.kube/config` or specified by `KUBECONFIG` environment variable
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4. **Service Account**: When running inside a Kubernetes pod, uses the mounted service account token
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### Environment Variables
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Common environment variables for configuration:
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- `KUBERNETES_MASTER` - Kubernetes API server URL
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- `KUBERNETES_NAMESPACE` - Default namespace
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- `KUBERNETES_AUTH_TOKEN` - Authentication token
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- `KUBERNETES_CA_CERTIFICATE_FILE` - CA certificate file path
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- `KUBERNETES_CLIENT_CERTIFICATE_FILE` - Client certificate file path
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- `KUBERNETES_CLIENT_KEY_FILE` - Client key file path
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- `KUBERNETES_TRUST_CERTIFICATES` - Trust all certificates (true/false)
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- `KUBERNETES_DISABLE_HOSTNAME_VERIFICATION` - Disable hostname verification (true/false)
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### System Properties
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Corresponding system properties use the `kubernetes.` prefix:
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- `kubernetes.master` - Kubernetes API server URL
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- `kubernetes.namespace` - Default namespace
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- `kubernetes.auth.token` - Authentication token
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- `kubernetes.certs.ca.file` - CA certificate file path
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- `kubernetes.certs.client.file` - Client certificate file path
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- `kubernetes.certs.client.key.file` - Client key file path
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- `kubernetes.trust.certificates` - Trust all certificates
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- `kubernetes.disable.hostname.verification` - Disable hostname verification