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VladislavAtanasov95VladislavAtanasov95
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Transparent proxy: TP Loader Cloud SDK native integration
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‎cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/DefaultNetworkValidator.java‎

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package com.sap.cloud.sdk.cloudplatform.connectivity;
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import java.io.IOException;
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import java.net.InetSocketAddress;
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import java.net.Socket;
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import java.net.UnknownHostException;
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import javax.annotation.Nonnull;
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import com.sap.cloud.sdk.cloudplatform.connectivity.exception.DestinationAccessException;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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/**
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* Default implementation of {@link NetworkValidator} that performs TCP socket-based connectivity validation.
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*
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* <p>
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* This implementation uses standard Java socket connections to validate that a remote host and port combination is
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* reachable and accepting connections. It establishes a temporary TCP connection to the target endpoint and immediately
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* closes it upon successful establishment.
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*
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* <p>
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* <strong>Validation Process:</strong>
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* <ol>
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* <li>Creates a new TCP socket</li>
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* <li>Attempts to connect to the specified host and port with a timeout</li>
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* <li>Immediately closes the connection if successful</li>
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* <li>Throws appropriate exceptions for failures</li>
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* </ol>
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*
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* <p>
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* <strong>Timeout Configuration:</strong> The validation uses a fixed timeout of {@value #HOST_REACH_TIMEOUT}
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* milliseconds to prevent indefinite blocking on unreachable endpoints.
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*
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* <p>
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* <strong>Error Handling:</strong>
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* <ul>
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* <li>{@link UnknownHostException} - Host cannot be resolved to an IP address</li>
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* <li>{@link IOException} - Network connectivity issues or connection refused</li>
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* </ul>
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*
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* @see NetworkValidator
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* @see TransparentProxy
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* @since 5.24.0
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*/
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class DefaultNetworkValidator extends NetworkValidator {
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private static final int HOST_REACH_TIMEOUT = 5000;
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private static final Logger log = LoggerFactory.getLogger(DefaultNetworkValidator.class);
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/**
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* {@inheritDoc}
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*
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* <p>
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* This implementation creates a TCP socket connection to the specified host and port to verify connectivity. The
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* connection is immediately closed after successful establishment.
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*
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* @param host {@inheritDoc}
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* @param port {@inheritDoc}
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* @throws DestinationAccessException {@inheritDoc}
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* <p>
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* Specific error conditions:
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* <ul>
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* <li>Host resolution failure - when DNS lookup fails</li>
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* <li>Connection failure - when host is unreachable or port is closed</li>
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* <li>Network timeouts - when connection attempt exceeds timeout</li>
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* </ul>
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*/
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@Override
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void verifyHostConnectivity(@Nonnull final String host, final int port)
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throws DestinationAccessException {
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log.info("Verifying that transparent proxy host is reachable on {}:{}", host, port);
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try (Socket socket = new Socket()) {
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socket.connect(new InetSocketAddress(host, port), HOST_REACH_TIMEOUT);
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log.info("Successfully verified successfully that transparent proxy host is reachable on {}:{}", host, port);
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} catch (final UnknownHostException e) {
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throw new DestinationAccessException(String.format("Host [%s] could not be resolved", host), e);
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} catch (final IOException e) {
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throw new DestinationAccessException(
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String.format("Host [%s] on port [%d] is not reachable", host, port),
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e);
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}
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}
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}

‎cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/NetworkValidator.java‎

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package com.sap.cloud.sdk.cloudplatform.connectivity;
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import javax.annotation.Nonnull;
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import com.sap.cloud.sdk.cloudplatform.connectivity.exception.DestinationAccessException;
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/**
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* Abstract class for validating network connectivity to remote hosts and ports.
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*
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* <p>
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* This abstract class defines the contract for network validation implementations used by transparent proxy components
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* to ensure that registered hosts are reachable before completing the registration process.
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*
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* <p>
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* Implementations should perform actual network connectivity tests to verify that the specified host and port
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* combination is accessible from the current environment. This validation helps prevent registration of unreachable
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* endpoints that would cause runtime failures.
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*
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* <p>
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* <strong>Usage Context:</strong> This abstract class is primarily used by {@link TransparentProxy} during host
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* registration to validate network connectivity before accepting the registration.
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*
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* @see DefaultNetworkValidator
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* @see TransparentProxy
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* @since 5.24.0
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*/
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abstract class NetworkValidator
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{
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/**
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* Validates connectivity to the specified host and port combination.
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*
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* <p>
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* This method should attempt to establish a network connection to the given host and port to verify that the
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* endpoint is reachable and accepting connections. The validation should complete within a reasonable timeout
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* period.
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*
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* <p>
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* If the host cannot be resolved or the connection cannot be established, this method should throw a
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* {@link DestinationAccessException} with descriptive error information.
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*
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* @param host
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* the hostname or IP address to validate connectivity to. Must not be null or empty
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* @param port
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* the port number to test connectivity on. Should be a valid port number (1-65535)
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* @throws DestinationAccessException
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* if the host cannot be resolved, the connection cannot be established, or any other network-related
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* validation failure occurs
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* @throws IllegalArgumentException
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* if host is null or port is invalid
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*/
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abstract void verifyHostConnectivity( @Nonnull String host, int port )
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throws DestinationAccessException;
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}

‎cloudplatform/connectivity-destination-service/src/main/java/com/sap/cloud/sdk/cloudplatform/connectivity/TransparentProxy.java‎

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package com.sap.cloud.sdk.cloudplatform.connectivity;
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import java.net.URI;
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import java.net.URISyntaxException;
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import javax.annotation.Nonnull;
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import com.sap.cloud.sdk.cloudplatform.connectivity.exception.DestinationAccessException;
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import io.vavr.control.Try;
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import lombok.extern.slf4j.Slf4j;
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/**
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* A transparent proxy loader that enables routing traffic through a single registered gateway host.
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*
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* <p>
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* This class provides a mechanism to register a proxy gateway that will handle all destination requests transparently.
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* Once registered, all destination lookups will be routed through the configured gateway host and port.
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*
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* <p>
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* <strong>Key Features:</strong>
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* <ul>
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* <li>Single gateway registration - only one proxy can be registered at a time</li>
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* <li>Host validation - ensures hosts don't contain paths and are reachable</li>
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* <li>Automatic scheme normalization - defaults to HTTP if no scheme provided</li>
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* <li>Network connectivity validation before registration</li>
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* </ul>
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*
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* <p>
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* <strong>Usage Example:</strong>
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*
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* <pre>{@code
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* // Register with default port 80
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* TransparentProxy.register("gateway.svc.cluster.local");
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*
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* // Register with custom port
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* TransparentProxy.register("http://gateway.svc.cluster.local", 8080);
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* }</pre>
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*
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* <p>
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* <strong>Thread Safety:</strong> This class uses static state and is not thread-safe. Registration should be performed
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* during application initialization.
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*
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* @since 5.24.0
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*/
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@Slf4j
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public class TransparentProxy implements DestinationLoader {
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private static final Integer DEFAULT_PORT = 80;
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private static final String SCHEME_SEPARATOR = "://";
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private static final String HTTP_SCHEME = org.apache.http.HttpHost.DEFAULT_SCHEME_NAME + SCHEME_SEPARATOR;
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private static final String PATH_SEPARATOR = "/";
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private static final String PORT_SEPARATOR = ":";
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private static final String HOST_CONTAINS_PATH_ERROR_MESSAGE_TEMPLATE =
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"Host '%s' contains a path '%s'. Paths are not allowed in host registration.";
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static String uri;
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static NetworkValidator networkValidator = new DefaultNetworkValidator();
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/**
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* Registers a transparent proxy gateway using the default port 80.
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*
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* <p>
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* This method registers the specified host as a transparent proxy gateway that will handle all subsequent
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* destination requests. The host will be validated for reachability and must not contain any path components.
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*
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* <p>
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* If no scheme is provided, HTTP will be used by default. The final URI will be constructed as:
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* {@code <normalized-host>:80}
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*
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* @param host the gateway host to register (e.g., "gateway.svc.cluster.local") Must not contain paths or be null
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* @throws DestinationAccessException if the proxy is already registered, the host contains a path, or the host is not reachable on port 80
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* @throws IllegalArgumentException if host is null
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* @see #register(String, Integer)
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*/
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public static void register(@Nonnull final String host) {
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registerLoader(host, DEFAULT_PORT);
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}
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/**
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* Registers a transparent proxy gateway with a specified port.
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*
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* <p>
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* This method registers the specified host and port as a transparent proxy gateway that will handle all subsequent
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* destination requests. The host will be validated for reachability on the specified port and must not contain any
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* path components.
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*
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* <p>
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* If no scheme is provided, HTTP will be used by default. The final URI will be constructed as:
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* {@code <normalized-host>:<port>}
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*
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* @param host the gateway host to register (e.g., "gateway" or "<a href="http://gateway">...</a>") Must not contain
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* paths or be null
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* @param port the port number to use for the gateway connection. Must not be null and should be a valid port number
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* (1-65535)
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* @throws DestinationAccessException if the proxy is already registered, the host contains a path, or the host is not reachable on the
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* specified port
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* @throws IllegalArgumentException if host or port is null
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* @see #register(String)
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*/
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public static void register(@Nonnull final String host, @Nonnull final Integer port) {
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registerLoader(host, port);
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}
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private static void registerLoader(@Nonnull final String host, final Integer port) {
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if (uri != null) {
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throw new DestinationAccessException(
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"TransparentProxy is already registered. Only one registration is allowed.");
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}
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try {
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final String normalizedHost = normalizeHostWithScheme(host);
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final String hostForVerification = getHostForVerification(host, normalizedHost);
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verifyHostConnectivity(hostForVerification, port);
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uri = String.format("%s%s%d", normalizedHost, PORT_SEPARATOR, port);
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DestinationAccessor.prependDestinationLoader(new TransparentProxy());
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} catch (final URISyntaxException e) {
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throw new DestinationAccessException("Invalid host format: " + host, e);
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}
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}
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@Nonnull
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private static String getHostForVerification(@Nonnull String host, String normalizedHost) throws URISyntaxException {
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final URI parsedUri = new URI(normalizedHost);
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final String path = parsedUri.getPath();
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if (path != null && !path.isEmpty()) {
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throw new DestinationAccessException(
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String.format(HOST_CONTAINS_PATH_ERROR_MESSAGE_TEMPLATE, host, path));
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}
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final String hostForVerification = parsedUri.getHost();
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if (hostForVerification == null) {
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throw new DestinationAccessException("Invalid host format: " + host);
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}
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return hostForVerification;
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}
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@Nonnull
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private static String normalizeHostWithScheme(@Nonnull final String host) {
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if (host.contains(SCHEME_SEPARATOR)) {
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return host;
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}
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return HTTP_SCHEME + host;
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}
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private static void verifyHostConnectivity(@Nonnull final String host, final int port) {
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networkValidator.verifyHostConnectivity(host, port);
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}
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@Nonnull
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@Override
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public Try<Destination> tryGetDestination(@Nonnull final String destinationName) {
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return Try.success(TransparentProxyDestination.gateway(destinationName, uri).build());
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}
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@Nonnull
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@Override
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public Try<Destination>
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tryGetDestination(@Nonnull final String destinationName, @Nonnull DestinationOptions options) {
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return Try.success(TransparentProxyDestination.gateway(destinationName, uri).build());
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}
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}

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