Transport and Status

/**
 * gRPC-based implementation of TransportChannel
 * Provides access to underlying gRPC channels and DirectPath optimization
 */
public abstract class GrpcTransportChannel implements TransportChannel {
    /** Get the gRPC transport name identifier */
    public static String getGrpcTransportName();
    
    /** Create a new builder for transport channel */
    public static Builder newBuilder();
    
    /** Create transport channel from managed channel */
    public static GrpcTransportChannel create(ManagedChannel channel);
    
    /** Get the underlying gRPC channel */
    public Channel getChannel();
    
    /** Check if using DirectPath optimization */
    public boolean isDirectPath();
    
    /** Shutdown the transport channel */
    public void shutdown();
    
    /** Check if transport is shutdown */
    public boolean isShutdown();
    
    /** Check if transport is terminated */
    public boolean isTerminated();
    
    /** Shutdown transport immediately */
    public void shutdownNow();
    
    /** Await termination with timeout */
    public boolean awaitTermination(long duration, TimeUnit unit) throws InterruptedException;
    
    /** Close the transport channel */
    public void close();
}

/**
 * Builder for GrpcTransportChannel configuration
 */
public abstract static class GrpcTransportChannel.Builder {
    /** Set the managed channel */
    public Builder setManagedChannel(ManagedChannel managedChannel);
    
    /** Set channel pooling settings */
    public Builder setChannelPoolSettings(ChannelPoolSettings channelPoolSettings);
    
    /** Set keep-alive time */
    public Builder setKeepAliveTime(Duration keepAliveTime);
    
    /** Set keep-alive timeout */
    public Builder setKeepAliveTimeout(Duration keepAliveTimeout);
    
    /** Set keep-alive without calls */
    public Builder setKeepAliveWithoutCalls(Boolean keepAliveWithoutCalls);
    
    /** Set interceptor provider */
    public Builder setInterceptorProvider(GrpcInterceptorProvider interceptorProvider);
    
    /** Build the transport channel */
    public GrpcTransportChannel build();
}

/**
 * gRPC-specific status code implementation
 * Maps gRPC status codes to GAX StatusCode interface
 */
public abstract class GrpcStatusCode implements StatusCode {
    /** Create status code from gRPC status code */
    public static GrpcStatusCode of(Status.Code grpcCode);
    
    /** Get the GAX status code */
    public StatusCode.Code getCode();
    
    /** Get the gRPC status code */
    public Status.Code getGrpcCode();
    
    /** Check if status represents a timeout */
    public boolean isTimeout();
    
    /** Check if status is retryable */
    public boolean isRetryable();
    
    /** Get string representation */
    public String toString();
}

/**
 * Descriptor for gRPC transport providing metadata and capabilities
 */
public class GrpcTransportDescriptor implements TransportDescriptor {
    /** Get the transport name */
    public String getTransportName();
    
    /** Get supported authentication types */
    public Set<String> getSupportedAuthTypes();
    
    /** Check if transport supports streaming */
    public boolean supportsStreaming();
    
    /** Check if transport supports operation cancellation */
    public boolean supportsCancellation();
    
    /** Get maximum message size supported */
    public long getMaxMessageSize();
    
    /** Check if DirectPath is supported */
    public boolean supportsDirectPath();
}

/**
 * Standard gRPC to GAX status code mappings
 */
public class GrpcStatusCodeMapping {
    /** Map from gRPC Status.Code to GAX StatusCode.Code */
    public static final Map<Status.Code, StatusCode.Code> GRPC_TO_GAX_MAPPING;
    
    /** Map from GAX StatusCode.Code to gRPC Status.Code */
    public static final Map<StatusCode.Code, Status.Code> GAX_TO_GRPC_MAPPING;
    
    /** Convert gRPC status to GAX status */
    public static StatusCode.Code toGaxCode(Status.Code grpcCode);
    
    /** Convert GAX status to gRPC status */
    public static Status.Code toGrpcCode(StatusCode.Code gaxCode);
    
    /** Check if status code is retryable */
    public static boolean isRetryable(Status.Code grpcCode);
    
    /** Check if status code represents timeout */
    public static boolean isTimeout(Status.Code grpcCode);
}

/**
 * Maps gRPC exceptions to GAX exceptions
 */
public class GrpcExceptionMapping {
    /** Convert gRPC StatusException to ApiException */
    public static ApiException toApiException(StatusException statusException);
    
    /** Convert gRPC StatusRuntimeException to ApiException */
    public static ApiException toApiException(StatusRuntimeException statusRuntimeException);
    
    /** Extract retry information from exception */
    public static RetryInfo extractRetryInfo(Throwable exception);
    
    /** Check if exception is retryable */
    public static boolean isRetryable(Throwable exception);
}

/**
 * Configuration options for gRPC transport
 */
public static class GrpcTransportOptions {
    /** Set maximum inbound message size */
    public GrpcTransportOptions withMaxInboundMessageSize(int size);
    
    /** Set maximum inbound metadata size */
    public GrpcTransportOptions withMaxInboundMetadataSize(int size);
    
    /** Enable keep-alive */
    public GrpcTransportOptions withKeepAlive(Duration time, Duration timeout);
    
    /** Enable compression */
    public GrpcTransportOptions withCompression(String compression);
    
    /** Set user agent */
    public GrpcTransportOptions withUserAgent(String userAgent);
    
    /** Enable DirectPath */
    public GrpcTransportOptions withDirectPath(boolean enabled);
}

/**
 * Utilities for monitoring gRPC channel state
 */
public class ChannelStateMonitor {
    /** Get current channel connectivity state */
    public static ConnectivityState getChannelState(ManagedChannel channel);
    
    /** Wait for channel state change */
    public static boolean waitForStateChange(
        ManagedChannel channel, 
        ConnectivityState sourceState, 
        long timeout, 
        TimeUnit unit);
    
    /** Check if channel is ready */
    public static boolean isChannelReady(ManagedChannel channel);
    
    /** Check if channel is shutdown */
    public static boolean isChannelShutdown(ManagedChannel channel);
}

import com.google.api.gax.grpc.GrpcTransportChannel;
import io.grpc.ManagedChannel;
import io.grpc.ManagedChannelBuilder;

// Create managed channel
ManagedChannel managedChannel = ManagedChannelBuilder
    .forAddress("your-service.googleapis.com", 443)
    .useTransportSecurity()
    .build();

// Create transport channel
GrpcTransportChannel transportChannel = GrpcTransportChannel.create(managedChannel);

// Use the transport channel
Channel channel = transportChannel.getChannel();
boolean isDirectPath = transportChannel.isDirectPath();

import com.google.api.gax.grpc.ChannelPoolSettings;

// Create transport channel with builder
ChannelPoolSettings poolSettings = ChannelPoolSettings.builder()
    .setMinChannelCount(2)
    .setMaxChannelCount(10)
    .build();

GrpcTransportChannel transportChannel = GrpcTransportChannel.newBuilder()
    .setManagedChannel(managedChannel)
    .setChannelPoolSettings(poolSettings)
    .setKeepAliveTime(Duration.ofMinutes(2))
    .setKeepAliveTimeout(Duration.ofSeconds(30))
    .build();

import com.google.api.gax.grpc.GrpcStatusCode;
import com.google.api.gax.rpc.StatusCode;
import io.grpc.Status;

// Create status code from gRPC status
GrpcStatusCode statusCode = GrpcStatusCode.of(Status.Code.UNAVAILABLE);

// Check status properties
StatusCode.Code gaxCode = statusCode.getCode();
boolean isRetryable = statusCode.isRetryable();
boolean isTimeout = statusCode.isTimeout();

// Use in exception handling
try {
    // Make gRPC call
} catch (StatusRuntimeException e) {
    GrpcStatusCode code = GrpcStatusCode.of(e.getStatus().getCode());
    if (code.getCode() == StatusCode.Code.UNAVAILABLE) {
        // Handle service unavailable
    } else if (code.getCode() == StatusCode.Code.DEADLINE_EXCEEDED) {
        // Handle timeout
    }
}

import com.google.api.gax.rpc.ApiException;
import io.grpc.StatusException;
import io.grpc.StatusRuntimeException;

// Handle gRPC exceptions
try {
    // Make gRPC call
} catch (StatusRuntimeException e) {
    // Convert to GAX exception
    ApiException apiException = GrpcExceptionMapping.toApiException(e);
    
    if (apiException.isRetryable()) {
        // Retry the operation
    } else {
        // Handle non-retryable error
        throw apiException;
    }
} catch (StatusException e) {
    ApiException apiException = GrpcExceptionMapping.toApiException(e);
    // Handle exception
}

import java.util.concurrent.TimeUnit;

// Proper shutdown sequence
try {
    // Use transport channel
    // ... perform operations ...
    
} finally {
    // Graceful shutdown
    transportChannel.shutdown();
    
    // Wait for termination
    if (!transportChannel.awaitTermination(30, TimeUnit.SECONDS)) {
        // Force shutdown if graceful shutdown times out
        transportChannel.shutdownNow();
        
        // Wait again for force shutdown
        if (!transportChannel.awaitTermination(5, TimeUnit.SECONDS)) {
            System.err.println("Transport channel did not terminate gracefully");
        }
    }
}

import io.grpc.ConnectivityState;

// Monitor channel state
ManagedChannel channel = transportChannel.getChannel();
ConnectivityState currentState = ChannelStateMonitor.getChannelState(channel);

switch (currentState) {
    case READY:
        System.out.println("Channel is ready for calls");
        break;
    case CONNECTING:
        System.out.println("Channel is connecting");
        break;
    case TRANSIENT_FAILURE:
        System.out.println("Channel experienced a failure, will retry");
        break;
    case IDLE:
        System.out.println("Channel is idle");
        break;
    case SHUTDOWN:
        System.out.println("Channel is shutdown");
        break;
}

// Wait for channel to become ready
boolean stateChanged = ChannelStateMonitor.waitForStateChange(
    channel, currentState, 30, TimeUnit.SECONDS);

if (stateChanged && ChannelStateMonitor.isChannelReady(channel)) {
    // Channel is now ready
    System.out.println("Channel is ready for calls");
}

// Check DirectPath status
if (transportChannel.isDirectPath()) {
    System.out.println("Using DirectPath optimization for Google Cloud");
    // DirectPath provides optimized networking for Google Cloud services
} else {
    System.out.println("Using standard gRPC transport");
}

// Get transport name
String transportName = GrpcTransportChannel.getGrpcTransportName();
System.out.println("Transport: " + transportName);