Logging Framework

/**
 * Interface for logging context
 */
public interface LoggingContext {
    /**
     * Get the log partition for this context
     * @return Log partition identifier
     */
    String getLogPartition();
    
    /**
     * Get the log path fragment for this context  
     * @return Path fragment for log organization
     */
    String getLogPathFragment();
    
    /**
     * Get system tags for this logging context
     * @return Map of system tags
     */
    Map<String, String> getSystemTags();
}

/**
 * Abstract base class for logging contexts
 */
public abstract class AbstractLoggingContext implements LoggingContext {
    protected AbstractLoggingContext();
    
    @Override
    public abstract String getLogPartition();
    
    @Override
    public abstract String getLogPathFragment();
    
    @Override
    public Map<String, String> getSystemTags();
    
    /**
     * Add a system tag
     */
    protected void addSystemTag(String key, String value);
}

/**
 * Logging context for CDAP components
 */
public class ComponentLoggingContext extends AbstractLoggingContext {
    public ComponentLoggingContext(String componentName);
    public ComponentLoggingContext(String componentName, String instanceId);
    
    @Override
    public String getLogPartition();
    
    @Override
    public String getLogPathFragment();
    
    /**
     * Get the component name
     */
    public String getComponentName();
    
    /**
     * Get the instance ID
     */
    public String getInstanceId();
}

/**
 * Logging context for namespace-specific operations
 */
public class NamespaceLoggingContext extends AbstractLoggingContext {
    public NamespaceLoggingContext(String namespaceId);
    
    @Override
    public String getLogPartition();
    
    @Override
    public String getLogPathFragment();
    
    /**
     * Get the namespace ID
     */
    public String getNamespaceId();
}

/**
 * Logging context for service-specific operations
 */
public class ServiceLoggingContext extends AbstractLoggingContext {
    public ServiceLoggingContext(String serviceName, String serviceId);
    public ServiceLoggingContext(String serviceName, String serviceId, String runId);
    
    @Override
    public String getLogPartition();
    
    @Override
    public String getLogPathFragment();
    
    /**
     * Get the service name
     */
    public String getServiceName();
    
    /**
     * Get the service ID
     */
    public String getServiceId();
    
    /**
     * Get the run ID
     */
    public String getRunId();
}

/**
 * Logger utilities
 */
public class Loggers {
    /**
     * Get logger for a class
     */
    public static <T> Logger getLogger(Class<T> clazz);
    
    /**
     * Get logger with specified name
     */
    public static Logger getLogger(String name);
    
    /**
     * Get logger for a class with logging context
     */
    public static <T> Logger getLogger(Class<T> clazz, LoggingContext loggingContext);
    
    /**
     * Set logging context for current thread
     */
    public static void setLoggingContext(LoggingContext loggingContext);
    
    /**
     * Get logging context for current thread
     */
    public static LoggingContext getLoggingContext();
    
    /**
     * Clear logging context for current thread
     */
    public static void clearLoggingContext();
}

/**
 * Interface for log sampling decisions
 */
public interface LogSampler {
    /**
     * Decide whether to accept a log entry
     * @param logLevel The log level
     * @param loggerName The logger name
     * @param message The log message
     * @return true if log should be accepted
     */
    boolean accept(String logLevel, String loggerName, String message);
}

/**
 * Log sampler implementations
 */
public class LogSamplers {
    /**
     * Accept all log entries (no sampling)
     */
    public static LogSampler acceptAll();
    
    /**
     * Accept no log entries (drop all)
     */
    public static LogSampler acceptNone();
    
    /**
     * Sample based on rate (e.g., accept 1 in every N)
     */
    public static LogSampler rateBased(int rate);
    
    /**
     * Sample based on time window (e.g., max N logs per minute)
     */
    public static LogSampler timeBased(int maxLogsPerWindow, long windowSizeMs);
    
    /**
     * Sample based on log level
     */
    public static LogSampler levelBased(String minLevel);
    
    /**
     * Combine multiple samplers with AND logic
     */
    public static LogSampler and(LogSampler... samplers);
    
    /**
     * Combine multiple samplers with OR logic
     */
    public static LogSampler or(LogSampler... samplers);
}

/**
 * Audit log entry representation
 */
public class AuditLogEntry {
    public AuditLogEntry(String user, String operation, String entityType, 
                        String entityId, long timestamp);
    
    /**
     * Get the user who performed the operation
     */
    public String getUser();
    
    /**
     * Get the operation performed
     */
    public String getOperation();
    
    /**
     * Get the type of entity operated on
     */
    public String getEntityType();
    
    /**
     * Get the ID of the entity operated on
     */
    public String getEntityId();
    
    /**
     * Get the timestamp of the operation
     */
    public long getTimestamp();
    
    /**
     * Get additional metadata
     */
    public Map<String, String> getMetadata();
    
    /**
     * Add metadata entry
     */
    public AuditLogEntry addMetadata(String key, String value);
    
    /**
     * Convert to JSON representation
     */
    public String toJson();
}

import io.cdap.cdap.common.logging.*;
import org.slf4j.Logger;

// Using logging contexts
public class ApplicationService {
    private static final Logger LOG = Loggers.getLogger(ApplicationService.class);
    
    public void deployApplication(String namespaceId, String appId, ApplicationSpec spec) {
        // Set namespace logging context
        NamespaceLoggingContext loggingContext = new NamespaceLoggingContext(namespaceId);
        Loggers.setLoggingContext(loggingContext);
        
        try {
            LOG.info("Deploying application: {}", appId);
            
            // Component-specific logging context
            ComponentLoggingContext componentContext = 
                new ComponentLoggingContext("app-fabric", "instance-1");
            Loggers.setLoggingContext(componentContext);
            
            performDeployment(spec);
            LOG.info("Application deployed successfully: {}", appId);
            
        } catch (Exception e) {
            LOG.error("Failed to deploy application: {}", appId, e);
            throw e;
        } finally {
            Loggers.clearLoggingContext();
        }
    }
    
    private void performDeployment(ApplicationSpec spec) {
        Logger componentLogger = Loggers.getLogger(ApplicationService.class, 
                                                  Loggers.getLoggingContext());
        componentLogger.debug("Processing application spec: {}", spec.getName());
        // Deployment logic...
    }
}

// Service with logging context
public class DatasetService {
    private final ServiceLoggingContext loggingContext;
    private final Logger LOG;
    
    public DatasetService(String serviceId, String runId) {
        this.loggingContext = new ServiceLoggingContext("dataset-service", serviceId, runId);
        this.LOG = Loggers.getLogger(DatasetService.class, loggingContext);
    }
    
    public void createDataset(String datasetId, DatasetSpec spec) {
        LOG.info("Creating dataset: {} with type: {}", datasetId, spec.getType());
        
        try {
            // Dataset creation logic
            datasetManager.create(datasetId, spec);
            LOG.info("Dataset created successfully: {}", datasetId);
        } catch (Exception e) {
            LOG.error("Failed to create dataset: {}", datasetId, e);
            throw e;
        }
    }
}

// Log sampling configuration
public class LoggingConfig {
    public void configureSampling() {
        // Rate-based sampling: accept 1 in every 100 logs
        LogSampler rateSampler = LogSamplers.rateBased(100);
        
        // Time-based sampling: max 10 logs per minute
        LogSampler timeSampler = LogSamplers.timeBased(10, 60000);
        
        // Level-based sampling: only WARN and above
        LogSampler levelSampler = LogSamplers.levelBased("WARN");
        
        // Combined sampling: rate AND level
        LogSampler combinedSampler = LogSamplers.and(rateSampler, levelSampler);
        
        // Apply sampler (implementation specific)
        applySampler(combinedSampler);
    }
    
    private void applySampler(LogSampler sampler) {
        // Configure logging framework with sampler
        System.out.println("Configured log sampler: " + sampler.getClass().getSimpleName());
    }
}

// Audit logging
public class AuditService {
    private final Logger auditLogger = Loggers.getLogger("AUDIT");
    
    public void auditApplicationDeployment(String user, String namespaceId, 
                                         String appId, boolean success) {
        AuditLogEntry entry = new AuditLogEntry(
            user, 
            success ? "APPLICATION_DEPLOY" : "APPLICATION_DEPLOY_FAILED",
            "APPLICATION",
            appId,
            System.currentTimeMillis()
        )
        .addMetadata("namespace", namespaceId)
        .addMetadata("success", String.valueOf(success));
        
        auditLogger.info(entry.toJson());
    }
    
    public void auditDatasetAccess(String user, String datasetId, String operation) {
        AuditLogEntry entry = new AuditLogEntry(
            user,
            "DATASET_" + operation.toUpperCase(),
            "DATASET",
            datasetId,
            System.currentTimeMillis()
        )
        .addMetadata("operation", operation)
        .addMetadata("source", "dataset-service");
        
        auditLogger.info(entry.toJson());
    }
}

// Advanced logging with thread-local context
public class ThreadContextLogging {
    private static final Logger LOG = Loggers.getLogger(ThreadContextLogging.class);
    
    public void processRequest(String namespaceId, String requestId) {
        // Set context for entire request processing
        NamespaceLoggingContext context = new NamespaceLoggingContext(namespaceId);
        context.addSystemTag("requestId", requestId);
        context.addSystemTag("threadId", Thread.currentThread().getName());
        
        Loggers.setLoggingContext(context);
        
        try {
            LOG.info("Processing request: {}", requestId);
            
            // Spawn sub-tasks that inherit logging context
            CompletableFuture.supplyAsync(() -> {
                Logger taskLogger = Loggers.getLogger(ThreadContextLogging.class,
                                                    Loggers.getLoggingContext());
                taskLogger.debug("Executing sub-task for request: {}", requestId);
                return performSubTask();
            }).get();
            
            LOG.info("Request processing completed: {}", requestId);
            
        } catch (Exception e) {
            LOG.error("Request processing failed: {}", requestId, e);
        } finally {
            Loggers.clearLoggingContext();
        }
    }
    
    private String performSubTask() {
        // Sub-task logic with inherited logging context
        return "result";
    }
}