State Backend and Operator Restore Testing

/**
 * Abstract base class for operator restore testing scenarios
 */
public abstract class AbstractOperatorRestoreTestBase {
    
    /**
     * Test operator restore from savepoint or checkpoint
     * @throws Exception if restore testing fails
     */
    protected abstract void testRestore() throws Exception;
    
    /**
     * Create savepoint from running job for restore testing
     * @param jobGraph job to create savepoint from
     * @return String path to created savepoint
     * @throws Exception if savepoint creation fails
     */
    protected String createSavepoint(JobGraph jobGraph) throws Exception;
    
    /**
     * Restore job from savepoint and validate state
     * @param jobGraph job to restore
     * @param savepointPath path to savepoint
     * @throws Exception if restore or validation fails
     */
    protected void restoreFromSavepoint(JobGraph jobGraph, String savepointPath) throws Exception;
    
    /**
     * Configure state backend for testing
     * @param backend state backend configuration
     */
    protected void configureStateBackend(StateBackend backend);
}

/**
 * Base class for testing keyed operator restore scenarios
 */
public abstract class AbstractKeyedOperatorRestoreTestBase 
    extends AbstractOperatorRestoreTestBase {
    
    /**
     * Test keyed state restore with different key serializers
     * @param keySerializer serializer for key type
     * @param valueSerializer serializer for value type  
     * @throws Exception if keyed restore test fails
     */
    protected <K, V> void testKeyedStateRestore(
        TypeSerializer<K> keySerializer,
        TypeSerializer<V> valueSerializer) throws Exception;
    
    /**
     * Validate keyed state after restore
     * @param expectedState expected state values after restore
     * @param actualState actual restored state
     * @return boolean indicating state validity
     */
    protected <K, V> boolean validateKeyedState(
        Map<K, V> expectedState, 
        Map<K, V> actualState);
    
    /**
     * Create keyed state test job with configurable state
     * @param initialState initial state values
     * @return JobGraph configured for keyed state testing
     */
    protected <K, V> JobGraph createKeyedStateJob(Map<K, V> initialState);
}

/**
 * Base class for testing non-keyed operator restore scenarios
 */
public abstract class AbstractNonKeyedOperatorRestoreTestBase 
    extends AbstractOperatorRestoreTestBase {
    
    /**
     * Test operator state restore with list state
     * @param initialListState initial list state values
     * @throws Exception if non-keyed restore test fails
     */
    protected <T> void testListStateRestore(List<T> initialListState) throws Exception;
    
    /**
     * Test operator state restore with union list state
     * @param initialUnionState initial union state values
     * @throws Exception if union state restore test fails  
     */
    protected <T> void testUnionListStateRestore(List<T> initialUnionState) throws Exception;
    
    /**
     * Test operator state restore with broadcast state
     * @param initialBroadcastState initial broadcast state
     * @throws Exception if broadcast state restore test fails
     */
    protected <K, V> void testBroadcastStateRestore(
        Map<K, V> initialBroadcastState) throws Exception;
    
    /**
     * Validate operator state after restore
     * @param expectedState expected operator state
     * @param actualState actual restored operator state
     * @return boolean indicating state validity
     */
    protected boolean validateOperatorState(
        OperatorState expectedState,
        OperatorState actualState);
}

/**
 * Base class for testing state backend switching scenarios
 */
public abstract class SavepointStateBackendSwitchTestBase {
    
    /**
     * Test switching state backend while preserving state correctness
     * @throws Exception if state backend switching test fails
     */
    protected abstract void testSwitchingStateBackend() throws Exception;
    
    /**
     * Test switch from memory state backend to filesystem
     * @param filesystemPath path for filesystem state backend
     * @throws Exception if backend switch fails
     */
    protected void testMemoryToFilesystemSwitch(String filesystemPath) throws Exception;
    
    /**
     * Test switch from filesystem state backend to RocksDB
     * @param rocksDbPath path for RocksDB state backend
     * @throws Exception if backend switch fails
     */
    protected void testFilesystemToRocksDbSwitch(String rocksDbPath) throws Exception;
    
    /**
     * Test switch from RocksDB state backend back to memory
     * @throws Exception if backend switch fails
     */
    protected void testRocksDbToMemorySwitch() throws Exception;
    
    /**
     * Validate state consistency after backend switch
     * @param originalState state before switch
     * @param restoredState state after switch
     * @return boolean indicating state consistency
     */
    protected boolean validateStateConsistency(
        StateSnapshot originalState,
        StateSnapshot restoredState);
}

/**
 * Specifications for state backend switching test scenarios
 */
public class BackendSwitchSpecs {
    
    /**
     * Specification for memory to filesystem switch
     */
    public static class MemoryToFilesystemSpec {
        /**
         * Constructor for memory to filesystem switch spec
         * @param targetPath filesystem path for state storage
         * @param asyncSnapshot enable asynchronous snapshots
         */
        public MemoryToFilesystemSpec(String targetPath, boolean asyncSnapshot);
        
        public String getTargetPath();
        public boolean isAsyncSnapshot();
    }
    
    /**
     * Specification for filesystem to RocksDB switch
     */
    public static class FilesystemToRocksDbSpec {
        /**
         * Constructor for filesystem to RocksDB switch spec
         * @param rocksDbPath RocksDB storage path
         * @param incrementalCheckpoints enable incremental checkpoints
         */
        public FilesystemToRocksDbSpec(String rocksDbPath, boolean incrementalCheckpoints);
        
        public String getRocksDbPath();
        public boolean isIncrementalCheckpoints();
    }
    
    /**
     * Create specification for complete backend switch test
     * @param memoryToFs memory to filesystem spec
     * @param fsToRocksDb filesystem to RocksDB spec
     * @return CompleteSwitchSpec for full backend switching test
     */
    public static CompleteSwitchSpec createCompleteSwitchSpec(
        MemoryToFilesystemSpec memoryToFs,
        FilesystemToRocksDbSpec fsToRocksDb);
}

/**
 * Utility class for state restore testing operations
 */
public class StateRestoreTestUtils {
    
    /**
     * Create test job with configurable state for restore testing
     * @param stateConfig state configuration parameters
     * @return JobGraph configured for state restore testing
     */
    public static JobGraph createStatefulTestJob(StateConfiguration stateConfig);
    
    /**
     * Execute job and create savepoint at specified interval
     * @param jobGraph job to execute
     * @param savepointIntervalMs interval between savepoints
     * @return List of savepoint paths created
     * @throws Exception if execution or savepoint creation fails
     */
    public static List<String> executeAndCreateSavepoints(
        JobGraph jobGraph, 
        long savepointIntervalMs) throws Exception;
    
    /**
     * Compare state snapshots for consistency validation
     * @param snapshot1 first state snapshot
     * @param snapshot2 second state snapshot
     * @return StateComparisonResult containing comparison details
     */
    public static StateComparisonResult compareStateSnapshots(
        StateSnapshot snapshot1,
        StateSnapshot snapshot2);
    
    /**
     * Extract state from running job for validation
     * @param jobId identifier of running job
     * @return StateSnapshot containing current job state
     * @throws Exception if state extraction fails
     */
    public static StateSnapshot extractJobState(JobID jobId) throws Exception;
}

/**
 * Configuration for stateful test jobs
 */
public class StateConfiguration {
    
    /**
     * Constructor for state configuration
     * @param keyedStateSize number of keyed state entries
     * @param operatorStateSize size of operator state
     * @param checkpointInterval checkpoint interval in milliseconds
     */
    public StateConfiguration(
        int keyedStateSize, 
        int operatorStateSize, 
        long checkpointInterval);
    
    public int getKeyedStateSize();
    public int getOperatorStateSize();
    public long getCheckpointInterval();
}

/**
 * Result of state snapshot comparison
 */
public class StateComparisonResult {
    
    /**
     * Check if state snapshots are identical
     * @return boolean indicating state identity
     */
    public boolean isIdentical();
    
    /**
     * Get differences between state snapshots
     * @return List of StateDifference objects
     */
    public List<StateDifference> getDifferences();
    
    /**
     * Get summary of comparison results
     * @return String summary of state comparison
     */
    public String getComparisonSummary();
}

import org.apache.flink.test.state.operator.restore.*;

// Basic keyed state restore test
public class KeyedStateRestoreTest extends AbstractKeyedOperatorRestoreTestBase {
    
    @Test
    public void testSimpleKeyedStateRestore() throws Exception {
        // Create initial state
        Map<String, Integer> initialState = new HashMap<>();
        initialState.put("key1", 100);
        initialState.put("key2", 200);
        initialState.put("key3", 300);
        
        // Create job with keyed state
        JobGraph job = createKeyedStateJob(initialState);
        
        // Test restore scenario
        testKeyedStateRestore(
            StringSerializer.INSTANCE,
            IntSerializer.INSTANCE);
    }
    
    @Override
    protected void testRestore() throws Exception {
        // Create savepoint
        String savepointPath = createSavepoint(createKeyedStateJob(getTestState()));
        
        // Modify job configuration
        JobGraph modifiedJob = createModifiedKeyedStateJob();
        
        // Restore and validate
        restoreFromSavepoint(modifiedJob, savepointPath);
    }
}

// Non-keyed state restore test
public class OperatorStateRestoreTest extends AbstractNonKeyedOperatorRestoreTestBase {
    
    @Test
    public void testListStateRestore() throws Exception {
        List<String> initialListState = Arrays.asList("item1", "item2", "item3");
        testListStateRestore(initialListState);
    }
    
    @Test
    public void testUnionListStateRestore() throws Exception {
        List<Integer> initialUnionState = Arrays.asList(1, 2, 3, 4, 5);
        testUnionListStateRestore(initialUnionState);
    }
    
    @Test 
    public void testBroadcastStateRestore() throws Exception {
        Map<String, String> initialBroadcastState = new HashMap<>();
        initialBroadcastState.put("config1", "value1");
        initialBroadcastState.put("config2", "value2");
        
        testBroadcastStateRestore(initialBroadcastState);
    }
}

// State backend switching test
public class StateBackendSwitchTest extends SavepointStateBackendSwitchTestBase {
    
    @Test
    public void testCompleteBackendSwitching() throws Exception {
        testSwitchingStateBackend();
    }
    
    @Override
    protected void testSwitchingStateBackend() throws Exception {
        // Start with memory backend
        configureStateBackend(new MemoryStateBackend());
        
        // Create job and run briefly
        JobGraph job = StateRestoreTestUtils.createStatefulTestJob(
            new StateConfiguration(1000, 500, 5000L));
        String memoryState = createSavepoint(job);
        
        // Switch to filesystem backend
        testMemoryToFilesystemSwitch("/tmp/flink-state");
        
        // Switch to RocksDB backend  
        testFilesystemToRocksDbSwitch("/tmp/rocksdb-state");
        
        // Switch back to memory backend
        testRocksDbToMemorySwitch();
    }
    
    @Test
    public void testBackendSwitchWithComplexState() throws Exception {
        // Create specifications for backend switching
        MemoryToFilesystemSpec memToFs = new BackendSwitchSpecs.MemoryToFilesystemSpec(
            "/tmp/fs-state", true);
        FilesystemToRocksDbSpec fsToRocks = new BackendSwitchSpecs.FilesystemToRocksDbSpec(
            "/tmp/rocks-state", true);
        
        BackendSwitchSpecs.CompleteSwitchSpec switchSpec = 
            BackendSwitchSpecs.createCompleteSwitchSpec(memToFs, fsToRocks);
        
        // Execute complete switching test
        executeBackendSwitchTest(switchSpec);
    }
}

// Comprehensive state restore validation
public class StateRestoreValidationTest {
    
    @Test
    public void testStateConsistencyAcrossRestores() throws Exception {
        StateConfiguration config = new StateConfiguration(5000, 1000, 2000L);
        JobGraph job = StateRestoreTestUtils.createStatefulTestJob(config);
        
        // Create multiple savepoints
        List<String> savepoints = StateRestoreTestUtils.executeAndCreateSavepoints(
            job, 10000L);
        
        // Validate state consistency across savepoints
        for (int i = 0; i < savepoints.size() - 1; i++) {
            StateSnapshot snapshot1 = loadStateSnapshot(savepoints.get(i));
            StateSnapshot snapshot2 = loadStateSnapshot(savepoints.get(i + 1));
            
            StateComparisonResult comparison = 
                StateRestoreTestUtils.compareStateSnapshots(snapshot1, snapshot2);
            
            // Validate progressive state changes
            assertTrue(comparison.getDifferences().size() > 0);
            assertFalse(comparison.isIdentical());
        }
    }
}