alibaba/canal · error · NullPointerException

null memoryLogPositionManager

Error message

null memoryLogPositionManager

What it means

FileMixedLogPositionManager composes a MemoryLogPositionManager to hold the hot in-memory copy and a file store for persistence. The memory delegate is mandatory; a null value throws NullPointerException at construction. Without it the read-through cache and staging area do not exist.

Source

Thrown at parse/src/main/java/com/alibaba/otter/canal/parse/index/FileMixedLogPositionManager.java:64

    @SuppressWarnings("serial")
    private final LogPosition        nullPosition = new LogPosition() {
                                                  };

    private MemoryLogPositionManager memoryLogPositionManager;

    private long                     period;
    private Set<String>              persistTasks;

    public FileMixedLogPositionManager(File dataDir, long period, MemoryLogPositionManager memoryLogPositionManager){
        if (dataDir == null) {
            throw new NullPointerException("null dataDir");
        }
        if (period <= 0) {
            throw new IllegalArgumentException("period must be positive, given: " + period);
        }
        if (memoryLogPositionManager == null) {
            throw new NullPointerException("null memoryLogPositionManager");
        }
        this.dataDir = dataDir;
        this.period = period;
        this.memoryLogPositionManager = memoryLogPositionManager;

        this.dataFileCaches = MigrateMap.makeComputingMap(this::getDataFile);

        this.executorService = Executors.newScheduledThreadPool(1);
        this.persistTasks = Collections.synchronizedSet(new HashSet<>());
    }

    @Override
    public void start() {
        super.start();

        if (!dataDir.exists()) {
            try {
                FileUtils.forceMkdir(dataDir);

View on GitHub (pinned to 87be50e876)

Solutions

1. Ensure a fresh, non-started MemoryLogPositionManager is injected as the third constructor argument.
2. Verify Spring/bean config actually defines and links the memoryLogPositionManager.
3. Avoid reusing a memory manager instance that another component already owns.

Example fix

// before
new FileMixedLogPositionManager(dir, period, null);

// after
MemoryLogPositionManager mem = new MemoryLogPositionManager();
new FileMixedLogPositionManager(dir, period, mem);

MemoryLogPositionManager mem = Objects.requireNonNull(memoryMgr, "memoryLogPositionManager");
new FileMixedLogPositionManager(dir, period, mem);

boolean hasMemoryManager(MemoryLogPositionManager m) { return m != null; }

When it happens

Trigger: Calling the FileMixedLogPositionManager constructor with memoryLogPositionManager == null, e.g. when the memory manager bean was not created or was already started/closed by another component.

Common situations: Spring wiring omitted the memoryLogPositionManager property; the manager was set to null by a custom factory; a refactor passed the wrong argument order.

Related errors

• nul secondary LogPositionManager
• null metaManager
• null memoryLogPositionManager
• null dataDir
• null zkClient

AI-assisted analysis of alibaba/canal@87be50e876 (2026-08-14). Data as JSON: /api/errors/732a84077991006a. Report an issue: GitHub.