apache/dubbo · error · IOException

should mark before reset!

Error message

should mark before reset!

What it means

Thrown by the reset() of the mark-buffering InputStream from StreamUtils.markSupportedInputStream when reset() is called before mark() has ever been called (mInMarked is false). Reset requires a marked position to rewind to; without one there is no replay point, so it raises IOException("should mark before reset!"). This mirrors the contract of java.io.InputStream.reset().

Source

Thrown at dubbo-common/src/main/java/org/apache/dubbo/common/io/StreamUtils.java:201

             */
            @Override
            public synchronized void mark(int readlimit) {
                mInMarked = true;
                mInReset = false;

                // mark buffer is not empty
                int count = mCount - mPosition;
                if (count > 0) {
                    System.arraycopy(mMarkBuffer, mPosition, mMarkBuffer, 0, count);
                    mCount = count;
                    mPosition = 0;
                }
            }

            @Override
            public synchronized void reset() throws IOException {
                if (!mInMarked) {
                    throw new IOException("should mark before reset!");
                }

                mInReset = true;
                mPosition = 0;
            }

            @Override
            public boolean markSupported() {
                return true;
            }

            @Override
            public int available() throws IOException {
                int available = is.available();

                if (mInMarked && mInReset) {
                    available += mCount - mPosition;
                }

View on GitHub (pinned to 3a3043227f)

Solutions

1. Always pair: call mark(readlimit) before any reset() on the same instance.
2. Track marked state yourself and only reset() when you have marked: if (marked) { m.reset(); marked = false; }
3. Prefer try-with-resources and re-open the stream rather than relying on reset for replay when mark state is uncertain.

Example fix

// before
InputStream m = StreamUtils.markSupportedInputStream(in);
m.reset(); // -> IOException: should mark before reset!
// after
InputStream m = StreamUtils.markSupportedInputStream(in);
m.mark(1024);
// ... read ...
m.reset();

boolean marked = false;
m.mark(1024); marked = true;
// ... read ...
if (marked) { m.reset(); marked = false; }

try {
    m.reset();
} catch (IOException e) {
    // no mark set — re-open the stream instead of replaying
    in = reopen();
}

When it happens

Trigger: Calling reset() on a StreamUtils-marked stream without a prior mark(); calling reset() after the mark was implicitly cleared (e.g. after a full buffer cycle on some flows); reuse of a stream instance across operations where only the second calls reset().

Common situations: Reset-without-mark copy-paste; conditional code path that skips mark() on a fast path but still calls reset(); state machine that resets on error without ensuring mark happened.

Related errors

• Mark buffer is full!
• Negative initial size: ${size}
• Read-ahead limit < 0
• Stream closed
• Negative buffer size

AI-assisted analysis of apache/dubbo@3a3043227f (2026-08-14). Data as JSON: /api/errors/9831448bfde5b471. Report an issue: GitHub.