eclipse-vertx/vert.x · error · IllegalArgumentException

Ping data must be exactly 8 bytes

Error message

Ping data must be exactly 8 bytes

What it means

HTTP/2 PING frames carry exactly 8 bytes of opaque payload per RFC 7540. Http2ConnectionImpl.ping(Buffer) validates the buffer length and throws IllegalArgumentException otherwise, before writing the ping to the connection.

Source

Thrown at vertx-core/src/main/java/io/vertx/core/http/impl/http2/codec/Http2ConnectionImpl.java:436

      }
      promise.complete();
    };
    updateSettingsHandlers.add(pending);
    handler.writeSettings(settingsUpdate).addListener(fut -> {
      if (!fut.isSuccess()) {
        synchronized (Http2ConnectionImpl.this) {
          updateSettingsHandlers.remove(pending);
        }
        promise.fail(fut.cause());
      }
    });
    return promise.future();
  }

  @Override
  public Future<Buffer> ping(Buffer data) {
    if (data.length() != 8) {
      throw new IllegalArgumentException("Ping data must be exactly 8 bytes");
    }
    Promise<Buffer> promise = context.promise();
    handler.writePing(data.getLong(0)).addListener(fut -> {
      if (fut.isSuccess()) {
        synchronized (Http2ConnectionImpl.this) {
          pongHandlers.add(promise);
        }
      } else {
        promise.fail(fut.cause());
      }
    });
    return promise.future();
  }

  @Override
  public synchronized HttpConnection pingHandler(Handler<Buffer> handler) {
    pingHandler = handler;
    return this;

View on GitHub (pinned to fb308bd8c3)

Solutions

1. Build exactly an 8-byte Buffer, e.g. Buffer.buffer(8).setLong(0, System.nanoTime()).
2. Check data.length() == 8 before calling ping().
3. If you need larger payloads, send them over a data stream instead of PING.

Example fix

// before
conn.ping(Buffer.buffer("ping-me"));
// after
Buffer payload = Buffer.buffer(8).setLong(0, System.nanoTime());
conn.ping(payload);

if (data == null || data.length() != 8) throw new IllegalArgumentException("PING payload must be 8 bytes");

boolean isValidPingPayload(Buffer b) { return b != null && b.length() == 8; }

try { conn.ping(data); } catch (IllegalArgumentException e) { conn.ping(Buffer.buffer(8).setLong(0, 0L)); }

When it happens

Trigger: Calling connection.ping(buffer) with a buffer whose length() is not 8 (e.g. 0-byte, 4-byte timestamp, 16-byte token).

Common situations: Measuring latency with a System.nanoTime() encoded in 8 bytes but accidentally wrapping the wrong byte count; padding or prefixing the payload with extra bytes; reusing a generic nonce generator producing different sizes.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Ping data must be exactly 8 bytes
• HTTP/1.x connections don't support PING
• Invalid reset code value
• Invalid window size: ${windowSize}
• Invalid window size: ${windowSize}

AI-assisted analysis of eclipse-vertx/vert.x@fb308bd8c3 (2026-09-06). Data as JSON: /api/errors/52e10aa622f8a939. Report an issue: GitHub.