aeron-io/aeron · error · AeronEvent

exceeded session limit, streamId=

Error message

exceeded session limit, streamId=${streamId} sourceAddress=${srcAddress}

What it means

DataPacketDispatcher.onSetupMessage throws AeronEvent when a stream's session limit (streamSessionLimit) is exceeded: a SETUP packet arrived for a new session on a stream that already tracks the maximum number of active sessions, so the driver refuses to create interest for another session.

Solutions

1. Raise the driver's session limit configuration so the subscription can accept more concurrent sessions
2. Identify and stop stray publishers sending to the same channel/stream (duplicate processes, leftover instances)
3. Filter senders with network/firewall rules so only intended sources publish

Example fix

// before
mediaDriver = MediaDriver.launch(new MediaDriver.Context() /* default session limit */);
// after
ctx.sessionLimit(64); // allow more concurrent sessions per stream
mediaDriver = MediaDriver.launch(ctx);

int activeSessions = countActiveSessions(streamId); if (activeSessions >= sessionLimit) { /* refuse or alert before senders hit the limit */ }

try { dispatcher.onSetupMessage(...); } catch (AeronEvent e) { log.warn("session limit reached: " + e.getMessage()); }

When it happens

Trigger: Receiving a SETUP frame on a stream where isSessionLimitLimit(streamSessionLimit) is true — i.e. more distinct sender sessionIds than the configured session limit are trying to publish to the same stream/channel the subscription listens on.

Common situations: Many publishers (or duplicate/looping publishers, misconfigured senders reusing endpoints) connecting to a single subscription; attacks or accidental multicast fan-in; too-low aeron.driver.session-limit style configuration.

Related errors

• channel error -
• could not resolve control address:
• could not resolve endpoint address:
• failed get replay image for sessionId=" +…
• mtuLength= > MAX_UDP_PAYLOAD_LENGTH=

AI-assisted analysis of aeron-io/aeron@6d60124e15 (2026-09-12). Data as JSON: /api/errors/93f2db12a14aa90f. Report an issue: GitHub.

Appendix: source

Thrown at aeron-driver/src/main/java/io/aeron/driver/DataPacketDispatcher.java:344

     * @param srcAddress      the message came from.
     * @param transportIndex  on which the message was received.
     */
    public void onSetupMessage(
        final ReceiveChannelEndpoint channelEndpoint,
        final SetupFlyweight msg,
        final InetSocketAddress srcAddress,
        final int transportIndex)
    {
        final int streamId = msg.streamId();
        final StreamInterest streamInterest = streamInterestByIdMap.get(streamId);

        if (null != streamInterest)
        {
            final int sessionId = msg.sessionId();

            if (streamInterest.isSessionLimitExceeded(streamSessionLimit))
            {
                throw new AeronEvent("exceeded session limit, streamId=" + streamId + " sourceAddress=" + srcAddress);
            }

            final PublicationImage image = streamInterest.findActive(sessionId);
            final SessionState sessionInterest = streamInterest.sessionInterestByIdMap.get(sessionId);

            if (null != image)
            {
                image.addDestinationConnectionIfUnknown(transportIndex, srcAddress);
            }
            else if (null != sessionInterest)
            {
                if (PENDING_SETUP_FRAME == sessionInterest)
                {
                    streamInterest.sessionInterestByIdMap.put(sessionId, INIT_IN_PROGRESS);

                    createPublicationImage(
                        channelEndpoint,
                        transportIndex,

View on GitHub (pinned to 6d60124e15)