What causes "Cannot open channel on " in conductor-oss/conductor?

Wire an AMQPRetryPattern so channel-creation IOExceptions are retried (and, on retry, the connection may be re-established).

conductor-oss/conductor · error · RuntimeException

Cannot open <connType> channel on <addresses>

Error message

Cannot open <connType> channel on <addresses>

What it means

getOrCreateChannel caught an IOException from rmqConnection.createChannel() and retrySettings is null, so the failure propagates immediately. An IOException here usually means the underlying connection is already closed (createChannel on a closed connection throws) or the broker rejected the channel operation.

Source

Thrown at amqp/src/main/java/com/netflix/conductor/contribs/queue/amqp/AMQPConnection.java:231

        while (true) {
            try {
                LOGGER.debug("Creating a channel for " + connType);
                locChn = rmqConnection.createChannel();
                if (locChn == null || !locChn.isOpen()) {
                    throw new RuntimeException("Fail to open " + connType + " channel");
                }
                locChn.addShutdownListener(
                        cause -> {
                            LOGGER.error(
                                    connType + " Channel has been shutdown: {}",
                                    cause.getMessage(),
                                    cause);
                        });
                return locChn;
            } catch (final IOException e) {
                AMQPRetryPattern retry = retrySettings;
                if (retry == null) {
                    throw new RuntimeException(
                            "Cannot open "
                                    + connType
                                    + " channel on "
                                    + Arrays.stream(addresses)
                                            .map(address -> address.toString())
                                            .collect(Collectors.joining(",")),
                            e);
                }
                try {
                    retry.continueOrPropogate(e, retryIndex);
                } catch (Exception ex) {
                    throw new RuntimeException(
                            "Retries completed. Cannot open "
                                    + connType
                                    + " channel on "
                                    + Arrays.stream(addresses)
                                            .map(address -> address.toString())
                                            .collect(Collectors.joining(",")),

View on GitHub (pinned to cf7c3e4a8a)

Solutions

Wire an AMQPRetryPattern so channel-creation IOExceptions are retried (and, on retry, the connection may be re-established).
Confirm getOrCreateChannel(ConnectionType, String) is the entry point used: it re-checks isOpen() and recreates the connection before borrowing a channel.
Check the broker connection log for the cause of the underlying close.
Verify network stability between the client and broker.

Example fix

// before: no retry -> a stale connection fails the channel open immediately
AMQPObservableQueue q = builder.build(useExchange, uri, type); // retrySettings null path

// after: configure retry so createChannel is retried after connection recovery
AMQPRetryPattern retry = new AMQPRetryPattern(limit, duration, type);

Defensive patterns

Strategy: retry

Try / catch

try {
    amqpConnection.getOrCreateChannel(type, name);
} catch (RuntimeException e) {
    if (e.getCause() instanceof IOException) {
        // channel creation failed on a stale/closed connection; back off and retry
    }
    throw e;
}

Prevention

Wire a non-null AMQPRetryPattern so channel-creation IOExceptions are retried.
Always enter through getOrCreateChannel(ConnectionType, String), which refreshes a closed connection first.
Keep connections healthy so createChannel does not run against a stale connection.

When it happens

Trigger: borrowChannel calls getOrCreateChannel while the publisher/subscriber connection has silently closed underneath; createChannel throws IOException; because retrySettings is null the no-retry branch throws.

Common situations: The cached connection was closed by the broker or network but the cached reference has not yet been refreshed; a broker restart left stale connection state; channel opened against a connection whose isOpen() check passed but which then failed.

Related errors

AI-assisted analysis of conductor-oss/conductor@cf7c3e4a8a (2026-08-14). Data as JSON: /api/errors/daacdb2ba9a34c26. Report an issue: GitHub.