What causes "Failed to remove event execution for event: %s, handler: %s" in conductor-oss/conductor?

Confirm Cassandra health and that the delete consistency is reachable.

conductor-oss/conductor · error · TransientException

Failed to remove event execution for event: %s, handler: %s

Error message

Failed to remove event execution for event: %s, handler: %s

What it means

removeEventExecution wraps DriverException in a TransientException naming the event and handler. Deletion failures are treated as retriable and the framework RetryTemplate retries up to 3 times.

Source

Thrown at cassandra-persistence/src/main/java/com/netflix/conductor/cassandra/dao/CassandraExecutionDAO.java:705

    }

    @Override
    public void removeEventExecution(EventExecution eventExecution) {
        try {
            recordCassandraDaoEventRequests("removeEventExecution", eventExecution.getEvent());
            session.execute(
                    deleteEventExecutionStatement.bind(
                            eventExecution.getMessageId(),
                            eventExecution.getName(),
                            eventExecution.getId()));
        } catch (DriverException e) {
            Monitors.error(CLASS_NAME, "removeEventExecution");
            String errorMsg =
                    String.format(
                            "Failed to remove event execution for event: %s, handler: %s",
                            eventExecution.getEvent(), eventExecution.getName());
            LOGGER.error(errorMsg, e);
            throw new TransientException(errorMsg);
        }
    }

    @VisibleForTesting
    List<EventExecution> getEventExecutions(
            String eventHandlerName, String eventName, String messageId) {
        try {
            return session
                    .execute(selectEventExecutionsStatement.bind(messageId, eventHandlerName))
                    .all()
                    .stream()
                    .filter(row -> !row.isNull(PAYLOAD_KEY))
                    .map(row -> readValue(row.getString(PAYLOAD_KEY), EventExecution.class))
                    .collect(Collectors.toList());
        } catch (DriverException e) {
            String errorMsg =
                    String.format(
                            "Failed to fetch event executions for event: %s, handler: %s",

View on GitHub (pinned to cf7c3e4a8a)

Solutions

Confirm Cassandra health and that the delete consistency is reachable.
Monitor tombstone/compaction activity on the events table if deletes are slow/timing out.
Tune driver timeouts and rely on the framework retry; inspect the logged cause if it fails through.
Ensure RF supports the configured consistency under node loss.

Defensive patterns

Strategy: retry

Try / catch

RetryTemplate retry = RetryTemplate.builder().retryOn(TransientException.class).maxAttempts(3).noBackoff().build();
retry.execute(ctx -> { executionDAO.removeEventExecution(eventExecution); return null; });

Prevention

Watch tombstone/compaction pressure on the events table from frequent deletes.
Keep driver timeouts sized for delete latency.
Maintain RF high enough to tolerate node loss at the configured consistency.

When it happens

Trigger: Deleting an EventExecution row fails at the driver level — node down, delete timeout, consistency not met.

Common situations: Cluster degradation; tombstone/compaction pressure causing delete latency; driver pool exhaustion.

Related errors

AI-assisted analysis of conductor-oss/conductor@cf7c3e4a8a (2026-08-14). Data as JSON: /api/errors/1b7b72839c0b7c59. Report an issue: GitHub.