SolaceIO.Write: Overriding PUB_ACK_WINDOW_SIZE to

Error message

SolaceIO.Write: Overriding PUB_ACK_WINDOW_SIZE to {} since HIGHER_THROUGHPUT mode was selected

What it means

When HIGHER_THROUGHPUT submission mode is selected, Solace publisher SessionService overrides PUB_ACK_WINDOW_SIZE to BATCHED_PUB_ACK_WINDOW. If the user had set a different ack window, this WARN tells them their value is replaced. Informational only.

Solutions

Accept the override (it is the mode's intended behavior).
If a custom ack window matters, use SubmissionMode.CUSTOM with your full JCSMP properties.
Remove the explicit PUB_ACK_WINDOW_SIZE to silence the warning.

Example fix

// before
props.setProperty(JCSMPProperties.PUB_ACK_WINDOW_SIZE, 51);
.withSubmissionMode(SubmissionMode.HIGHER_THROUGHPUT);
// after: keep custom value via CUSTOM mode
.withSubmissionMode(SubmissionMode.CUSTOM);

Defensive patterns

Strategy: validation

Validate before calling

Integer ackWindow = (Integer) props.getProperty(JCSMPProperties.PUB_ACK_WINDOW_SIZE);
if (mode == SubmissionMode.HIGHER_THROUGHPUT && ackWindow != null && ackWindow != BATCHED_PUB_ACK_WINDOW) {
  LOG.warn("Custom PUB_ACK_WINDOW_SIZE " + ackWindow + " will be overridden");
}

Prevention

Use SubmissionMode.CUSTOM when a hand-tuned ack window matters.
Document custom JCSMP settings next to the write transform config.
Review broker-side batching behavior after mode changes.

When it happens

Trigger: write().withSubmissionMode(HIGHER_THROUGHPUT) combined with an explicit JCSMPProperties.PUB_ACK_WINDOW_SIZE that differs from BATCHED_PUB_ACK_WINDOW.

Common situations: Users hand-tuning ack windows for throughput/latency tradeoffs but then also selecting a built-in submission mode that re-applies its own defaults.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/6388e3bc66e3fbc4. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/io/solace/src/main/java/org/apache/beam/sdk/io/solace/broker/SessionService.java:227

    // PUB_ACK_WINDOW_SIZE heavily affects performance when publishing persistent
    // messages. It can be a value between 1 and 255. This is the batch size for the ack
    // received from Solace. A value of 1 will have the lowest latency, but a very low
    // throughput and a monumental backpressure.

    // Retrieve current values of the properties
    Boolean msgCbProp = props.getBooleanProperty(JCSMPProperties.MESSAGE_CALLBACK_ON_REACTOR);
    Integer ackWindowSize = props.getIntegerProperty(JCSMPProperties.PUB_ACK_WINDOW_SIZE);

    switch (mode) {
      case HIGHER_THROUGHPUT:
        // Check if it was set by user, show override warning
        if (msgCbProp != null && msgCbProp) {
          LOG.warn(
              "SolaceIO.Write: Overriding MESSAGE_CALLBACK_ON_REACTOR to false since"
                  + " HIGHER_THROUGHPUT mode was selected");
        }
        if ((ackWindowSize != null && ackWindowSize != BATCHED_PUB_ACK_WINDOW)) {
          LOG.warn(
              "SolaceIO.Write: Overriding PUB_ACK_WINDOW_SIZE to {} since"
                  + " HIGHER_THROUGHPUT mode was selected",
              BATCHED_PUB_ACK_WINDOW);
        }

        // Override the properties
        // Use a dedicated thread for callbacks, increase the ack window size
        props.setProperty(JCSMPProperties.MESSAGE_CALLBACK_ON_REACTOR, false);
        props.setProperty(JCSMPProperties.PUB_ACK_WINDOW_SIZE, BATCHED_PUB_ACK_WINDOW);
        LOG.info(
            "SolaceIO.Write: Using HIGHER_THROUGHPUT mode, MESSAGE_CALLBACK_ON_REACTOR is FALSE,"
                + " PUB_ACK_WINDOW_SIZE is {}",
            BATCHED_PUB_ACK_WINDOW);
        break;
      case LOWER_LATENCY:
        // Check if it was set by user, show override warning
        if (msgCbProp != null && !msgCbProp) {
          LOG.warn(

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