apache/pulsar · warning · IllegalArgumentException

Current size and other size not equals

Error message

Current size and other size not equals

What it means

MultiMessageIdImpl.compareTo requires both multi-ids to cover the same number of topics/partitions; if either map is null or their sizes differ it throws IllegalArgumentException('Current size and other size not equals'). A position across partitions can only be ordered element-wise when the partition sets match.

Source

Thrown at pulsar-client/src/main/java/org/apache/pulsar/client/impl/MultiMessageIdImpl.java:69

    }

    // If all messageId in map are same size, and all bigger/smaller than the other, return valid value.
    @Override
    public int compareTo(MessageId o) {
        if (!(o instanceof MultiMessageIdImpl)) {
            throw new IllegalArgumentException(
                "expected MultiMessageIdImpl object. Got instance of " + o.getClass().getName());
        }

        MultiMessageIdImpl other = (MultiMessageIdImpl) o;
        Map<String, MessageId> otherMap = other.getMap();

        if ((map == null || map.isEmpty()) && (otherMap == null || otherMap.isEmpty())) {
            return 0;
        }

        if (otherMap == null || map == null || otherMap.size() != map.size()) {
            throw new IllegalArgumentException("Current size and other size not equals");
        }

        int result = 0;
        for (Entry<String, MessageId> entry : map.entrySet()) {
            MessageId otherMessage = otherMap.get(entry.getKey());
            if (otherMessage == null) {
                throw new IllegalArgumentException(
                    "Other MessageId not have topic " + entry.getKey());
            }

            int currentResult = entry.getValue().compareTo(otherMessage);
            if (result == 0) {
                result = currentResult;
            } else if (currentResult == 0) {
                continue;
            } else if (result != currentResult) {
                throw new IllegalArgumentException(
                    "Different MessageId in Map get different compare result");

View on GitHub (pinned to 820761864e)

Solutions

1. Re-checkpoint cursors after any partition-count change; don't compare cursors taken before/after a partition resize
2. Handle the extra partitions explicitly: drop them from the newer cursor or default the missing ones to earliest/latest before comparing
3. If comparing for resume logic, compare only the intersection of topics and treat missing topics as earliest
4. Catch IllegalArgumentException and rebuild the cursor from per-partition state

Example fix

// before
int r = oldCursor.compareTo(newCursor); // throws if partition counts differ
// after
Map<String, MessageId> oldMap = oldCursor.getMap();
Map<String, MessageId> newMap = newCursor.getMap();
if (oldMap.size() != newMap.size()) {
    // topic was re-partitioned; rebuild cursor for current partition count
    oldMap = rebuildCursorForCurrentPartitions(newMap.keySet());
}
int r = oldCursor.compareTo(newCursor);

boolean canCompare(MultiMessageIdImpl a, MultiMessageIdImpl b) {
    return a.getMap() != null && b.getMap() != null
        && a.getMap().size() == b.getMap().size();
}

boolean samePartitionCount(MultiMessageIdImpl a, MultiMessageIdImpl b) {
    return a.getMap().size() == b.getMap().size();
}

try {
    int r = a.compareTo(b);
} catch (IllegalArgumentException e) {
    // topic re-partitioned: rebuild cursors for the current partition count
}

When it happens

Trigger: Comparing two MultiMessageIdImpl built from different numbers of partitions — typically after the partitioned topic was resized (more partitions added) between the two snapshots, or one snapshot came from an empty/null map.

Common situations: Checkpoint restore after increasing partition count of a partitioned topic; comparing an early empty cursor with a later full one; mixing cursors from differently configured topics.

Related errors

• expected MultiMessageIdImpl object. Got instance of
• Other MessageId not have topic
• Different MessageId in Map get different compare result
• isDuplicated cannot accept
• ResourceGroupCreate: Invalid null ResourceGroup config

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/ef51300b0cd58111. Report an issue: GitHub.