apache/cassandra · warning · IllegalArgumentException

The next training or importing can occur only at least after

Error message

The next training or importing can occur only at least after %s from the last training which happened at %s. You can train again no earlier than at %s.

What it means

To avoid excessive training churn, the manager enforces a minimum interval (config.minTrainingFrequency, in minutes) between training or importing operations for a table. checkTrainingFrequency compares the last training timestamp against now and throws IllegalArgumentException when the request comes too soon, reporting when the next training is allowed.

Source

Thrown at src/java/org/apache/cassandra/db/compression/CompressionDictionaryManager.java:356

               .minTrainingFrequency(CompressionDictionaryTrainingConfig.getMinTrainingFrequency(compressionParams.getOtherOptions()))
               .chunkSize(compressionParams.chunkLength())
               .build();
    }


    private void checkTrainingFrequency(LightweightCompressionDictionary lastDictionary, CompressionDictionaryTrainingConfig config)
    {
        Instant lastTraining = lastDictionary == null ? null : lastDictionary.createdAt;

        // if there is no dictionary trained so far or min frequency is 0 - that is we can train as often as we want -
        // then do not check if we can
        if (lastTraining != null && config.minTrainingFrequency != 0)
        {
            Instant now = FBUtilities.now();
            if (lastTraining.isAfter(now.minus(config.minTrainingFrequency, ChronoUnit.MINUTES)))
            {
                Instant nextEarliestTraining = lastTraining.plus(config.minTrainingFrequency, ChronoUnit.MINUTES);
                throw new IllegalArgumentException(format("The next training or importing can occur only at least after %s from the last training which happened at %s. " +
                                                          "You can train again no earlier than at %s.",
                                                          new DurationSpec.IntMinutesBound(config.minTrainingFrequency, TimeUnit.MINUTES),
                                                          lastTraining,
                                                          nextEarliestTraining));
            }
        }
    }

    private void storeDictionary(CompressionDictionary dictionary)
    {
        if (!isEnabled)
        {
            return;
        }

        SystemDistributedKeyspace.storeCompressionDictionary(keyspaceName, tableName, tableId, dictionary);
        cache.add(dictionary);
    }

View on GitHub (pinned to 88fd0f6a0e)

Solutions

Wait until the reported nextEarliestTraining time before invoking train() or importCompressionDictionary() again.
Set minTrainingFrequency to 0 in the training parameters to disable the frequency check when appropriate (e.g. tests).
Make automation idempotent: record last-training time and only fire when the interval has elapsed.
Use force=true semantics carefully — the frequency check still applies via checkTrainingFrequency.

Example fix

// before
manager.train(true, params); // every minute — throws
// after
Map<String, String> params = Map.of("min_training_frequency", "0"); // or schedule after the allowed interval
manager.train(true, params);

Defensive patterns

Strategy: validation

Validate before calling

Instant lastTraining = manager.getLastTrainingTime();
Duration minFreq = Duration.ofMinutes(manager.getMinTrainingFrequency());
if (lastTraining == null || lastTraining.isBefore(Instant.now().minus(minFreq))) manager.train(force, params);

Try / catch

try { manager.train(force, params); } catch (IllegalArgumentException e) { /* too soon: parse nextEarliestTraining and schedule retry */ }

Prevention

Record last-training timestamps in automation and respect the interval
Back off and retry after the reported earliest time
Set min_training_frequency to 0 only for tests

When it happens

Trigger: Calling train() or importCompressionDictionary() sooner than minTrainingFrequency minutes after the table's last recorded training, when minTrainingFrequency != 0 and a last-training timestamp exists.

Common situations: Automation scripts retrying training in a tight loop; multiple operators triggering training back-to-back; re-running an import right after training; setting a large minTrainingFrequency and forgetting it when testing.

Related errors

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/085f48b30fe40e9e. Report an issue: GitHub.