apache/cassandra · error · ConfigurationException

is not a valid size in bytes

Error message

%s %s is not a valid size in bytes: %s

What it means

Thrown when the target_sstable_size string cannot be parsed as a number of bytes by FBUtilities.parseHumanReadableBytes; the NumberFormatException is wrapped into a ConfigurationException. The option must be a human-readable byte size like '160MiB' or a plain long byte count.

Solutions

1. Provide a valid human-readable size string, e.g. 'target_sstable_size': '160MiB'.
2. Use a plain integer byte count if unit suffixes are causing problems.
3. Remove the option to fall back to the default target sstable size.

Example fix

// before
'target_sstable_size': '160 MB!'
// after
'target_sstable_size': '160MiB'

try { FBUtilities.parseHumanReadableBytes(opts.get("target_sstable_size")); } catch (NumberFormatException e) { /* reject before schema change */ }

try { alterTable(); } catch (ConfigurationException e) { fixAndRetry(e.getMessage()); }

When it happens

Trigger: Controller.validateOptions receives a target_sstable_size value that parseHumanReadableBytes rejects (non-numeric text, malformed unit suffix, empty string), e.g. via CREATE TABLE compaction options or ALTER TABLE.

Common situations: Typos such as '160 MiB' with unexpected characters, '10GBX', locale-formatted numbers ('10,000'), or passing a decimal like '1.5GB' where the parser expects an integer quantity.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• is not a parsable long (base10) for
• concurrent_compactors should be strictly greater than 0…
• Could not set new local compaction strategy
• Disabling compaction by setting compaction thresholds to 0…
• Fan factor cannot be lower than 2 in

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/76835c015a6c4683. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/compaction/unified/Controller.java:538

            {
                double targetSize = FBUtilities.parseHumanReadable(s, null, "B");
                if (targetSize >= Long.MAX_VALUE) {
                    throw new ConfigurationException(String.format("%s %s is out of range of Long.",
                                                                    TARGET_SSTABLE_SIZE_OPTION,
                                                                    s));
                }
                if (targetSize < MIN_TARGET_SSTABLE_SIZE)
                {
                    throw new ConfigurationException(String.format("%s %s is not acceptable, size must be at least %s",
                                                                   TARGET_SSTABLE_SIZE_OPTION,
                                                                   s,
                                                                   FBUtilities.prettyPrintMemory(MIN_TARGET_SSTABLE_SIZE)));
                }
                targetSSTableSize = (long) Math.ceil(targetSize);
            }
            catch (NumberFormatException e)
            {
                throw new ConfigurationException(String.format("%s %s is not a valid size in bytes: %s",
                                                               TARGET_SSTABLE_SIZE_OPTION,
                                                               s,
                                                               e.getMessage()),
                                                 e);
            }
        }

        s = options.remove(FLUSH_SIZE_OVERRIDE_OPTION);
        if (s != null)
        {
            try
            {
                long flushSize = FBUtilities.parseHumanReadableBytes(s);
                if (flushSize < MIN_TARGET_SSTABLE_SIZE)
                    throw new ConfigurationException(String.format("%s %s is not acceptable, size must be at least %s",
                                                                   FLUSH_SIZE_OVERRIDE_OPTION,
                                                                   s,
                                                                   FBUtilities.prettyPrintMemory(MIN_TARGET_SSTABLE_SIZE)));

View on GitHub (pinned to 88fd0f6a0e)