apache/cassandra · error · ConfigurationException

dc name must not be empty

Error message

dc name must not be empty

What it means

ParameterizedFastPathStrategy.WeightDc.validateDC rejects a datacenter name in the accord fast_path 'dcs' option that is empty after trimming, throwing a ConfigurationException ('dc name must not be empty'). The dcs option is a comma-separated list of <dc>[:<weight>] entries used to weight Accord fast-path electorate selection.

Source

Thrown at src/java/org/apache/cassandra/service/accord/topology/ParameterizedFastPathStrategy.java:126

        @Override
        public int compareTo(@Nonnull WeightedDc that)
        {
            int cmp = Integer.compare(this.weight, that.weight);
            if (cmp != 0) return cmp;
            return this.name.compareTo(that.name);
        }

        public String toString()
        {
            return autoWeight ? name : name + ':' + weight;
        }

        static String validateDC(String dc)
        {
            dc = dc.trim();
            if (dc.isEmpty())
                throw cfe("dc name must not be empty", DCS);
            return dc;
        }

        static int validateWeight(String w)
        {
            int weight = Integer.parseInt(w);
            if (weight < 0)
                throw cfe("DC weights must be zero or positive");
            return weight;
        }

        static WeightedDc fromString(String s, int idx)
        {
            s = s.trim();
            if (s.isEmpty())
                throw cfe("%s entries must not be empty", DCS);

            String[] parts = COLON_SEPARATOR.split(s);

View on GitHub (pinned to 88fd0f6a0e)

Solutions

1. Remove stray commas so the dcs list contains only non-empty entries, e.g. dcs=dc1:1,dc2:2
2. Verify each DC name matches an actual datacenter defined in the cluster (use nodetool describecluster/describecluster datacenters)
3. Re-run the CREATE/ALTER statement with the corrected dcs value

Example fix

// before
ALTER KEYSPACE ks WITH options = {fast_path: {'size':'4', 'dcs':'dc1:1,,dc3'}}

// after
ALTER KEYSPACE ks WITH options = {fast_path: {'size':'4', 'dcs':'dc1:1,dc3'}}

String dcs = "dc1:1,dc2";
List<String> bad = java.util.Arrays.stream(dcs.split(","))
    .map(String::trim).filter(String::isEmpty).collect(java.util.stream.Collectors.toList());
if (!bad.isEmpty()) throw new IllegalArgumentException("dcs contains empty entries; fix commas");

try { applyFastPathOption(opts); } catch (org.apache.cassandra.exceptions.ConfigurationException e) {
    if (e.getMessage().contains("must not be empty"))
        log.error("Remove empty dc entries from the dcs list");
}

When it happens

Trigger: Configuring a keyspace/table fast_path parameterized strategy with a dcs string containing an empty DC entry, e.g. 'dcs=,dc1' or 'dc1:2,,dc2', so fromString -> validateDC receives ''.

Common situations: Trailing or double commas when hand-writing the dcs list in a CREATE/ALTER keyspace option or cassandra.yaml-like config; copy-paste with a lost DC name; generated config with empty variable for the DC name.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• accord.journal_directory must not be the same as any data_fi
• accord.cache_size option was set incorrectly to '<value>', s
• the local data center must be part of the repair; requested
• No accord transaction should be executed when accord.enabled
• Cannot change transactional mode to %s for %s.%s with accord

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/1237ad3e56e480ed. Report an issue: GitHub.