apache/cassandra · error · RuntimeException

Unable to serialize password_policy configuration

Error message

Unable to serialize password_policy configuration

What it means

Guardrails.getPasswordPolicyConfig (part of the Guardrails public API) serializes the password policy configuration object to JSON using JsonUtils.JSON_OBJECT_MAPPER. Any Throwable during serialization is swallowed and replaced by a RuntimeException('Unable to serialize password_policy configuration') — the original cause is discarded.

Solutions

1. Check the server log around the failure for the underlying Jackson error — this wrapper discards the cause, so reproduce with the same config to see it
2. Reset the password policy to a known-good value (default config) via setPasswordPolicy, then retry
3. Verify the Cassandra and Jackson versions are consistent (shaded jars / classpath pollution of a different jackson-databind)
4. Inspect what was passed to setPasswordPolicy most recently; fix or remove the invalid config

Example fix

// before
PasswordPolicyConfig custom = buildConfig(); // type not Jackson-serializable
// after
Use a config type with standard getters (POJO/record) compatible with JSON_OBJECT_MAPPER, or revert to Guardrails' default config

// Before reading, verify the policy config was set from a known-good source
Object cfg = guardrails.getPasswordPolicyConfig();
if (cfg == null) logger.warn("No password policy config set; default will be serialized");

try {
    String json = guardrails.getPasswordPolicyConfig();
} catch (RuntimeException e) {
    if (e.getMessage().equals("Unable to serialize password_policy configuration")) {
        logger.error("Password policy config not Jackson-serializable; resetting to default", e);
        guardrails.setPasswordPolicy(defaultJson);
    }
}

When it happens

Trigger: Calling getPasswordPolicyConfig() when the stored password policy configuration object cannot be mapped to JSON by Jackson (e.g. an unmappable/irregular type or a getter throwing), typically after a custom or corrupt config was set via setPasswordPolicy.

Common situations: A configuration object type missing Jackson-accessible accessors; a classpath/Jackson version mismatch; setting a malformed policy programmatically before reading it back.

Understand the failure class

Background: "JSON serialization failed", "not JSON serializable", "Failed to serialize": why JSON marshaling errors happen and how to fix them — this error's family across 46 libraries.

Related errors

• It was not possible to generate a valid password in
• must be positive.
• The shortest password to pass the failing validator for any
• Unable to serialize minimum_client_driver_versions_warned…
• Unable to serialize…

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/b3c8588cdea578a7. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/guardrails/Guardrails.java:1587

        return DEFAULT_CONFIG.getMaximumReplicationFactorFailThreshold();
    }

    @Override
    public void setMaximumReplicationFactorThreshold (int warn, int fail)
    {
        DEFAULT_CONFIG.setMaximumReplicationFactorThreshold(warn, fail);
    }

    @Override
    public String getPasswordPolicy()
    {
        try
        {
            return JsonUtils.JSON_OBJECT_MAPPER.writeValueAsString(passwordPolicy.getConfig());
        }
        catch (Throwable t)
        {
            throw new RuntimeException("Unable to serialize password_policy configuration");
        }
    }

    @Override
    public String getRoleNamePolicy()
    {
        try
        {
            return JsonUtils.JSON_OBJECT_MAPPER.writeValueAsString(roleNamePolicy.getConfig());
        }
        catch (Throwable t)
        {
            throw new RuntimeException("Unable to serialize role_name_policy configuration");
        }
    }

    @Override
    public void setPasswordPolicy(String value)

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