languagetool-org/languagetool · error · IllegalArgumentException

Invalid value for cacheSize: , use 0 to deactivate cache

Error message

Invalid value for cacheSize: , use 0 to deactivate cache

What it means

The 'cacheSize' server property controls the size of LanguageTool's result cache and must be >= 0 (0 disables the cache). A negative value is rejected with this IllegalArgumentException during server configuration parsing.

Source

Thrown at languagetool-server/src/main/java/org/languagetool/server/HTTPServerConfig.java:396

          throw new IllegalArgumentException("The AfterTheDeadline mode is not supported anymore in LanguageTool 3.8 or later");
        }
        String rulesConfigFilePath = getOptionalProperty(props, "rulesFile", null);
        if (rulesConfigFilePath != null) {
          rulesConfigFile = new File(rulesConfigFilePath);
          if (!rulesConfigFile.exists() || !rulesConfigFile.isFile()) {
            throw new RuntimeException("Rules Configuration file cannot be found: " + rulesConfigFile);
          }
        }
        String remoteRulesConfigFilePath = getOptionalProperty(props, "remoteRulesFile", null);
        if (remoteRulesConfigFilePath != null) {
          remoteRulesConfigFile = new File(remoteRulesConfigFilePath);
          if (!remoteRulesConfigFile.exists() || !remoteRulesConfigFile.isFile()) {
            throw new RuntimeException("Remote rules configuration file cannot be found: " + remoteRulesConfigFile);
          }
        }
        cacheSize = Integer.parseInt(getOptionalProperty(props, "cacheSize", "0"));
        if (cacheSize < 0) {
          throw new IllegalArgumentException("Invalid value for cacheSize: " + cacheSize + ", use 0 to deactivate cache");
        }
        if (props.containsKey("cacheTTLSeconds") && !props.containsKey("cacheSize")) {
          throw new IllegalArgumentException("Use of cacheTTLSeconds without also setting cacheSize has no effect.");
        }
        cacheTTLSeconds = Integer.parseInt(getOptionalProperty(props, "cacheTTLSeconds", "300"));
        maxErrorsPerWordRate = Float.parseFloat(getOptionalProperty(props, "maxErrorsPerWordRate", "0"));
        suggestionsEnabled = Boolean.parseBoolean(getOptionalProperty(props, "suggestionsEnabled", "true"));
        maxSpellingSuggestions = Integer.parseInt(getOptionalProperty(props, "maxSpellingSuggestions", "0"));
        blockedReferrers = Arrays.asList(getOptionalProperty(props, "blockedReferrers", "").split(",\\s*"));
        setTrustedSources(getOptionalProperty(props, "trustedSources", null));
        String premiumAlwaysValue = props.getProperty("premiumAlways");
        if (premiumAlwaysValue != null) {
          premiumAlways = Boolean.parseBoolean(premiumAlwaysValue.trim());
          if (premiumAlways) {
            System.out.println("*** Running in PREMIUM-ALWAYS mode");
          }
        }
        premiumOnly = Boolean.valueOf(getOptionalProperty(props, "premiumOnly", "false").trim());

View on GitHub (pinned to 2e990059ce)

Solutions

1. Set 'cacheSize=0' in server.properties to disable the cache
2. Use a positive value (e.g. cacheSize=1000) to enable the cache with that entry count
3. Re-validate provisioning templates that substitute the cacheSize value

Example fix

// before (server.properties)
cacheSize=-1

// after (server.properties)
cacheSize=0

String v = props.getProperty("cacheSize");
if (v != null && Integer.parseInt(v.trim()) < 0) {
    throw new IllegalStateException("cacheSize must be >= 0 (0 disables cache)");
}

try {
    serverConfig = new HTTPServerConfig(props);
} catch (IllegalArgumentException e) {
    if (e.getMessage().startsWith("Invalid value for cacheSize")) {
        props.setProperty("cacheSize", "0");
        serverConfig = new HTTPServerConfig(props);
    } else { throw e; }
}

When it happens

Trigger: Starting the HTTP server with 'cacheSize' set to a negative number (e.g. cacheSize=-1) in the server properties file.

Common situations: Copy-pasted tuning advice that used -1 as 'disabled' (the correct value is 0); variable interpolation in provisioning templates resolving to a negative default.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Use of cacheTTLSeconds without also setting cacheSize has no
• The AfterTheDeadline mode is not supported anymore in Langua
• Rules Configuration file cannot be found:
• Remote rules configuration file cannot be found:
• Cannot use premiumOnly=true with non-premium version

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/86551cb925d6e084. Report an issue: GitHub.