xai-org/x-algorithm · error · ConfigFailure

Regex maximumCacheItems must be greater than 0

Error message

Regex maximumCacheItems must be greater than 0

What it means

BotMaker's regex subsystem validates its RegexOptions config at registration time. maximumCacheItems controls the size of the compiled-regex LRU/expiration cache, and a non-positive value would make the cache unusable (zero or negative capacity), so ConfigFailure is thrown during config validation before any regex runs.

Source

Thrown at botmaker/src/scala/com/twitter/botmaker/runtime/config/RegexConfigs.scala:41

  final def getRegexOptions: RegexConfig = regexOptions

  final def addRegexOptions(config: RegexConfig): Unit = {

    if (config.maximumPendingRequests <= 0) {
      throw ConfigFailure(
        s"Regex maximumPendingRequests must be greater than 0"
      )
    }

    if (config.timeoutMilis <= 0) {
      throw ConfigFailure(
        s"Regex timeoutMilis must be greater than 0"
      )
    }

    if (config.maximumCacheItems <= 0) {
      throw ConfigFailure(
        s"Regex maximumCacheItems must be greater than 0"
      )
    }

    if (config.cacheExpirationMillis <= 0) {
      throw ConfigFailure(
        s"Regex cacheExpirationMillis must be greater than 0"
      )
    }

    regexOptions = config
  }
}

View on GitHub (pinned to 24c60942c5)

Solutions

1. Set maximumCacheItems to a positive value (e.g. 1024) in the RegexOptions you register
2. If the value comes from a config file/env var, check for typos or missing keys that yield 0
3. If you intended no caching, pick a small positive value; zero-capacity caches are not supported

Example fix

// before
regexOptions = RegexOptions(
  timeoutMillis = 1000,
  maximumCacheItems = 0,
  cacheExpirationMillis = 60000)

// after
regexOptions = RegexOptions(
  timeoutMillis = 1000,
  maximumCacheItems = 1024,
  cacheExpirationMillis = 60000)

def validateRegexOptions(o): assert o.timeoutMillis > 0 and o.maximumCacheItems > 0 and o.cacheExpirationMillis > 0, f"bad regex options: {o}"

try:
    registerRegexOptions(opts)
except ConfigFailure as e:
    if "maximumCacheItems" in str(e):
        opts = replace(opts, maximumCacheItems=1024)
        registerRegexOptions(opts)
    else:
        raise

When it happens

Trigger: Calling the regex config setter with RegexOptions where maximumCacheItems <= 0, e.g. maximumCacheItems = 0 or a negative number, during service/bot config assembly at startup.

Common situations: Copying a config template and forgetting to fill in cache size; deriving maximumCacheItems from an unset env var or config key that defaults to 0; disabling the cache intentionally by setting 0 (not supported).

Understand the failure class

Background: Config validation failed: what "invalid value for {key}" and settings-rejection errors mean across 19 open-source libraries — this error's family across 19 libraries.

Related errors

• Regex cacheExpirationMillis must be greater than 0
• ScheduledEvent ${config.eventType} intervalMillis must be a
• Conflict config name:${nameSeq.mkString}
• Event type '$eventType' does not match $eventTypeRegex.
• Field name '$fieldName' does not match $fieldNameRegex.

AI-assisted analysis of xai-org/x-algorithm@24c60942c5 (2026-08-28). Data as JSON: /api/errors/3b9e981e46c1f816. Report an issue: GitHub.