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REDIS_READ_ACCESS_FUNCTIONS.md

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Redis Read Access Functions

Overview

Multiple functions in RateLimitingUtil.scala read counter data from Redis independently. This creates potential inconsistency and code duplication.

Current Functions Reading Redis Counters

1. underConsumerLimits (line ~152-159)

  • Uses: EXISTS + GET
  • Returns: Boolean (are we under limit?)
  • Handles missing key: Returns true (under limit)
  • Purpose: Enforcement - check if request should be allowed

2. incrementConsumerCounters (line ~185-195)

  • Uses: TTL + (SET or INCR)
  • Returns: (ttl, count) as tuple
  • Handles missing key (TTL=-2): Creates new key with value 1
  • Purpose: Tracking - increment counter after allowed request

3. ttl (line ~208-217)

  • Uses: TTL only
  • Returns: Long (normalized TTL)
  • Handles missing key (TTL=-2): Returns 0
  • Purpose: Helper - get remaining time for a period

4. getCallCounterForPeriod (line ~223-250)

  • Uses: TTL + GET
  • Returns: ((Option[Long], Option[Long]), period)
  • Handles missing key (TTL=-2): Returns (Some(0), Some(0))
  • Purpose: Reporting - display current usage to API consumers

Redis TTL Semantics

  • -2: Key does not exist
  • -1: Key exists with no expiry (shouldn't happen in our rate limiting)
  • >0: Seconds until key expires

Issues

  1. Code duplication: Redis interaction logic repeated across functions
  2. Inconsistency risk: Each function interprets Redis state independently
  3. Multiple sources of truth: No single canonical way to read counter state

Recommendation

Refactor to have ONE canonical function that reads and normalizes counter state from Redis:

private def getCounterState(consumerKey: String, period: LimitCallPeriod): (Long, Long) = {
  // Single place to read and normalize Redis counter data
  // Returns (calls, ttl) with -2 handled as 0
}

All other functions should use this single source of truth.

Status

  • Enforcement functions work correctly
  • Reporting improved (returns 0 instead of None for missing keys)
  • Refactoring to single read function: Not yet implemented