Api: ✨ Chat History Search API (redis score system changed)

[psychology50]

작업 이유

• Implement a Chat History Retrieval API by Chat Room
• Modify the storage method for chat history in Redis.

작업 사항

1️⃣ Api Specification

• request
  • url: GET /v2/chat-rooms/{chatRoomId}/chats?chatRoomId=&lastMessageId=&size=
    • pre-condition: authenticated user, chat room accessible by userId
    • parameter
      • chatRoomId
      • lastMessageId: oldest message ID read by the client
      • size: content size (Optional)
• response

  {
    "code": ""
    "data": {
      "chats": {
        "contents": [
          {
            "chatRoomId": 0,
            "chatId": 0,
            "content": "string",
            "contentType": "TEXT",
            "categoryType": "NORMAL",
            "createdAt": "2024-11-10 14:05:10",
            "senderId": 0
          },
        ],
        "currentPageNumber": 0,
        "pageSize": 0,
        "numberOfElements": 0,
        "hasNext": true
    }
  }

2️⃣ Redis Sorted Set Score Type Problem

The issue was first discovered during integration testing.
With N data entries saved and querying the oldest message ID as lastMessageId, it should return 0.

However, the same lastMessageId messages kept appearing.

Revealing that Redis' sorted set score type only supports double values, causing precision loss for the long type chatId used as a score.
This was resolved by implementing lexicographical sorting, using a format of {timestamp}:{counter} as follows:

/**
* TSID를 lexicographical sorting이 가능한 형태의 문자열로 변환
* format: {timestamp부분:16진수}:{counter부분:4자리}
*/
private String formatTsidKey(long tsid) {
    String tsidStr = String.valueOf(tsid);

    String timestamp = tsidStr.substring(0, tsidStr.length() - COUNTER_DIGITS);
    String counter = tsidStr.substring(tsidStr.length() - COUNTER_DIGITS);

    return timestamp + ":" + counter;
}

리뷰어가 중점적으로 확인해야 하는 부분

• Potential performance degradation from the new method, but not critical given expected traffic.
• Code has seen many rapid changes; feedback on areas needing improvement is appreciated.

발견한 이슈

• Many commands with REV are now deprecated in Redis, yet Data Redis still supports them, so no changes were made.
• Due to complexity, we have decided to clear existing chat history with the iOS team's consent.