yugabyte/yugabyte-db

[DocDB] Enable printing out why each RocksDB flush is being done

Closed

#25,615 opened on 2025年1月14日

GitHub で見る
 (3 comments) (0 reactions) (1 assignee)C (8,229 stars) (1,003 forks)batch import
area/docdbgood first issuekind/enhancementpriority/medium

説明

Jira Link: DB-14868

Description

We have had two incidents now where inability to figure out why RocksDB flushes were occurring was key and extremely hard to figure out.

This task is to build instrumentation to make this easier in the future.

That is, create a runtime-settable gflag that turns on logging messages that for each flush describe why it is being done.

Reasons might include:

  • to stay under the global MemTable limit
  • to stay under the local MemTable limit
  • by request of a flush table RPC call
  • flush requested by DoCleanupIntentFiles

The above is almost certainly not a complete list. Ideally this task instruments all the calls to flush.

Although not ideal, it's probably acceptable for the reason log message to be given earlier than the log message announcing the flush itself as long as they can be correlated.

Ideally backport this to all versions in use.

Issue Type

kind/enhancement

Warning: Please confirm that this issue does not contain any sensitive information

  • I confirm this issue does not contain any sensitive information.

コントリビューターガイド

技術スタック
cppc
領域
databaseobservability
Issue 種別
feature
難度新しい貢献者にとっての実装難度です。1 は非常に小さな変更、5 は専門的な作業です。
4
推定時間経験ある貢献者が調査、実装、テスト、pull request 準備にかけるおおよその時間範囲です。
3-5 days
活動状況Issue が今どれだけ取り組みやすいかを示します。新しい、活発、古い、ブロック中、またはメンテナー入力待ちなどです。
blocked
明確さ期待される変更、受け入れ条件、次の手順がどれだけ明確かを示します。
clear
前提条件
C++ programmingRocksDB internalsYugabyteDB build systemgflags configuration
初心者向け度初回貢献者にどれだけ取り組みやすいかを 1-100 で推定したスコアです。
20
調査方針
Identify all call sites where RocksDB flush is triggered (e.g., in src/rocksdb/db/db impl.cc). Add a runtime gflag (e.g., 'rocksdb flush reason logging') that enables logging the reason before each flush. The reason can be passed through a new argument to flush functions. Correlate with existing flush log messages. See comments on the issue for possible reasons list.