ChunkCache drops a dirty chunk if saving it during eviction fails

Aperta
  • Qualcosa non va?
#372 0 commenti 0 reazioni 0 assegnatari Vedi su GitHub

Nessuno ha ancora preso questa issue.

Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
35/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
cloud, java
Ambito
data-engineering

Direzione di ricerca

Start with ChunkCache and the eviction listener wired through Caffeine's .executor(Runnable::run), plus the chunkSaver.save call that catches IOException and NonWritableChannelException. The issue suggests a side map drained by flush() or excluding dirty chunks from eviction, but the design choice is open. Done means a dirty chunk survives a failed save during eviction and is written or reported by force(), which needs fault-injected tests since reproduction is unclear.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

I was reading ChunkCache while working on #370 and noticed this:

try {
    chunkSaver.save(index, chunk);
} catch (IOException | NonWritableChannelException e) {
    exceptionsDuringWrite.add(e);
}
bufferPool.recycle(chunk.data());

By the time this runs the chunk is already out of the cache, so if the save fails there is nothing left to retry. The exception is recorded and surfaces later in force(), but the data is gone, and the write() that produced it had already returned, so from the caller's side it looks written.

The cache holds at most five idle chunks (MAX_CACHED_CLEARTEXT_CHUNKS), so writing a file with more chunks evicts dirty ones as a matter of course. A transient ENOSPC or EIO at the wrong moment is enough.

I have not tried to reproduce it. It needs the save to fail exactly during eviction, so I guess it takes fault injection rather than a real filesystem.

It also does not look like a one-liner: the listener runs inside Caffeine's eviction (.executor(Runnable::run)), so re-inserting from there would just evict again. Keeping failed chunks in a side map drained by flush(), or keeping dirty chunks out of eviction altogether, both seem plausible.

Happy to take this if you think it is worth fixing.

Lingua principale
Java
Stelle
110
Fork
39
Merge medio
1g 28m
PR unite (30g)
4

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