Classify possible failure points of distributed applications

Question

Classify the possible failure points of a distributed application.

Answer 1

Client is not able to locate server: return error

Lost request messages: simple time-out mechanisms

Lost replies: timeout mechanisms

• Make operation idempotent
• Use sequence numbers, mark retransmissions

Server failures: did failure take place before or after operation?

• At least once semantics (SUNRPC)
• At most once
• No guarantee

Client failure: what happens to server computation?
Referred to as an orphan

Extermination:

• logging at client stub and explicitly kill orphans
• Overhead of keeping disk logs

Reincarnation:

• Divide the time into epochs between failures and delete computations from old epochs
• Gentle reincarnation: upon a new epoch broadcast, try to locate owner first (delete only if no owner)

Expiration: give each RPC a fixed quantum T; explicitly request extensions