The document discusses optimizations to reduce network communication for update transactions in Glusterfs replication. It describes the current 5 stages of transactions and proposes optimizations like eager-locking files to delay post-operations, and skipping pre-operation stages for metadata transactions to reduce network operations from 5 to closer to 1. The document ends with an invitation for questions.

1. Glusterfs Session #14
Replication update transaction

2. Scope
- Update transaction
- Data/Metadata operation
- Optimizations to reduce the network communication

3. Update operation
- 5 stages of transaction
- Lock - Take inodelk
- Pre-Op - Perform xattrop that marks trusted.afr.dirty xattr.
- Op - Actual fop
- Post-Op - Mark pending xattrop to indicate pending heals on partial failure, otherwise remove
dirty xattr
- Unlock - Unlock inodelk

4. Update operation
- Demo/Code reading

5. Optimizations
- Transaction takes 5 network operations
- This increases the latency quite a bit
- We need to get the network operations as close to 1 as possible

6. Eager-lock, delayed post-op for streaming writes
- Take full file lock
- In all success case, delay post-op by a second waiting for more writes, so that
the lock, pre-op phases can be skipped
- When contention is detected, skip delay and perform post-op/unlock

7. Skip pre-op operation for metadata/entry transactions
- Don’t perform pre-op operation, only on partial failure, do pending operation
directly
- Handle the other corner cases on next lookup

8. Q & A