Emc IP Holding Company LLC

Raeanne Marks

Tanuj Khurana

Ronald Steinke

Jonathan Mark Walton

Steven Hubbell

Jason Vigil

Karthik Palaiappan

Implementations are provided herein for causally ordering events within a distributed file system. Each node within the distributed file system, when processing an event, can collect object/version pairs associated with event (e.g., an object identifier and an object version number of the object at the time of the event). Object/version pairs can be identified and labeled as reliable or unreliable based on the operation performed on the inode as a part of the event. Relationships between events can be established when two events modify the same object and one event has a lower revision number. If the two object/revision pairs are in a relationship, an unreliable relationship can be deemed a weak edge and a reliable relationship can be deemed a strong edge. Using the strong and weak edges associated with object/revision pairs, a causal order of events can be generated.

Mitigating causality discrepancies caused by stale versioning

Implementations are provided herein for using inode revision numbers associated with a modified LIN and a set of Parent LINs to causally order transactions within a distributed file system. Any time an inode is changed, its inode revision number can be incremented by 1. When events within file system are processed causing an inode or a set of inodes to be modified, an event transaction log entry can made. The event transaction log entry can denote a description of the event, a set of modified inode and inode revision number pairs, and a set of parent inode and inode revision number pairs. Entries in the event transaction log can be used to build an inode map for each inode implicated in the event transaction log. The inode map can be used to build a set of direct causal dependencies for each transaction in the event transaction log. The set of direct causal dependencies can be used to generate a causal ordering of the transactions in the event transaction log, that in some implementations, can be made available to external services.

Causally ordering distributed file system events

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Raeanne Marks