Synopsis

Banyan: Coordination-free Distributed Transactions over Mergeable Types

Synopsis by

Shashank Shekhar Dubey

Guide: Dr. KC Sivaramakrishnan

RISE Lab

Dept. of Computer Science & Engineering

IIT Madras

Brief discussion on Banyan: The problem in hand and the proposed solution

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Operational semantics
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Why build distributed systems?

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Scalability
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Fault-tolerance
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High availability
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High throughput
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Low latency
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Why build distributed systems?

Why build distributed systems?

Latency

Latency

Latency

Problem with eventual consistency

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Conflicts while merging replicas
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Mergeable Replicated Data Types (MRDT)

Distributed variant of ordinary data types

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Inbuilt ability to reconcile conflicts
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Challenges:

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Data distribution
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Recursive merge
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Storage requirement
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Operational Semantics

Banyan

Operational Semantics

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Core language => Operations
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Mathematical rules => Transactions
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Operational Semantics

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Understanding of system
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Verification
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Programming Model

Programming Model

Public Branch

Private Branch

Isolated R/W operations at each private branch

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Remote Refresh
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Publish
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Refresh
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Banyan objects:

Blob

Tree

Commit

Key-Value : [a;b;c] -> v

Initial state:

a

lb

V1

C1

write B1 [a] v1:

B1

Tag Store

Block Store

write B1 [a] v1

write B1 [b;c] v2:

write B1 [b;d] v3:

Garbage Collection

Garbage Collection

Cassandra : 4.9 MB

Banyan : 1.8 GB

376 x

Space usage: Cassandra vs Banyan

Garbage Collection

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Usual approach : Node reachability
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Our approach : Node accessibility
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Bugs found in Irmin

Prefering shorter path when merging conflicting updates

Non-commutative merge in case of modify/delete conflict

Thank you