committer

README

committer

Two-phase (2PC) and three-phase (3PC) protocols implementaion in Golang. Committer uses BadgerDB for persistence.

protocols description:

• http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.63.7048&rep=rep1&type=pdf (2PC)

• http://courses.cs.vt.edu/~cs5204/fall00/distributedDBMS/sreenu/3pc.html (3PC)

Configuring

All config parameters may be specified via command-line flags

flag	description	default	example
role	role of the node (coordinator of follower)	follower	-role=coordinator
nodeaddr	node address	localhost:3050	-nodeaddr=localhost:3051
coordinator	coordinator address	""	-coordinator=localhost:3050
committype	two-phase or three-phase commit mode	three-phase	-committype=two-phase
timeout	timeout after which the message is considered unacknowledged (only for three-phase mode, because two-phase is blocking by design)	1000	-timeout=500
dbpath	database path on filesystem	./badger	-dbpath=/tmp/badger
withtrace	use distributed tracer or not (true/false)	false	-withtrace=true
followers	comma-separated list of followers' addresses	""	-followers=localhost:3052,localhost:3053,localhost:3053
whitelist	comma-separated list of allowed hosts	127.0.0.1	-whitelist=192.168.0.105,192.168.0.101

example follower:

./committer -withtrace=false -role=follower -nodeaddr=localhost:3001 -committype=three-phase -timeout=1000 -dbpath=/tmp/badger/follower

example coordinator:

./committer -withtrace=false -role=coordinator -nodeaddr=localhost:3000 -followers=localhost:3001 -committype=three-phase -timeout=1000 -dbpath=/tmp/badger/coordinator

Hooks

Hooks for requests checking on Propose and Commit stage. It's just a function that receives *pb.ProposeRequest or *pb.CommitRequest and returns true or false. Function body incorporate all validation logic.

Example hooks can be found at hooks/src/hooks.go.

You can replace code in the hooks/src/hooks.go file used by committer to inject your validation logic into the handlers.

Tracing

Start Zipkin:

docker run -d -p 9411:9411 openzipkin/zipkin

Set --withtrace true command-line flag or withtrace: true config option in config file before starting committer.

Start committer, open http://localhost:9411/zipkin

Example trace with 3 followers and 1 coordinator

make show-trace -j

open http://localhost:9411/zipkin/dependency

Testing

functional tests: make tests

Testing with example client

compile executables:

make prepare

run coordinator:

make run-example-coordinator

run follower in another shell:

make run-example-follower

run example client:

go run ./examples/client/client.go

Planned Implement a flexible transaction log mechanism. Current in-mem implementation is not reliable.