This talk is for developers new to formal verification of algorithms. It will be an introduction to TLA+, which is a formal specification language. It’s a tool to design systems and algorithms, then programmatically verify that those systems don’t have critical bugs. It’s the software equivalent of a blueprint. At ING we are using TLA+ to reason about the split-brain situations that occur in distributed systems and how to deal with those. Achieving correctness of such an SBR (Split Brain Resolver) algorithm is challenging and TLA+ helped in finding complex or subtle problems. The key takeaway from the talk will be to let developers know about TLA+ and motivate them to apply it when designing new applications or distributed systems. This talk was prepared and given together with Bekir Oguz

4. Baker on Github
h ps://github.com/ing-bank/baker

6. WHAT IS TLA+WHAT IS TLA+

24. Code on Github
h ps://github.com/JordyMoos/talk-tla-transfer

27. Code on Github
h ps://github.com/JordyMoos/talk-tla-hanoi

36. NETWORK PARTITIONNETWORK PARTITION

37. How to implement a Split Brain Resolver algorithm?
Members
Leader
Unreachable nodes

38. What might happen at any me?
New member joins
Member leaves
Member unreachable
Member reachable
Leader changed
Who survives when a split happens?

39. Code on Github
h ps://github.com/ing-bank/baker/blob/split-brain-
resolver/tla/ClusterV6.tla

40. Benefits of TLA+
High level thinking
Tes ng before coding
Documenta on

41. Thank you! Ques ons?