# How Accurate Clocks Improve Observability in Distributed Systems

DevFeed: [How Accurate Clocks Improve Observability in Distributed Systems](<https://devfeed.tech/articles/it-s-about-time-12547.md>)

Original publisher: [Read original article](<http://brooker.co.za/blog/2023/11/27/about-time.html>)

Author: Marc Brooker

Published: 2023-11-27T00:00:00Z

Content type: article

Language: en

Sources: [Marc Brooker's Blog](<https://devfeed.tech/sources/marc-brooker-s-blog.md>), [Marc Brooker's Blog](<https://devfeed.tech/sources/marc-brooker-s-blog-2.md>)

Topics: [distributed-systems](<https://devfeed.tech/topics/distributed-systems.md>), [Amazon EC2](<https://devfeed.tech/topics/amazon-ec2.md>), [observability](<https://devfeed.tech/topics/observability.md>), [Amazon Web Services](<https://devfeed.tech/topics/aws.md>)

Tags: [aws](<https://devfeed.tech/tags/aws.md>), [causality](<https://devfeed.tech/tags/causality.md>), [distributed-systems](<https://devfeed.tech/tags/distributed-systems.md>), [ec2](<https://devfeed.tech/tags/ec2.md>), [observability](<https://devfeed.tech/tags/observability.md>)

## AI overview

This article examines how increasingly accurate time synchronization, including microsecond-accurate clocks in Amazon EC2, can affect distributed-system design. It focuses on observability and explains that accurate timestamps make establishing causality and ordering events easier.

## Source excerpt

It's About Time! What's the time? Time to get a watch. My friend Al Vermeulen used to say time is for the amusement of humans1. Al's sentiment is still the common one among distributed systems builders: real wall-clock physical time is great for human-consumption (like log timestamps and UI presentation), but shouldn't be relied on by computer for things like actually affect the operation of the system. This remains a solid starting point, the right default position, but the picture has always been more subtle. Recently, the availability of ever-better time synchronization has made it even more subtle. This post will attempt to unravel some of that subtlety. Today is a good day to talk about time, because last week AWS announced (more details here) microsecond-accurate time synchronization in EC2, improving on what was already very good. All this means is that if you have an EC2 instance2 you can expect its clock to by accurate to within microseconds of the physical time. It turns out that having microsecond-level time accuracy makes some distributed systems stuff much easier than it was in the past. In hopes of understanding the controversy over using real time in systems, let's descend level-by-level into how we might entangle physical time more deeply in our system designs. Level 0: Observability, and the Amusement of Humans ... reality, the name we give to the common experience3 When we try understand how a system works, or why it's not working, the first task is to establish causality. Thing A caused thing B. Here in our weird little universe, we need thing A to have happened before thing B for A to have caused B. Time is useful for this. Prosecutor: Why, Mr Load Balancer, did you stop sending traffic to Mrs Server? Mr LB: Simply, sir, because she stopped processing my traffic! Mrs Server, from the gallery: Liar! Liar! I only stopped processing because you stopped sending! If we can't trust the order of our logs (or other events), finding causality is difficult.