Event Sourcing • Martin Fowler • YOW! 2016

very useful
best regards

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Well to be fair, git doesn't exactly do ES, it rather does a combination of ES + state. Meaning, each commit contains the whole state. Does it reuse the unchanged files between adjacent commits - most probably, but still - the current state is taken by going to the latest commit, instead of replaying the whole event history.

First part of the presentation: oh well, it looks so useful. Last part of the presentation: oh well, it gets a mess.

I found the description of git at the start s bit misleading for people less familiar with git. It's a common misconception that a git commit records changes/events. Every git commit is in fact, in a very real way, a complete snapshot of state of all the files at that point in time (with fancy tricks for compression). Nothing needs to be replayed to reconstruct that state, the latest commit has all the information you need.

The first thing that pop in my mind at the beginning ... didn't get addressed in the talk.
If you can roll back anywhere in the event log ... you SHOULD keep the program code in sync ! If I change something last week to process some event, that event would have been processed differently a month ago !
But then, maybe you want to reprocess that event with the new code..who know?

They do, but as the event sinks converge/time passes, the old logs are purged.
They don’t use the log as the ongoing, permanent source of truth. So you don’t get rewind and you can’t rebuild from event 0 and so on.

I am hooked on event sourcing. I just spent 3 years building a very large system based on ddd + cqrs + event sourcing and honestly I feel like a god. I could never have wrangled all that complexity without such thinking. And what's most amazing is the fact that it's all language/platform agnostic. There's no magic. I could recreate my entire system in any language with zero difficulty. Although, despite the agnosticism, I'm excited about how well this thinking maps to elixir/beam. Honestly, if you're not doing ddd, cqrs, event sourcing and elixir, you are behind in the evolution of our field.

He missed out that most RDBMSs use a log internally as the source of truth, which aids with replication and resilience.