as someone who hasn't implemented transactions in microservices before, I have only seen the bank transfer example and it seems adequate and easy to understand - I wouldn't know what limitations it has
It doesn’t exist. This isn’t how banks transfer funds between accounts.
It’s fake. As a result, you can’t actually evaluate the engineering trade offs of the proposed solution.
Here’s the thing: do you even need transactions (in the sense of ACID transactions that are resolved heuristically, as described in this article) between your microservices? Likely not.
And what are the implications of having to wait around for PGSQL and Mongo negotiate a transaction between a third data store? Probably blocking and latency and all the associated problems which will lead to … not use transaction across service boundaries.
The trick is to work out what you would do if you had to implement the entire system on paper in a 50s style office with triplicate carbon paper. Then do that, but with computers.
That is not a trick, it is a false analogy. Two humans in eyesight line can be assured that they have exchanged messages successfully. Two computers cannot due to recursing acknowledgements (byzantine generals).
No, it’s not a false analogy. Go look at an old office building and consider whether people really are “in eyesight line” - assuredly they are not.
The unreliable messaging links (internal mail) mean that resilience against missed messages and guards against not making progress must be built into the business process instead of an infrastructure layer.
edit: totally misunderstood parent, my bad. disregard the following.
> - Take a bag for which “all marbles in this bag are black” is false
> - Add a black marble to that bag
> - After that, “all marbles in the bag are black” becomes true
This reasoning is not correct. If the bag contains exactly a red marble at the start, "all marbles in this bag are black" is false as you required, but it breaks the claim at the end that "all marbles in the bag are black".
There is in fact no bag that fulfills your reasoning, even the empty bag wouldn't (when starting to write my reply I had erroneously assumed so)
If a bag contains exactly one red marble at the start then all marbles in this bag are black is in fact false, but when you throw in a black marble the value does NOT suddenly become true, as the red marble still exists, which is exactly the point of the scenario: adding a black marble to a bag where that claim is false shouldn't make the bag suddenly become true, and it still didn't in your example... it would, though, if the empty bag were defined to be false (which it should not be based on this argument).
I loved The Creative Act: A Way of Being. The book is organized into short chapters, each about a certain part of the creative process or perspective of the author.
While I don't agree with everything shared, the crisp and clear way it's written allows for great reflection and inspiration.
I've described it to friends as a work book for artists and creatives. Every chapter simmering for days and helping to refine the creative process.
