| 22 Jun 2021 |
 tomberek | I’m not understanding where you intend state would be kept. Or where this state machine would run. (I’ve found it possible, I’m just not grokking specifically what you intend.) | 21:41:19 |
 David Arnold | I am a bit bisased, since I have somewhat knowledge of how zeebe works: it's a state machine that otherwise does event sourcing into a data lake. +- | 22:04:10 |
| David Arnold | It's messages all the way down, and they modify constitute the state. | 22:05:07 |
| tomberek | I pulled a trick recently where I put state into Git (it was very slow moving state, human time-scales) and Hydra would pick it up and run a DAG of the changed transformations. Along with an auto-scaling group for builders, it made a data ingestion system with many nice qualities inherited from Nix. | 22:24:45 |
| David Arnold | Iirc the state in zeebe is distributed among the brokers without central db for running workflow instances, once terminated they (or alternatively all events during execution) are persisted into the data lake. | 22:26:58 |
| David Arnold | Brokers may have a local in-mempry db or something. | 22:27:17 |
| tomberek | So events are considered independent? | 22:28:11 |
| David Arnold | But it's basically pure event sourcing between brokers, which is a handy byproduct of the message queue used (don't know which) | 22:28:19 |
| David Arnold | No, I guess events are considered unique (at most once, at least once semantics) | 22:29:00 |
| David Arnold | Not sure though. | 22:29:09 |
| David Arnold | Zeebe:
- apiserver + broker
- message queue
- elasticsearch (datalake)
| 22:30:23 |
| David Arnold | That's about it. | 22:30:34 |
| David Arnold | Ok the broker has fancy features such as distributed runtime state and the workflow engine 😀 | 22:31:08 |
| David Arnold | Each bpmn action has roughly/conceptually two events/messages:
JobStart + JobFinish | 22:33:29 |
| David Arnold | And workers need to understand those and return meaningful output (JobFinish message) | 22:34:11 |
| David Arnold | It's actually pretty simple. | 22:36:05 |
| David Arnold | The biggest challange is packaging zeebe / OPA for nixpkgs. | 22:36:33 |
| 23 Jun 2021 |
 Taneb | How do the "Previous Hydra evaluation" and "Previous Hydra buld" input types work? | 15:21:59 |
