# zig compatibility notes

comparison of zig implementation with python prefect server.

## RetryFailedFlows

### matching behavior ✓

| aspect | python | zig |
|--------|--------|-----|
| from_states | {RUNNING} | StateTypeSet.init(&.{.RUNNING}) |
| to_states | {FAILED} | StateTypeSet.init(&.{.FAILED}) |
| retry check | `retries is None or run_count > retries` | `ctx.retries orelse return; if (ctx.run_count > max_retries) return;` |
| scheduled time | `now + timedelta(seconds=retry_delay or 0)` | `now_us + delay_seconds * 1_000_000` |
| retry state | `AwaitingRetry` (SCHEDULED) | `SCHEDULED` with name "AwaitingRetry" |
| response | `reject_transition(state, reason="Retrying")` | `REJECT` status |

### implemented ✓

| behavior | status |
|----------|--------|
| retry_type = "in_process" on retry | ✓ via `set_retry_type_in_process` flag |
| resuming = false on retry | ✓ via `set_resuming_false` flag |
| pause_keys = [] on retry | ✓ via `clear_pause_keys` flag |
| retry_type = null when exhausted | ✓ via `clear_retry_type` flag |

### not needed

- **old client compatibility** (API < 0.8.3): python resets failed task runs to AwaitingRetry state - not needed for new clients

## schema compatibility

### empirical_policy JSON

python schema:
```json
{
  "retries": int | null,
  "retry_delay": int | null,
  "pause_keys": [],
  "resuming": false,
  "retry_type": null | "in_process" | "reschedule",
  "max_retries": 0,        // deprecated
  "retry_delay_seconds": 0  // deprecated
}
```

zig reads: `retries`, `retry_delay` from this JSON
zig stores: as TEXT (sqlite) or JSONB (postgres) - compatible

### storage types

| column | postgres python | postgres zig | sqlite python | sqlite zig |
|--------|-----------------|--------------|---------------|------------|
| id | UUID | UUID | CHAR(36) | CHAR(36) |
| timestamps | TIMESTAMP(tz) | TIMESTAMP(tz) | DATETIME | DATETIME |
| empirical_policy | JSONB | JSONB | JSON | TEXT |

## migration path

our zig server stores data compatible with python prefect server:
- UUIDs as standard format
- timestamps as ISO 8601 UTC
- JSON/JSONB for policy fields

data created by zig server can be read by python server (and vice versa).