ML-171: research and plan

2026-05-09 06:29:38 +01:00
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+---
+id: ML-171
+title: >-
+  Fix Oban Web crons page crash: MatchError in sparkline from SQLite datetime
+  string
+status: To Do
+assignee: []
+created_date: "2026-05-09 05:28"
+labels:
+  - bug
+  - oban-web
+  - sqlite
+dependencies: []
+references:
+  - >-
+    https://github.com/oban-bg/oban_web/blob/main/lib/oban/web/live/crons/table_component.ex#L78-L85
+  - >-
+    https://github.com/oban-bg/oban_web/blob/main/lib/oban/web/queries/cron_query.ex#L164-L177
+modified_files:
+  - lib/music_library_web/live/oban/crons/table_component.ex
+priority: medium
+---
+
+## Description
+
+<!-- SECTION:DESCRIPTION:BEGIN -->
+
+## Summary
+
+The `/dev/oban/crons` dashboard page crashes with `Elixir.MatchError` when rendering cron job history sparklines. This happens because Oban Web's `TableComponent.sparkline/1` calls `DateTime.from_naive!/2` which expects a `NaiveDateTime` struct, but receives a raw ISO 8601 string from SQLite.
+
+## Root Cause
+
+In `Oban.Web.CronQuery.cron_history/2` (deps/oban_web/lib/oban/web/queries/cron_query.ex:164-177), the query selects:
+
+```elixir
+finished_at: fragment("COALESCE(?, ?, ?)", j.completed_at, j.cancelled_at, j.discarded_at)
+```
+
+SQLite stores `utc_datetime_usec` fields as ISO 8601 text. While regular field references like `j.scheduled_at` are properly decoded to `DateTime` structs by Ecto, the `fragment()` call bypasses type decoding and returns a raw string like `"2026-05-08T11:00:00.708342Z"`.
+
+The sparkline function at `Oban.Web.Crons.TableComponent` line 81 then fails:
+
+```elixir
+(job.finished_at || job.attempted_at || job.scheduled_at)
+|> DateTime.from_naive!("Etc/UTC")  # 💥 expects NaiveDateTime, gets string
+```
+
+## Error Details
+
+- **ErrorTracker ID**: 4039
+- **Occurrences**: 2 (both on 2026-05-08)
+- **View**: Oban.Web.DashboardLive (crons page)
+- **Fingerprint**: `2C5253F1AB9B5D61231B7579E912FD2F7C155738DBB4325275F14E844C5D7B0C`
+
+## Approach
+
+The `sparkline/1` function is marked as `@doc overridable: 1` in Oban Web, so we can override it in the app. The fix should handle both `DateTime` structs (PostgreSQL) and ISO 8601 strings (SQLite) by parsing strings through `DateTime.from_iso8601!/1` first.
+
+Alternatively, the fix could be applied upstream in Oban Web's `CronQuery` to use a typed fragment or cast the `COALESCE` result.
+
+<!-- SECTION:DESCRIPTION:END -->
+
+## Acceptance Criteria
+
+<!-- AC:BEGIN -->
+
+- [ ] #1 Visiting /dev/oban/crons no longer crashes with MatchError
+- [ ] #2 Cron history sparklines render correctly showing job state colors
+- [ ] #3 The fix handles both DateTime structs (PostgreSQL) and ISO 8601 strings (SQLite)
+- [ ] #4 The overridden sparkline/1 function preserves the same visual output as upstream
+<!-- AC:END -->