From fe5228b3063c883de32f3e1ce7affa3faf1f9ae6 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Tue, 31 Mar 2026 17:16:40 -0500
Subject: [PATCH] Prevent duplicate PropagationGridWorker jobs via Oban unique
 constraint
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Worker now uses unique: [period: 3600, states: [:available, :scheduled,
:executing, :retryable]] so Oban atomically prevents duplicates.
FreshnessMonitor simplified — no longer does manual oban_jobs query.
---
 .../propagation/freshness_monitor.ex          | 19 ++++---------------
 .../workers/propagation_grid_worker.ex        |  3 ++-
 2 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/lib/microwaveprop/propagation/freshness_monitor.ex b/lib/microwaveprop/propagation/freshness_monitor.ex
index 9aea7485..71df9917 100644
--- a/lib/microwaveprop/propagation/freshness_monitor.ex
+++ b/lib/microwaveprop/propagation/freshness_monitor.ex
@@ -53,20 +53,9 @@ defmodule Microwaveprop.Propagation.FreshnessMonitor do
   end
 
   defp enqueue_if_not_queued do
-    # Only enqueue if there isn't already a pending/running grid worker job
-    import Ecto.Query
-
-    pending =
-      Microwaveprop.Repo.exists?(
-        from(j in "oban_jobs",
-          where:
-            j.worker == "Microwaveprop.Workers.PropagationGridWorker" and
-              j.state in ["available", "scheduled", "executing"]
-        )
-      )
-
-    if !pending do
-      Oban.insert(PropagationGridWorker.new(%{}))
-    end
+    # Oban unique constraint on PropagationGridWorker prevents duplicates —
+    # if a job is already available/scheduled/executing/retryable within the
+    # last hour, insert is a no-op.
+    Oban.insert(PropagationGridWorker.new(%{}))
   end
 end
diff --git a/lib/microwaveprop/workers/propagation_grid_worker.ex b/lib/microwaveprop/workers/propagation_grid_worker.ex
index 0fb0417d..2289422b 100644
--- a/lib/microwaveprop/workers/propagation_grid_worker.ex
+++ b/lib/microwaveprop/workers/propagation_grid_worker.ex
@@ -7,7 +7,8 @@ defmodule Microwaveprop.Workers.PropagationGridWorker do
 
   use Oban.Worker,
     queue: :propagation,
-    max_attempts: 3
+    max_attempts: 3,
+    unique: [period: 3600, states: [:available, :scheduled, :executing, :retryable]]
 
   alias Microwaveprop.Propagation
   alias Microwaveprop.Propagation.Grid