Fix RecordNotUnique crash on concurrent sync attempt creation

VERSION

@@ -1 +1 @@
-2.1.6
+2.1.7

app/jobs/concerns/sync_attempt_manageable.rb

@@ -6,6 +6,13 @@ module SyncAttemptManageable
   private
 
   def find_or_create_sync_attempt(source, attempt_id)
-    attempt_id ? SyncAttempt.find(attempt_id) : SyncAttempt.create!(calendar_source: source, status: :queued)
+    return SyncAttempt.find(attempt_id) if attempt_id
+
+    SyncAttempt.create!(calendar_source: source, status: :queued)
+  rescue ActiveRecord::RecordNotUnique
+    # Another worker already created the active attempt for this source
+    # (enforced by idx_unique_active_sync_attempt_per_source) -- reuse it
+    # instead of crashing the job.
+    source.sync_attempts.where(status: ["queued", "running"]).order(created_at: :desc).first || raise
   end
 end

app/services/calendar_hub/auto_sync_scheduler.rb

@@ -36,7 +36,15 @@ def schedule_syncs(sources)
 
       schedule.each do |source_id, scheduled_at|
         source = sources_by_id[source_id] || CalendarSource.find(source_id)
-        attempt = SyncAttempt.create!(calendar_source: source, status: :queued)
+
+        begin
+          attempt = SyncAttempt.create!(calendar_source: source, status: :queued)
+        rescue ActiveRecord::RecordNotUnique
+          # Another worker already created an active attempt for this source
+          # (enforced by idx_unique_active_sync_attempt_per_source) between
+          # find_sources_due_for_sync and here -- skip it, it's already scheduled.
+          next
+        end
 
         if scheduled_at <= @now
           SyncCalendarJob.perform_later(source.id, attempt_id: attempt.id)

test/jobs/sync_calendar_job_test.rb

@@ -85,6 +85,22 @@ class SyncCalendarJobTest < ActiveJob::TestCase
     assert(source.sync_attempts.exists?(status: "success"))
   end
 
+  test "reuses existing active attempt when concurrent creation hits the unique constraint" do
+    source = calendar_sources(:provider)
+    existing_attempt = source.sync_attempts.create!(status: :queued)
+
+    # Simulate another worker winning the race to create the active attempt
+    # for this source (enforced by idx_unique_active_sync_attempt_per_source).
+    SyncAttempt.expects(:create!).with(calendar_source: source, status: :queued)
+      .raises(ActiveRecord::RecordNotUnique.new("UNIQUE constraint failed"))
+
+    CalendarHub::Sync::EnhancedSyncService.expects(:new).with(source: source, observer: existing_attempt).returns(mock(call: true))
+
+    SyncCalendarJob.perform_now(source.id)
+
+    assert_equal "success", existing_attempt.reload.status
+  end
+
   # FEAT-006: Sync failure tracking
 
   test "records sync success and resets consecutive_sync_failures" do

test/services/calendar_hub/auto_sync_scheduler_test.rb

@@ -172,6 +172,28 @@ class AutoSyncSchedulerTest < ActiveJob::TestCase
       assert_includes(due_sources, @source2)
     end
 
+    test "schedule_syncs skips a source when a concurrent attempt already exists" do
+      @source1.update!(last_synced_at: 1.hour.ago)
+      @source2.update!(last_synced_at: 1.hour.ago)
+
+      scheduler = ::CalendarHub::AutoSyncScheduler.new
+      sources = scheduler.find_sources_due_for_sync
+
+      assert_equal(2, sources.count)
+
+      # Simulate another worker winning the race to create the active attempt
+      # for source1 between find_sources_due_for_sync and schedule_syncs -- the
+      # real DB constraint (idx_unique_active_sync_attempt_per_source) is what
+      # schedule_syncs must tolerate.
+      SyncAttempt.create!(calendar_source: @source1, status: :queued)
+
+      assert_enqueued_jobs(1, only: SyncCalendarJob) do
+        result = scheduler.schedule_syncs(sources)
+
+        assert_equal(1, result)
+      end
+    end
+
     test "schedule_syncs does not re-fetch sources already in memory" do
       @source1.update!(last_synced_at: 1.hour.ago)
       @source2.update!(last_synced_at: 1.hour.ago)