Open SQLite with WAL and bound delivery re-dispatch by ownership (closes #256)

internal/handlers/event_body.go

@@ -92,11 +92,10 @@ func (h *Handlers) HandleEventBodyDownload() http.HandlerFunc {
 // once per range.
 //
 // One consequence is worth keeping in view: the read finishes
-// before the client is written to, so no read lock is held for
-// the length of a slow download. These per-webhook databases
-// run in SQLite's default journal mode rather than WAL, so a
-// lock held that long would block the receiver from recording
-// new events.
+// before the client is written to, so nothing is held open for
+// the length of a slow download. Under WAL a read no longer
+// blocks the receiver, but it does pin the WAL against
+// checkpointing, and a download can last minutes.
 func (h *Handlers) serveEventBody(
 	w http.ResponseWriter,
 	r *http.Request,

internal/handlers/event_resubmit.go

@@ -139,10 +139,10 @@ func (h *Handlers) resubmitEvent(
 	}
 
 	// Read before the write transaction is opened. The body can be up
-	// to the 1 MB ingest cap, and holding a read of it inside the
-	// transaction would extend how long the per-webhook database is
-	// locked against the receiver, which runs these files in
-	// SQLite's default journal mode rather than WAL.
+	// to the 1 MB ingest cap, and every transaction on these files
+	// takes the write lock at BEGIN (_txlock=immediate, see
+	// internal/database/sqlite_open.go), so reading inside it would
+	// hold that lock against the receiver for the length of the read.
 	src, found, err := loadResubmitSource(
 		webhookDB, webhook.ID, eventID.String(),
 	)