Queue the smallest backfill jobs first and show queued state

docs/media-scraper.md

@@ -158,9 +158,10 @@ Previews run after every walk:
   before their previews were cached. One job per chat groups every paused, done, or failed scrape
   of that chat, so a paused-and-resumed scrape stays in one job. Jobs run one at a time, in
   batches, and report pending/cached/failed counts, per-kind pending, throughput, and an ETA. The
-  Bot tab drives them: **Start backfill**, per-job Start/Pause, and **Pause all**. On daemon boot
+  Bot tab drives them: **Start backfill**, per-job Start/Pause, and **Pause all**. Jobs with the
-  jobs start automatically when the Backfilling setting **Start automatically on daemon boot** is
+  least pending work start first, so small chats clear instead of waiting behind a long one; a job
-  on.
+  that is started but waiting for the queue reads `queued`. On daemon boot jobs start automatically
+  when the Backfilling setting **Start automatically on daemon boot** is on.
 - Transient fetch failures keep the row pending and count up `preview_attempts`. After the
   **Tries before giving up** setting (default 3) the row is marked `unreachable after N attempt(s)`,
   so dead hosts (Gfycat, Streamable) stop burning batches forever.

media-scrape/src/backfill.ts

@@ -40,7 +40,8 @@ export interface BackfillMember {
 export interface BackfillJobStatus {
     chatId: string;
     guildId: string | null;
-    state: "idle" | "running" | "paused" | "done";
+    /** `queued` means started, but another job holds the queue. */
+    state: "idle" | "queued" | "running" | "paused" | "done";
     members: BackfillMember[];
     pending: number;
     cached: number;
@@ -188,6 +189,8 @@ export class BackfillQueue {
         const groups = this.plan();
         const jobs: BackfillJobStatus[] = [];
 
+        const anyClaimed = [...this.jobs.values()].some(candidate => candidate.claimed);
+
         for (const [chatId, group] of groups) {
             // Hide chats that are fully backfilled unless their job did work this session.
             const tracked = this.jobs.get(chatId);
@@ -196,11 +199,13 @@ export class BackfillQueue {
 
             const perMinute = tracked?.perMinute ?? this.estimatedPerMinute(settings, gaps);
             const etaMs = pending > 0 && perMinute > 0 ? Math.round((pending / perMinute) * 60_000) : null;
+            const state =
+                tracked?.state === "running" && anyClaimed && !tracked.claimed ? "queued" : (tracked?.state ?? "idle");
 
             jobs.push({
                 chatId,
                 guildId: group.guildId,
-                state: tracked?.state ?? "idle",
+                state,
                 members: group.members,
                 pending,
                 cached: group.members.reduce((sum, member) => sum + member.cached, 0),
@@ -280,11 +285,14 @@ export class BackfillQueue {
         return perRow > 0 ? 60_000 / perRow : 6000;
     }
 
-    /** Start every job with pending rows, or one chat's job. */
+    /** Start every job with pending rows, or one chat's job. Smallest jobs first: they finish. */
     start(chatId?: string): void {
         const status = this.list();
+        const order = chatId
+            ? status.jobs
+            : [...status.jobs].sort((a, b) => a.pending - b.pending);
 
-        for (const job of status.jobs) {
+        for (const job of order) {
             if (chatId && job.chatId !== chatId) continue;
             if (job.pending <= 0) continue;
 

poc/public/media.css

@@ -740,3 +740,8 @@
     color: color-mix(in srgb, var(--color-neutral-400) 55%, transparent);
     font-style: italic;
 }
+
+.vk-bot-state-queued {
+    background: color-mix(in srgb, var(--color-neutral-400) 18%, transparent);
+    color: var(--color-neutral-300);
+}

poc/public/media.js

@@ -615,7 +615,7 @@
             row.append(progress);
 
             const actions = el("div", "vk-bot-job-actions");
-            if (job.state === "running") {
+            if (job.state === "running" || job.state === "queued") {
                 actions.append(button("Pause", () => void backfillAction("pause", job.chatId)));
             } else if (job.pending > 0) {
                 actions.append(button("Start", () => void backfillAction("start", job.chatId)));