record: resync the view when the bot changes servers mid-recording

daemon.ts

@@ -126,7 +126,12 @@ const stamp = (): string => new Date().toISOString().replace(/[:.]/g, '-').slice
 const record = {
   async start (file = path.join(opts.dir, `${opts.name}-${stamp()}.mp4`), recordOpts?: RecordOpts): Promise<string> {
     if (recording) throw new Error(`already recording to ${recording.file}`)
-    recording = await startRecording(bot, path.resolve(file), recordOpts)
+    const target = path.resolve(file)
+    recording = await startRecording(bot, target, recordOpts, err => {
+      // ffmpeg went away on its own; the file is done, so drop the recording the daemon holds.
+      if (recording?.file === target) recording = null
+      log('recording ended', target, err.message)
+    })
     log('recording', recording.file)
     return recording.file
   },

protocol.ts

@@ -44,7 +44,7 @@ export interface BotStatus {
   lastEnd?: { at: string, reason: string }
   lastError?: { at: string, message: string }
   /** Present while a recording runs. `dropped` frames are absent from the file. */
-  recording?: { file: string, dropped: number, queued: number }
+  recording?: { file: string, dropped: number, queued: number, ended: string | null }
 }
 
 /** Set when the bot's connection is gone, so a caller sees it even though the exec itself ran. */

record.ts

@@ -22,6 +22,8 @@ export interface RecordingStats {
   dropped: number
   /** Bytes handed to ffmpeg's stdin and not yet taken. */
   queued: number
+  /** Set once ffmpeg has exited: null after stop(), the reason after an exit on its own. */
+  ended: string | null
 }
 
 export interface Recording {
@@ -66,7 +68,7 @@ function ffmpeg (args: string[]): { proc: ChildProcess, done: Promise<void> } {
   return { proc, done }
 }
 
-export async function startRecording (bot: Bot, file: string, opts: RecordOpts = {}): Promise<Recording> {
+export async function startRecording (bot: Bot, file: string, opts: RecordOpts = {}, onEnd?: (err: Error) => void): Promise<Recording> {
   const { width = 640, height = 360, fps = 20, viewDistance = 4, numWorkers = 1, duty = 0.25 } = opts
   await ensureDisplay(width, height)
   if (!bot.entity) await new Promise<void>(resolve => bot.once('spawn', resolve))
@@ -111,6 +113,27 @@ export async function startRecording (bot: Bot, file: string, opts: RecordOpts =
   follow()
   bot.on('move', follow)
 
+  // A server transfer or dimension change makes mineflayer unload every column of the bot's world
+  // (bot.world is mutated in place, not replaced). WorldView has no chunkColumnUnload listener, so
+  // it keeps the pre-transfer geometry and never meshes the new world. login precedes the swap and
+  // the following spawn is when bot.entity and the new columns are ready, so resync there: drop the
+  // chunks the viewer still holds and reload from the current world. (Superseded once
+  // prismarine-viewer handles the unload itself.)
+  let reloginPending = false
+  const onLogin = (): void => { reloginPending = true }
+  const onSpawn = (): void => {
+    if (!reloginPending) return
+    reloginPending = false
+    const wv = worldView as unknown as { loadedChunks: Record<string, boolean>, unloadChunk: (p: { x: number, z: number }) => void }
+    for (const key of Object.keys(wv.loadedChunks)) {
+      const [x, z] = key.split(',').map(Number)
+      wv.unloadChunk({ x, z })
+    }
+    void worldView.init(bot.entity.position)
+  }
+  bot.on('login', onLogin)
+  bot.on('spawn', onSpawn)
+
   // Frames before the atlas uploads and chunks mesh are blank sky. The first frame is
   // deferred until the atlas is set, some sections are meshed, and none are outstanding.
   const sleep = (ms: number): Promise<void> => new Promise(r => setTimeout(r, ms))
@@ -136,6 +159,27 @@ export async function startRecording (bot: Bot, file: string, opts: RecordOpts =
   const video = ffmpeg([...raw, '-r', String(fps), '-i', 'pipe:0', '-vf', 'vflip', '-c:v', 'libx264', '-preset', 'veryfast', '-pix_fmt', 'yuv420p', file])
 
   const stdin = video.proc.stdin!
+  // When ffmpeg exits, a write already in flight rejects async with EPIPE; the meaningful signal is
+  // video.done, so swallow the stream error rather than let it crash the daemon.
+  stdin.on('error', () => {})
+  // null while recording; the reason once ffmpeg has gone. Both stop() and an exit on ffmpeg's own
+  // (crash, disk full, killed) route through teardown; `stopping` tells them apart.
+  let ended: string | null = null
+  let stopping = false
+  const teardown = (): void => {
+    bot.off('move', follow)
+    bot.off('login', onLogin)
+    bot.off('spawn', onSpawn)
+    worldView.removeListenersFromBot(bot)
+    try { viewer.dispose() } catch {}
+    destroyGl()
+  }
+  // ffmpeg exiting before stop() means the file is being abandoned; there is nothing to render into
+  // any more, so stop the loop and let the daemon drop the recording.
+  void video.done.then(
+    () => { if (!stopping) { ended = 'ffmpeg exited before the recording was stopped'; if (timer) clearTimeout(timer); teardown(); onEnd?.(new Error(ended)) } },
+    (e: Error) => { if (!stopping) { ended = e.message; if (timer) clearTimeout(timer); teardown(); onEnd?.(e) } }
+  )
   const pixels = Buffer.alloc(width * height * 4)
   let last: Buffer | null = null
   const frameMs = 1000 / fps
@@ -147,6 +191,7 @@ export async function startRecording (bot: Bot, file: string, opts: RecordOpts =
   let inflight = 0
   let timer: NodeJS.Timeout | null = null
   const tick = (): void => {
+    if (ended !== null || !stdin.writable) return
     const due = Math.floor((performance.now() - t0) / frameMs) + 1
     let cost = 0
     if (inflight === 0 && written < due) {
@@ -177,7 +222,7 @@ export async function startRecording (bot: Bot, file: string, opts: RecordOpts =
 
   return {
     file,
-    stats: () => ({ dropped, queued: stdin.writableLength }),
+    stats: () => ({ dropped, queued: stdin.writableLength, ended }),
     async snapshot (out) {
       if (!last) throw new Error('no frame yet')
       const png = ffmpeg([...raw, '-i', 'pipe:0', '-vf', 'vflip', '-frames:v', '1', out])
@@ -186,9 +231,14 @@ export async function startRecording (bot: Bot, file: string, opts: RecordOpts =
       return out
     },
     async stop () {
+      stopping = true
       if (timer) clearTimeout(timer)
       timer = null
+      // ffmpeg already gone on its own: teardown ran, nothing left to close.
+      if (ended !== null) return file
       bot.off('move', follow)
+      bot.off('login', onLogin)
+      bot.off('spawn', onSpawn)
       worldView.removeListenersFromBot(bot)
       // Closing ffmpeg's stdin writes the moov atom; it must run even if GL teardown throws.
       stdin.end()