Protocol/Server: implement STATE_DELTA + PART partitioning and per-tick minimal changes
- Protocol: SnakeDelta structure; build_state_delta(_body); build_part - Server: compute per-snake changes (move/grow/blocked-shrink), apples diffs - Partition large deltas by snake changes with apples in first part; use update_id - Send STATE_DELTA when under MTU; else PART packets referencing STATE_DELTA
This commit is contained in:
Vladyslav Doloman
134
server/server.py
134
server/server.py
@@ -16,9 +16,10 @@ from .protocol import (
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build_config_update,
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build_input_broadcast,
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build_state_full,
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BodyTLV,
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build_state_full,
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quic_varint_encode,
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build_state_delta,
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build_state_delta_body,
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build_part,
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SnakeDelta,
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pack_header,
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parse_input,
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parse_join,
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@@ -32,11 +33,16 @@ class ServerRuntime:
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state: GameState
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seq: int = 0
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version: int = 1
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update_id: int = 0
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def next_seq(self) -> int:
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self.seq = (self.seq + 1) & 0xFFFF
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return self.seq
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def next_update_id(self) -> int:
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self.update_id = (self.update_id + 1) & 0xFFFF
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return self.update_id
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class GameServer:
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def __init__(self, transport: DatagramServerTransport, config: ServerConfig):
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@@ -157,6 +163,8 @@ class GameServer:
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st = self.runtime.state
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cfg = self.runtime.config
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apples_eaten: List[Coord] = []
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apples_before = set(st.apples)
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changes: List[SnakeDelta] = []
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# Prepare snapshot of tails to allow moving into own tail when it vacates
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tails: Dict[int, Coord] = {}
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for sid, s in st.snakes.items():
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@@ -187,6 +195,18 @@ class GameServer:
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if s.length > 1:
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tx, ty = s.body.pop()
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st.occupancy.pop((tx, ty), None)
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changes.append(
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SnakeDelta(
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snake_id=sid,
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head_moved=False,
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tail_removed=(s.length > 1),
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grew=False,
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blocked=True,
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new_head_x=hx,
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new_head_y=hy,
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direction=s.direction,
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)
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)
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continue
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# Move or grow
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s.blocked = False
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@@ -198,40 +218,98 @@ class GameServer:
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# eat apple; no tail removal this tick
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st.apples.remove((nx, ny))
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apples_eaten.append((nx, ny))
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changes.append(
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SnakeDelta(
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snake_id=sid,
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head_moved=True,
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tail_removed=False,
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grew=True,
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blocked=False,
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new_head_x=nx,
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new_head_y=ny,
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direction=s.direction,
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)
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)
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else:
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# normal move: remove tail (unless length==0)
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tx, ty = s.body.pop()
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if (tx, ty) in st.occupancy:
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st.occupancy.pop((tx, ty), None)
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changes.append(
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SnakeDelta(
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snake_id=sid,
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head_moved=True,
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tail_removed=True,
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grew=False,
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blocked=False,
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new_head_x=nx,
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new_head_y=ny,
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direction=s.direction,
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)
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)
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# Replenish apples to target
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self._ensure_apples()
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apples_after = set(st.apples)
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apples_added = sorted(list(apples_after - apples_before))
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apples_removed = sorted(list(apples_before - apples_after))
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# Broadcast a basic delta (currently full snakes + apples as delta)
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snakes_dirs: List[Tuple[int, int, int, int, List[Direction]]] = []
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for s in st.snakes.values():
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dirs: List[Direction] = []
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coords = list(s.body)
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for i in range(len(coords) - 1):
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x0, y0 = coords[i]
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x1, y1 = coords[i + 1]
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if x1 == x0 and y1 == y0 - 1:
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dirs.append(Direction.UP)
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elif x1 == x0 + 1 and y1 == y0:
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dirs.append(Direction.RIGHT)
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elif x1 == x0 and y1 == y0 + 1:
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dirs.append(Direction.DOWN)
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elif x1 == x0 - 1 and y1 == y0:
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dirs.append(Direction.LEFT)
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hx, hy = coords[0]
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snakes_dirs.append((s.snake_id, s.length, hx, hy, dirs))
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delta = build_state_full(
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version=self.runtime.version,
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seq=self.runtime.next_seq(),
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tick=st.tick,
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snakes=snakes_dirs,
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apples=st.apples,
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update_id = self.runtime.next_update_id()
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# Serialize full delta body once, then partition if large
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full_body = build_state_delta_body(
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update_id=update_id,
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changes=changes,
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apples_added=apples_added,
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apples_removed=apples_removed,
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)
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for session in list(self.sessions.values()):
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await self.transport.send(delta, TransportPeer(session.peer))
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MTU = 1200 # soft limit for payload to avoid fragmentation
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if len(full_body) <= MTU:
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packet = pack_header(self.runtime.version, PacketType.STATE_DELTA, 0, self.runtime.next_seq(), st.tick & 0xFFFF) + full_body
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for session in list(self.sessions.values()):
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await self.transport.send(packet, TransportPeer(session.peer))
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else:
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# Partition by splitting snake changes across parts; include apples only in the first part
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parts: List[bytes] = []
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remaining = list(changes)
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idx = 0
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part_index = 0
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while remaining:
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chunk: List[SnakeDelta] = []
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# greedy pack until size would exceed MTU
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# start with apples only for first part
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add_ap = apples_added if part_index == 0 else []
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rem_ap = apples_removed if part_index == 0 else []
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# Try adding changes one by one
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for i, ch in enumerate(remaining):
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tmp_body = build_state_delta_body(update_id=update_id, changes=chunk + [ch], apples_added=add_ap, apples_removed=rem_ap)
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if len(tmp_body) > MTU and chunk:
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break
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if len(tmp_body) > MTU:
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# even a single change + apples doesn't fit; force single
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chunk.append(ch)
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i += 1
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break
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chunk.append(ch)
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# Remove chunked items
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remaining = remaining[len(chunk) :]
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# Build chunk body
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chunk_body = build_state_delta_body(update_id=update_id, changes=chunk, apples_added=add_ap, apples_removed=rem_ap)
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parts.append(chunk_body)
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part_index += 1
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# Emit PART packets
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total = len(parts)
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for i, body in enumerate(parts):
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pkt = build_part(
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version=self.runtime.version,
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seq=self.runtime.next_seq(),
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tick=st.tick & 0xFFFF,
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update_id=update_id,
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part_index=i,
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parts_total=total,
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inner_type=PacketType.STATE_DELTA,
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chunk_payload=body,
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)
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for session in list(self.sessions.values()):
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await self.transport.send(pkt, TransportPeer(session.peer))
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# --- Join / Spawn ---
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