mirror of
https://github.com/jcreek/CosmicClash.git
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Josh Creek
4fb7ddfecf
multiplayer-todo.md and multiplayer-next.md tracked overlapping information in two places. Fold everything into multiplayer-next.md (architecture decisions, wire format, task breakdown with checkboxes, gotchas list, testing notes) and delete multiplayer-todo.md. Section numbers are unchanged, so existing code comments citing them by section/task number still resolve; update every such reference to point at the new filename.
135 lines
6.7 KiB
GDScript
135 lines
6.7 KiB
GDScript
extends Node
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# Autoload (project.godot [autoload] NetSim). Debug-only, seeded
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# latency/jitter/loss/duplicate decorator around outgoing RPC dispatch —
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# task 2.8. A pure passthrough (send() calls dispatch.call() immediately)
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# unless CLI flags are given, so every existing test and the real game are
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# byte-for-byte unaffected by this autoload merely existing.
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#
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# CLI (read once, in this process's own OS.get_cmdline_user_args()):
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# --net-sim-latency=<ms> one-way delay added before each wrapped send
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# --net-sim-jitter=<ms> extra uniform-random 0..jitter added per send
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# --net-sim-loss=<0..1> fraction of sends dropped entirely (never sent)
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# --net-sim-dup=<0..1> probability a send is ALSO sent a second time
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# --net-sim-seed=<int> RNG seed (default fixed, so a bad run reproduces
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# unless a CI/local run deliberately wants a
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# different one — same "seeded so failures
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# reproduce" bar as §11's testing section sets)
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#
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# "Asymmetric-capable" per §7 task 2.8 is not a separate feature: each
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# process reads only its own CLI args and only delays its own outgoing
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# sends, so running the host and client with different flags (e.g. a
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# lossy-upload client against a clean host) already produces asymmetric
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# behaviour with no extra plumbing.
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#
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# Call sites build a zero-argument Callable that performs the actual
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# rpc_id()/rpc() dispatch, so NetSim never needs to know per-call argument
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# shapes. IMPORTANT for callers that embed a timestamp in the call (e.g.
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# NetworkManager's _ping/_pong): capture Time.get_ticks_msec() *before*
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# calling send(), not inside the wrapped Callable — the delay is meant to
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# simulate wire transit *after* the packet is "sent", so a timestamp taken
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# inside the delayed closure would silently absorb this process's own
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# outbound leg out of any round-trip measurement built on top of it.
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#
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# Wraps MatchSim.send_input / send_snapshot per the doc's task 2.8 scope,
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# plus NetworkManager's _ping/_pong dispatch — the latter is a deliberate
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# addition beyond the literal task text: it's the only RTT measurement that
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# already exists and is already tested (tests/clock_smoke.gd, task 1.8), so
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# routing it through NetSim is what makes "`--net-sim-latency 80` measurably
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# raises observed RTT" (this task's own stated acceptance criterion)
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# checkable today, without waiting on Phase 3's per-peer snapshot echo.
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const DEFAULT_SEED := 20260820
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var latency_ms := 0.0
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var jitter_ms := 0.0
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var loss_fraction := 0.0
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var dup_fraction := 0.0
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var _rng := RandomNumberGenerator.new() # owned instance — never the global RNG, task 0.7's rule
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func _ready() -> void:
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var seed_value := DEFAULT_SEED
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for arg: String in OS.get_cmdline_user_args():
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if arg.begins_with("--net-sim-latency="):
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latency_ms = maxf(0.0, arg.get_slice("=", 1).to_float())
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elif arg.begins_with("--net-sim-jitter="):
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jitter_ms = maxf(0.0, arg.get_slice("=", 1).to_float())
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elif arg.begins_with("--net-sim-loss="):
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loss_fraction = clampf(arg.get_slice("=", 1).to_float(), 0.0, 1.0)
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elif arg.begins_with("--net-sim-dup="):
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dup_fraction = clampf(arg.get_slice("=", 1).to_float(), 0.0, 1.0)
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elif arg.begins_with("--net-sim-seed="):
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seed_value = arg.get_slice("=", 1).to_int()
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_rng.seed = seed_value
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func is_active() -> bool:
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return latency_ms > 0.0 or jitter_ms > 0.0 or loss_fraction > 0.0 or dup_fraction > 0.0
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# target_peer_id: the specific remote peer this dispatch is addressed to
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# (rpc_id's target), or -1 for a broadcast / not a targeted send. Only used
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# to re-validate a delayed send right before it actually fires — see _fire.
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func send(dispatch: Callable, target_peer_id: int = -1) -> void:
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if not is_active():
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dispatch.call()
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return
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if _rng.randf() < loss_fraction:
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return
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_schedule(dispatch, target_peer_id, (latency_ms + _rng.randf() * jitter_ms) / 1000.0)
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if _rng.randf() < dup_fraction:
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_schedule(dispatch, target_peer_id, (latency_ms + _rng.randf() * jitter_ms) / 1000.0)
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func _schedule(dispatch: Callable, target_peer_id: int, delay_sec: float) -> void:
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if delay_sec <= 0.0:
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dispatch.call()
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return
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# process_always = true: a simulated wire delay must keep counting down
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# even if the local SceneTree pauses (match_mode.gd's goal-pause does
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# this today; multiplayer-next.md §8 already flags get_tree().paused
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# stopping the client's own send/receive loop as a separate refactor
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# item). Pausing this timer too would let a paused client's in-flight
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# packets pile up and arrive in a burst on unpause instead of on their
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# simulated schedule.
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get_tree().create_timer(delay_sec, true).timeout.connect(func() -> void: _fire(dispatch, target_peer_id))
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# Re-validates the target right before a DELAYED send actually fires.
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# NetSim's whole point is to hold a packet in flight past the moment it was
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# queued, and in that window the target peer (or this process's own
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# connection) can legitimately be gone — a disconnect mid-match, or this
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# process's own shutdown() already having reset multiplayer_peer to a fresh
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# OfflineMultiplayerPeer. Firing anyway reproduced two real bugs while
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# building this task: "Attempt to call RPC with unknown peer ID" (stale
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# remote target — networked_match.gd's own get_peers() filter on
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# _broadcast_snapshot only checked validity at *schedule* time, and the
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# target had disconnected by the time the delayed send actually fired) and
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# "'_recv_input' on yourself is not allowed by selected mode" (this
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# process's own peer was already torn down, so peer id 1 now refers to
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# itself instead of the server). The synchronous (delay_sec <= 0 / NetSim
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# inactive) path is deliberately NOT re-validated here — nothing has had
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# time to change since the caller's own validation, and matching the
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# pre-NetSim behaviour exactly there is what keeps NetSim a true no-op when
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# no CLI flags are given.
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#
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# Known residual gap, judged not worth the complexity for debug-only
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# tooling: if this process shuts down AND reconnects (a fresh host()/join())
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# within one delayed send's hold time, multiplayer_peer is a real peer again
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# and get_peers() may coincidentally contain the same target_peer_id from
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# the new session, so a stale send from the old session could slip through.
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# Closing that fully would need a generation counter bumped on every
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# shutdown/host/join and stamped on each scheduled send — disproportionate
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# for a latency simulator that only ever runs in manual/CI testing.
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func _fire(dispatch: Callable, target_peer_id: int) -> void:
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var peer := multiplayer.multiplayer_peer
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if peer == null or peer is OfflineMultiplayerPeer:
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return
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if peer is ENetMultiplayerPeer and peer.get_connection_status() != MultiplayerPeer.CONNECTION_CONNECTED:
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return
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if target_peer_id != -1 and target_peer_id not in multiplayer.get_peers():
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return
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dispatch.call()
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