foundry_evm_core/fork/
multi.rs

1//! Support for running multiple fork backends.
2//!
3//! The design is similar to the single `SharedBackend`, `BackendHandler` but supports multiple
4//! concurrently active pairs at once.
5
6use super::CreateFork;
7use crate::Env;
8use alloy_consensus::BlockHeader;
9use alloy_primitives::{U256, map::HashMap};
10use alloy_provider::network::BlockResponse;
11use foundry_config::Config;
12use foundry_fork_db::{BackendHandler, BlockchainDb, SharedBackend, cache::BlockchainDbMeta};
13use futures::{
14    FutureExt, StreamExt,
15    channel::mpsc::{Receiver, Sender, channel},
16    stream::Fuse,
17    task::{Context, Poll},
18};
19use revm::context::BlockEnv;
20use std::{
21    fmt::{self, Write},
22    pin::Pin,
23    sync::{
24        Arc,
25        atomic::AtomicUsize,
26        mpsc::{Sender as OneshotSender, channel as oneshot_channel},
27    },
28    time::Duration,
29};
30
31/// The _unique_ identifier for a specific fork, this could be the name of the network a custom
32/// descriptive name.
33#[derive(Clone, Debug, PartialEq, Eq, Hash)]
34pub struct ForkId(pub String);
35
36impl ForkId {
37    /// Returns the identifier for a Fork from a URL and block number.
38    pub fn new(url: &str, num: Option<u64>) -> Self {
39        let mut id = url.to_string();
40        id.push('@');
41        match num {
42            Some(n) => write!(id, "{n:#x}").unwrap(),
43            None => id.push_str("latest"),
44        }
45        Self(id)
46    }
47
48    /// Returns the identifier of the fork.
49    pub fn as_str(&self) -> &str {
50        &self.0
51    }
52}
53
54impl fmt::Display for ForkId {
55    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
56        self.0.fmt(f)
57    }
58}
59
60impl<T: Into<String>> From<T> for ForkId {
61    fn from(id: T) -> Self {
62        Self(id.into())
63    }
64}
65
66/// The Sender half of multi fork pair.
67/// Can send requests to the `MultiForkHandler` to create forks.
68#[derive(Clone, Debug)]
69#[must_use]
70pub struct MultiFork {
71    /// Channel to send `Request`s to the handler.
72    handler: Sender<Request>,
73    /// Ensures that all rpc resources get flushed properly.
74    _shutdown: Arc<ShutDownMultiFork>,
75}
76
77impl MultiFork {
78    /// Creates a new pair and spawns the `MultiForkHandler` on a background thread.
79    pub fn spawn() -> Self {
80        trace!(target: "fork::multi", "spawning multifork");
81
82        let (fork, mut handler) = Self::new();
83
84        // Spawn a light-weight thread just for sending and receiving data from the remote
85        // client(s).
86        let fut = async move {
87            // Flush cache every 60s, this ensures that long-running fork tests get their
88            // cache flushed from time to time.
89            // NOTE: we install the interval here because the `tokio::timer::Interval`
90            // requires a rt.
91            handler.set_flush_cache_interval(Duration::from_secs(60));
92            handler.await
93        };
94        match tokio::runtime::Handle::try_current() {
95            Ok(rt) => _ = rt.spawn(fut),
96            Err(_) => {
97                trace!(target: "fork::multi", "spawning multifork backend thread");
98                _ = std::thread::Builder::new()
99                    .name("multi-fork-backend".into())
100                    .spawn(move || {
101                        tokio::runtime::Builder::new_current_thread()
102                            .enable_all()
103                            .build()
104                            .expect("failed to build tokio runtime")
105                            .block_on(fut)
106                    })
107                    .expect("failed to spawn thread")
108            }
109        }
110
111        trace!(target: "fork::multi", "spawned MultiForkHandler thread");
112        fork
113    }
114
115    /// Creates a new pair multi fork pair.
116    ///
117    /// Use [`spawn`](Self::spawn) instead.
118    #[doc(hidden)]
119    pub fn new() -> (Self, MultiForkHandler) {
120        let (handler, handler_rx) = channel(1);
121        let _shutdown = Arc::new(ShutDownMultiFork { handler: Some(handler.clone()) });
122        (Self { handler, _shutdown }, MultiForkHandler::new(handler_rx))
123    }
124
125    /// Returns a fork backend.
126    ///
127    /// If no matching fork backend exists it will be created.
128    pub fn create_fork(&self, fork: CreateFork) -> eyre::Result<(ForkId, SharedBackend, Env)> {
129        trace!("Creating new fork, url={}, block={:?}", fork.url, fork.evm_opts.fork_block_number);
130        let (sender, rx) = oneshot_channel();
131        let req = Request::CreateFork(Box::new(fork), sender);
132        self.handler.clone().try_send(req).map_err(|e| eyre::eyre!("{:?}", e))?;
133        rx.recv()?
134    }
135
136    /// Rolls the block of the fork.
137    ///
138    /// If no matching fork backend exists it will be created.
139    pub fn roll_fork(
140        &self,
141        fork: ForkId,
142        block: u64,
143    ) -> eyre::Result<(ForkId, SharedBackend, Env)> {
144        trace!(?fork, ?block, "rolling fork");
145        let (sender, rx) = oneshot_channel();
146        let req = Request::RollFork(fork, block, sender);
147        self.handler.clone().try_send(req).map_err(|e| eyre::eyre!("{:?}", e))?;
148        rx.recv()?
149    }
150
151    /// Returns the `Env` of the given fork, if any.
152    pub fn get_env(&self, fork: ForkId) -> eyre::Result<Option<Env>> {
153        trace!(?fork, "getting env config");
154        let (sender, rx) = oneshot_channel();
155        let req = Request::GetEnv(fork, sender);
156        self.handler.clone().try_send(req).map_err(|e| eyre::eyre!("{:?}", e))?;
157        Ok(rx.recv()?)
158    }
159
160    /// Updates block number and timestamp of given fork with new values.
161    pub fn update_block(&self, fork: ForkId, number: U256, timestamp: U256) -> eyre::Result<()> {
162        trace!(?fork, ?number, ?timestamp, "update fork block");
163        self.handler
164            .clone()
165            .try_send(Request::UpdateBlock(fork, number, timestamp))
166            .map_err(|e| eyre::eyre!("{:?}", e))
167    }
168
169    /// Updates the fork's entire env
170    ///
171    /// This is required for tx level forking where we need to fork off the `block - 1` state but
172    /// still need use env settings for `env`.
173    pub fn update_block_env(&self, fork: ForkId, env: BlockEnv) -> eyre::Result<()> {
174        trace!(?fork, ?env, "update fork block");
175        self.handler
176            .clone()
177            .try_send(Request::UpdateEnv(fork, env))
178            .map_err(|e| eyre::eyre!("{:?}", e))
179    }
180
181    /// Returns the corresponding fork if it exists.
182    ///
183    /// Returns `None` if no matching fork backend is available.
184    pub fn get_fork(&self, id: impl Into<ForkId>) -> eyre::Result<Option<SharedBackend>> {
185        let id = id.into();
186        trace!(?id, "get fork backend");
187        let (sender, rx) = oneshot_channel();
188        let req = Request::GetFork(id, sender);
189        self.handler.clone().try_send(req).map_err(|e| eyre::eyre!("{:?}", e))?;
190        Ok(rx.recv()?)
191    }
192
193    /// Returns the corresponding fork url if it exists.
194    ///
195    /// Returns `None` if no matching fork is available.
196    pub fn get_fork_url(&self, id: impl Into<ForkId>) -> eyre::Result<Option<String>> {
197        let (sender, rx) = oneshot_channel();
198        let req = Request::GetForkUrl(id.into(), sender);
199        self.handler.clone().try_send(req).map_err(|e| eyre::eyre!("{:?}", e))?;
200        Ok(rx.recv()?)
201    }
202}
203
204type Handler = BackendHandler;
205type CreateFuture =
206    Pin<Box<dyn Future<Output = eyre::Result<(ForkId, CreatedFork, Handler)>> + Send>>;
207type CreateSender = OneshotSender<eyre::Result<(ForkId, SharedBackend, Env)>>;
208type GetEnvSender = OneshotSender<Option<Env>>;
209
210/// Request that's send to the handler.
211#[derive(Debug)]
212enum Request {
213    /// Creates a new ForkBackend.
214    CreateFork(Box<CreateFork>, CreateSender),
215    /// Returns the Fork backend for the `ForkId` if it exists.
216    GetFork(ForkId, OneshotSender<Option<SharedBackend>>),
217    /// Adjusts the block that's being forked, by creating a new fork at the new block.
218    RollFork(ForkId, u64, CreateSender),
219    /// Returns the environment of the fork.
220    GetEnv(ForkId, GetEnvSender),
221    /// Updates the block number and timestamp of the fork.
222    UpdateBlock(ForkId, U256, U256),
223    /// Updates the block the entire block env,
224    UpdateEnv(ForkId, BlockEnv),
225    /// Shutdowns the entire `MultiForkHandler`, see `ShutDownMultiFork`
226    ShutDown(OneshotSender<()>),
227    /// Returns the Fork Url for the `ForkId` if it exists.
228    GetForkUrl(ForkId, OneshotSender<Option<String>>),
229}
230
231enum ForkTask {
232    /// Contains the future that will establish a new fork.
233    Create(CreateFuture, ForkId, CreateSender, Vec<CreateSender>),
234}
235
236/// The type that manages connections in the background.
237#[must_use = "futures do nothing unless polled"]
238pub struct MultiForkHandler {
239    /// Incoming requests from the `MultiFork`.
240    incoming: Fuse<Receiver<Request>>,
241
242    /// All active handlers.
243    ///
244    /// It's expected that this list will be rather small (<10).
245    handlers: Vec<(ForkId, Handler)>,
246
247    // tasks currently in progress
248    pending_tasks: Vec<ForkTask>,
249
250    /// All _unique_ forkids mapped to their corresponding backend.
251    ///
252    /// Note: The backend can be shared by multiple ForkIds if the target the same provider and
253    /// block number.
254    forks: HashMap<ForkId, CreatedFork>,
255
256    /// Optional periodic interval to flush rpc cache.
257    flush_cache_interval: Option<tokio::time::Interval>,
258}
259
260impl MultiForkHandler {
261    fn new(incoming: Receiver<Request>) -> Self {
262        Self {
263            incoming: incoming.fuse(),
264            handlers: Default::default(),
265            pending_tasks: Default::default(),
266            forks: Default::default(),
267            flush_cache_interval: None,
268        }
269    }
270
271    /// Sets the interval after which all rpc caches should be flushed periodically.
272    pub fn set_flush_cache_interval(&mut self, period: Duration) -> &mut Self {
273        self.flush_cache_interval =
274            Some(tokio::time::interval_at(tokio::time::Instant::now() + period, period));
275        self
276    }
277
278    /// Returns the list of additional senders of a matching task for the given id, if any.
279    #[expect(irrefutable_let_patterns)]
280    fn find_in_progress_task(&mut self, id: &ForkId) -> Option<&mut Vec<CreateSender>> {
281        for task in &mut self.pending_tasks {
282            if let ForkTask::Create(_, in_progress, _, additional) = task
283                && in_progress == id
284            {
285                return Some(additional);
286            }
287        }
288        None
289    }
290
291    fn create_fork(&mut self, fork: CreateFork, sender: CreateSender) {
292        let fork_id = ForkId::new(&fork.url, fork.evm_opts.fork_block_number);
293        trace!(?fork_id, "created new forkId");
294
295        // There could already be a task for the requested fork in progress.
296        if let Some(in_progress) = self.find_in_progress_task(&fork_id) {
297            in_progress.push(sender);
298            return;
299        }
300
301        // Need to create a new fork.
302        let task = Box::pin(create_fork(fork));
303        self.pending_tasks.push(ForkTask::Create(task, fork_id, sender, Vec::new()));
304    }
305
306    fn insert_new_fork(
307        &mut self,
308        fork_id: ForkId,
309        fork: CreatedFork,
310        sender: CreateSender,
311        additional_senders: Vec<CreateSender>,
312    ) {
313        self.forks.insert(fork_id.clone(), fork.clone());
314        let _ = sender.send(Ok((fork_id.clone(), fork.backend.clone(), fork.opts.env.clone())));
315
316        // Notify all additional senders and track unique forkIds.
317        for sender in additional_senders {
318            let next_fork_id = fork.inc_senders(fork_id.clone());
319            self.forks.insert(next_fork_id.clone(), fork.clone());
320            let _ = sender.send(Ok((next_fork_id, fork.backend.clone(), fork.opts.env.clone())));
321        }
322    }
323
324    /// Update the fork's block entire env
325    fn update_env(&mut self, fork_id: ForkId, env: BlockEnv) {
326        if let Some(fork) = self.forks.get_mut(&fork_id) {
327            fork.opts.env.evm_env.block_env = env;
328        }
329    }
330    /// Update fork block number and timestamp. Used to preserve values set by `roll` and `warp`
331    /// cheatcodes when new fork selected.
332    fn update_block(&mut self, fork_id: ForkId, block_number: U256, block_timestamp: U256) {
333        if let Some(fork) = self.forks.get_mut(&fork_id) {
334            fork.opts.env.evm_env.block_env.number = block_number;
335            fork.opts.env.evm_env.block_env.timestamp = block_timestamp;
336        }
337    }
338
339    fn on_request(&mut self, req: Request) {
340        match req {
341            Request::CreateFork(fork, sender) => self.create_fork(*fork, sender),
342            Request::GetFork(fork_id, sender) => {
343                let fork = self.forks.get(&fork_id).map(|f| f.backend.clone());
344                let _ = sender.send(fork);
345            }
346            Request::RollFork(fork_id, block, sender) => {
347                if let Some(fork) = self.forks.get(&fork_id) {
348                    trace!(target: "fork::multi", "rolling {} to {}", fork_id, block);
349                    let mut opts = fork.opts.clone();
350                    opts.evm_opts.fork_block_number = Some(block);
351                    self.create_fork(opts, sender)
352                } else {
353                    let _ =
354                        sender.send(Err(eyre::eyre!("No matching fork exists for {}", fork_id)));
355                }
356            }
357            Request::GetEnv(fork_id, sender) => {
358                let _ = sender.send(self.forks.get(&fork_id).map(|fork| fork.opts.env.clone()));
359            }
360            Request::UpdateBlock(fork_id, block_number, block_timestamp) => {
361                self.update_block(fork_id, block_number, block_timestamp);
362            }
363            Request::UpdateEnv(fork_id, block_env) => {
364                self.update_env(fork_id, block_env);
365            }
366            Request::ShutDown(sender) => {
367                trace!(target: "fork::multi", "received shutdown signal");
368                // We're emptying all fork backends, this way we ensure all caches get flushed.
369                self.forks.clear();
370                self.handlers.clear();
371                let _ = sender.send(());
372            }
373            Request::GetForkUrl(fork_id, sender) => {
374                let fork = self.forks.get(&fork_id).map(|f| f.opts.url.clone());
375                let _ = sender.send(fork);
376            }
377        }
378    }
379}
380
381// Drives all handler to completion.
382// This future will finish once all underlying BackendHandler are completed.
383impl Future for MultiForkHandler {
384    type Output = ();
385
386    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
387        let this = self.get_mut();
388
389        // Receive new requests.
390        loop {
391            match this.incoming.poll_next_unpin(cx) {
392                Poll::Ready(Some(req)) => this.on_request(req),
393                Poll::Ready(None) => {
394                    // Channel closed, but we still need to drive the fork handlers to completion.
395                    trace!(target: "fork::multi", "request channel closed");
396                    break;
397                }
398                Poll::Pending => break,
399            }
400        }
401
402        // Advance all tasks.
403        for n in (0..this.pending_tasks.len()).rev() {
404            let task = this.pending_tasks.swap_remove(n);
405            match task {
406                ForkTask::Create(mut fut, id, sender, additional_senders) => {
407                    if let Poll::Ready(resp) = fut.poll_unpin(cx) {
408                        match resp {
409                            Ok((fork_id, fork, handler)) => {
410                                if let Some(fork) = this.forks.get(&fork_id).cloned() {
411                                    this.insert_new_fork(
412                                        fork.inc_senders(fork_id),
413                                        fork,
414                                        sender,
415                                        additional_senders,
416                                    );
417                                } else {
418                                    this.handlers.push((fork_id.clone(), handler));
419                                    this.insert_new_fork(fork_id, fork, sender, additional_senders);
420                                }
421                            }
422                            Err(err) => {
423                                let _ = sender.send(Err(eyre::eyre!("{err}")));
424                                for sender in additional_senders {
425                                    let _ = sender.send(Err(eyre::eyre!("{err}")));
426                                }
427                            }
428                        }
429                    } else {
430                        this.pending_tasks.push(ForkTask::Create(
431                            fut,
432                            id,
433                            sender,
434                            additional_senders,
435                        ));
436                    }
437                }
438            }
439        }
440
441        // Advance all handlers.
442        for n in (0..this.handlers.len()).rev() {
443            let (id, mut handler) = this.handlers.swap_remove(n);
444            match handler.poll_unpin(cx) {
445                Poll::Ready(_) => {
446                    trace!(target: "fork::multi", "fork {:?} completed", id);
447                }
448                Poll::Pending => {
449                    this.handlers.push((id, handler));
450                }
451            }
452        }
453
454        if this.handlers.is_empty() && this.incoming.is_done() {
455            trace!(target: "fork::multi", "completed");
456            return Poll::Ready(());
457        }
458
459        // Periodically flush cached RPC state.
460        if this
461            .flush_cache_interval
462            .as_mut()
463            .map(|interval| interval.poll_tick(cx).is_ready())
464            .unwrap_or_default()
465            && !this.forks.is_empty()
466        {
467            trace!(target: "fork::multi", "tick flushing caches");
468            let forks = this.forks.values().map(|f| f.backend.clone()).collect::<Vec<_>>();
469            // Flush this on new thread to not block here.
470            std::thread::Builder::new()
471                .name("flusher".into())
472                .spawn(move || {
473                    forks.into_iter().for_each(|fork| fork.flush_cache());
474                })
475                .expect("failed to spawn thread");
476        }
477
478        Poll::Pending
479    }
480}
481
482/// Tracks the created Fork
483#[derive(Debug, Clone)]
484struct CreatedFork {
485    /// How the fork was initially created.
486    opts: CreateFork,
487    /// Copy of the sender.
488    backend: SharedBackend,
489    /// How many consumers there are, since a `SharedBacked` can be used by multiple
490    /// consumers.
491    num_senders: Arc<AtomicUsize>,
492}
493
494impl CreatedFork {
495    pub fn new(opts: CreateFork, backend: SharedBackend) -> Self {
496        Self { opts, backend, num_senders: Arc::new(AtomicUsize::new(1)) }
497    }
498
499    /// Increment senders and return unique identifier of the fork.
500    fn inc_senders(&self, fork_id: ForkId) -> ForkId {
501        format!(
502            "{}-{}",
503            fork_id.as_str(),
504            self.num_senders.fetch_add(1, std::sync::atomic::Ordering::Relaxed)
505        )
506        .into()
507    }
508}
509
510/// A type that's used to signaling the `MultiForkHandler` when it's time to shut down.
511///
512/// This is essentially a sync on drop, so that the `MultiForkHandler` can flush all rpc cashes.
513///
514/// This type intentionally does not implement `Clone` since it's intended that there's only once
515/// instance.
516#[derive(Debug)]
517struct ShutDownMultiFork {
518    handler: Option<Sender<Request>>,
519}
520
521impl Drop for ShutDownMultiFork {
522    fn drop(&mut self) {
523        trace!(target: "fork::multi", "initiating shutdown");
524        let (sender, rx) = oneshot_channel();
525        let req = Request::ShutDown(sender);
526        if let Some(mut handler) = self.handler.take()
527            && handler.try_send(req).is_ok()
528        {
529            let _ = rx.recv();
530            trace!(target: "fork::cache", "multifork backend shutdown");
531        }
532    }
533}
534
535/// Creates a new fork.
536///
537/// This will establish a new `Provider` to the endpoint and return the Fork Backend.
538async fn create_fork(mut fork: CreateFork) -> eyre::Result<(ForkId, CreatedFork, Handler)> {
539    let provider = fork.evm_opts.fork_provider_with_url(&fork.url)?;
540
541    // Initialise the fork environment.
542    let (env, block) = fork.evm_opts.fork_evm_env_with_provider(&fork.url, &provider).await?;
543    fork.env = env;
544    let meta = BlockchainDbMeta::new(fork.env.evm_env.block_env.clone(), fork.url.clone());
545
546    // We need to use the block number from the block because the env's number can be different on
547    // some L2s (e.g. Arbitrum).
548    let number = block.header().number();
549
550    // Determine the cache path if caching is enabled.
551    let cache_path = if fork.enable_caching {
552        Config::foundry_block_cache_dir(fork.env.evm_env.cfg_env.chain_id, number)
553    } else {
554        None
555    };
556
557    let db = BlockchainDb::new(meta, cache_path);
558    let (backend, handler) = SharedBackend::new(provider, db, Some(number.into()));
559    let fork = CreatedFork::new(fork, backend);
560    let fork_id = ForkId::new(&fork.opts.url, Some(number));
561
562    Ok((fork_id, fork, handler))
563}
foundry_evm_core/fork/multi.rs

foundry_evm_core/fork/
multi.rs
