feat: add paginated logs

CHANGELOG.md

@@ -160,6 +160,8 @@
 
 ### Unreleased
 
+- Stream of paginated logs that load logs in small pages
+  [1285](https://github.com/gakonst/ethers-rs/pull/1285)
 - Load previous logs before subscribing to new logs in case fromBlock is set
   [1264](https://github.com/gakonst/ethers-rs/pull/1264)
 - Add retries to the pending transaction future

ethers-core/src/types/log.rs

@@ -371,6 +371,27 @@ impl Filter {
         self.topics[3] = Some(topic.into());
         self
     }
+
+    pub fn is_paginatable(&self) -> bool {
+        match self.block_option {
+            FilterBlockOption::AtBlockHash(_hash) => false,
+            FilterBlockOption::Range { from_block, to_block: _ } => {
+                if from_block.is_none() {
+                    return false
+                }
+                from_block.unwrap().as_number().is_some()
+            }
+        }
+    }
+
+    pub fn get_from_block(&self) -> Option<U64> {
+        match self.block_option {
+            FilterBlockOption::AtBlockHash(_hash) => None,
+            FilterBlockOption::Range { from_block, to_block: _ } => {
+                from_block.map(|block| block.as_number()).unwrap_or(None)
+            }
+        }
+    }
 }
 
 /// Union type for representing a single value or a vector of values inside a filter

ethers-providers/src/lib.rs

@@ -18,6 +18,9 @@ pub use pending_transaction::PendingTransaction;
 mod pending_escalator;
 pub use pending_escalator::EscalatingPending;
 
+mod log_query;
+pub use log_query::LogQuery;
+
 mod stream;
 pub use futures_util::StreamExt;
 pub use stream::{interval, FilterWatcher, TransactionStream, DEFAULT_POLL_INTERVAL};
@@ -421,6 +424,15 @@ pub trait Middleware: Sync + Send + Debug {
         self.inner().get_logs(filter).await.map_err(FromErr::from)
     }
 
+    /// Returns a stream of logs are loaded in pages of given page size
+    fn get_logs_paginated<'a>(
+        &'a self,
+        filter: &Filter,
+        page_size: u64,
+    ) -> LogQuery<'a, Self::Provider> {
+        self.inner().get_logs_paginated(filter, page_size)
+    }
+
     async fn new_filter(&self, filter: FilterKind<'_>) -> Result<U256, Self::Error> {
         self.inner().new_filter(filter).await.map_err(FromErr::from)
     }

ethers-providers/src/log_query.rs

@@ -0,0 +1,132 @@
+use super::{JsonRpcClient, Middleware, PinBoxFut, Provider};
+use ethers_core::types::{Filter, Log, U64};
+use futures_core::stream::Stream;
+use std::{
+    collections::VecDeque,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+pub struct LogQuery<'a, P> {
+    provider: &'a Provider<P>,
+    filter: Filter,
+    from_block: Option<U64>,
+    page_size: u64,
+    current_logs: VecDeque<Log>,
+    last_block: Option<U64>,
+    state: LogQueryState<'a>,
+}
+
+enum LogQueryState<'a> {
+    Initial,
+    LoadLastBlock(PinBoxFut<'a, U64>),
+    LoadLogs(PinBoxFut<'a, Vec<Log>>),
+    Consume,
+}
+
+impl<'a, P> LogQuery<'a, P>
+where
+    P: JsonRpcClient,
+{
+    pub fn new(provider: &'a Provider<P>, filter: &Filter) -> Self {
+        Self {
+            provider,
+            filter: filter.clone(),
+            from_block: filter.get_from_block(),
+            page_size: 10000,
+            current_logs: VecDeque::new(),
+            last_block: None,
+            state: LogQueryState::Initial,
+        }
+    }
+
+    /// set page size for pagination
+    pub fn with_page_size(mut self, page_size: u64) -> Self {
+        self.page_size = page_size;
+        self
+    }
+}
+
+macro_rules! rewake_with_new_state {
+    ($ctx:ident, $this:ident, $new_state:expr) => {
+        $this.state = $new_state;
+        $ctx.waker().wake_by_ref();
+        return Poll::Pending
+    };
+}
+
+impl<'a, P> Unpin for LogQuery<'a, P> {}
+
+impl<'a, P> Stream for LogQuery<'a, P>
+where
+    P: JsonRpcClient,
+{
+    type Item = Log;
+
+    fn poll_next(mut self: Pin<&mut Self>, ctx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        match &mut self.state {
+            LogQueryState::Initial => {
+                if !self.filter.is_paginatable() {
+                    // if not paginatable, load logs and consume
+                    let filter = self.filter.clone();
+                    let provider = self.provider;
+                    let fut = Box::pin(async move { provider.get_logs(&filter).await });
+                    rewake_with_new_state!(ctx, self, LogQueryState::LoadLogs(fut));
+                } else {
+                    // if paginatable, load last block
+                    let fut = self.provider.get_block_number();
+                    rewake_with_new_state!(ctx, self, LogQueryState::LoadLastBlock(fut));
+                }
+            }
+            LogQueryState::LoadLastBlock(fut) => {
+                self.last_block = Some(
+                    futures_util::ready!(fut.as_mut().poll(ctx))
+                        .expect("error occurred loading last block"),
+                );
+
+                let from_block = self.filter.get_from_block().unwrap();
+                let to_block = from_block + self.page_size;
+                self.from_block = Some(to_block);
+
+                let filter = self.filter.clone().from_block(from_block).to_block(to_block);
+                let provider = self.provider;
+                // load first page of logs
+                let fut = Box::pin(async move { provider.get_logs(&filter).await });
+                rewake_with_new_state!(ctx, self, LogQueryState::LoadLogs(fut));
+            }
+            LogQueryState::LoadLogs(fut) => {
+                let logs = futures_util::ready!(fut.as_mut().poll(ctx))
+                    .expect("error occurred loading logs");
+                self.current_logs = VecDeque::from(logs);
+                rewake_with_new_state!(ctx, self, LogQueryState::Consume);
+            }
+            LogQueryState::Consume => {
+                let log = self.current_logs.pop_front();
+                if log.is_none() {
+                    // consumed all the logs
+                    if !self.filter.is_paginatable() {
+                        Poll::Ready(None)
+                    } else {
+                        // load new logs if there are still more pages to go through
+                        let from_block = self.from_block.unwrap();
+                        let to_block = from_block + self.page_size;
+
+                        // no more pages to load, and everything is consumed
+                        if from_block > self.last_block.unwrap() {
+                            return Poll::Ready(None)
+                        }
+                        // load next page
+                        self.from_block = Some(to_block);
+
+                        let filter = self.filter.clone().from_block(from_block).to_block(to_block);
+                        let provider = self.provider;
+                        let fut = Box::pin(async move { provider.get_logs(&filter).await });
+                        rewake_with_new_state!(ctx, self, LogQueryState::LoadLogs(fut));
+                    }
+                } else {
+                    Poll::Ready(log)
+                }
+            }
+        }
+    }
+}

ethers-providers/src/provider.rs

@@ -2,7 +2,7 @@ use crate::{
     ens, erc, maybe,
     pubsub::{PubsubClient, SubscriptionStream},
     stream::{FilterWatcher, DEFAULT_POLL_INTERVAL},
-    FromErr, Http as HttpProvider, JsonRpcClient, JsonRpcClientWrapper, MockProvider,
+    FromErr, Http as HttpProvider, JsonRpcClient, JsonRpcClientWrapper, LogQuery, MockProvider,
     PendingTransaction, QuorumProvider, RwClient, SyncingStatus,
 };
 
@@ -647,6 +647,10 @@ impl<P: JsonRpcClient> Middleware for Provider<P> {
         self.request("eth_getLogs", [filter]).await
     }
 
+    fn get_logs_paginated<'a>(&'a self, filter: &Filter, page_size: u64) -> LogQuery<'a, P> {
+        LogQuery::new(self, filter).with_page_size(page_size)
+    }
+
     /// Streams matching filter logs
     async fn watch<'a>(
         &'a self,