fix: remove adapter <> api deadlock (#108)

Adapter sends price update notifications to the subscriber
API connection actor but at the same time the subscriber
actor can get blcoked on receiving messages (e.g. product
info) from Adapter. If the channel from Adapter to the
subscriber gets full the Adapter can get blocked and
this results in a deadlock. This situation propagates
and queues messages in other actors and WS messages
from the clients will grow in an unbounded queue that
results in a constant memory growth (leak).

This change simply makes the Adaptor to subscriber API
connection nonblocking by dropping messages if the channels
are full.

Author: ali-behjati

src/agent/pythd/adapter.rs

@@ -214,7 +214,7 @@ impl Adapter {
                 Some(message) = self.message_rx.recv() => {
                     if let Err(err) = self.handle_message(message).await {
                         error!(self.logger, "{}", err);
-            debug!(self.logger, "error context"; "context" => format!("{:?}", err));
+                        debug!(self.logger, "error context"; "context" => format!("{:?}", err));
                     }
                 }
                 _ = self.shutdown_rx.recv() => {
@@ -224,7 +224,7 @@ impl Adapter {
                 _ = self.notify_price_sched_interval.tick() => {
                     if let Err(err) = self.send_notify_price_sched().await {
                         error!(self.logger, "{}", err);
-            debug!(self.logger, "error context"; "context" => format!("{:?}", err));
+                        debug!(self.logger, "error context"; "context" => format!("{:?}", err));
                     }
                 }
             }
@@ -508,12 +508,14 @@ impl Adapter {
 
     async fn send_notify_price_sched(&self) -> Result<()> {
         for subscription in self.notify_price_sched_subscriptions.values().flatten() {
+            // Send the notify price sched update without awaiting. This results in raising errors
+            // if the channel is full which normally should not happen. This is because we do not
+            // want to block the adapter if the channel is full.
             subscription
                 .notify_price_sched_tx
-                .send(NotifyPriceSched {
+                .try_send(NotifyPriceSched {
                     subscription: subscription.subscription_id,
-                })
-                .await?;
+                })?;
         }
 
         Ok(())
@@ -580,19 +582,19 @@ impl Adapter {
 
         // Send the Notify Price update to each subscription
         for subscription in subscriptions {
-            subscription
-                .notify_price_tx
-                .send(NotifyPrice {
-                    subscription: subscription.subscription_id,
-                    result:       PriceUpdate {
-                        price,
-                        conf,
-                        status: Self::price_status_to_str(status),
-                        valid_slot,
-                        pub_slot,
-                    },
-                })
-                .await?;
+            // Send the notify price update without awaiting. This results in raising errors if the
+            // channel is full which normally should not happen. This is because we do not want to
+            // block the adapter if the channel is full.
+            subscription.notify_price_tx.try_send(NotifyPrice {
+                subscription: subscription.subscription_id,
+                result:       PriceUpdate {
+                    price,
+                    conf,
+                    status: Self::price_status_to_str(status),
+                    valid_slot,
+                    pub_slot,
+                },
+            })?;
         }
 
         Ok(())

src/agent/remote_keypair_loader.rs

@@ -314,8 +314,7 @@ async fn handle_key_requests(
                 match response_tx.send(copied_keypair) {
                     Ok(()) => {}
                     Err(_e) => {
-                        warn!(logger, "remote_keypair_loader: Could not send back secondary keypair to channel";
-                        );
+                        warn!(logger, "remote_keypair_loader: Could not send back secondary keypair to channel");
                     }
                 }
             }

src/agent/solana/exporter.rs

@@ -462,7 +462,7 @@ impl Exporter {
         self.update_our_prices(&publish_keypair.pubkey());
 
         debug!(self.logger, "Exporter: filtering prices permissioned to us";
-               "our_prices" => format!("{:?}", self.our_prices),
+               "our_prices" => format!("{:?}", self.our_prices.keys()),
                "publish_pubkey" => publish_keypair.pubkey().to_string(),
         );
 
@@ -594,7 +594,6 @@ impl Exporter {
                     trace!(
                         self.logger,
                         "Exporter: No more permissioned price accounts in channel, using cached value";
-                        "cached_value" => format!("{:?}", self.our_prices),
                     );
                     break;
                 }