fix(validator_client): raise soft fd limit (#4796)

* fix(validator_client): raise soft fd limit

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into rkrasiuk/raise-vc-fdlimit

* cargo lock

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into rkrasiuk/raise-vc-fdlimit

validator_client/Cargo.toml

@@ -61,3 +61,4 @@ sysinfo = { workspace = true }
 system_health = { path = "../common/system_health" }
 logging = { workspace = true }
 strum = { workspace = true }
+fdlimit = "0.3.0"

validator_client/src/lib.rs

@@ -47,7 +47,7 @@ use notifier::spawn_notifier;
 use parking_lot::RwLock;
 use preparation_service::{PreparationService, PreparationServiceBuilder};
 use reqwest::Certificate;
-use slog::{error, info, warn, Logger};
+use slog::{debug, error, info, warn, Logger};
 use slot_clock::SlotClock;
 use slot_clock::SystemTimeSlotClock;
 use std::fs::File;
@@ -121,6 +121,27 @@ impl<E: EthSpec> ProductionValidatorClient<E> {
     pub async fn new(context: RuntimeContext<E>, config: Config) -> Result<Self, String> {
         let log = context.log().clone();
 
+        // Attempt to raise soft fd limit. The behavior is OS specific:
+        // `linux` - raise soft fd limit to hard
+        // `macos` - raise soft fd limit to `min(kernel limit, hard fd limit)`
+        // `windows` & rest - noop
+        match fdlimit::raise_fd_limit().map_err(|e| format!("Unable to raise fd limit: {}", e))? {
+            fdlimit::Outcome::LimitRaised { from, to } => {
+                debug!(
+                    log,
+                    "Raised soft open file descriptor resource limit";
+                    "old_limit" => from,
+                    "new_limit" => to
+                );
+            }
+            fdlimit::Outcome::Unsupported => {
+                debug!(
+                    log,
+                    "Raising soft open file descriptor resource limit is not supported"
+                );
+            }
+        };
+
         info!(
             log,
             "Starting validator client";