From be4e7cf1921e47fb3a7656c7dfc6a4185a837c3b Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Sat, 5 Sep 2020 10:29:38 +1000
Subject: [PATCH] Use spawn_blocking for validator keystores

---
 .../src/initialized_validators.rs             | 34 +++++++++++++------
 validator_client/src/lib.rs                   |  1 +
 2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/validator_client/src/initialized_validators.rs b/validator_client/src/initialized_validators.rs
index 436dcb4bae3..64912e09bcb 100644
--- a/validator_client/src/initialized_validators.rs
+++ b/validator_client/src/initialized_validators.rs
@@ -54,6 +54,8 @@ pub enum Error {
     PasswordUnknown(PathBuf),
     /// There was an error reading from stdin.
     UnableToReadPasswordFromUser(String),
+    /// There was an error running a tokio async task.
+    TokioJoin(tokio::task::JoinError),
 }
 
 /// A method used by a validator to sign messages.
@@ -279,7 +281,7 @@ pub struct InitializedValidators {
 
 impl InitializedValidators {
     /// Instantiates `Self`, initializing all validators in `definitions`.
-    pub fn from_definitions(
+    pub async fn from_definitions(
         definitions: ValidatorDefinitions,
         validators_dir: PathBuf,
         strict_lockfiles: bool,
@@ -292,7 +294,7 @@ impl InitializedValidators {
             validators: HashMap::default(),
             log,
         };
-        this.update_validators()?;
+        this.update_validators().await?;
         Ok(this)
     }
 
@@ -328,7 +330,7 @@ impl InitializedValidators {
     /// validator will be removed from `self.validators`.
     ///
     /// Saves the `ValidatorDefinitions` to file, even if no definitions were changed.
-    pub fn set_validator_status(
+    pub async fn set_validator_status(
         &mut self,
         voting_public_key: &PublicKey,
         enabled: bool,
@@ -342,7 +344,7 @@ impl InitializedValidators {
             def.enabled = enabled;
         }
 
-        self.update_validators()?;
+        self.update_validators().await?;
 
         self.definitions
             .save(&self.validators_dir)
@@ -362,7 +364,7 @@ impl InitializedValidators {
     /// A validator is considered "already known" and skipped if the public key is already known.
     /// I.e., if there are two different definitions with the same public key then the second will
     /// be ignored.
-    fn update_validators(&mut self) -> Result<(), Error> {
+    async fn update_validators(&mut self) -> Result<(), Error> {
         for def in self.definitions.as_slice() {
             if def.enabled {
                 match &def.signing_definition {
@@ -371,11 +373,23 @@ impl InitializedValidators {
                             continue;
                         }
 
-                        match InitializedValidator::from_definition(
-                            def.clone(),
-                            self.strict_lockfiles,
-                            &self.log,
-                        ) {
+                        // Decoding a local keystore can take several seconds, therefore it's best
+                        // to keep if off the core executor. This also has the fortunate effect of
+                        // interrupting the potentially long-running task during shut down.
+                        let inner_def = def.clone();
+                        let strict_lockfiles = self.strict_lockfiles;
+                        let inner_log = self.log.clone();
+                        let result = tokio::task::spawn_blocking(move || {
+                            InitializedValidator::from_definition(
+                                inner_def,
+                                strict_lockfiles,
+                                &inner_log,
+                            )
+                        })
+                        .await
+                        .map_err(Error::TokioJoin)?;
+
+                        match result {
                             Ok(init) => {
                                 self.validators
                                     .insert(init.voting_public_key().clone(), init);
diff --git a/validator_client/src/lib.rs b/validator_client/src/lib.rs
index 220d82a66ae..c9b3094fb9e 100644
--- a/validator_client/src/lib.rs
+++ b/validator_client/src/lib.rs
@@ -93,6 +93,7 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
             config.strict_lockfiles,
             log.clone(),
         )
+        .await
         .map_err(|e| format!("Unable to initialize validators: {:?}", e))?;
 
         info!(