Use OS file locks in validator client (#1958)

## Issue Addressed

Closes #1823

## Proposed Changes

* Use OS-level file locking for validator keystores, eliminating problems with lockfiles lingering after ungraceful shutdowns (`SIGKILL`, power outage). I'm using the `fs2` crate because it's cross-platform (unlike `file-lock`), and it seems to have the most downloads on crates.io.
* Deprecate + disable `--delete-lockfiles` CLI param, it's no longer necessary
* Delete the `validator_dir::Manager`, as it was mostly dead code and was only used in the `validator list` command, which has been rewritten to read the validator definitions YAML instead.

## Additional Info

Tested on:

- [x] Linux
- [x] macOS
- [x] Docker Linux
- [x] Docker macOS
- [ ] Windows

common/eth2_wallet_manager/Cargo.toml

@@ -9,6 +9,7 @@ edition = "2018"
 [dependencies]
 eth2_keystore = { path = "../../crypto/eth2_keystore" }
 eth2_wallet = { path = "../../crypto/eth2_wallet" }
+lockfile = { path = "../lockfile" }
 
 [dev-dependencies]
 tempfile = "3.1.0"

common/eth2_wallet_manager/src/locked_wallet.rs

@@ -3,7 +3,7 @@ use crate::{
     Error,
 };
 use eth2_wallet::{Uuid, ValidatorKeystores, Wallet};
-use std::fs::{remove_file, OpenOptions};
+use lockfile::Lockfile;
 use std::path::{Path, PathBuf};
 
 pub const LOCK_FILE: &str = ".lock";
@@ -26,6 +26,7 @@ pub const LOCK_FILE: &str = ".lock";
 pub struct LockedWallet {
     wallet_dir: PathBuf,
     wallet: Wallet,
+    _lockfile: Lockfile,
 }
 
 impl LockedWallet {
@@ -49,20 +50,12 @@ impl LockedWallet {
             return Err(Error::MissingWalletDir(wallet_dir));
         }
 
-        let lockfile = wallet_dir.join(LOCK_FILE);
-        if lockfile.exists() {
-            return Err(Error::WalletIsLocked(wallet_dir));
-        } else {
-            OpenOptions::new()
-                .write(true)
-                .create_new(true)
-                .open(lockfile)
-                .map_err(Error::UnableToCreateLockfile)?;
-        }
+        let _lockfile = Lockfile::new(wallet_dir.join(LOCK_FILE))?;
 
         Ok(Self {
             wallet: read(&wallet_dir, uuid)?,
             wallet_dir,
+            _lockfile,
         })
     }
 
@@ -99,13 +92,3 @@ impl LockedWallet {
         Ok(keystores)
     }
 }
-
-impl Drop for LockedWallet {
-    /// Clean-up the lockfile.
-    fn drop(&mut self) {
-        let lockfile = self.wallet_dir.clone().join(LOCK_FILE);
-        if let Err(e) = remove_file(&lockfile) {
-            eprintln!("Unable to remove {:?}: {:?}", lockfile, e);
-        }
-    }
-}

common/eth2_wallet_manager/src/wallet_manager.rs

@@ -3,6 +3,7 @@ use crate::{
     LockedWallet,
 };
 use eth2_wallet::{bip39::Mnemonic, Error as WalletError, Uuid, Wallet, WalletBuilder};
+use lockfile::LockfileError;
 use std::collections::HashMap;
 use std::ffi::OsString;
 use std::fs::{create_dir_all, read_dir, OpenOptions};
@@ -21,10 +22,9 @@ pub enum Error {
     WalletNameUnknown(String),
     WalletDirExists(PathBuf),
     IoError(io::Error),
-    WalletIsLocked(PathBuf),
     MissingWalletDir(PathBuf),
-    UnableToCreateLockfile(io::Error),
     UuidMismatch((Uuid, Uuid)),
+    LockfileError(LockfileError),
 }
 
 impl From<io::Error> for Error {
@@ -45,6 +45,12 @@ impl From<FilesystemError> for Error {
     }
 }
 
+impl From<LockfileError> for Error {
+    fn from(e: LockfileError) -> Error {
+        Error::LockfileError(e)
+    }
+}
+
 /// Defines the type of an EIP-2386 wallet.
 ///
 /// Presently only `Hd` wallets are supported.
@@ -358,7 +364,7 @@ mod tests {
         );
 
         match LockedWallet::open(&base_dir, &uuid_a) {
-            Err(Error::WalletIsLocked(_)) => {}
+            Err(Error::LockfileError(_)) => {}
             _ => panic!("did not get locked error"),
         };
 
@@ -368,7 +374,7 @@ mod tests {
             .expect("should open wallet a after previous instance is dropped");
 
         match LockedWallet::open(&base_dir, &uuid_b) {
-            Err(Error::WalletIsLocked(_)) => {}
+            Err(Error::LockfileError(_)) => {}
             _ => panic!("did not get locked error"),
         };