Prevent multiple test-validators from using the same ledger directory

Cargo.lock

@@ -1085,6 +1085,17 @@ dependencies = [
  "ieee754",
 ]
 
+[[package]]
+name = "fd-lock"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a15bec795244d49f5ee3024bdc6c3883fb035f7f6601d4a4821c3d5d60784454"
+dependencies = [
+ "failure",
+ "libc",
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "feature-probe"
 version = "0.1.1"
@@ -5096,6 +5107,7 @@ dependencies = [
  "chrono",
  "clap",
  "console",
+ "fd-lock",
  "indicatif",
  "libc",
  "log 0.4.11",

validator/Cargo.toml

@@ -14,6 +14,7 @@ base64 = "0.12.3"
 clap = "2.33.1"
 chrono = { version = "0.4.11", features = ["serde"] }
 console = "0.11.3"
+fd-lock = "1.1.1"
 indicatif = "0.15.0"
 log = "0.4.11"
 rand = "0.7.0"

validator/src/bin/solana-test-validator.rs

@@ -188,19 +188,28 @@ fn main() {
         }
     }
 
+    if !ledger_path.exists() {
+        fs::create_dir(&ledger_path).unwrap_or_else(|err| {
+            eprintln!(
+                "Error: Unable to create directory {}: {}",
+                ledger_path.display(),
+                err
+            );
+            exit(1);
+        })
+    }
+
+    let mut ledger_fd_lock = fd_lock::FdLock::new(std::fs::File::open(&ledger_path).unwrap());
+    let _ledger_lock = ledger_fd_lock.try_lock().unwrap_or_else(|_| {
+        eprintln!(
+            "Error: Unable to lock {} directory. Check if another solana-test-validator is running",
+            ledger_path.display()
+        );
+        exit(1);
+    });
+
     let validator_log_symlink = ledger_path.join("validator.log");
     let logfile = if output != Output::Log {
-        if !ledger_path.exists() {
-            fs::create_dir(&ledger_path).unwrap_or_else(|err| {
-                eprintln!(
-                    "Error: Unable to create directory {}: {}",
-                    ledger_path.display(),
-                    err
-                );
-                exit(1);
-            })
-        }
-
         let validator_log_with_timestamp = format!(
             "validator-{}.log",
             SystemTime::now()