Fix a race condition in SystemLogs using an actor for a thread-safe access to process

Author: dkovba

Sources/CLI/System/SystemLogs.swift

@@ -30,6 +30,33 @@ extension Application {
             abstract: "Fetch system logs for `container` services"
         )
 
+        private actor ProcessManager {
+            private let process = Process()
+
+            func configure(args: [String]) {
+                process.launchPath = "/usr/bin/env"
+                process.arguments = args
+                process.standardOutput = FileHandle.standardOutput
+                process.standardError = FileHandle.standardError
+            }
+
+            func run() throws {
+                try process.run()
+            }
+
+            func waitUntilExit() {
+                process.waitUntilExit()
+            }
+
+            func terminate() {
+                process.terminate()
+            }
+
+            var terminationStatus: Int32 {
+                process.terminationStatus
+            }
+        }
+
         @OptionGroup
         var global: Flags.Global
 
@@ -43,12 +70,12 @@ extension Application {
         var follow: Bool = false
 
         func run() async throws {
-            let process = Process()
+            let processManager = ProcessManager()
             let sigHandler = AsyncSignalHandler.create(notify: [SIGINT, SIGTERM])
 
             Task {
                 for await _ in sigHandler.signals {
-                    process.terminate()
+                    await processManager.terminate()
                     Darwin.exit(0)
                 }
             }
@@ -62,21 +89,16 @@ extension Application {
                 }
                 args.append(contentsOf: ["--predicate", "subsystem = 'com.apple.container'"])
 
-                process.launchPath = "/usr/bin/env"
-                process.arguments = args
-
-                process.standardOutput = FileHandle.standardOutput
-                process.standardError = FileHandle.standardError
-
-                try process.run()
-                process.waitUntilExit()
+                await processManager.configure(args: args)
+                try await processManager.run()
+                await processManager.waitUntilExit()
             } catch {
                 throw ContainerizationError(
                     .invalidArgument,
                     message: "failed to system logs: \(error)"
                 )
             }
-            throw ArgumentParser.ExitCode(process.terminationStatus)
+            throw ArgumentParser.ExitCode(await processManager.terminationStatus)
         }
     }
 }