Verify that child processes start correctly (#58)

* Verify that child processes start correctly

* Remove todo

* Update copyrights

* Make ktlint happy

Author: alexstaeding

launcher/src/main/kotlin/org/sourcegrade/jagr/launcher/executor/ProcessWorker.kt

@@ -1,7 +1,7 @@
 /*
  *   Jagr - SourceGrade.org
- *   Copyright (C) 2021-2024 Alexander Städing
- *   Copyright (C) 2021-2024 Contributors
+ *   Copyright (C) 2021-2025 Alexander Städing
+ *   Copyright (C) 2021-2025 Contributors
  *
  *     This program is free software: you can redistribute it and/or modify
  *     it under the terms of the GNU Affero General Public License as published by
@@ -59,8 +59,25 @@ class ProcessWorker(
         status = WorkerStatus.READY
     }
 
+    /**
+     * Ensures that [process] has been initialized correctly.
+     *
+     * This should be only called once per process.
+     */
+    private fun checkBoot() {
+        // wait for child process to start
+        val line = process.inputReader(Charsets.UTF_8).readLine()
+        if (line != MARK_CHILD_BOOT) {
+            throw IllegalStateException(
+                "Child process did not start correctly:\n" +
+                    process.errorStream.reader().readText(),
+            )
+        }
+    }
+
     override fun assignJob(job: GradingJob) {
         check(this.job == null) { "Worker already has a job!" }
+        checkBoot()
         status = WorkerStatus.RUNNING
         coroutineScope.launch {
             try {
@@ -141,5 +158,6 @@ class ProcessWorker(
     companion object {
         const val MARK_LOG_MESSAGE_BYTE = 2
         const val MARK_RESULT_BYTE = 7
+        const val MARK_CHILD_BOOT = "jagr-child-boot"
     }
 }

src/main/kotlin/org/sourcegrade/jagr/Main.kt

@@ -1,7 +1,7 @@
 /*
  *   Jagr - SourceGrade.org
- *   Copyright (C) 2021-2022 Alexander Staeding
- *   Copyright (C) 2021-2022 Contributors
+ *   Copyright (C) 2021-2025 Alexander Städing
+ *   Copyright (C) 2021-2025 Contributors
  *
  *     This program is free software: you can redistribute it and/or modify
  *     it under the terms of the GNU Affero General Public License as published by
@@ -27,6 +27,7 @@ import com.github.ajalt.clikt.parameters.types.choice
 import org.sourcegrade.jagr.launcher.env.Environment
 import org.sourcegrade.jagr.launcher.env.Jagr
 import org.sourcegrade.jagr.launcher.env.logger
+import org.sourcegrade.jagr.launcher.executor.ProcessWorker
 
 fun main(vararg args: String) {
     try {
@@ -53,6 +54,7 @@ class MainCommand : CliktCommand() {
 
     override fun run() {
         if (child) {
+            println(ProcessWorker.MARK_CHILD_BOOT)
             Environment.initializeChildProcess()
             ChildProcGrading().grade()
         } else {