From 01c756fb8b64dd47ee3b18c9d59f771cedd3ac40 Mon Sep 17 00:00:00 2001
From: Martin Vahlensieck <martin.vahlensieck@unibas.ch>
Date: Tue, 4 Jun 2024 12:50:48 +0200
Subject: [PATCH] Add option to notify systemd on startup

Because this loads a native library, it requires Java 21 with preview features enables.
---
 build.gradle                                  | 12 +++--
 .../client/PolyphenyControlConnector.java     | 14 ------
 .../control/main/ControlCommand.java          | 48 ++++++++++++++++++-
 3 files changed, 55 insertions(+), 19 deletions(-)

diff --git a/build.gradle b/build.gradle
index 2a97721..9348a79 100644
--- a/build.gradle
+++ b/build.gradle
@@ -58,13 +58,17 @@ sourceSets {
     }
 }
 
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
+}
+
 tasks.withType(JavaCompile).configureEach {
     options.encoding = "UTF-8"
-    sourceCompatibility = "11"
-    targetCompatibility = "11"
+    options.compilerArgs += "--enable-preview"
 }
 
-
 configurations {
     webjars
 }
@@ -175,7 +179,7 @@ artifacts {
 
 
 task extractWebjars(type: Copy) {
-    configurations.webjars.each {jar ->
+    configurations.webjars.each { jar ->
         from zipTree(jar)
         into "$buildDir/webjars"
         duplicatesStrategy = DuplicatesStrategy.EXCLUDE
diff --git a/control-connector/src/main/java/org/polypheny/control/client/PolyphenyControlConnector.java b/control-connector/src/main/java/org/polypheny/control/client/PolyphenyControlConnector.java
index 5b0e599..8cefa10 100644
--- a/control-connector/src/main/java/org/polypheny/control/client/PolyphenyControlConnector.java
+++ b/control-connector/src/main/java/org/polypheny/control/client/PolyphenyControlConnector.java
@@ -174,11 +174,6 @@ String getStatus() {
     }
 
 
-    public int checkForAnyRunningPolyphenyInstances() {
-        return Integer.parseInt( executeGet( "/control/checkAnyRunningPolyphenyInstances" ) );
-    }
-
-
     private String executeGet( String command ) {
         HttpResponse<String> httpResponse;
         try {
@@ -191,15 +186,6 @@ private String executeGet( String command ) {
     }
 
 
-    private void executePost( String command, String data ) {
-        try {
-            Unirest.post( controlUrl + command ).body( data ).asString();
-        } catch ( UnirestException e ) {
-            log.error( "Exception while sending request", e );
-        }
-    }
-
-
     private class WebSocket extends WebSocketClient {
 
         private final Gson gson = new Gson();
diff --git a/src/main/java/org/polypheny/control/main/ControlCommand.java b/src/main/java/org/polypheny/control/main/ControlCommand.java
index 2cc5455..30cd757 100644
--- a/src/main/java/org/polypheny/control/main/ControlCommand.java
+++ b/src/main/java/org/polypheny/control/main/ControlCommand.java
@@ -20,6 +20,13 @@
 import com.github.rvesse.airline.annotations.Command;
 import com.github.rvesse.airline.annotations.Option;
 import com.typesafe.config.Config;
+import java.lang.foreign.Arena;
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.Linker;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.SymbolLookup;
+import java.lang.foreign.ValueLayout;
+import java.lang.invoke.MethodHandle;
 import java.util.HashMap;
 import org.polypheny.control.authentication.AuthenticationFileManager;
 import org.polypheny.control.control.ConfigManager;
@@ -31,7 +38,10 @@
 public class ControlCommand extends AbstractCommand {
 
     @Option(name = { "-p", "--port" }, description = "Overwrite port of the Polypheny Control dashboard and API.")
-    private final int port = -1;
+    private int port = -1;
+
+    @Option(name = { "--notify" }, description = "Notify systemd when server is listening.")
+    private boolean notify = false;
 
     @Option(name = { "-x", "--suppress-warning" }, description = "Suppress the auth warnings on startup.")
     protected boolean suppressWarning = false;
@@ -63,6 +73,16 @@ public int _run_() {
             server = new Server( control, ConfigManager.getConfig().getInt( "pcrtl.control.port" ) );
         }
 
+        if ( notify ) {
+            try {
+                notifySystemd();
+            } catch ( Throwable t ) {
+                server.shutdown();
+                System.err.println( "Failed to notify systemd: " + t.getMessage() );
+                return 1;
+            }
+        }
+
         Runtime.getRuntime().addShutdownHook( new Thread( () -> running = false ) );
 
         while ( running ) {
@@ -80,6 +100,32 @@ public int _run_() {
     }
 
 
+    @SuppressWarnings("preview")
+    private static void notifySystemd() {
+        // When adding another architecture, ensure that the sizes of the types below are correct.
+        if ( !System.getProperty( "os.arch" ).equals( "amd64" ) ) {
+            throw new RuntimeException( "Unexpected OS architecture" );
+        }
+        try ( Arena a = Arena.ofConfined() ) {
+            Linker l = Linker.nativeLinker();
+            SymbolLookup systemd = SymbolLookup.libraryLookup( "libsystemd.so.0", a );
+            MethodHandle sd_notify = l.downcallHandle(
+                    systemd.find( "sd_notify" ).orElseThrow(),
+                    FunctionDescriptor.ofVoid( ValueLayout.JAVA_INT, ValueLayout.ADDRESS )
+            );
+            MemorySegment m = a.allocateUtf8String( "READY=1" );
+            sd_notify.invokeExact( 0, m );
+        } catch ( IllegalArgumentException e ) {
+            if ( e.getMessage().contains( "Cannot open library" ) ) {
+                throw new RuntimeException( "libsystemd is required for --notify" );
+            }
+            throw e;
+        } catch ( Throwable e ) {
+            throw new RuntimeException( e );
+        }
+    }
+
+
     private static void warnNoUserAccounts() {
         System.out.println( "WARNING: No Users Exist. Polypheny-Control executes and manages Polypheny-DB." );
         System.out.println( "WARNING: For security reasons it is advisable to create at least one user." );