Merge branch 'state-machine' into 'master'

Refactor graceful shutdown

See merge request mangadex/mangadex_at_home!36

CHANGELOG.md

@@ -6,6 +6,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 ### Added
+- [2020-06-20] Added `graceful_shutdown_wait_seconds` client setting
 
 ### Changed
 

src/main/java/mdnet/base/MangaDexClient.java

@@ -1,279 +0,0 @@
-package mdnet.base;
-
-import ch.qos.logback.classic.LoggerContext;
-import mdnet.base.settings.ClientSettings;
-import mdnet.base.server.ApplicationKt;
-import mdnet.base.server.WebUiKt;
-import mdnet.base.settings.ServerSettings;
-import mdnet.cache.DiskLruCache;
-import mdnet.cache.HeaderMismatchException;
-import org.http4k.server.Http4kServer;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.io.*;
-import java.time.Instant;
-import java.util.Collections;
-import java.util.LinkedHashMap;
-import java.util.Map;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
-
-import static mdnet.base.Constants.JACKSON;
-
-public class MangaDexClient {
-	private final static Logger LOGGER = LoggerFactory.getLogger(MangaDexClient.class);
-
-	private final ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
-	private final ServerHandler serverHandler;
-	private final ClientSettings clientSettings;
-
-	private final Map<Instant, Statistics> statsMap = Collections
-			.synchronizedMap(new LinkedHashMap<Instant, Statistics>(240) {
-				@Override
-				protected boolean removeEldestEntry(Map.Entry eldest) {
-					return this.size() > 240;
-				}
-			});
-	private final AtomicReference<Statistics> statistics;
-	private final AtomicBoolean isHandled;
-
-	private ServerSettings serverSettings;
-	private Http4kServer engine; // if this is null, then the server has shutdown
-	private Http4kServer webUi;
-	private DiskLruCache cache;
-
-	// these variables are for runLoop();
-	private int counter = 0;
-	private long lastBytesSent = 0;
-	// a non-negative number here means we are shutting down
-	private int gracefulCounter = -1;
-	private Runnable gracefulAction;
-
-	public MangaDexClient(ClientSettings clientSettings) {
-		this.clientSettings = clientSettings;
-		this.serverHandler = new ServerHandler(clientSettings);
-		this.statistics = new AtomicReference<>();
-		this.isHandled = new AtomicBoolean();
-
-		try {
-			cache = DiskLruCache.open(new File("cache"), 1, 1,
-					clientSettings.getMaxCacheSizeInMebibytes() * 1024 * 1024 /* MiB to bytes */);
-
-			DiskLruCache.Snapshot snapshot = cache.get("statistics");
-			if (snapshot != null) {
-				statistics.set(JACKSON.readValue(snapshot.getInputStream(0), Statistics.class));
-				snapshot.close();
-			} else {
-				statistics.set(new Statistics());
-			}
-		} catch (HeaderMismatchException e) {
-			LOGGER.warn("Cache version may be outdated - remove if necessary");
-			Main.dieWithError(e);
-		} catch (IOException e) {
-			LOGGER.warn("Cache version may be corrupt - remove if necessary");
-			Main.dieWithError(e);
-		}
-	}
-
-	public void runLoop() {
-		loginAndStartServer();
-		if (serverSettings.getLatestBuild() > Constants.CLIENT_BUILD) {
-			if (LOGGER.isWarnEnabled()) {
-				LOGGER.warn("Outdated build detected! Latest: {}, Current: {}", serverSettings.getLatestBuild(),
-						Constants.CLIENT_BUILD);
-			}
-		}
-
-		lastBytesSent = statistics.get().getBytesSent();
-		statsMap.put(Instant.now(), statistics.get());
-
-		if (clientSettings.getWebSettings() != null) {
-			webUi = WebUiKt.getUiServer(clientSettings.getWebSettings(), statistics, statsMap);
-			webUi.start();
-		}
-
-		if (LOGGER.isInfoEnabled()) {
-			LOGGER.info("Mangadex@Home Client initialization completed successfully. Starting normal operation.");
-		}
-
-		executorService.scheduleWithFixedDelay(() -> {
-			try {
-				// Converting from 15 seconds loop to 45 second loop
-				if (counter / 3 == 80) {
-					counter = 0;
-					lastBytesSent = statistics.get().getBytesSent();
-
-					if (engine == null) {
-						if (LOGGER.isInfoEnabled()) {
-							LOGGER.info("Restarting server stopped due to hourly bandwidth limit");
-						}
-
-						loginAndStartServer();
-					}
-				} else {
-					counter++;
-				}
-
-				if (gracefulCounter == 0) {
-					logout();
-					if (LOGGER.isInfoEnabled()) {
-						LOGGER.info("Waiting another 15 seconds for graceful shutdown ({} out of {} tries)",
-								gracefulCounter + 1, 4);
-					}
-					gracefulCounter++;
-				} else if (gracefulCounter > 0) {
-					if (!isHandled.get() || gracefulCounter == 4 || engine == null) {
-						if (LOGGER.isInfoEnabled()) {
-							if (!isHandled.get()) {
-								LOGGER.info("No requests received, shutting down");
-							} else {
-								LOGGER.info("Max tries attempted, shutting down");
-							}
-						}
-
-						if (engine != null) {
-							stopServer();
-						}
-						if (gracefulAction != null) {
-							gracefulAction.run();
-						}
-
-						// reset variables
-						gracefulCounter = -1;
-						gracefulAction = null;
-					} else {
-						if (LOGGER.isInfoEnabled()) {
-							LOGGER.info("Waiting another 15 seconds for graceful shutdown ({} out of {} tries)",
-									gracefulCounter + 1, 4);
-						}
-						gracefulCounter++;
-					}
-					isHandled.set(false);
-				} else {
-					if (counter % 3 == 0) {
-						pingControl();
-					}
-					updateStats();
-				}
-
-			} catch (Exception e) {
-				LOGGER.warn("statistics update failed", e);
-			}
-
-		}, 15, 15, TimeUnit.SECONDS);
-	}
-
-	private void pingControl() {
-		// if the server is offline then don't try and refresh certs
-		if (engine == null) {
-			return;
-		}
-
-		long currentBytesSent = statistics.get().getBytesSent() - lastBytesSent;
-		if (clientSettings.getMaxMebibytesPerHour() != 0
-				&& clientSettings.getMaxMebibytesPerHour() * 1024 * 1024 /* MiB to bytes */ < currentBytesSent) {
-			if (LOGGER.isInfoEnabled()) {
-				LOGGER.info("Shutting down server as hourly bandwidth limit reached");
-			}
-
-			// Give enough time for graceful shutdown
-			if (240 - counter > 3) {
-				LOGGER.info("Graceful shutdown started");
-				gracefulCounter = 0;
-			}
-		}
-
-		ServerSettings n = serverHandler.pingControl(serverSettings);
-
-		if (LOGGER.isInfoEnabled()) {
-			LOGGER.info("Server settings received: {}", n);
-		}
-
-		if (n != null) {
-			if (n.getLatestBuild() > Constants.CLIENT_BUILD) {
-				if (LOGGER.isWarnEnabled()) {
-					LOGGER.warn("Outdated build detected! Latest: {}, Current: {}", n.getLatestBuild(),
-							Constants.CLIENT_BUILD);
-				}
-			}
-
-			if (n.getTls() != null || !n.getImageServer().equals(serverSettings.getImageServer())) {
-				// certificates or upstream url must have changed, restart webserver
-				if (LOGGER.isInfoEnabled()) {
-					LOGGER.info("Doing internal restart of HTTP server to refresh certs/upstream URL");
-				}
-
-				LOGGER.info("Graceful shutdown started");
-				gracefulCounter = 0;
-				gracefulAction = this::loginAndStartServer;
-			}
-		}
-	}
-
-	private void updateStats() throws IOException {
-		statistics.updateAndGet(n -> n.copy(n.getRequestsServed(), n.getCacheHits(), n.getCacheMisses(),
-				n.getBrowserCached(), n.getBytesSent(), cache.size()));
-
-		statsMap.put(Instant.now(), statistics.get());
-
-		DiskLruCache.Editor editor = cache.edit("statistics");
-		if (editor != null) {
-			JACKSON.writeValue(editor.newOutputStream(0), statistics.get());
-			editor.commit();
-		}
-	}
-
-	private void loginAndStartServer() {
-		serverSettings = serverHandler.loginToControl();
-		if (serverSettings == null) {
-			Main.dieWithError("Failed to get a login response from server - check API secret for validity");
-		}
-		engine = ApplicationKt.getServer(cache, serverSettings, clientSettings, statistics, isHandled);
-		engine.start();
-
-		if (LOGGER.isInfoEnabled()) {
-			LOGGER.info("Internal HTTP server was successfully started");
-		}
-	}
-
-	private void logout() {
-		serverHandler.logoutFromControl();
-	}
-
-	private void stopServer() {
-		if (LOGGER.isInfoEnabled()) {
-			LOGGER.info("Shutting down HTTP server");
-		}
-		engine.stop();
-		if (LOGGER.isInfoEnabled()) {
-			LOGGER.info("Internal HTTP server has gracefully shut down");
-		}
-		engine = null;
-	}
-
-	public void shutdown() {
-		LOGGER.info("Graceful shutdown started");
-		gracefulCounter = 0;
-		AtomicBoolean readyToExit = new AtomicBoolean(false);
-		gracefulAction = () -> {
-			if (webUi != null) {
-				webUi.close();
-			}
-			try {
-				cache.close();
-			} catch (IOException e) {
-				LOGGER.error("Cache failed to close", e);
-			}
-			readyToExit.set(true);
-		};
-		while (!readyToExit.get()) {
-		}
-		executorService.shutdown();
-		LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
-		loggerContext.stop();
-	}
-}

src/main/java/mdnet/cache/DiskLruCache.java

@@ -250,8 +250,7 @@ public final class DiskLruCache implements Closeable {
 					|| !Integer.toString(valueCount).equals(valueCountString) || !"".equals(blank)) {
 				throw new HeaderMismatchException(
 						new String[]{magic, version, appVersionString, valueCountString, blank},
-						new String[]{MAGIC, VERSION_1, Integer.toString(appVersion), Integer.toString(valueCount), ""}
+						new String[]{MAGIC, VERSION_1, Integer.toString(appVersion), Integer.toString(valueCount), ""});
-					);
 			}
 
 			int lineCount = 0;

src/main/java/mdnet/cache/HeaderMismatchException.java

@@ -4,7 +4,7 @@ import java.io.IOException;
 import java.util.Arrays;
 
 public class HeaderMismatchException extends IOException {
-    public HeaderMismatchException(String[] actual, String[] expected) {
+	public HeaderMismatchException(String[] actual, String[] expected) {
-        super("expected header " + Arrays.toString(expected) + ", found " + Arrays.toString(actual));
+		super("expected header " + Arrays.toString(expected) + ", found " + Arrays.toString(actual));
-    }
+	}
 }

src/main/kotlin/mdnet/base/Constants.kt

@@ -4,10 +4,9 @@ import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
 import java.time.Duration
 
 object Constants {
-    const val CLIENT_BUILD = 11
+    const val CLIENT_BUILD = 12
     const val CLIENT_VERSION = "1.0"
     const val WEBUI_VERSION = "0.1.1"
     val MAX_AGE_CACHE: Duration = Duration.ofDays(14)
-    @JvmField
     val JACKSON = jacksonObjectMapper()
 }

src/main/kotlin/mdnet/base/Main.kt

@@ -30,7 +30,7 @@ object Main {
             dieWithError("Expected one argument: path to config file, or nothing")
         }
 
-        val settings: ClientSettings = try {
+        val settings = try {
             JACKSON.readValue<ClientSettings>(FileReader(file))
         } catch (e: UnrecognizedPropertyException) {
             dieWithError("'${e.propertyName}' is not a valid setting")
@@ -55,7 +55,6 @@ object Main {
         client.runLoop()
     }
 
-    @JvmStatic
     fun dieWithError(e: Throwable): Nothing {
         if (LOGGER.isErrorEnabled) {
             LOGGER.error("Critical Error", e)
@@ -64,7 +63,6 @@ object Main {
         exitProcess(1)
     }
 
-    @JvmStatic
     fun dieWithError(error: String): Nothing {
         if (LOGGER.isErrorEnabled) {
             LOGGER.error("Critical Error: {}", error)

src/main/kotlin/mdnet/base/MangaDexClient.kt

@@ -0,0 +1,299 @@
+/* ktlint-disable no-wildcard-imports */
+package mdnet.base
+
+import ch.qos.logback.classic.LoggerContext
+import com.fasterxml.jackson.module.kotlin.readValue
+import mdnet.base.Constants.JACKSON
+import mdnet.base.Main.dieWithError
+import mdnet.base.server.getServer
+import mdnet.base.server.getUiServer
+import mdnet.base.settings.ClientSettings
+import mdnet.base.settings.ServerSettings
+import mdnet.cache.DiskLruCache
+import mdnet.cache.HeaderMismatchException
+import org.http4k.server.Http4kServer
+import org.slf4j.LoggerFactory
+import java.io.File
+import java.io.IOException
+import java.time.Instant
+import java.util.*
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.Executors
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicBoolean
+import java.util.concurrent.atomic.AtomicReference
+
+sealed class State
+// server is not running
+object Uninitialized : State()
+// server has shut down
+object Shutdown : State()
+// server is in the process of shutting down
+data class GracefulShutdown(val lastRunning: Running, val counts: Int = 0, val nextState: State = Uninitialized, val action: () -> Unit = {}) : State()
+// server is currently running
+data class Running(val server: Http4kServer, val settings: ServerSettings) : State()
+
+class MangaDexClient(private val clientSettings: ClientSettings) {
+    // this must remain singlethreaded because of how the state mechanism works
+    private val executorService = Executors.newSingleThreadScheduledExecutor()
+    // state must only be accessed from the thread on the executorService
+    private var state: State = Uninitialized
+
+    private val serverHandler: ServerHandler = ServerHandler(clientSettings)
+    private val statsMap: MutableMap<Instant, Statistics> = Collections
+        .synchronizedMap(object : LinkedHashMap<Instant, Statistics>(240) {
+            override fun removeEldestEntry(eldest: Map.Entry<Instant, Statistics>): Boolean {
+                return this.size > 240
+            }
+        })
+    private val statistics: AtomicReference<Statistics> = AtomicReference(Statistics())
+    private val isHandled: AtomicBoolean = AtomicBoolean(false)
+    private var webUi: Http4kServer? = null
+    private val cache: DiskLruCache
+
+    init {
+        try {
+            cache = DiskLruCache.open(
+                File("cache"), 1, 1,
+                clientSettings.maxCacheSizeInMebibytes * 1024 * 1024 /* MiB to bytes */
+            )
+            cache.get("statistics")?.use {
+                statistics.set(JACKSON.readValue<Statistics>(it.getInputStream(0)))
+            }
+        } catch (e: HeaderMismatchException) {
+            LOGGER.warn("Cache version may be outdated - remove if necessary")
+            dieWithError(e)
+        } catch (e: IOException) {
+            LOGGER.warn("Cache version may be corrupt - remove if necessary")
+            dieWithError(e)
+        }
+    }
+
+    fun runLoop() {
+        loginAndStartServer()
+        statsMap[Instant.now()] = statistics.get()
+
+        if (clientSettings.webSettings != null) {
+            webUi = getUiServer(clientSettings.webSettings, statistics, statsMap)
+            webUi!!.start()
+        }
+        if (LOGGER.isInfoEnabled) {
+            LOGGER.info("Mangadex@Home Client initialized. Starting normal operation.")
+        }
+
+        executorService.scheduleAtFixedRate({
+            try {
+                statistics.updateAndGet {
+                    it.copy(bytesOnDisk = cache.size())
+                }
+                statsMap[Instant.now()] = statistics.get()
+                val editor = cache.edit("statistics")
+                if (editor != null) {
+                    JACKSON.writeValue(editor.newOutputStream(0), statistics.get())
+                    editor.commit()
+                }
+            } catch (e: Exception) {
+                LOGGER.warn("Statistics update failed", e)
+            }
+        }, 15, 15, TimeUnit.SECONDS)
+
+        var lastBytesSent = statistics.get().bytesSent
+        executorService.scheduleAtFixedRate({
+            try {
+                lastBytesSent = statistics.get().bytesSent
+
+                val state = this.state
+                if (state is GracefulShutdown) {
+                    if (LOGGER.isInfoEnabled) {
+                        LOGGER.info("Aborting graceful shutdown started due to hourly bandwidth limit")
+                    }
+                    this.state = state.lastRunning
+                }
+                if (state is Uninitialized) {
+                    if (LOGGER.isInfoEnabled) {
+                        LOGGER.info("Restarting server stopped due to hourly bandwidth limit")
+                    }
+                    loginAndStartServer()
+                }
+            } catch (e: Exception) {
+                LOGGER.warn("Hourly bandwidth check failed", e)
+            }
+        }, 1, 1, TimeUnit.HOURS)
+
+        val timesToWait = clientSettings.gracefulShutdownWaitSeconds / 15
+        executorService.scheduleAtFixedRate({
+            try {
+                val state = this.state
+                if (state is GracefulShutdown) {
+                    when {
+                        state.counts == 0 -> {
+                            if (LOGGER.isInfoEnabled) {
+                                LOGGER.info("Starting graceful shutdown")
+                            }
+                            logout()
+                            isHandled.set(false)
+                            this.state = state.copy(counts = state.counts + 1)
+                        }
+                        state.counts == timesToWait || !isHandled.get() -> {
+                            if (LOGGER.isInfoEnabled) {
+                                if (!isHandled.get()) {
+                                    LOGGER.info("No requests received, shutting down")
+                                } else {
+                                    LOGGER.info("Max tries attempted (${state.counts} out of $timesToWait), shutting down")
+                                }
+                            }
+
+                            stopServer(state.nextState)
+                            state.action()
+                        }
+                        else -> {
+                            if (LOGGER.isInfoEnabled) {
+                                LOGGER.info(
+                                    "Waiting another 15 seconds for graceful shutdown (${state.counts} out of $timesToWait)"
+                                )
+                            }
+                            isHandled.set(false)
+                            this.state = state.copy(counts = state.counts + 1)
+                        }
+                    }
+                }
+            } catch (e: Exception) {
+                LOGGER.warn("Main loop failed", e)
+            }
+        }, 15, 15, TimeUnit.SECONDS)
+
+        executorService.scheduleWithFixedDelay({
+            try {
+                val state = this.state
+                if (state is Running) {
+                    val currentBytesSent = statistics.get().bytesSent - lastBytesSent
+                    if (clientSettings.maxMebibytesPerHour != 0L && clientSettings.maxMebibytesPerHour * 1024 * 1024 /* MiB to bytes */ < currentBytesSent) {
+                        if (LOGGER.isInfoEnabled) {
+                            LOGGER.info("Shutting down server as hourly bandwidth limit reached")
+                        }
+                        this.state = GracefulShutdown(lastRunning = state)
+                    }
+
+                    pingControl()
+                }
+            } catch (e: Exception) {
+                LOGGER.warn("Main loop failed", e)
+            }
+        }, 45, 45, TimeUnit.SECONDS)
+    }
+
+    private fun pingControl() {
+        val state = this.state as Running
+
+        val newSettings = serverHandler.pingControl(state.settings)
+        if (LOGGER.isInfoEnabled) {
+            LOGGER.info("Server settings received: {}", newSettings)
+        }
+        if (newSettings != null) {
+            if (newSettings.latestBuild > Constants.CLIENT_BUILD) {
+                if (LOGGER.isWarnEnabled) {
+                    LOGGER.warn(
+                        "Outdated build detected! Latest: {}, Current: {}", newSettings.latestBuild,
+                        Constants.CLIENT_BUILD
+                    )
+                }
+            }
+            if (newSettings.tls != null || newSettings.imageServer != state.settings.imageServer) {
+                // certificates or upstream url must have changed, restart webserver
+                if (LOGGER.isInfoEnabled) {
+                    LOGGER.info("Doing internal restart of HTTP server to refresh certs/upstream URL")
+                }
+                this.state = GracefulShutdown(lastRunning = state) {
+                    loginAndStartServer()
+                }
+            }
+        }
+    }
+
+    private fun loginAndStartServer() {
+        this.state as Uninitialized
+
+        val serverSettings = serverHandler.loginToControl()
+            ?: dieWithError("Failed to get a login response from server - check API secret for validity")
+        val server = getServer(cache, serverSettings, clientSettings, statistics, isHandled).start()
+
+        if (serverSettings.latestBuild > Constants.CLIENT_BUILD) {
+            if (LOGGER.isWarnEnabled) {
+                LOGGER.warn(
+                    "Outdated build detected! Latest: {}, Current: {}", serverSettings.latestBuild,
+                    Constants.CLIENT_BUILD
+                )
+            }
+        }
+
+        state = Running(server, serverSettings)
+        if (LOGGER.isInfoEnabled) {
+            LOGGER.info("Internal HTTP server was successfully started")
+        }
+    }
+
+    private fun logout() {
+        serverHandler.logoutFromControl()
+    }
+
+    private fun stopServer(nextState: State = Uninitialized) {
+        val state = this.state.let {
+            when (it) {
+                is Running ->
+                    it
+                is GracefulShutdown ->
+                    it.lastRunning
+                else ->
+                    throw AssertionError()
+            }
+        }
+
+        if (LOGGER.isInfoEnabled) {
+            LOGGER.info("Shutting down HTTP server")
+        }
+        state.server.stop()
+        if (LOGGER.isInfoEnabled) {
+            LOGGER.info("Internal HTTP server has shut down")
+        }
+        this.state = nextState
+    }
+
+    fun shutdown() {
+        LOGGER.info("Mangadex@Home Client stopping")
+
+        val latch = CountDownLatch(1)
+        executorService.schedule({
+            val state = this.state
+            if (state is Running) {
+                this.state = GracefulShutdown(state, nextState = Shutdown) {
+                    latch.countDown()
+                }
+                latch.await()
+            } else if (state is GracefulShutdown) {
+                this.state = state.copy(nextState = Shutdown) {
+                    latch.countDown()
+                }
+            } else if (state is Uninitialized || state is Shutdown) {
+                this.state = Shutdown
+                latch.countDown()
+            }
+        }, 0, TimeUnit.SECONDS)
+        latch.await()
+
+        webUi?.close()
+        try {
+            cache.close()
+        } catch (e: IOException) {
+            LOGGER.error("Cache failed to close", e)
+        }
+
+        executorService.shutdown()
+        LOGGER.info("Mangadex@Home Client stopped")
+
+        (LoggerFactory.getILoggerFactory() as LoggerContext).stop()
+    }
+
+    companion object {
+        private val LOGGER = LoggerFactory.getLogger(MangaDexClient::class.java)
+    }
+}

src/main/kotlin/mdnet/base/server/ImageServer.kt

@@ -31,8 +31,7 @@ import javax.crypto.CipherInputStream
 import javax.crypto.CipherOutputStream
 import javax.crypto.spec.SecretKeySpec
 
-private const val THREADS_TO_ALLOCATE = 262144 // 2**18 // Honestly, no reason to not just let 'er rip. Inactive connections will expire on their own :D
+private const val THREADS_TO_ALLOCATE = 262144 // 2**18
-private val LOGGER = LoggerFactory.getLogger(ImageServer::class.java)
 
 class ImageServer(private val cache: DiskLruCache, private val statistics: AtomicReference<Statistics>, private val upstreamUrl: String, private val database: Database, private val handled: AtomicBoolean) {
     init {
@@ -252,6 +251,10 @@ class ImageServer(private val cache: DiskLruCache, private val statistics: Atomi
                 }
             }
             .header("X-Cache", if (cached) "HIT" else "MISS")
+
+    companion object {
+        private val LOGGER = LoggerFactory.getLogger(ImageServer::class.java)
+    }
 }
 
 private fun getRc4(key: ByteArray): Cipher {

src/main/kotlin/mdnet/base/settings/ClientSettings.kt

@@ -13,6 +13,7 @@ data class ClientSettings(
     val clientPort: Int = 443,
     @field:Secret val clientSecret: String = "PASTE-YOUR-SECRET-HERE",
     val threads: Int = 4,
+    val gracefulShutdownWaitSeconds: Int = 60,
     val webSettings: WebSettings? = null
 )