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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package net.morimekta.tiny.server;
import net.morimekta.terminal.args.ArgException;
import net.morimekta.terminal.args.ArgHelp;
import net.morimekta.terminal.args.ArgNameFormat;
import net.morimekta.terminal.args.ArgParser;
import net.morimekta.terminal.args.annotations.ArgNaming;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;
import static java.nio.charset.StandardCharsets.UTF_8;
import static net.morimekta.terminal.args.Flag.flag;
import static net.morimekta.terminal.args.Option.optionLong;
import static net.morimekta.terminal.args.ValueParser.ui32;
import static net.morimekta.tiny.logback.LoggingUtil.flushConsoleLogging;
import static net.morimekta.tiny.logback.LoggingUtil.initLogForwarding;
/**
* Tiny microservice application base class. Extend this class to set up the
* server itself, and use the static {@link #start(TinyApplication, String...)}
* method to actually start it.
*/
public abstract class TinyApplication {
private static final Logger LOGGER = LoggerFactory.getLogger(TinyApplication.class);
private final String applicationName;
private final AtomicReference context;
protected TinyApplication(String applicationName) {
setUpUncaughtExceptionHandler();
this.applicationName = Objects.requireNonNull(applicationName, "applicationName == null");
this.context = new AtomicReference<>();
}
/**
* Override this method if you want to have a special uncaught exception handler,
* or if you need to keep some other default uncaught exception handler.
*/
protected void setUpUncaughtExceptionHandler() {
// Ensure there is an uncaught exception handler. But do not replace any
// the user may have already set.
Thread.setDefaultUncaughtExceptionHandler((thread, throwable) -> LOGGER.error(
"Uncaught exception in thread {}: {}",
thread.getName(),
throwable.getMessage(),
throwable));
}
/**
* This method is called during the initialization phase of setting up the
* tiny server. This is done before the HTTP server is started.l
*
* @param argBuilder The argument parser builder to parse command line arguments.
* @param contextBuilder The application context builder.
*/
protected abstract void initialize(ArgParser.Builder argBuilder, TinyApplicationContext.Builder contextBuilder);
/**
* This method is called after the HTTP server is started, but before the
* service is considered "ready".
*
* @param context The application context.
* @throws Exception If starting the app failed.
*/
protected abstract void onStart(TinyApplicationContext context) throws Exception;
/**
* This method is called immediately when the service should start shutting
* down. The service is already considered "not ready", but the HTTP server
* will stay alive as long as this method does not return.
*
* @param context The application context of the service.
* @throws Exception If stopping the service failed.
*/
protected void beforeStop(TinyApplicationContext context) throws Exception {
// not implemented.
}
/**
* This method is called after the HTTP service has been stopped, but before
* the application exits.
*
* @param context The application context of the service.
* @throws Exception If stopping the service failed.
*/
protected void afterStop(TinyApplicationContext context) throws Exception {
// not implemented.
}
/**
* @return The application name.
*/
public final String getApplicationName() {
return applicationName;
}
/**
* @return The application version.
*/
public String getApplicationVersion() {
return "latest";
}
/**
* @return The application description.
*/
public String getApplicationDescription() {
return "A Tiny-Server Application";
}
/**
* Stop the server and trigger the internal stop mechanisms.
*/
public final void stop() {
LOGGER.info("Stopping server.");
var context = this.context.getAndSet(null);
if (context == null) {
return;
}
// Triggers readiness to start failing.
if (context.setStopping()) {
try {
beforeStop(context);
} catch (Exception e) {
LOGGER.warn("Exception in beforeStop(): {}", e.getMessage(), e);
} finally {
context.getStoppingSemaphore().release(100);
}
} else {
try {
context.getStoppingSemaphore().acquire();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
context.stopServer();
try {
afterStop(context);
} catch (Exception e) {
LOGGER.warn("Exception in afterStop(): {}", e.getMessage(), e);
}
flushConsoleLogging();
}
public final void drain() {
LOGGER.info("Draining server.");
var context = this.context.get();
if (context == null) {
return;
}
// Triggers readiness to start failing.
if (context.setStopping()) {
try {
beforeStop(context);
} catch (Exception e) {
LOGGER.warn("Exception in beforeStop(): {}", e.getMessage(), e);
} finally {
context.getStoppingSemaphore().release(100);
}
}
}
/**
* Start the server. If the server start failed for any reason, will forcefully exit
* the program.
*
*
{@code
* public class MyServer extends TinyServer {
* // implement...
*
* public static void main(String[] args) {
* TinyApplication.start(new MyServer(), args);
* }
* }
* }
*
* @param app The tiny server application to start.
* @param args Arguments form command line.
*/
public static void start(TinyApplication app, String... args) {
try {
startUnsafe(app, args);
} catch (Exception e) {
// Untestable, as it will abort the test ...
System.exit(1);
}
}
/**
* Same as the {@link #start(TinyApplication, String...)} method, but will throw
* the exception. Visible for testing.
*
* @param app The tiny server application to start.
* @param args Arguments form command line.
* @throws Exception If startup failed for any reason.
*/
public static void startUnsafe(TinyApplication app, String... args) throws Exception {
initLogForwarding();
ArgParser parser = null;
ArgNaming argNaming = app.getClass().getAnnotation(ArgNaming.class);
ArgNameFormat defaultFormat = argNaming != null ? argNaming.value() : ArgNameFormat.SNAKE;
try {
var argParserBuilder = ArgParser.argParser(
app.getApplicationName(),
app.getApplicationVersion(),
app.getApplicationDescription());
argParserBuilder.generateArgsNameFormat(defaultFormat);
var help = new AtomicBoolean();
argParserBuilder.add(flag("--help", "?h", "Show help", help::set));
var contextBuilder = new TinyApplicationContext.Builder(app);
argParserBuilder.add(optionLong("--" + defaultFormat.format("admin_host"),
"Set IP address the admin server should listen to.",
contextBuilder::setAdminHost)
.defaultValue("0.0.0.0").metaVar("IP"));
argParserBuilder.add(optionLong("--" + defaultFormat.format("admin_port"),
"Set HTTP port the admin server should listen to.",
ui32(contextBuilder::setAdminPort))
.defaultValue("0").metaVar("PORT"));
argParserBuilder.add(optionLong("--" + defaultFormat.format("admin_threads"),
"Number of threads to use for admin server.",
ui32(contextBuilder::setAdminServerThreads))
.defaultValue(10).metaVar("THR"));
app.initialize(argParserBuilder, contextBuilder);
parser = argParserBuilder.parse(args);
if (help.get()) {
ArgHelp.argHelp(parser).printHelp(System.out);
return;
}
parser.validate();
app.startInternal(contextBuilder.build());
} catch (ArgException e) {
if (e.getParser() != null) {
LOGGER.error("{}\n{}", e.getMessage(), getHelp(e.getParser()), e);
} else if (parser != null) {
LOGGER.error("{}\n{}", e.getMessage(), getHelp(parser), e);
}
flushConsoleLogging();
throw e;
} catch (RuntimeException e) {
if (parser != null) {
// Exception validating arguments.
LOGGER.error("{}\n{}", e.getMessage(), getHelp(parser), e);
} else {
LOGGER.error("{}", e.getMessage(), e);
}
flushConsoleLogging();
throw e;
} catch (IOException e) {
LOGGER.error("IO Exception: {}", e.getMessage(), e);
flushConsoleLogging();
throw e;
} catch (Exception e) {
LOGGER.error("Exception: {}", e.getMessage(), e);
flushConsoleLogging();
throw e;
}
}
// ---- PRIVATE ----
private void startInternal(TinyApplicationContext context) throws Exception {
try {
onStart(context);
} catch (Exception e) {
LOGGER.error("Exception in onStarted(): {}", e.getMessage(), e);
context.stopServer();
throw e;
}
this.context.set(context);
Thread stopServerThread = new Thread(this::stop);
stopServerThread.setDaemon(false);
stopServerThread.setName("TinyServerShutdownHook");
Runtime.getRuntime().addShutdownHook(stopServerThread);
context.setReady();
}
private static String getHelp(ArgParser parser) {
try (var out = new ByteArrayOutputStream();
var writer = new PrintStream(out, true, UTF_8)) {
ArgHelp.argHelp(parser)
.usageWidth(80)
.printPreamble(writer);
return out.toString(UTF_8);
} catch (IOException e) {
return ""; // should be impossible.
}
}
}
