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Fix busy-waiting loops for Server Session / App.java #3016

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Fix busy-waiting loops for Server Session / App.java #3016

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48 changes: 24 additions & 24 deletions server-session/src/main/java/com/iluwatar/sessionserver/App.java
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,9 @@
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import lombok.extern.slf4j.Slf4j;

/**
Expand Down Expand Up @@ -75,37 +78,34 @@ public static void main(String[] args) throws IOException {
server.start();

// Start background task to check for expired sessions
sessionExpirationTask();
startSessionExpirationTask();

LOGGER.info("Server started. Listening on port 8080...");
}

private static void sessionExpirationTask() {
new Thread(() -> {
while (true) {
try {
LOGGER.info("Session expiration checker started...");
Thread.sleep(SESSION_EXPIRATION_TIME); // Sleep for expiration time
Instant currentTime = Instant.now();
synchronized (sessions) {
synchronized (sessionCreationTimes) {
Iterator<Map.Entry<String, Instant>> iterator =
sessionCreationTimes.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry<String, Instant> entry = iterator.next();
if (entry.getValue().plusMillis(SESSION_EXPIRATION_TIME).isBefore(currentTime)) {
sessions.remove(entry.getKey());
iterator.remove();
}
private static void startSessionExpirationTask() {
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
Runnable sessionExpirationChecker = () -> {
try {
LOGGER.info("Session expiration checker started...");
Instant currentTime = Instant.now();
synchronized (sessions) {
synchronized (sessionCreationTimes) {
Comment on lines +92 to +93
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Could we use ConcurrentHashMap for sessions and sessionCreationTimes allowing us to remove the need for synchronization blocks?

Iterator<Map.Entry<String, Instant>> iterator = sessionCreationTimes.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry<String, Instant> entry = iterator.next();
if (entry.getValue().plusMillis(SESSION_EXPIRATION_TIME).isBefore(currentTime)) {
sessions.remove(entry.getKey());
iterator.remove();
Comment on lines +97 to +99
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Add debug logging for session removal

}
}
}
LOGGER.info("Session expiration checker finished!");
} catch (InterruptedException e) {
LOGGER.error("An error occurred: ", e);
Thread.currentThread().interrupt();
}
LOGGER.info("Session expiration checker finished!");
} catch (Exception e) {
LOGGER.error("An error occurred: ", e);
}
}).start();
};
scheduler.scheduleAtFixedRate(sessionExpirationChecker, 0, SESSION_EXPIRATION_TIME, TimeUnit.MILLISECONDS);
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We should also shut down the scheduler when the program exits. Something like this:

Runtime.getRuntime().addShutdownHook(new Thread(() -> {
        scheduler.shutdown();
        try {
            if (!scheduler.awaitTermination(60, TimeUnit.SECONDS)) {
                scheduler.shutdownNow();
            }
        } catch (InterruptedException e) {
            scheduler.shutdownNow();
        }
    }));

}
}
}
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