Added session max count

Author: Alathreon

JShellAPI/src/main/java/org/togetherjava/jshellapi/Config.java

@@ -7,12 +7,14 @@ public record Config(
         long regularSessionTimeoutSeconds,
         long oneTimeSessionTimeoutSeconds,
         long evalTimeoutSeconds,
+        long maxAliveSessions,
         int schedulerThreadCount,
         long schedulerSessionKillScanRate) {
     public Config {
         if(regularSessionTimeoutSeconds <= 0) throw new RuntimeException("Invalid value " + regularSessionTimeoutSeconds);
         if(oneTimeSessionTimeoutSeconds <= 0) throw new RuntimeException("Invalid value " + oneTimeSessionTimeoutSeconds);
         if(evalTimeoutSeconds <= 0) throw new RuntimeException("Invalid value " + evalTimeoutSeconds);
+        if(maxAliveSessions <= 0) throw new RuntimeException("Invalid value " + maxAliveSessions);
         if(schedulerThreadCount <= 0) throw new RuntimeException("Invalid value " + schedulerThreadCount);
         if(schedulerSessionKillScanRate <= 0) throw new RuntimeException("Invalid value " + schedulerSessionKillScanRate);
     }

JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellSessionService.java

@@ -63,6 +63,9 @@ private synchronized JShellService createSession(String id, long sessionTimeout,
         if(hasSession(id)) {    //Just in case race condition happens just before createSession
             return jshellSessions.get(id);
         }
+        if(jshellSessions.size() >= config.maxAliveSessions()) {
+            throw new DockerException("Too many sessions.");
+        }
         JShellService service = new JShellService(this, id, sessionTimeout, renewable, evalTimeout);
         jshellSessions.put(id, service);
         return service;

JShellAPI/src/main/resources/application.properties

@@ -4,6 +4,7 @@ jshellapi.regularSessionTimeoutSeconds=1800
 # 10 * 60 = 600
 jshellapi.oneTimeSessionTimeoutSeconds=600
 jshellapi.evalTimeoutSeconds=15
+jshellapi.maxAliveSessions=10
 
 # Internal config
 jshellapi.schedulerThreadCount=1