diff --git a/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/DockerService.java b/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/DockerService.java
index c5abcbb..a2ffb69 100644
--- a/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/DockerService.java
+++ b/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/DockerService.java
@@ -131,7 +131,13 @@ public void onNext(Frame object) {
     }
 
     public void killContainerByName(String name) {
-        for (Container container : client.listContainersCmd().withNameFilter(Set.of(name)).exec()) {
+        LOGGER.debug("Fetching container to kill {}.", name);
+        List<Container> containers = client.listContainersCmd().withNameFilter(Set.of(name)).exec();
+        LOGGER.debug("Number of containers to kill: {} for name {}.", containers.size(), name);
+        if (containers.size() != 1) {
+            LOGGER.error("There is more than 1 container for name {}.", name);
+        }
+        for (Container container : containers) {
             client.killContainerCmd(container.getId()).exec();
         }
     }
diff --git a/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellService.java b/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellService.java
index 7d40afa..9ecc0c8 100644
--- a/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellService.java
+++ b/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellService.java
@@ -206,6 +206,7 @@ public String id() {
 
     @Override
     public void close() {
+        LOGGER.debug("Close called for session {}.", id);
         try {
             dockerService.killContainerByName(containerName());
             try {
diff --git a/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellSessionService.java b/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellSessionService.java
index c6411ef..496dd0e 100644
--- a/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellSessionService.java
+++ b/JShellAPI/src/main/java/org/togetherjava/jshellapi/service/JShellSessionService.java
@@ -28,6 +28,7 @@ public class JShellSessionService {
     private void initScheduler() {
         scheduler = Executors.newSingleThreadScheduledExecutor();
         scheduler.scheduleAtFixedRate(() -> {
+            LOGGER.info("Scheduler heartbeat: started.");
             jshellSessions.keySet()
                 .stream()
                 .filter(id -> jshellSessions.get(id).isClosed())
@@ -36,6 +37,7 @@ private void initScheduler() {
                 .stream()
                 .filter(id -> jshellSessions.get(id).shouldDie())
                 .toList();
+            LOGGER.info("Scheduler heartbeat: sessions ready to die: {}", toDie);
             for (String id : toDie) {
                 try {
                     deleteSession(id);
@@ -49,10 +51,13 @@ private void initScheduler() {
 
     void notifyDeath(String id) {
         JShellService shellService = jshellSessions.remove(id);
-        if (shellService == null)
+        if (shellService == null) {
+            LOGGER.debug("Notify death on already removed session {}.", id);
             return;
+        }
         if (!shellService.isClosed()) {
             LOGGER.error("JShell Service isn't dead when it should for id {}.", id);
+            return;
         }
         LOGGER.info("Session {} died.", id);
     }
@@ -82,8 +87,11 @@ public JShellService oneTimeSession(@Nullable StartupScriptId startupScriptId)
 
     public void deleteSession(String id) throws DockerException {
         JShellService service = jshellSessions.remove(id);
-        service.stop();
-        scheduler.schedule(service::close, 500, TimeUnit.MILLISECONDS);
+        try {
+            service.stop();
+        } finally {
+            scheduler.schedule(service::close, 500, TimeUnit.MILLISECONDS);
+        }
     }
 
     private synchronized JShellService createSession(SessionInfo sessionInfo)
diff --git a/README.md b/README.md
index b2029e4..d5299a6 100644
--- a/README.md
+++ b/README.md
@@ -29,10 +29,21 @@ JShellAPI is a REST API, and whenever some code is received, it will create a se
 # How to build JShellAPI in and run it in Docker
 - Launch Docker
 - Run `jibDockerBuild` to create the image
+- Create a folder outside the project
+- `cd` to this folder
+- Copy `docker-compose.yaml` inside it
 - Optionally, create `config/application.yaml` where you can put custom config (see the actual [application.yaml](JShellAPI/src/main/resources/application.yaml))
-- If you don't create it, delete the `command: ["--spring.config.location=file:///home/backend/config/application.yaml"]` line in the `docker-compose.yaml`
+* * If you don't create it, delete the `command: ["--spring.config.location=file:///home/backend/config/application.yaml"]` line in the `docker-compose.yaml`
 - Run `docker compose build` or `docker-compose build` in the folder, depending on your version of Docker.
 - Run `docker compose start` or `docker-compose start` in the folder, depending on your version of Docker.
+- Note that some folders or files may be created automatically inside this folder
+- File tree representation:
+```
+-folder outside the project
+    -docker-compose.yaml
+    -config (optionnal)
+        -application.yaml
+```
 
 ## How to use JShellApi ?
 See [JShellAPI README](JShellAPI/README.MD)