ZOOKEEPER-4515: ZK Cli quit command always logs error

1. For connection closing state scenario, changed the log level to debug
2. When JVM exiting with code 0, then logging info instead of error

Author: Mohammad Arshad <arshad@apache.org>

Reviewers: tison <wander4096@gmail.com>, Enrico Olivelli <eolivelli@apache.org>

Closes #1856 from arshadmohammad/ZOOKEEPER-4515-cli and squashes the following commits:

e7e248bd5 [Mohammad Arshad] Logging error only when exit code is non zero
31e124a2a [Mohammad Arshad] ZOOKEEPER-4515: ZK Cli quit command always logs error 1. For connection closing state scenario, changed the log level to debug 2. When JVM exiting with code 0, then logging info instead of error

(cherry picked from commit e5f84f46283d70b618ce00f2df51f4bfe31d9a44)
Signed-off-by: Mohammad Arshad <arshad@apache.org>

2 files changed, 18 insertions, 6 deletions

diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/ClientCnxn.java b/zookeeper-server/src/main/java/org/apache/zookeeper/ClientCnxn.java
index ed955540e..c3f0079c6 100644
--- a/zookeeper-server/src/main/java/org/apache/zookeeper/ClientCnxn.java
+++ b/zookeeper-server/src/main/java/org/apache/zookeeper/ClientCnxn.java
@@ -1294,10 +1294,11 @@ public class ClientCnxn {
                 } catch (Throwable e) {
                     if (closing) {
                         // closing so this is expected
-                        LOG.warn(
-                            "An exception was thrown while closing send thread for session 0x{}.",
-                            Long.toHexString(getSessionId()),
-                            e);
+                        if (LOG.isDebugEnabled()) {
+                            LOG.debug(
+                                "An exception was thrown while closing send thread for session 0x{}.",
+                                Long.toHexString(getSessionId()), e);
+                        }
                         break;
                     } else {
                         LOG.warn(
diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/util/ServiceUtils.java b/zookeeper-server/src/main/java/org/apache/zookeeper/util/ServiceUtils.java
index 68a25ebb4..99cc685b3 100644
--- a/zookeeper-server/src/main/java/org/apache/zookeeper/util/ServiceUtils.java
+++ b/zookeeper-server/src/main/java/org/apache/zookeeper/util/ServiceUtils.java
@@ -39,7 +39,14 @@ public abstract class ServiceUtils {
      */
     @SuppressFBWarnings("DM_EXIT")
     public static final Consumer<Integer> SYSTEM_EXIT = (code) -> {
-        LOG.error("Exiting JVM with code {}", code);
+        String msg = "Exiting JVM with code {}";
+        if (code == 0) {
+            // JVM exits normally
+            LOG.info(msg, code);
+        } else {
+            // JVM exits with error
+            LOG.error(msg, code);
+        }
         System.exit(code);
     };
 
@@ -47,8 +54,12 @@ public abstract class ServiceUtils {
      * No-op strategy, useful for tests.
      */
     public static final Consumer<Integer> LOG_ONLY = (code) -> {
-        LOG.error("Fatal error, JVM should exit with code {}. "
+        if (code != 0) {
+            LOG.error("Fatal error, JVM should exit with code {}. "
                 + "Actually System.exit is disabled", code);
+        } else {
+            LOG.info("JVM should exit with code {}. Actually System.exit is disabled", code);
+        }
     };
 
     private static Consumer<Integer> systemExitProcedure = SYSTEM_EXIT;