fix: max_in_use_session metric time

Author: surbhigarg92

google-cloud-spanner/src/main/java/com/google/cloud/spanner/SessionPool.java

@@ -2060,7 +2060,15 @@ void maintainPool() {
         }
         this.prevNumSessionsAcquired = SessionPool.this.numSessionsAcquired;
       }
+
+      // Reset the start time for recording the maximum number of sessions
+      // in the pool.
       Instant currTime = clock.instant();
+      if (currTime.isAfter(SessionPool.this.lastResetTime.plus(Duration.ofMinutes(10)))) {
+        SessionPool.this.maxSessionsInUse = SessionPool.this.numSessionsInUse;
+        SessionPool.this.lastResetTime = currTime;
+      }
+
       removeIdleSessions(currTime);
       // Now go over all the remaining sessions and see if they need to be kept alive explicitly.
       keepAliveSessions(currTime);
@@ -2309,6 +2317,9 @@ enum Position {
   @GuardedBy("lock")
   private int maxSessionsInUse = 0;
 
+  @GuardedBy("lock")
+  private Instant lastResetTime = Clock.INSTANCE.instant();
+
   @GuardedBy("lock")
   private long numSessionsAcquired = 0;