diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/server/Request.java b/zookeeper-server/src/main/java/org/apache/zookeeper/server/Request.java
index 27fa4e2dff7..8a8bb833a68 100644
--- a/zookeeper-server/src/main/java/org/apache/zookeeper/server/Request.java
+++ b/zookeeper-server/src/main/java/org/apache/zookeeper/server/Request.java
@@ -168,18 +168,26 @@ public boolean isThrottlable() {
                 && this.type != OpCode.createSession;
     }
 
+    private long approximateSize = 0;
+
     public byte[] getSerializeData() {
         if (this.hdr == null) {
             return null;
         }
         try {
-            return Util.marshallTxnEntry(this.hdr, this.txn, this.txnDigest);
+            byte[] bytes = Util.marshallTxnEntry(this.hdr, this.txn, this.txnDigest);
+            approximateSize = bytes.length;
+            return bytes;
         } catch (IOException e) {
             LOG.error("This really should be impossible.", e);
             return new byte[32];
         }
     }
 
+    public long getApproximateSize() {
+        return approximateSize;
+    }
+
     /**
      * If this is a create or close request for a local-only session.
      */
diff --git a/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZKDatabase.java b/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZKDatabase.java
index d98c97f2c07..1b61620e8bd 100644
--- a/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZKDatabase.java
+++ b/zookeeper-server/src/main/java/org/apache/zookeeper/server/ZKDatabase.java
@@ -33,6 +33,7 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
@@ -92,9 +93,16 @@ public class ZKDatabase {
     public static final String COMMIT_LOG_COUNT = "zookeeper.commitLogCount";
     public static final int DEFAULT_COMMIT_LOG_COUNT = 500;
     public int commitLogCount;
+    public static final String COMMIT_LOG_SIZE = "zookeeper.commitLogSize";
+    public static final double DEFAULT_COMMIT_LOG_SIZE = Runtime.getRuntime().maxMemory() * 0.2;
+    public double commitLogSize;
     protected Queue<Proposal> committedLog = new ArrayDeque<>();
     protected ReentrantReadWriteLock logLock = new ReentrantReadWriteLock();
     private volatile boolean initialized = false;
+    /**
+     * committedLog bytes size.
+     */
+    private AtomicLong totalCommittLogSize = new AtomicLong(0);
 
     /**
      * Number of txn since last snapshot;
@@ -137,12 +145,11 @@ public ZKDatabase(FileTxnSnapLog snapLog) {
             commitLogCount = Integer.parseInt(
                     System.getProperty(COMMIT_LOG_COUNT,
                             Integer.toString(DEFAULT_COMMIT_LOG_COUNT)));
-            if (commitLogCount < DEFAULT_COMMIT_LOG_COUNT) {
+            if (commitLogCount <= 0) {
                 commitLogCount = DEFAULT_COMMIT_LOG_COUNT;
                 LOG.warn(
-                    "The configured commitLogCount {} is less than the recommended {}, going to use the recommended one",
-                    COMMIT_LOG_COUNT,
-                    DEFAULT_COMMIT_LOG_COUNT);
+                    "The configured commitLogCount {} is less than zero, going to use the recommended value {}",
+                    COMMIT_LOG_COUNT, DEFAULT_COMMIT_LOG_COUNT);
             }
         } catch (NumberFormatException e) {
             LOG.error(
@@ -151,7 +158,24 @@ public ZKDatabase(FileTxnSnapLog snapLog) {
                 DEFAULT_COMMIT_LOG_COUNT);
             commitLogCount = DEFAULT_COMMIT_LOG_COUNT;
         }
-        LOG.info("{}={}", COMMIT_LOG_COUNT, commitLogCount);
+        try {
+            commitLogSize = Double.parseDouble(
+                    System.getProperty(COMMIT_LOG_SIZE,
+                            Double.toString(DEFAULT_COMMIT_LOG_SIZE)));
+            if (commitLogSize <= 0) {
+                commitLogSize = DEFAULT_COMMIT_LOG_SIZE;
+                LOG.warn(
+                        "The configured commitLogSize {} is less than the zero, going to use the recommended value {}",
+                        COMMIT_LOG_SIZE, DEFAULT_COMMIT_LOG_SIZE);
+            }
+        } catch (NumberFormatException e) {
+            LOG.error(
+                    "Error parsing {} - use default value {}",
+                    COMMIT_LOG_SIZE,
+                    DEFAULT_COMMIT_LOG_SIZE);
+            commitLogSize = DEFAULT_COMMIT_LOG_SIZE;
+        }
+        LOG.info("{}={}, {}={}", COMMIT_LOG_COUNT, commitLogCount, COMMIT_LOG_SIZE, commitLogSize);
     }
 
     /**
@@ -182,6 +206,7 @@ public void clear() {
         try {
             lock.lock();
             committedLog.clear();
+            totalCommittLogSize.set(0);
         } finally {
             lock.unlock();
         }
@@ -320,17 +345,24 @@ public void addCommittedProposal(Request request) {
         WriteLock wl = logLock.writeLock();
         try {
             wl.lock();
-            if (committedLog.size() > commitLogCount) {
-                committedLog.remove();
-                minCommittedLog = committedLog.peek().getZxid();
-            }
             if (committedLog.isEmpty()) {
                 minCommittedLog = request.zxid;
-                maxCommittedLog = request.zxid;
             }
             PureRequestProposal p = new PureRequestProposal(request);
             committedLog.add(p);
             maxCommittedLog = p.getZxid();
+            totalCommittLogSize.addAndGet(request.getApproximateSize());
+            while (committedLog.size() > 0
+                    && (committedLog.size() > commitLogCount || totalCommittLogSize.get() > commitLogSize)) {
+                committedLog.remove();
+                Proposal peek = committedLog.peek();
+                if (peek == null) {
+                    minCommittedLog = 0;
+                    maxCommittedLog = 0;
+                } else {
+                    minCommittedLog = p.getZxid();
+                }
+            }
         } finally {
             wl.unlock();
         }