Move lz4 decompress to backend executor

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/CachedSchemaTransaction.java

@@ -107,7 +107,9 @@ private void listenChanges() {
             if ("invalid".equals(args[0])) {
                 HugeType type = (HugeType) args[1];
                 Id id = (Id) args[2];
-                this.arrayCaches.remove(type, id);
+                if (id.number() && id.asLong() > 0) {
+                    this.arrayCaches.remove(type, id);
+                }
 
                 id = generateId(type, id);
                 Object value = this.idCache.get(id);

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/store/raft/RaftSharedContext.java

@@ -267,9 +267,6 @@ public void notifyCache(HugeType type, Id id) {
             eventHub = this.params.graphEventHub();
         } else if (type.isSchema()) {
             eventHub = this.params.schemaEventHub();
-            if (id.number() && id.asLong() < 0) {
-                return;
-            }
         } else {
             return;
         }

hugegraph-core/src/main/java/com/baidu/hugegraph/config/CoreOptions.java

@@ -252,15 +252,23 @@ public static synchronized CoreOptions instance() {
     public static final ConfigOption<Integer> RAFT_RPC_BUF_LOW_WATER_MARK =
             new ConfigOption<>(
                     "raft.rpc_buf_low_water_mark",
-                    "",
+                    "The ChannelOutboundBuffer's low water mark of netty, " +
+                    "when buffer size less than this size, the method " +
+                    "ChannelOutboundBuffer.isWritable() will return true, " +
+                    "it means that low downstream pressure or good network",
                     positiveInt(),
                     10 * 1024 * 1024
             );
 
     public static final ConfigOption<Integer> RAFT_RPC_BUF_HIGH_WATER_MARK =
             new ConfigOption<>(
                     "raft.rpc_buf_high_water_mark",
-                    "",
+                    "The ChannelOutboundBuffer's high water mark of netty, " +
+                    "only when buffer size exceed this size, the method " +
+                    "ChannelOutboundBuffer.isWritable() will return false, " +
+                    "it means that the downstream pressure is too great to " +
+                    "process the request or network is very congestion, " +
+                    "upstream needs to limit rate at this time",
                     positiveInt(),
                     20 * 1024 * 1024
             );

hugegraph-core/src/main/java/com/baidu/hugegraph/util/LZ4Util.java

@@ -55,7 +55,7 @@ public static BytesBuffer compress(byte[] bytes, int blockSize,
             throw new BackendException("Failed to compress", e);
         }
         /*
-         * If need perform reading outside the method,
+         * If need to perform reading outside the method,
          * remember to call forReadWritten()
          */
         return buf;
@@ -87,7 +87,7 @@ public static BytesBuffer decompress(byte[] bytes, int blockSize,
             throw new BackendException("Failed to decompress", e);
         }
         /*
-         * If need perform reading outside the method,
+         * If need to perform reading outside the method,
          * remember to call forReadWritten()
          */
         return buf;