Monitoring Clients

You can use the Clients menu item to monitor all the clients that are connected to your Hazelcast cluster.

Only basic information for clients, like client instance name, address, type and labels, is shown by default. The values for other fields are shown as N/A. As a prerequisite for seeing the full information, you need to enable the client statistics before starting your clients. This can be done by setting the hazelcast.client.statistics.enabled system property to true on the client. Please see the Client System Properties section in the Hazelcast documentation for more information. After you enable the client statistics, you can monitor your clients using the Management Center.

You can see a list of all the clients in your cluster by clicking on the Clients menu item on the left panel. A new page is opened on the right, as shown below. The page has two tabs: Connection and Filter. The Connection tab is opened by default. This tab shows the list of all the clients. See the Changing Cluster Client Filtering section for the Filter tab’s description.

Client Grid View

By default, hostname of the client is shown in the address column. You can change it to show its IP address or its canonical hostname instead by using the Address Type combo box. Note that this will also cause the client details page to show the IP address or the canonical hostname.

You can filter the clients shown and you can also sort the table by clicking on the column headers. Clicking on a client name will open a new page for monitoring that client on the right, as shown below.

Monitoring Client Detailed

The Heap Memory Utilization chart shows the memory usage on the selected client with three different metrics (maximum, used and total memory) represented by different colors. You can open this chart as a separate window using the maximize button placed at top right of it; this gives you a clearer view of the chart.

General is a dynamically updated window tab showing general information about the client. Below are brief explanations for each piece of information:

  • Name: Name of the client instance.

  • Address: Local IP address of the client that is used for connecting to members.

  • Type: Type of the client.

  • Enterprise: Yes, if the client is an Hazelcast Enterprise client.

  • Member Connection: Shows to which member a client is currently connected to. Please note that ALL means a client is configured so that it might connect to all members of a cluster, i.e., it might not have a connection to all members all the time.

  • Version: Version of the client.

  • Last Connection to Cluster: Time that the client connected to the cluster. It is reset on each reconnection.

  • Last Statistics Collection: Time when the latest update for the statistics is collected from the client.

  • User Executor Queue Size: Number of waiting tasks in the client user executor.

  • Labels: List of client labels (as defined by the client).

Next to the General tab, the Runtime tab shows the processor number, uptime, and maximum, total and free memory sizes of the selected client. These values are collected from the default MXBeans provided by the Java Virtual Machine (JVM). Descriptions from the Javadocs and some explanations are below:

  • Number of Processors: Number of processors available to the client (JVM).

  • Up Time: Uptime of the client (JVM).

  • Maximum Memory: Maximum amount of memory that the client (JVM) will attempt to use.

  • Total Memory: Amount of total heap memory currently available for current and future objects in the client (JVM).

  • Free Memory: Amount of free heap memory in the client (JVM).

  • Used Memory: Amount of used heap memory in the client (JVM).

Next to the Runtime tab, the OS tab shows statistics about the operating system of the client. These values are collected from the default MXBeans provided by the Java Virtual Machine (JVM). Descriptions from the Javadocs and some explanations are below:

  • Free Physical Memory: Amount of free physical memory.

  • Committed Virtual Memory: Amount of virtual memory that is guaranteed to be available to the running process.

  • Total Physical Memory: Total amount of physical memory.

  • Free Swap Space: Amount of free swap space. Swap space is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space.

  • Total Swap Space: Total amount of swap space.

  • Maximum File Descriptor Count: Maximum number of file descriptors. File descriptor is an integer number that uniquely represents an opened file in the operating system.

  • Open File Descriptor Count: Number of open file descriptors.

  • Process CPU Time: CPU time used by the process on which the member (JVM) is running.

  • System Load Average: System load average for the last minute. The system load average is the average over a period of time of this sum: (the number of runnable entities queued to the available processors) + (the number of runnable entities running on the available processors). The way in which the load average is calculated is operating system specific but it is typically a damped time-dependent average.

Some of the Runtime/OS statistics may not be available for your client’s JVM implementation/operating system. N/A is shown for these types of statistics. Please refer to your JVM/operating system documentation for further details.

The Client Near Cache Statistics table shows statistics related to the Near Cache of a client. There are two separate tables; one for maps and one for caches.

  • Map/Cache Name: Name of the map or cache.

  • Creation Time: Creation time of this Near Cache on the client.

  • Evictions: Number of evictions of Near Cache entries owned by the client.

  • Expirations: Number of TTL and max-idle expirations of Near Cache entries owned by the client.

  • Hits: Number of hits (reads) of Near Cache entries owned by the client.

  • Misses: Number of misses of Near Cache entries owned by the client.

  • Owned Entry Count: Number of Near Cache entries owned by the client.

  • Owned Entry Memory Cost: Memory cost of Near Cache entries owned by the client.

  • LP Duration: Duration of the last Near Cache key persistence (when the pre-load feature is enabled).

  • LP Key Count: Number of Near Cache key persistences (when the pre-load feature is enabled).

  • LP Time: Time of the last Near Cache key persistence (when the pre-load feature is enabled).

  • LP Written Bytes: Written number of bytes of the last Near Cache key persistence (when the pre-load feature is enabled).

  • LP Failure: Failure reason of the last Near Cache persistence (when the pre-load feature is enabled).

Please note that you can configure the time interval for which the client statistics are collected and sent to the cluster, using the system property hazelcast.client.statistics.period.seconds. See the System Properties section in the Hazelcast documentation for more information.