Java virtual machine

The jmx-sflow-agent project is an open source implementation of sFlow monitoring for Java Virtual Machines (JVM). Instrumenting Java using sFlow provides scalable, real-time monitoring for applications such as Hadoop, Cassandra and Tomcat that typically involve large numbers of virtual machines.

The sFlow Host Structures extension describes a set of standard metrics for monitoring physical and virtual machines. The jmx-sflow-agent extends the set of physical server metrics exported by a Host sFlow agent which exports the physical server metrics.

The jmx-sflow-agent exports the generic virtual machine structures. In addition, the jmx-sflow-agent uses the Java Management Extensions (JMX) interface to collect performance statistics about java threads, heap/non-heap memory, garbage collection, compilation and class loading. These additional metrics are exported along with the generic virtual machine statistics.

The jmx-sflow-agent software is designed to integrate with the Host sFlow agent to provide a complete picture of server performance. Download, install and configure Host sFlow before proceeding to install the tomcat-sflow-valve - see Installing Host sFlow on a Linux Server. There are a number of options for analyzing cluster performance using Host sFlow, including Ganglia and sFlowTrend.

Next, download the sflowagent.jar file from https://github.com/sflow/jmx-sflow-agent. Copy the sflowagent.jar file into the same directory as your Java application. Enabling the sFlow instrumentation involves including -javaagent:sflowagent.jar argument when starting the Java application.

The following example shows how instrumentation is added to MyApp:

java -javaagent:sflowagent.jar\
     -Dsflow.hostname=vm.test\
     -Dsflow.uuid=564dd23c-453d-acd2-fa64-85da86713620\
     -Dsflow.dsindex=80001\
     MyApp

Arguments can be passed to the sFlow module as system properties:

• sflow.hostname, optionally assign a "hostname" to identify the virtual machine. Choose a naming strategy that is helpful in identifying virtual machine instances, for example: "hadoop.node1" etc. The hostname is exported in the sFlow host_descr structure.
• sflow.uuid, optionally assign a UUID to the virtual machine so that it can be uniquely identified. The UUID is exported in the sFlow host_descr structure.
• sflow.dsindex, uniquely identifies the data source associated with this virtual machine on this server. The dsindex number only needs to be set if more than one virtual machine is running on the server. For virtual machines offering network services, use TCP/UDP port number associated with the service as the dsindex, otherwise, use numbers in the range 65536-99999 to avoid clashes with other sFlow agents on the server.

The sFlow module shares Host sFlow's configuration and will automatically send data to the set of sFlow analyzers specified in the Host sFlow configuration file, picking up any configuration changes without the need to restart the Java application.

Finally, the real potential of of the Java virtual machine sFlow agent is as part of a broader sFlow monitoring system providing scaleable, real-time, visibility into applications, servers, storage and networking across the entire data center.