Name
jstatd - monitor the creation and termination of instrumented Java HotSpot VMs
Synopsis
WARNING: This command is experimental, unsupported, and deprecated. It will be removed in a future release.
jstatd [options]
- options
-
This represents the
jstatdcommand-line options. See Options for the jstatd Command.
Description
The jstatd command is an RMI server application that
monitors for the creation and termination of instrumented Java HotSpot
VMs and provides an interface to enable remote monitoring tools,
jstat and jps, to attach to JVMs that are
running on the local host and collect information about the JVM
process.
The jstatd server requires an RMI registry on the local
host. The jstatd server attempts to attach to the RMI
registry on the default port, or on the port you specify with the
-p port option. If an RMI registry is not
found, then one is created within the jstatd application
that's bound to the port that's indicated by the -p
port option or to the default RMI registry port when the
-p port option is omitted. You can stop the
creation of an internal RMI registry by specifying the -nr
option.
Options for the jstatd Command
-nr-
This option does not attempt to create an internal RMI registry within
the
jstatdprocess when an existing RMI registry isn't found. -pport-
This option sets the port number where the RMI registry is expected to
be found, or when not found, created if the
-nroption isn't specified. -rrmiport- This option sets the port number to which the RMI connector is bound. If not specified a random available port is used.
-nrminame-
This option sets the name to which the remote RMI object is bound in the
RMI registry. The default name is
JStatRemoteHost. If multiplejstatdservers are started on the same host, then the name of the exported RMI object for each server can be made unique by specifying this option. However, doing so requires that the unique server name be included in the monitoring client'shostidandvmidstrings. -Joption-
This option passes a Java
optionto the JVM, where the option is one of those described on the reference page for the Java application launcher. For example,-J-Xms48msets the startup memory to 48 MB. See java.
Security
The jstatd server can monitor only JVMs for which it has
the appropriate native access permissions. Therefore, the
jstatd process must be running with the same user
credentials as the target JVMs. Some user credentials, such as the root
user in Linux and macOS operating systems, have permission to access the
instrumentation exported by any JVM on the system. A jstatd
process running with such credentials can monitor any JVM on the system,
but introduces additional security concerns.
The jstatd server doesn't provide any authentication of
remote clients. Therefore, running a jstatd server process
exposes the instrumentation export by all JVMs for which the
jstatd process has access permissions to any user on the
network. This exposure might be undesirable in your environment, and
therefore, local security policies should be considered before you start
the jstatd process, particularly in production environments
or on networks that aren't secure.
For security purposes, the jstatd server uses an RMI
ObjectInputFilter to allow only essential classes to be
deserialized.
If your security concerns can't be addressed, then the safest action
is to not run the jstatd server and use the
jstat and jps tools locally. However, when
using jps to get a list of instrumented JVMs, the list will
not include any JVMs running in docker containers.
Remote Interface
The interface exported by the jstatd process is
proprietary and guaranteed to change. Users and developers are
discouraged from writing to this interface.
Examples
The following are examples of the jstatd command. The
jstatd scripts automatically start the server in the
background.
Internal RMI Registry
This example shows how to start a jstatd session with an
internal RMI registry. This example assumes that no other server is
bound to the default RMI registry port (port 1099).
jstatd
External RMI Registry
This example starts a jstatd session with an external
RMI registry.
rmiregistry&
jstatd
This example starts a jstatd session with an external
RMI registry server on port 2020.
jrmiregistry 2020&
jstatd -p 2020
This example starts a jstatd session with an external
RMI registry server on port 2020 and JMX connector bound to
port 2021.
jrmiregistry 2020&
jstatd -p 2020 -r 2021
This example starts a jstatd session with an external
RMI registry on port 2020 that's bound to
AlternateJstatdServerName.
rmiregistry 2020&
jstatd -p 2020 -n AlternateJstatdServerName
Stop the Creation of an In-Process RMI Registry
This example starts a jstatd session that doesn't create
an RMI registry when one isn't found. This example assumes an RMI
registry is already running. If an RMI registry isn't running, then an
error message is displayed.
jstatd -nr
Enable RMI Logging
This example starts a jstatd session with RMI logging
capabilities enabled. This technique is useful as a troubleshooting aid
or for monitoring server activities.
jstatd -J-Djava.rmi.server.logCalls=true