Name
jstatd - monitor the creation and termination of instrumented Java HotSpot VMs
Synopsis
Note: This command is experimental and unsupported.
jstatd
[options]
- options
-
This represents the
jstatd
command-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
jstatd
process when an existing RMI registry isn't found. -p
port-
This option sets the port number where the RMI registry is expected to
be found, or when not found, created if the
-nr
option isn't specified. -r
rmiport- This option sets the port number to which the RMI connector is bound. If not specified a random available port is used.
-n
rminame-
This option sets the name to which the remote RMI object is bound in the
RMI registry. The default name is
JStatRemoteHost
. If multiplejstatd
servers 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'shostid
andvmid
strings. -J
option-
This option passes a Java
option
to the JVM, where the option is one of those described on the reference page for the Java application launcher. For example,-J-Xms48m
sets 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