Debugging

October 1, 2020 · View on GitHub

Andesite has plugins to support jattach for debugging. Prebuilt jars for them can be found on the releases page.

Jattach Plugin

All responses follow the format

{
    "exitCode": 123,
    "stderr": "",
    "stdout": ""
}

Returns agent properties

Prints heap and thread summary to the JVM's stdout. Returns no response to the client. Only included to cover all jattach commands.

Returns a file from the local machine. Useful to download heap dumps.

Query params:

key	type	description
path	string	path of the wanted file

Dumps the JVM heap to the specified path.

Query params:

key	type	description
path	string	path to write the heap dump to

Returns a list of all live objects, including the number of instances, bytes used and class name, grouped by class.

Runs a jcmd command. Use help or help --all for a list of valid commands.

Query params:

key	type	description
command	string	command to execute

Loads an agent library.

Query params:

key	type	description
path	string	path to the library
absolute	boolean	whether or not the provided path is absolute, defaults to false
options	string	options to pass to the agent. May be absent

Returns the value of a JVM flag.

Query params:

key	type	description
flag	string	flag to read

Returns the JVM system properties present.

Updates a flag. Not all flags may be updated. A list of flags that can be updated can be obtained with

curl http://your-andesite-instance/debug/jcmd?command=VM.flags%20-all | jj stdout | grep manageable

Query params:

key	type	description
flag	string	flag to update
value	string	value to set

Returns a thread dump of the VM