jfr(1) JDK Commands jfr(1)
NAME
jfr - parse and print Flight Recorder files
SYNOPSIS
To print the contents of a flight recording to standard out:
jfr print [options] file
To print metadata information about flight recording events:
jfr metadata file
To assemble chunk files into a flight recording file:
jfr assemble repository file
To disassemble a flight recording file into chunk files:
jfr disassmble [options] file
To view the summary statistics for a flight recording file:
jfr summary file
options
Optional: Specifies command-line options separated by spaces.
See the individual subcomponent sections for descriptions of the
available options.
file Specifies the name of the target flight recording file (.jfr).
repository
Specifies the location of the chunk files which are to be assem-
bled into a flight recording.
DESCRIPTION
The jfr command provides a tool for interacting with flight recorder
files (.jfr). The main function is to filter, summarize and output
flight recording files into human readable format. There is also sup-
port for merging and splitting recording files.
Flight recording files are created and saved as binary formatted files.
Having a tool that can extract the contents from a flight recording and
manipulate the contents and translate them into human readable format
helps developers to debug performance issues with Java applications.
Subcommands
The jfr command has several subcommands:
o print
o summary
o assemble
o disassemble
o metadata
jfr print subcommand
Use jfr print to print the contents of a flight recording file to stan-
dard out. The syntax is:
jfr print [--xml|--json] [--categories <filters>] [--events <filters>]
[--stack-depth <depth>] <file>
where:
--xml Print the recording in XML format
--json Print the recording in JSON format
--categories <filters>
Select events matching a category name. The filter is a com-
ma-separated list of names, simple and/or qualified, and/or
quoted glob patterns
--events <filters>
Select events matching an event name. The filter is a com-
ma-separated list of names, simple and/or qualified, and/or
quoted glob patterns
--stack-depth <depth>
Number of frames in stack traces, by default 5
<file> Location of the recording file (.jfr)
The default format for printing the contents of the flight recording
file is human readable form unless either xml or json is specified.
These options provide machine-readable output that can be further
parsed or processed by user created scripts.
Use jfr --help print to see example usage of filters.
To reduce the amount of data displayed, it is possible to filter out
events or categories of events. The filter operates on the symbolic
name of an event, set by using the @Name annotation, or the category
name, set by using the @Category annotation. If multiple filters are
used, events from both filters will be included. If no filter is used,
all the events will be printed. If a combination of a category filter
and event filter is used, the selected events will be the union of the
two filters.
For example, to show all GC events and the CPULoad event, the following
command could be used:
jfr print --categories GC --events CPULoad recording.jfr
Event values are formatted according to the content types that are be-
ing used. For example, a field with the jdk.jfr.Percentage annotation
that has the value 0.52 is formatted as 52%.
Stack traces are by default truncated to 5 frames, but the number can
be increased/decreased using the --stack-depth command-line option.
jfr summary subcommand
Use jfr summary to print statistics for a recording. For example, a
summary can illustrate the number of recorded events and how much disk
space they used. This is useful for troubleshooting and understanding
the impact of event settings.
The syntax is:
jfr summary <file>
where:
<file> Location of the flight recording file (.jfr)
jfr metadata subcommand
Use jfr metadata to view information about events, such as event names,
categories and field layout within a flight recording file. The syntax
is:
jfr metadata <file>
where:
<file> Location of the flight recording file (.jfr)
jfr assemble subcommand
Use jfr assemble to assemble chunk files into a recording file.
The syntax is:
jfr assemble <repository> <file>
where:
<repository>
Directory where the repository containing chunk files is located
<file> Location of the flight recording file (.jfr)
Flight recording information is written in chunks. A chunk contains
all of the information necessary for parsing. A chunk typically con-
tains events useful for troubleshooting. If a JVM should crash, these
chunks can be recovered and used to create a flight recording file us-
ing this jfr assemble command. These chunk files are concatenated in
chronological order and chunk files that are not finished (.part) are
excluded.
jfr disassemble subcommand
Use jfr disassemble to decompose a flight recording file into its chunk
file pieces. The syntax is:
jfr disassemble [--max-chunks <chunks>] [--output <directory>] <file>
where:
--output <directory>
The location to write the disassembled file, by default the cur-
rent directory
--max-chunks <chunks>
Maximum number of chunks per file, by default 5. The chunk size
varies, but is typically around 15 MB.
--max-size <size>
Maximum number of bytes per file.
<file> Location of the flight recording file (.jfr)
This function can be useful for repairing a broken file by removing the
faulty chunk. It can also be used to reduce the size of a file that is
too large to transfer. The resulting chunk files are named my-
file_1.jfr, myfile_2.jfr, etc. If needed, the resulting file names
will be padded with zeros to preserve chronological order. For exam-
ple, the chunk file name is myfile_001.jfr if the recording consists of
more than 100 chunks.
jfr version and help subcommands
Use jfr --version or jfr version to view the version string information
for this jfr command.
To get help on any of the jfr subcommands, use:
jfr <--help|help> [subcommand]
where:
[subcommand] is any of:
o print
o metadata
o summary
o assemble
o disassemble
JDK 15 2020 jfr(1)
openjdk 15.0.2 - Generated Tue Feb 23 16:15:13 CST 2021