Open Source Debugging v1.3.2

Open Source
Debugging Tools
m y favorite a pps to ease
de bugging pain

by Matthew McCullough of Ambient Ideas, LLC

Quick bits a bout me...

-Denver
pen source architect
-O
or of Mave n Refcard
-Auth
-NF JS speaker
-Mentor

Java
Network Web Service

OSS Debug
Tools

Filesystem JavaScript

Wh y open source
deb ugging tools?

We’re having a
problem on the web
site...web
service...whatever
you call it.

It returns the
correct <pointy>
code stuff for some
folks but not
others.

Purpose
‣ Command line URL tasks.
‣ Test web services.
‣ Inspect raw HTML pages.

cURL flags

-X [action]
Selects an HTTP verb (POST,GET, PUT, DELETE).

conditional content presentation

cURL flags

-H [HTTP header]
Set the Accept or Content-Type headers
(e.g. text/xml, or application/json)
Useful, if the web server/service parses them.

cURL examples
sponse
Re
est XML
R equ
curl -X GET -H "Accept: text/xml" http://localhost/agents/1

tion
n ac pp
cu rl i
ils a
Gra ting
w ith a etec
nt d
onte vice
c
ser

Cr eate
curl -X POST http://localhost/agents/?name=Ben

Read
curl -X GET http://localhost/agents/1

Up date
curl -X PUT http://localhost/agents/1/?name=Benny

De lete
curl -X DELETE http://localhost/agents/1

tion
n ac pp
cu rl i
Gra ils a
wi th a vice
EST ser
R

cURL flags
-d [variable]
or
--data [variable]
Set a data block to transmit to the URL.
Automatically sets the action to POST.

h n ame
wit
ST data
PO
curl -d "agent[name]=Ann Banks" http://localhost/agents/1

assin ga
cu rl p
var iable
d ata

cURL flags

-o [ﬁlename]
Output results to a ﬁle.
All formatting and encoding intact.

Supported Protocols
‣ HTTP
‣ HTTPS
‣ FTP
‣ FTPS
‣ TFTP
‣ SCP
‣ SFTP
‣ Telnet
‣ LDAP

The operations desk
called.

They say our apps is
using too much
network bandwidth.

Can you take a look
at the transmitted
data?

What’s being sent over
the wire?

TCPDump
Purpose
‣ Output headers of packets from a network.
‣ Filter results with powerful expressions.
‣ Save captured data to a ﬁle.

TCPDump

Useful for
‣ Debugging network trafﬁc.
‣ Examining socket communications.
‣ Inspecting web service calls.
‣ Examining network data as a 3rd party

TCPDump commands

tcpdump -i en1

TCPDump commands

tcpdump -i lo0

TCPDump commands

fo
in
et
ck
pa
d
se
ea
cr
In
tcpdump -i en1 -v

TCPDump commands

es
m
na
ot
,n
rs
be
m
nu
rt
po
tcpdump -i en1 -n

TCPDump commands

ut
tp
ou
I
CI
AS
tcpdump -i en1 -A

TCPDump commands

tu
tp
ou
I
CI
AS
+
EX
H
tcpdump -i en1 -X

TCPDump commands

on
si
es
pr
Ex
tcpdump -i en1 icmp

TCPDump commands

on
si
es
pr
Ex
tcpdump -i en1 tcp port 80

Destination Address

Source Address

Length
DSAP
SSAP
Control

SNAP

Data
Ethernet Frame, up to 1514 bytes

FCS

TCPDump commands

h
gt
en
l
ap
sn
tcpdump -i en1 -s 1514

TCPDump commands

s
et
ck
pa
20
re
tu
p
Ca
tcpdump -i en1 -c20

Wireshark (Cross Platform)

Purpose
Network protocol analyzer.
A GUI on tcpdump

Wireshark

Useful features
Online and ofﬂine operation.
Reading TCPDump data ﬁles.

Wireshark

Useful features
Logical packet parsing, display.
Decryption.

Wireshark usage

Gotcha on Mac OSX
At a terminal, upon each boot, type:
sudo chown YOURUSERNAME /dev/bpf*

Gotcha on Windows
Promiscuous mode doesn’t always work.

Eavesdrop (mac)

Purpose
-A Mac-speciﬁc network packet inspector.
-Listens to TCP trafﬁc between machines.

Why does our app
crash whenever we
have a lot of users?

Oh, 10... or 1000.
Something like that.

JMeter (Cross Platform)

Purpose
Load test or sequence test HTML, EJBs, SOAP,
and many other interfaces.

JMeter (Cross Platform)

Useful For
Testing web sites under strain.
Finding load-induced problems.
Graphing performance metrics.

What’s your favorite
Open Source Debugging Tool?

❶ System.out.println(brokenobj
System.out.println(broke
System.out.println(brokenobj);
nobj)
Sy stem.out.printl n(brokenobj);
System.out.prin tln(brokenobj);
System.out.println(brokenobj)
Syst em.out.println(brokenobj);
ystem.out.println(brokenobj);
ystem.out.println(broken
obj);
System.out.println(brokenob
System.out.pri ntln(brokenobj)

What JVM options
did we use when we
started up the app
server?

I’m gonna need a
list of the other java
processes running on
that box too.

jps -l
Sh
ow
fu
ll
pa
ck
age
na
m
e

Sh
ow

jps -l -v
Sh fu
ow ll
pa
JV ck
M ag
e
ar na
gu
m m
en e
ts

Sh
ow
Sh fu
ow ll
pa
JV ck
M ag
jps -l -v -m
Sh ar e
na
ow gu
m m
e
m en
ts
ain
()
ar
gu
m
en
ts

y
lic
Po
ur
Yo
jstatd -J-Djava.security.policy=allowall.pol

grant codebase "file:${java.home}/../lib/tools.jar" {
permission java.security.AllPermission;
};

y
lic
Po
ur

rt
Yo

Po
jstatd -J-Djava.security.policy=your.pol -p 1099

Sh
ow
ga
rb
ag
e

jstat -gcutil <pid>
co
lle
ct
io
n

es
pl
m
sa
n
ee

sn
tw

io
tit
be
pe
s
re
m
jstat -gcutil <pid> 500 999

es
lin
X
y
er
ev
er
ad
he
ow
Sh

jstat -gcutil -h5 <pid> 500 999

jmap -dump:ﬁle=myﬁle <pid>

We added a new
method to a class.

Is it on the
server-deployed copy
of the app?

e
os
rb
Ve

javap -v classﬁle

Ve
rb
os
In e
te
rn
al
ty
pe
javap -v -s classﬁle si
gn
at
ur
es

Ve
rb
In os
te e
Di rna
sp l t
la yp
y e
va
ria sign
bl at
e
javap -v -s -l classﬁle
ur
ta es
bl
es

Ve
rb
In os
te e
rn
Di
sp al
la ty
y pe
va si
Sh ria gn
bl atu
ow e
Pr ta res
bl
iva es
te
m
et
ho
ds
javap -v -s -l -private classﬁle

We’re having, um
some “problems”
with the app in
production.

You’ll need to
figure it out on the
live production app.

No, you can’t restart
the app!

No, you can’t put
Eclipse on the
production box!!

Purpose
Deeply inspect many metrics of Java processes.

Useful for
‣ Discovering the GC cycles of your app.

Useful for
‣ Finding the largest memory usage culprits.

Useful for
‣ Difﬁng memory snapshots.

Useful for
‣ Injecting btrace code.

Useful for
‣ Injecting btrace code.
‣ Snapping heapdumps.

Gotcha
Download version 1.1.1 even if your JDK includes 1.0.
Standalone version always ahead of JVM version.

We don’t have
screens on our
servers.

Can you run these
VisualVeeeEmmmms
remotely?

y
lic
Po
ur
Yo
jstatd -J-Djava.security.policy=your.pol

Remotely
‣ Attach VisualVM
‣ Run any VisualVM debugging tool
‣ Run JPS

Is the
deployed version of
the bean compatible
with the copy we are
about to release?

Yeah, we don’t set
serialVersionUID

MyBean: static ﬁnal long serialVersionUID = -4193605393175618625L;

Eclipse Memory Analyzer
(MAT)

Find out what
objects are using so
much memory in the
app!

EclipseMemoryAnalyzer

Purpose
‣ Visually investigate memory usage inside
a heap dump.

Purpose
Investigate memory usage.

Useful for
Visualizing memory footprint.
Finding memory leaks.
Querying through (OQL) allocated memory.
Discovering heavy memory allocation sources.

Gotcha
Doesn’t create heap dumps, just analyzes.
Available as a plugin or standalone RCP app.

EclipseMemoryAnalyzer in action

Can you put a
few debugging
“sysouts” into that
running app not he
server?

BTrace Tracing

Origins
DTrace on Sun Solaris
Ported to other UNIX platforms

Now available as BTrace for Java

BTrace Tracing
Production-time
Operates on deployed code
Runtime injection of tracing statements

Ken Sipe, contributing

BTrace Tracing

Code
Tracing written in Java.
Doesn’t have to be compiled.

BTrace Tracing

Console
It’s core strength.
Original target.

BTrace Tracing

GUI
Tightly integrated with VisualVM

SOAPUI

Purpose
‣ Test, mock, and visualize web services.

SOAPUI
Useful for
‣ Testing your app against a stub web
service.
‣ Testing a public web service via a GUI.

FireBug
Purpose
Visually inspect an entire HTML DOM.

Useful for
Testing HTML and CSS changes.
Making realtime changes to the DOM.
Monitoring network trafﬁc.
Debuging JavaScript.

fs_usage (Mac, Linux)

Purpose
Shows ﬁle activity.

Useful for
Examining which ﬁles are being written.
Discovering what component is disk bound.

fs_usage params

er

e
lt

m
fi

na
fo

d
an
in
e/

m
m
od

Co
M
fs_usage -f ﬁlesys java

lsof (Mac, Linux)

Purpose
Shows open ﬁles.

Useful for
Finding what PID is holding a ﬁle open.

lsof params

Find all
ﬁles
lsof o pen

lsof params
Find
hing
eryt as
ev

r
ID h

be
t his P

m
ag
pen

nu
o
fl
D
D
PI
PI

lsof -p 4347

lsof (Mac, Linux)

Purpose #2
Shows open network ports and PIDs.

Useful for
Finding what PID is holding a port open.

lsof params

W ait!
thou ght
I
you said
ﬁles?

lsof params

ol
oc
ot

rt
Po
Pr

lsof -iTCP:8080

ProcessMonitor (windows)

Purpose
Shows open ﬁles.
Enumerates network TCP handles.
Shows registry read/writes.

Useful for
Discovering network and disk activity causes.

Source Code search engines
for examples

‣ http://google.com/codesearch
‣ http://www.jexamples.com/
‣ http://www.codefetch.com/
‣ http://www.krugle.com/
‣ http://codesearch.developer.emc.com/
‣ http://www.codase.com/
‣ http://www.koders.com/

Twitter
@matthewmccull Matthew
Blog
http://www.ambientideas.com/blog
sidebar has all my social media links

Email
matthewm@ambientideas.com
GitHub
http://github.com/matthewmccullough

Resources
CURL
http://curl.haxx.se/

CygWin
http://www.cygwin.com/

TCPDump
http://www.tcpdump.org/

Wireshark
http://www.wireshark.org/

Eavesdrop
http://www.baurhome.net/software/eavesdrop/

Resources

Apache JMeter
http://jakarta.apache.org/jmeter/

JMeter Groovy Plugin
http://code.google.com/p/jmeter-groovy-sampler/

Resources
VisualVM
https://visualvm.dev.java.net/

GCHisto
https://gchisto.dev.java.net/

Eclipse Memory Analyzer
http://www.eclipse.org/mat/

BTrace
https://btrace.dev.java.net/

DTrace, XRay, Instruments
http://en.wikipedia.org/wiki/DTrace

Resources
SOAPui
http://www.soapui.org/

Firebug
http://getﬁrebug.com/

fs_usage
http://rentzsch.com/macosx/fs_usageIntro

lsof
http://www.akadia.com/services/lsof_intro.html

Process Monitor
http://technet.microsoft.com/en-us/sysinternals/bb896645.aspx

Image Credits
‣ http://www.ambientideasphotography.com
‣ http://upload.wikimedia.org/wikipedia/commons/a/a4/
BernardMadoff.jpg
‣ http://flickr.com/photos/triller/2226679393/
‣ http://flickr.com/photos/ektogamat/2687444500/
‣ http://flickr.com/photos/bfionline/2380398799/
‣ http://flickr.com/photos/symphoney/76513801/
‣ http://flickr.com/photos/foxypar4/2124673642/
‣ http://flickr.com/photos/morberg/3146874095/
‣ http://flickr.com/photos/triller/2226679393/

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