Most Java software problems come from the little “broken windows” – a null pointer here or there. Sometimes, however, you find yourself in a nasty section of town, with the heap, stack, and permgen brutally fighting for memory. Threads in nasty knife fights over resources. Sometimes just plain freaky things – how did I wind up with 1.5GB of HashSet allocations? In this edition of CSI: Seattle Java Edition, we’ll look at the tools available to combat these nasty foes and even see some of them in action – we will blow up a lot of application servers and JVMs in the process, with graphic results.

2. Who
Is
This
Guy?
 Will
Iverson
 wiverson@nukio.com
 Check
www.nukio.com
for
LinkedIn,
Twitter,
etc.
 Java
since
1995
 Pascal/C/C++
before
that…
 Apple,
Symantec,
Sun,
BEA…
 Four
books
on
Java
 Hibernate,
Web
Services,
Mac
OS
X
Java,
Jakarta
Commons
 Today:
Architect,
Consultant,
Manager,
Coach
 All
Star
Directories
 Nukio

3. The
Setup
 IT
has
dead
bodies
 What
happened…
and
next
steps?

4. Finding
Bodies
 Profiler?
 Heap
dumps
 Thread
dumps
 Stack
traces

5. Getting
Heap
Dumps
 Built-­‐in
Executables
(available
in
prod)
 java
(VM
flag,
dump
on
OOM)
 jmap
 jconsole
(JMX)
 jvisualvm
 All
profilers
 YourKit,
NetBeans,
Eclipse,
JProbe
 Only
available
in
dev

6. Getting
Thread
Dumps
 Built-­‐in
Executables
(available
in
prod)
 jstack
 jconsole
 Jvisualvm
 All
profilers
 Only
available
in
dev

7. Beat
Patrol
 Get
to
know
the
neighborhood
when
nothing
is
going
on…
 Heap
 Thread
Dump
 Profilers
(CPU)

8. Cases
 Memory
Problem
#1
 Memory
Problem
#2
 Thread
Dump
#1
 Thread
Dump
#2
 Thread
Dump
#3
 Memory
Problem
#3

9. What
about
Serial
Killers?
 Really
unique,
horrible
things
 Strange
deadlocks
 JVM
bugs
 Driver
bugs
 Avoid
Dark
Alleys
 Don’t
write
threading
code
unless
you
need
to…
 …and
you
probably
don’t
need
to.
 Tip:
try
an
in
memory
database
(HSQLDB
or
db40)
 Stateless,
parallel
operations
 KISS
 More
in
futures
section

10. Reconstructing
Crimes
 jstack
 jmap
(ha!)
 Attach
with
Visual
VM
 Attach
with
jconsole
 Use
Profilers
(skip
jhat)
 Cheap,
powerful

11. Most
Normal
Web
Apps
 Problem
is
with
db/JVM
interaction,
not
JVM
 Solution?
 P6spy
 JDBC
Driver
Shim
 Records
database
interaction
 Review
in
Excel
or
with
Iron
tools
 http://www.cascadetg.com/hibernate/
 Fit
to
target
 Yes,
I
know
your
1,000,000
TPS
billing
system
required
instruction
counting…
and
you
wound
up
sending
it
out
for
an
ASIC,
etc
etc
etc…

12. Tips
 Single
user
on
dev
is
a
nice
starting
spot,
but
starve
your
resources.
Allocate
min
to
server.
 Should
still
be
fast
as
all
heck.
 Memory
or
CPU
on
a
single
page
out
of
bounds
=
total
nightmare
on
server…
think
about
all
other
requests
coming
in.
 Know
your
targets
 Establish
a
baseline
and
a
simple
scorecard
 Know
your
database
 All
mainstream
databases
have
great
tools

13. Finding
the
Future
 Stateless
Services
 e.g.
Spring
MVC,
REST
 Avoid
Sessions
&
Wizards
 Shopping
cart…
that
stays
around
forever?
 Key/Value
Datastores
 BigTable,
MongoDB,
Amazon
S3
 Easy:
play
with
today
for
free
using
Google
AppEngine
 Enhance
Your
Platform
 Track
CPU/Memory
Usage
for
Page
Views
 Response
times
+
browser
rendering

14. Tip:
Better
to
NOT
find
in
Production
 Solution:
Solid
Automated
Tests,
Good
Perf
Environment
 “Can’t
afford
to
automate”
 “Can’t
afford
to
ship”

15. Shameless
Plug
 Agile
Testing
 CI,
TDD
 Expert
JUnit
 DBUnit,
HTMLUnit,
Selenium
 Automate
documentation
generation
 March
25th
–
26th
www.nukio.com