It's not just stock market charts that have patterns. Your application memory also has patterns. In this session, you are going to learn 6 unique memory patterns. Using these patterns, you can *predict* application outages well in advance and also optimize the application's performance.

1. Ram Lakshmanan
Architect - yCrash
Memory
patterns to predict
production outages
6000
5000
4000
3000
2000
1000
0
Nov 8, 14:00 Nov 8, 16:00 Nov 8, 18:00 Nov 8, 20:00 Nov 9, 00:00 Nov 9, 02:00 Nov 9, 04:00 Nov 9, 06:00 Nov 9, 08:00 Nov 9, 10:00
Time UTC -
05:00
Heap Usage (after GC)
Fig 1: Healthy saw-tooth GC pattern
Heap
Size
(mb)
100000 11 1100
1011
-xx: java Path
-xx: java
0000 0011 1100 1011
MEMORY
PATTERN
70
60
50
40
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10
0
Jul 22, 17:10 Jul 22, 17:20 Jul 22, 17:30 Jul 22, 17:40 Jul 22, 17:50 Jul 22, 18:00 Jul 22, 18:10
Time UTC - 04:00
Heap Usage (after GC)
Fig 2: Heavy caching GC pattern
Heap
Size
(gb)
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
0
Oct 23, 03:00 Oct 23, 04:00 Oct 23, 05:00 Oct 23, 06:00 Oct 23, 07:00 Oct 23, 08:00 Oct 23, 09:00 Oct 23, 10:00 Oct 23, 11:00
Time UTC - 07:00
Heap Usage (after
GC)
Fig 3: Acute memory leak GC pattern
Heap
Size
(mb)
25000
20000
1500
0
1000
0
5000
0
Oct 5,
23:00
Oct 6,
01:00
Oct 6,
03:00
Oct 6,
05:00
Oct 6,
07:00
Oct 6,
09:00
Oct 6,
11:00
Oct 6,
13:00
Oct 6,
15:00
Nov 6,
17:00
Nov 6,
19:00
Nov 6,
21:00
Time UTC - 00:00
Heap Usage (after
GC)
Fig 4: Consecutive Full GC pattern
Heap
Size
(gb)

2. Memory is a finite resource
HTTP Request
Objects
Application

3. Pattern 1: Healthy Saw-tooth

4. Pattern 2
https://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMjEvMTAvOS8tLWNhY2hlX2djLmxvZy0tMy00OS0zMg==&s=t&channel=WEB&s=t
: Heavy Cache

5. Pattern 3
https://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMjEvMTAvOS8tLWFjdXRlLW1lbW9yeS1sZWFrLS0zLTUzLTU5&channel=WEB&s=t
: Acute Memory Leak

6. Pattern 4
https://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMjIvMDcvMTgvbW9uZGVlLWdjLW1lbW9yeS1sZWFrLW5vdC1kZXRlY3RlZC0tMTktMzktMTc=&channel=WEB&s=t
: Memory Leak

7. Pattern 5: Consecutive Full GC
https://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMjEvMTAvOS8tLWNvbnNlY3V0aXZlLWZ1bGwtZ2MubG9nLS0zLTYtNDI=&channel=WEB&s=t

8. How to enable GC logs?
-XX:+PrintGCDetails -XX:+PrintGCDateStamps -Xloggc:<file-path>
Till Java 8
-Xlog:gc*:file=<file-path>
From Java 9
Enable GC logs always (no overhead)
https://blog.gceasy.io/2021/08/17/overhead-added-by-garbage-collection-logging/

9. Free Tools to analyze GC logs
https://developer.ibm.com/javasd
k/tools/
IBM GC & Memory visualizer
GC Viewer
https://github.com/chewiebug/G
CViewer
GCeasy
https://gceasy.io/
Google Garbage cat (cms)
https://code.google.com/archive/
a/eclipselabs.org/p/garbagecat
HP Jmeter
https://h20392.www2.hpe.com/p
ortal/swdepot/displayProductInfo
.do?productNumber=HPJMETER
03
02
01
05
04

10. Pattern 6: Metaspace Saturation
https://gceasy.io/my-gc-report.jsp?p=c2hhcmVkLzIwMjIvMDcvMTYvbWV0YXNwYWNlLW9vbWVycm9yLmdjLS0xOC0xNy0zMg==&s=t&channel=WEB

11. Memory different Regions
Young old metaspace native

12. Diagnose Memory Leak

13. BuggyApp (open source)
Simulates various performance problems
https://github.com/ycrash/buggyapp

14. Object Tree
MemoryLeakDemo
Object1
Object2
MapManager
Key1 Large String…1
Key2 Large String…2
key3 Large String…3
:
:
KeyN Large String…N
myMap

15. 1. GC Log
10. netstat
12. vmstat
2. Thread Dump
9. dmesg
3. Heap Dump
Open-source script : 360-degree data
6. ps
8. Disk Usage
5. top 13. iostat
11. ping
14. Kernel Params
15. App Logs
16. metadata
4. Heap Substitute
7. top -H
https://github.com/ycrash/yc-data-script

16. Thank you friends!
Ram Lakshmanan
ram@tier1app.com
@tier1app
linkedin.com/company/ycrash
This deck will be published in: https://blog.ycrash.io