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Monitoring with Ganglia
Matt Massie, Bernard Li, Brad Nicholes,
and Vladimir Vuksan
Beijing • Cambridge • Farnham • Köln • Sebastopol • Tokyo
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Monitoring with Ganglia
by Matt Massie, Bernard Li, Brad Nicholes, and Vladimir Vuksan
Copyright © 2013 Matthew Massie, Bernard Li, Brad Nicholes, Vladimir Vuksan. All rights reserved.
Printed in the United States of America.
Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472.
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Editors: Mike Loukides and Meghan Blanchette Indexer: Ellen Troutman-Zaig
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Copyeditor: Nancy Wolfe Kotary Interior Designer: David Futato
Proofreader: Kara Ebrahim Illustrator: Kara Ebrahim
November 2012: First Edition.
Revision History for the First Edition:
2012-11-7 First release
See http://oreilly.com/catalog/errata.csp?isbn=9781449329709 for release details.
Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of
O’Reilly Media, Inc. Monitoring with Ganglia, the image of a Porpita pacifica, and related trade dress are
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tained herein.
ISBN: 978-1-449-32970-9
[LSI]
1352302880
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Table of Contents
Preface ..................................................................... ix
1. Introducing Ganglia ..................................................... 1
It’s a Problem of Scale 1
Hosts ARE the Monitoring System 2
Redundancy Breeds Organization 3
Is Ganglia Right for You? 4
gmond: Big Bang in a Few Bytes 4
gmetad: Bringing It All Together 7
gweb: Next-Generation Data Analysis 8
But Wait! That’s Not All! 9
2. Installing and Configuring Ganglia ........................................ 11
Installing Ganglia 11
gmond 11
gmetad 14
gweb 16
Configuring Ganglia 20
gmond 20
gmetad 33
gweb 38
Postinstallation 40
Starting Up the Processes 41
Testing Your Installation 41
Firewalls 41
3. Scalability ............................................................ 43
Who Should Be Concerned About Scalability? 43
gmond and Ganglia Cluster Scalability 43
gmetad Storage Planning and Scalability 44
RRD File Structure and Scalability 44
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Acute IO Demand During gmetad Startup 46
gmetad IO Demand During Normal Operation 46
Forecasting IO Workload 47
Testing the IO Subsystem 48
Dealing with High IO Demand from gmetad 50
4. The Ganglia Web Interface .............................................. 53
Navigating the Ganglia Web Interface 53
The gweb Main Tab 53
Grid View 53
Cluster View 54
Host View 58
Graphing All Time Periods 58
The gweb Search Tab 60
The gweb Views Tab 60
The gweb Aggregated Graphs Tab 63
Decompose Graphs 64
The gweb Compare Hosts Tab 64
The gweb Events Tab 64
Events API 66
The gweb Automatic Rotation Tab 67
The gweb Mobile Tab 67
Custom Composite Graphs 67
Other Features 69
Authentication and Authorization 70
Configuration 70
Enabling Authentication 70
Access Controls 71
Actions 72
Configuration Examples 72
5. Managing and Extending Metrics ......................................... 73
gmond: Metric Gathering Agent 73
Base Metrics 75
Extended Metrics 77
Extending gmond with Modules 78
C/C++ Modules 79
Mod_Python 89
Spoofing with Modules 96
Extending gmond with gmetric 97
Running gmetric from the Command Line 97
Spoofing with gmetric 99
How to Choose Between C/C++, Python, and gmetric 100
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XDR Protocol 101
Packets 102
Implementations 103
Java and gmetric4j 103
Real World: GPU Monitoring with the NVML Module 104
Installation 104
Metrics 105
Configuration 105
6. Troubleshooting Ganglia ............................................... 107
Overview 107
Known Bugs and Other Limitations 107
Useful Resources 108
Release Notes 108
Manpages 108
Wiki 108
IRC 108
Mailing Lists 108
Bug Tracker 109
Monitoring the Monitoring System 109
General Troubleshooting Mechanisms and Tools 110
netcat and telnet 110
Logs 114
Running in Foreground/Debug Mode 114
strace and truss 115
valgrind: Memory Leaks and Memory Corruption 116
iostat: Checking IOPS Demands of gmetad 116
Restarting Daemons 117
gstat 117
Common Deployment Issues 119
Reverse DNS Lookups 119
Time Synchronization 119
Mixing Ganglia Versions Older than 3.1 with Current Versions 119
SELinux and Firewall 120
Typical Problems and Troubleshooting Procedures 120
Web Issues 120
gmetad Issues 125
rrdcached Issues 126
gmond Issues 126
7. Ganglia and Nagios ................................................... 129
Sending Nagios Data to Ganglia 130
Monitoring Ganglia Metrics with Nagios 133
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Principle of Operation 134
Check Heartbeat 135
Check a Single Metric on a Specific Host 135
Check Multiple Metrics on a Specific Host 136
Check Multiple Metrics on a Range of Hosts 136
Verify that a Metric Value Is the Same Across a Set of Hosts 137
Displaying Ganglia Data in the Nagios UI 138
Monitoring Ganglia with Nagios 139
Monitoring Processes 139
Monitoring Connectivity 140
Monitoring cron Collection Jobs 140
Collecting rrdcached Metrics 140
8. Ganglia and sFlow .................................................... 143
Architecture 145
Standard sFlow Metrics 147
Server Metrics 147
Hypervisor Metrics 149
Java Virtual Machine Metrics 150
HTTP Metrics 151
memcache Metrics 153
Configuring gmond to Receive sFlow 155
Host sFlow Agent 157
Host sFlow Subagents 158
Custom Metrics Using gmetric 160
Troubleshooting 161
Are the Measurements Arriving at gmond? 161
Are the Measurements Being Sent? 165
Using Ganglia with Other sFlow Tools 165
9. Ganglia Case Studies .................................................. 171
Tagged, Inc. 172
Site Architecture 172
Monitoring Configuration 173
Examples 175
SARA 180
Overview 180
Advantages 181
Customizations 182
Challenges 184
Conclusion 186
Reuters Financial Software 186
Ganglia in the QA Environment 186
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Ganglia in a Major Client Project 188
Lumicall (Mobile VoIP on Android) 190
Monitoring Mobile VoIP for the Enterprise 191
Ganglia Monitoring Within Lumicall 191
Implementing gmetric4j Within Lumicall 192
Lumicall: Conclusion 194
Wait, How Many Metrics? Monitoring at Quantcast 194
Reporting, Analysis, and Alerting 196
Ganglia as an Application Platform 198
Best Practices 198
Tools 199
Drawbacks 200
Conclusions 201
Many Tools in the Toolbox: Monitoring at Etsy 202
Monitoring Is Mandatory 202
A Spectrum of Tools 202
Embrace Diversity 203
Conclusion 204
A. Advanced Metric Configuration and Debugging ............................ 205
B. Ganglia and Hadoop/HBase ............................................. 215
Index ..................................................................... 221
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