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LINUX & APPLICATION SERVERS MONITORING TRICKS
Objective:
- Prevent server from going down,
- detect what caused the server to go down,
- get servers back after failure.
- Explain what caused the server to fail
I – Regularly watch your monitoring tool(s) (Nagios, Wily,top, …..)
On some of those tools, you can see a graph of the apps CPU Load Average, CPU Used Percentage, Disk Usage percentage, memory used percentage, Network Bandwidth, Swap Used percentage.
II – Check ulimit count (Number of files opened by applications like tomcat, oracle,…)
[Server]# ulimit -n
1024
If the number of files opened is getting closer to ulimit count (1024), increase the ulimit and talk to dev to identify and fix the process that is causing that.
To increase ulimit count for a specific application account, run the command ulimit –n [value]
Ulimit can be set to whatever you want. Its one of those things that’s put in place as a throttle to keep things from going too nuts. Some systems will actually just set it to unlimited.
III- Port Monitoring
Check number of connections to ports used by your apps
IV- Thread dump (stack trace of all threads ) If you have a high cpu percentage
[Server]# kill -3 (The output is printed in catalina.out) to see what is causing this and send it to developers.
V- Disk space /[drive_name] filling up quickly
Identify the file(s) that are filling up the disks. Most of the time ,it will be logs files.
[Server]# du -ks /[drive_name]/* | sort -nr | head
5719076 /[drive_name]/catalina
3675672 /[drive_name]/data
3287436 /[drive_name]/source
2044316 /[drive_name]/servers
319404 /[drive_name]/images
16 /[drive_name]/lost+found
By running this command on the larger folder, that will lead you to the files that eat the disk space.
Back up, remove or empty the file in question given that it won’t break the system.
If the log files are responsible for the disk filling up, let the developer know about it so that they can solve it. In the meantime, empty the log file with the command:
[Log_File_Location]# echo -n > Large_Log_File_Name.log
VI- Watch catalina.out and log4j.out after staging and live deploy, especially when you are restarting the servers.
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[Server]# tail -f log4j.log
VII- Start app servers properly
Before restarting app servers, make sure there is no app pid running for that specific server.
[Server_Name]$ ps -ef | grep oracle
Kill the pid for that server.
IX – Cpu Load level
I would say that if we peak under 70% CPU during high traffic, we are doing well and have room. A good level to be ticking over at would be 30% used.
[Server]# top
top – 12:37:29 up 47 days, 23:09, 4 users, load average: 0.20, 0.20, 0.22
Tasks: 189 total, 1 running, 178 sleeping, 10 stopped, 0 zombie
Cpu(s): 1.2%us, 0.1%sy, 0.0%ni, 97.5%id, 1.0%wa, 0.0%hi, 0.1%si, 0.0%st
X- Server specific status pings (To assure the server are up and serving contents)
Write scripts for this
XI- Garbage collection stats
If you are interested in any garbage collection stats there’s the gc.log files on each of the appservers (bad thing about it is it doesn’t do any date stamping so you can see how memory fluctuates but its a difficult to create a chart over time). In the past I’ve thought it might be good idea to write a cron that archived it daily so that you could at least break things down day by day.
XII- DB Connection
XIII- Load Average Monitoring script
Set up a cron that just email sysadmin when the load average is above 3.
XIV – Find out who is monopolizing or eating the CPUs
[Server]# ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10
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List of Freely available programming books - What is the single most influential book every Programmers should read
- Bjarne Stroustrup - The C++ Programming Language
- Brian W. Kernighan, Rob Pike - The Practice of Programming
- Donald Knuth - The Art of Computer Programming
- Ellen Ullman - Close to the Machine
- Ellis Horowitz - Fundamentals of Computer Algorithms
- Eric Raymond - The Art of Unix Programming
- Gerald M. Weinberg - The Psychology of Computer Programming
- James Gosling - The Java Programming Language
- Joel Spolsky - The Best Software Writing I
- Keith Curtis - After the Software Wars
- Richard M. Stallman - Free Software, Free Society
- Richard P. Gabriel - Patterns of Software
- Richard P. Gabriel - Innovation Happens Elsewhere
- Code Complete (2nd edition) by Steve McConnell
- The Pragmatic Programmer
- Structure and Interpretation of Computer Programs
- The C Programming Language by Kernighan and Ritchie
- Introduction to Algorithms by Cormen, Leiserson, Rivest & Stein
- Design Patterns by the Gang of Four
- Refactoring: Improving the Design of Existing Code
- The Mythical Man Month
- The Art of Computer Programming by Donald Knuth
- Compilers: Principles, Techniques and Tools by Alfred V. Aho, Ravi Sethi and Jeffrey D. Ullman
- Gödel, Escher, Bach by Douglas Hofstadter
- Clean Code: A Handbook of Agile Software Craftsmanship by Robert C. Martin
- Effective C++
- More Effective C++
- CODE by Charles Petzold
- Programming Pearls by Jon Bentley
- Working Effectively with Legacy Code by Michael C. Feathers
- Peopleware by Demarco and Lister
- Coders at Work by Peter Seibel
- Surely You're Joking, Mr. Feynman!
- Effective Java 2nd edition
- Patterns of Enterprise Application Architecture by Martin Fowler
- The Little Schemer
- The Seasoned Schemer
- Why's (Poignant) Guide to Ruby
- The Inmates Are Running The Asylum: Why High Tech Products Drive Us Crazy and How to Restore the Sanity
- The Art of Unix Programming
- Test-Driven Development: By Example by Kent Beck
- Practices of an Agile Developer
- Don't Make Me Think
- Agile Software Development, Principles, Patterns, and Practices by Robert C. Martin
- Domain Driven Designs by Eric Evans
- The Design of Everyday Things by Donald Norman
- Modern C++ Design by Andrei Alexandrescu
- Best Software Writing I by Joel Spolsky
- The Practice of Programming by Kernighan and Pike
- Pragmatic Thinking and Learning: Refactor Your Wetware by Andy Hunt
- Software Estimation: Demystifying the Black Art by Steve McConnel
- The Passionate Programmer (My Job Went To India) by Chad Fowler
- Hackers: Heroes of the Computer Revolution
- Algorithms + Data Structures = Programs
- Writing Solid Code
- JavaScript - The Good Parts
- Getting Real by 37 Signals
- Foundations of Programming by Karl Seguin
- Computer Graphics: Principles and Practice in C (2nd Edition)
- Thinking in Java by Bruce Eckel
- The Elements of Computing Systems
- Refactoring to Patterns by Joshua Kerievsky
- Modern Operating Systems by Andrew S. Tanenbaum
- The Annotated Turing
- Things That Make Us Smart by Donald Norman
- The Timeless Way of Building by Christopher Alexander
- The Deadline: A Novel About Project Management by Tom DeMarco
- The C++ Programming Language (3rd edition) by Stroustrup
- Patterns of Enterprise Application Architecture
- Computer Systems - A Programmer's Perspective
- Agile Principles, Patterns, and Practices in C# by Robert C. Martin
- Growing Object-Oriented Software, Guided by Tests
- Framework Design Guidelines by Brad Abrams
- Object Thinking by Dr. David West
- Advanced Programming in the UNIX Environment by W. Richard Stevens
- Hackers and Painters: Big Ideas from the Computer Age
- The Soul of a New Machine by Tracy Kidder
- CLR via C# by Jeffrey Richter
- The Timeless Way of Building by Christopher Alexander
- Design Patterns in C# by Steve Metsker
- Alice in Wonderland by Lewis Carol
- Zen and the Art of Motorcycle Maintenance by Robert M. Pirsig
- About Face - The Essentials of Interaction Design
- Here Comes Everybody: The Power of Organizing Without Organizations by Clay Shirky
- The Tao of Programming
- Computational Beauty of Nature
- Writing Solid Code by Steve Maguire
- Philip and Alex's Guide to Web Publishing
- Object-Oriented Analysis and Design with Applications by Grady Booch
- Effective Java by Joshua Bloch
- Computability by N. J. Cutland
- Masterminds of Programming
- The Tao Te Ching
- The Productive Programmer
- The Art of Deception by Kevin Mitnick
- The Career Programmer: Guerilla Tactics for an Imperfect World by Christopher Duncan
- Paradigms of Artificial Intelligence Programming: Case studies in Common Lisp
- Masters of Doom
- Pragmatic Unit Testing in C# with NUnit by Andy Hunt and Dave Thomas with Matt Hargett
- How To Solve It by George Polya
- The Alchemist by Paulo Coelho
- Smalltalk-80: The Language and its Implementation
- Writing Secure Code (2nd Edition) by Michael Howard
- Introduction to Functional Programming by Philip Wadler and Richard Bird
- No Bugs! by David Thielen
- Rework by Jason Freid and DHH
- JUnit in Action
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