Nagios Conference 2011 - William Leibzon - Nagios In Cloud Computing Environments

Nagios and Cloud Computing
Presentation by William Leibzon ( [email_address] ) Thanks for being here!
Nagios
Nagios 2011 Conference in Saint Paul, Minnesota

Cloud Computing
What is Cloud Computing? Virtualized systems independent of hardware and leased to various customers in what is referred to as Infrastructure as a Service
Image courtesy of thetechlabs.com

Virtualization and Cloud Computing
Virtualization
Separates Hardware from User Software - either one can be upgraded independent of the other
Efficient use of modern multi-core processors
Micro-Kernel design is simpler, easier to support
More Servers with Less Hardware
Unused system resources can be utilized in other types of servers with different resource usage
Less energy, more power efficient use of resources
Less rack space in expensive datacenters
Virtualization is the core of Cloud Computing

Cloud Computing Architecture
Virtualized Systems in a Cloud
Can be managed entirely remotely
Can move (even live) from one hardware to another
Can be shutdown, saved to disk and started again when required
Can be easily cloned to have another alike system started exactly when it is needed
Cloud allows to automate scaling up of infrastructure to handle peak traffic load while scaling down after to keep overall cost low
This requires monitoring of all system resources !

Cloud Solutions and Vendors
Hypervisors (Viritualization Kernels):
Commercial: VMware ESX, IBM Z/VM, Microsoft VirtualPC
Open-Source: Xen, KVM, OpenVZ, Quemu, VirtualBox
Xen originally implimented paravirtualization, which required modified OS and limited it to Linux. KVM and new Xen-HVM can do full virtualization, but require Quemu and CPU virtualization extensions (Intel's VT or AMD's SVM)
Virtualization and Cloud Software Suites
Commercial: VMware vCloud, Microsoft Azure
Open-Source: Eucalyptus, OpenNebula, OpenStack, Baracus
Commercial based on Open-Source: Citrix XenServer, Oracle VM, Ubuntu Enterprise Cloud, Redhat CloudForms, Parallels Virtuozzo
Cloud Infrastructure providers
Amazon EC2 (modified Xen), Rackspace (Xen), Linode (Xen), Savvis (Vmware), many many more...

Open-Source Cloud Software
Open-Source Hypervisors used in Cloud Systems
Xen - http://www.xen.org/
KVM - http://www.linux-kvm.org/
OpenVZ - http://www.openvz.org/
Open-Source Cloud Management Software
Eucalyptus - http://open.eucalyptus.com/
OpenNebula - http://www.opennebula.org/
OpenStack – http://www.openstack.org /
Baracus – http://baracus-project.org/
Proxmox - http://pve.proxmox.com/

Monitoring for the Cloud
Monitoring of hardware (host OS) & hypervisor
More static, hardware does not change as often
Monitoring of system resources often integrated into virtualizer and info not available to cloud customer
Monitoring of virtual systems
Dynamic, should be able to handle addition and removal of server instances
Focus on application and network performance
Ideally should monitor utilization and be able to launch new server instances (auto-scaling)
Monitoring system should itself be robust and handle more servers without impacting performance

Cloud Monitoring Architecture
Horizontal Scaling
Clouds can be as small as 10 servers and as as large as 10,000+. When developing architecture, you need to support its future growth from the start.
Scaling on Demand
A pro-active system should handle big changes in the number of cloud instances. You may have 2 webserver instances at 6am and grow to 20 at 10pm.
High Availability
Good system design should be fully fault-tolerant and application as a whole should continue to function without interruption if any one server instance dies
This means cluster !!!

Nagios Cluster Options
The base nagios-core package is for stand-alone monitoring where server does all service checks. It can be extended to Nagios Cluster with :
Passive Service Checks (Classic Distributed Model)
”Old Way” - NCSA used to forward results of checks from client servers to main nagios server, not robust
Shared database (Central Dashboard Model)
NDO-Mod and Merlin projects implement this with a combination of NEB modules, daemon & database
Worker Nodes (Load Balancing of Checks)
DNX and Mod-Gearman do it with combination of loaded NEB module, server daemon & client servers

Passive Service Checks
How
- One central server with all services, it does not do any checks listing them all passive
- Separate client nagios servers run plugins and do checks for specific sets of hosts, each has its own subset of full nagios config
- Scripts are setup that capture results from each client host and send them to central server using NSCA, it puts them into nagios command queue
Advantages
This will work with any nagios server, organizations have been doing it from at least 2002
Disadvantages
Requires a lot of custom scripting to organize nagios configs. Not reliable if server dies. Not robust to automate cloud instances being added and deleted
NCSA NCSA Nagios Client Server Nagios Client Server

Shared Database
Who: NDO-DB and Merlin
How
- Multiple Peer Nagios servers, each has different config file specifying which services it would check
- All servers use common database to share results of checks and status of services they are monitoring
Advantages
- There is no master nagios server. There is master DB server, however it is a better understood topic how to create a db cluster
- Using NEB avoids slow command-queue processing
Disadvantages
Partioning of monitoring infrastructure among servers is still manual process. It is not easy to use this for dynamic cloud environment, however it works very well for fault-tolerance

DNX and Mod-Gearman Worker Nodes
How
- Similarly to Passive Service Checks, there is a central Nagios Server, it does not execute any plugins.
- Unlike with Passive Checks, nagios does schedule checks. Thereafter NEB module takes over.
- Module passes information on which plugin(s) to run to DNX server (or Gearman server for Mod-Gearman) which manages worker nodes.
- Worker nodes are separate servers, each has special worker daemon running. The daemon communicates with management server and gets information (plugin command) on what to run. It then passes results back to management server and NEB module writes these results directly into nagios memory.

Advantages of DNX and Mod-Gearman
Robust and Scalable
Checks are automatically distributed among all cluster worker nodes (round-robin on equal basis by default)
All worker nodes are essentially the same and there is no additional re-configuration necessary to add a new node
This fully achieves Horizontal Scaling of nagios checks
Easy to Use in a Cloud Environment
As nodes are the same. Existing worker node can be replicated with no special config to start it
Adding node lets expand cluster on demand
Efficient Integration with Nagios
Using NEB loaded modules achieves low-level integration with nagios, much better than NCSA and command queue

Disadvantages of DNX and Mod-Gearman
Single Instance of Nagios Server
The solution has no direct disadvantages however it only achieves horizontal scaling of nagios checks.
This still relies on a single central nagios server to processes the results, send alerts and schedule new checks.
Does not achieve fault-tolerance
If central nagios server dies entire system is out
Author of this presentation does have a patch to DNX that allows results to be multicast to multiple instances of a nagios servers (second one of them would be stand-by and not scheduling checks only receiving results). This is experimental.

DNX Architecture
DNX Server and DNX Client (Worker) Daemons are multi-threaded. Client thread model is controlled by these commands:
Communication between Server and Client using own UDP protocol passing XML packets .
Almost all communication is from client to server. Client contacts DNX server dispatcher port, receives list of checks to run, runs them and returns results on collector port
DNX Client can support having common checks built into client. check_nrpe was included before, but was pulled out of a package as it required nagios source.
#poolInitial = 20 #poolMin = 20 #poolMax = 100 #poolGrow = 10 channelDispatcher = udp://10.1.1.1:12480 channelCollector = udp://10.1.1.1:12481

DNX System Internals DNX Server System Internals DNX Client (Worker Node) System Internals

Mod-Gearman MOD-Gearman System Nagios Checks and Mod-Gearman Queues

DNX vs Mod-Gearman
Single package, no external dependencies. Includes all job cluster control components
Hard to maintain and test for non-Linux environment
Can use localCheckPattern in server configuration to direct jobs. But it is not documented
Supports nagios-2.x with a patch and nagios-3.x as is
Client can be extended with nagios- specific features. Planned are: - Embedded Perl, check_icmp, - check_snmp, check_nrpe
Mod-Gearman is built around Gearman Project
Better maintained since Gearman has many uses
Enjoys benefits of wider testing on new releases
Easy to configure and direct to separate queues depending on hostgroup & servicegroup
Only supports nagios 3.x
Supports eventhandlers and not just checks !
Nagios-only features are hard to add at node level
DNX Mod-Gearman

Combining Shared Database and Worker Nodes
Nagios cluster options can be combined ! DNX or Mod-Gearman with Merlin or ADO are great fit : - DNX offers horizontal scaling for all checks and relieaves Nagios of need to run them - Merlin provides horizontal scaling and failover for Nagios itself for infrastructure of thousands of hosts

Ideal Fully Fault-Tolerant Nagios Cluster Architecture Replication udpecho cross-monitor Ideally you would have each of the above as a separate cloud server, but even those with 1000s of servers may find this hard to maintain udp udp heartbeat Nagios Server Merlin/ADO DB Merlin/ADO DB Backup DB Proxy Nagios Web Interface Server Backup Nagios Web Interface Server Standby DB Proxy Worker Node Worker Node Worker Node Worker Node Backup Nagios Server Performance Data (RRD) Server (like NagiosGrapher) Backup Performance Data (RRD) Server

Nagios Cloud Cluster with 4 hosts N P C D N P C D MAIN NAGIOS SERVER STANDBY NAGIOS SERVER
Standby Server has all checks disabled (except checking main nagios host)
Cross-monitor of other nagios does not use DNX cluster
If main server dies, backup takes over and registers itself in dynDNS server replacing primary.
DNX Clients use dynDNS address, they are restarted on server switch
replication cross-monitor Nagios Daemon Apache Mysql DB Merlin PNP w/ RRD DNX Server DNX Client DNX Client Nagios Daemon Apache Mysql DB Merlin PNP w/ RRD DNX Server

Configuration of a cloud host
The best way to configure monitoring of cloud hosts with multiple instances is to have a template and define all services by hostgroups Then starting new host of same type is just a matter of adding config like above but for w2, etc One of the alternatives is to add a few extra hosts to nagios config and disable all service checks on those hosts, enabling them using script when server is launched
define host { use wprod-server <--- Template for all Webservers host_name w1 alias webserv1 <---- This is second way to search address w1.dynamic.cloud1.mydomain <---- Local DNS hostgroups production,loadbalanced,linux_centos5,webserv parents loadbalancer1,loadbalancer2 contact_groups admins }

Auto-Scaling
Event handlers can be used or custom check.
Trigger based on total number of open http sockets (check_netstat, check_apache_status) from all servers
Write custom script that keeps number of currently active servers in DB or local file to set name of new server.
Have new server name as a parameter for launching cloud instance. Write startup scripts that use this to set hostname and register ip in local dynamic dns server.
For Amazon EC2, aws utility is very useful to automate launching of new servers. Get it at http://timkay.com/aws/
Extra nagios worker node is launched similarly and this is triggered when enough servers have been launched. Can also do it based on nagios stats (check_nagios)
Scale down after an hour or more of low resource usage, you can do it with a check that relies on RRD data

Use of SQL DB for Auto-Scaling This is for illustration of logic only. Not real code. CREATE TABLE ServerData ( id bigint(10) unsigned NOT NULL, name varchar(50) unsigned default NULL, connections bigint(20) unsigned default 0, started_on date default NULL, PRIMARY KEY(id)); After you got results of server check (like event handler that runs): UPDATE ServerData SET connections=<data from nagios check> WHERE name=<server host> Custom check to see if new server should be started: $count=sqlexec("SELECT COUNT(id) FROM ServerData") $sumit=sqlexec("SELECT SUM(Connections) FROM ServerData") $lastlaunched=sqlexec("SELECT MAX(started_on) FROM ServerData") if $sumit/$count > $threshold && ($now-$lastlatched)<600 { <figure out the name and id> launch_new_server_instance($newname) sqlexec(”INSERT INTO ServerData VALUES ($newid, $newname,0,CURDATE())”) enable_nagios_service_checks($newname) }

Additional Cloud Monitoring Tips
Cloud Servers are not entirely independent, and other servers on same hardware server may effect yours
For Virtualized OS System load checks are less useful and can show ”false” spikes in load. Put larger emphasis on 15-minute load and do more checks before alerts are sent
But if you control the cloud, find way to get cloud hardware system load. Write check showing physical server name
For load issues rely more on a number of connections (TCP session) and time to process each request. Do prior tests on how many connections one server should handle
Remember, you can always just launch a new server
Do not spend too much time investigating cause, take it out of production first, replace, and investigate later

Nagios Cluster Software
Nagios, NDO-Utils, NCSA – http://www.nagios.org/
DNX (Distributed Nagios eXecutor) -
http://dnx.sourceforge.net/
Mod-Gearman - http://labs.consol.de/lang/de/nagios/mod-gearman/
Gearman - http://gearman.org/
Merlin (Module for Effortless Redundancy and Loadbalancing by OP5) – http://www.op5.org/community/plugin-inventory/op5-projects/merlin
Check-Multisite (collect data from multiple servers) – http://www.my-plugin.de/check_multi/
Ganglia (open-source computing cluster monitoring, can be integrated with nagios) – http://www.ganglia.info

Demo & Questions
Questions ?

More Questions? Feedback? William Leibzon < [email_address] > My Nagios Page (mostly plugins) :
http://william.leibzon.org/nagios/

Nagios Conference 2011 - William Leibzon - Nagios In Cloud Computing Environments

by Nagios on Oct 03, 2011

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Nagios Conference 2011 - William Leibzon - Nagios In Cloud Computing Environments Presentation Transcript