Apache: The Simplest Load Balancing Cluster with Failover

Virtual IP address in a farm cluster

On the previous figure, the Apache application is running on the 3 servers (3 is an example, it can be 2 or more). Users are connected to a virtual IP address.

The virtual IP address is configured locally on each server in the farm cluster.

The input traffic to the virtual IP address is received by all the servers and split among them by a network filter inside each server's kernel.

SafeKit detects hardware and software failures, reconfigures network filters in the event of a failure, and offers configurable application checkers and recovery scripts.

Load balancing in a network filter

The network load balancing algorithm inside the network filter is based on the identity of the client packets (client IP address, client TCP port). Depending on the identity of the client packet input, only one filter in a server accepts the packet; the other filters in other servers reject it.

Once a packet is accepted by the filter on a server, only the CPU and memory of this server are used by the Apache application that responds to the request of the client. The output messages are sent directly from the application server to the client.

If a server fails, the SafeKit membership protocol reconfigures the filters in the network load balancing cluster to re-balance the traffic on the remaining available servers.

Stateful or stateless applications

With a stateful Apache application, there is session affinity. The same client must be connected to the same server on multiple TCP sessions to retrieve its context on the server. In this case, the SafeKit load balancing rule is configured on the client IP address. Thus, the same client is always connected to the same server on multiple TCP sessions. And different clients are distributed across different servers in the farm.

With a stateless Apache application, there is no session affinity. The same client can be connected to different servers in the farm on multiple TCP sessions. There is no context stored locally on a server from one session to another. In this case, the SafeKit load balancing rule is configured on the TCP client session identity. This configuration is the one which is the best for distributing sessions between servers, but it requires a TCP service without session affinity.

SafeKit quick installation guide with Apache

Package installation on Windows

Download the free version of SafeKit on 2 Windows nodes (or more).

Note: the free version includes all SafeKit features. At the end of the trial, you can activate permanent license keys without uninstalling the package.
To open the Windows firewall, on both nodes start a powershell as administrator, and type
```
c:/safekit/private/bin/firewallcfg add
```
To initialize the password for the default admin user of the web console, on both nodes start a powershell as administrator, and type
```
c:/safekit/private/bin/webservercfg.ps1 -passwd pwd
```
pwd must be the same on both nodes
For synchronizing SafeKit at boot and at shutdown, on both nodes start a powershell as administrator, and type only once
```
c:/safekit/private/bin/addStartupShutdown
```

Package installation on Linux

Install the free version of SafeKit on 2 Linux nodes (or more).

Note: the free trial includes all SafeKit features. At the end of the trial, you can activate permanent license keys without uninstalling the package.
After the download of safekit_xx.bin package, execute it to extract the rpm and the safekitinstall script and then execute the safekitinstall script
Answer yes to firewall automatic configuration
Set the password for the web console and the default user admin. Set the same password on both nodes

Step by step configuration

4. Configure the module

Choose an automatic start of the module at boot without delay.
Enter a virtual IP address. A virtual IP address is a standard IP address in the same IP network (same subnet) as the IP addresses of both nodes.
Application clients must be configured with the virtual IP address (or the DNS name associated with the virtual IP address).
Set the service port to load balance (ex.: TCP 80 for HTTP, TCP 443 for HTTPS...).
Set the load balancing rule (source address or source port in the client IP packet):
- with the source IP address of the client, the same client will be connected to the same node in the farm on multiple TCP sessions and retrieve its context on the node.
- with the source TCP port of the client, the same client will be connected to different nodes in the farm on multiple TCP sessions (without retrieving a context).
start_both and stop_both contain the start and the stop of Apache services. Check that the names of services in these scripts are those installed on both nodes else modify them in the scripts.

Note that if a process name is displayed in Process Checker, it will be monitored with a restart action in case of failure. Configuring a wrong process name will cause the module to stop right after its start.

This operation will report the configuration in the userconfig.xml, start_both, stop_both files on both nodes (more information in the training with the command line).

8. Testing

SafeKit brings a built-in test in the product:

Configure a rule for TCP port 9010 with a load balancing on source TCP port.
Connect an external workstation outside the farm nodes.
Start a browser on http://virtual-ip:9010/safekit/mosaic.html.

You should see a mosaic of colors depending on nodes answering to HTTP requests.

Stop one UP (green) node by scrolling down its contextual menu and clicking Stop.
Check that there is no more TCP connections on the stopped node and on the virtual IP address.

More information on tests in the User's Guide.

Learn more

Internals

Internal files of a SafeKit / Apache load balancing cluster with failover

Go to the Advanced Configuration tab in the console, for editing these files

Internal files of the Windows apache_farm.safe module

userconfig.xml on Windows (description in the User's Guide)

<!DOCTYPE safe>
<safe>
<macro name="VIRTUAL_IP" value="VIRTUAL_IP_TO_BE_DEFINED" />
<macro name="APACHE_PORT" value="TCP_PORT_TO_BE_DEFINED" />
<service mode="farm" maxloop="3" loop_interval="24">
  <!-- Farm topology configuration for the membership protocol -->
  <!-- Names or IP addresses on the default network are set during initialization in the console -->
  <farm>
    <lan name="default" />
  </farm>
  <!-- Virtual IP Configuration -->
  <!-- Use VIRTUAL_IP defined in macro above -->
  <vip>
    <interface_list>
      <interface check="on" arpreroute="on">
        <virtual_interface type="vmac_directed">
          <virtual_addr addr="%VIRTUAL_IP%" where="alias"/>
        </virtual_interface>
      </interface>
    </interface_list>
    <loadbalancing_list>
      <group name="APACHE">
        <!-- Set load-balancing rule on APACHE_PORT defined in macro above -->
        <rule port="%APACHE_PORT%" proto="tcp" filter="on_addr"/>
      </group>
    </loadbalancing_list>
  </vip>
  <!-- TCP Checker Configuration -->
  <!-- Use VIRTUAL_IP and APACHE_PORT defined in macros above -->
  <check>
    <tcp ident="HTTP_APACHE" when="both">
      <to
         addr="%VIRTUAL_IP%"
         port="%APACHE_PORT%"
         interval="10"
         timeout="5"
       />
    </tcp>
  </check>
  <!-- User scripts activation -->
  <user nicestoptimeout="300" forcestoptimeout="300" logging="userlog" />
</service>
</safe>

start_both.cmd on Windows

@echo off

rem Script called on all servers for starting applications

rem For logging into SafeKit log use:
rem "%SAFE%\safekit" printi | printe "message"

rem stdout goes into Application log
echo "Running start_both %*" 

set res=0

net start Apache2
if not %errorlevel% == 0 (
  %SAFE%\safekit printi "Apache start failed"
) else (
  %SAFE%\safekit printi "Apache started"
)

set res=%errorlevel%
if %res% == 0 goto end

:stop
set res=%errorlevel%
"%SAFE%\safekit" printe "start_both failed"

rem uncomment to stop SafeKit when critical
rem "%SAFE%\safekit" stop -i "start_both"

:end

stop_both.cmd on Windows

@echo off

rem Script called on all servers for stopping application

rem For logging into SafeKit log use:
rem "%SAFE%\safekit" printi | printe "message"

rem ----------------------------------------------------------
rem
rem 2 stop modes:
rem
rem - graceful stop
rem   call standard application stop with net stop
rem
rem - force stop (%1=force)
rem   kill application's processes
rem
rem ----------------------------------------------------------

rem stdout goes into Application log
echo "Running stop_both %*" 

set res=0

rem default: no action on forcestop
if "%1" == "force" goto end

%SAFE%\safekit printi "Stopping Apache..."
net stop Apache2

rem If necessary, uncomment to wait for the real stop of services
rem "%SAFEBIN%\sleep" 10

if %res% == 0 goto end

"%SAFE%\safekit" printe "stop_both failed"

:end

Internal files of the Linux apache_farm.safe module

userconfig.xml on Linux (description in the User's Guide)

<!DOCTYPE safe>
<safe>
<macro name="VIRTUAL_IP" value="VIRTUAL_IP_TO_BE_DEFINED" />
<macro name="APACHE_PORT" value="TCP_PORT_TO_BE_DEFINED" />
<service mode="farm" maxloop="3" loop_interval="24">
  <!-- Farm topology configuration for the membership protocol -->
  <!-- Names or IP addresses on the default network are set during initialization in the console -->
  <farm>
    <lan name="default" />
  </farm>
  <!-- Virtual IP Configuration -->
  <!-- Use VIRTUAL_IP defined in macro above -->
  <vip>
    <interface_list>
      <interface check="on" arpreroute="on">
        <virtual_interface type="vmac_directed">
          <virtual_addr addr="%VIRTUAL_IP%" where="alias"/>
        </virtual_interface>
      </interface>
    </interface_list>
    <loadbalancing_list>
      <group name="APACHE">
        <!-- Set load-balancing rule on APACHE_PORT defined in macro above -->
        <rule port="%APACHE_PORT%" proto="tcp" filter="on_addr"/>
      </group>
    </loadbalancing_list>
  </vip>
  <!-- TCP Checker Configuration -->
  <!-- Use VIRTUAL_IP and APACHE_PORT defined in macros above -->
  <check>
    <tcp ident="HTTP_APACHE" when="both">
      <to
         addr="%VIRTUAL_IP%"
         port="%APACHE_PORT%"
         interval="10"
         timeout="5"
       />
    </tcp>
  </check>
  <!-- User scripts activation -->
  <user nicestoptimeout="300" forcestoptimeout="300" logging="userlog" />
</service>
</safe>

start_both on Linux

#!/bin/sh 
# Script called on the primary server for starting applications 

# For logging into SafeKit log use:
# $SAFE/safekit printi | printe "message" 

#---------- Clean Apache residual processes 
# Call this function before starting Apache 
# to clean eventual resual Apache processes
clean_Apache()
{
  retval=0

  # $SAFE/safekit printw "Cleaning Apache processes"

  # example of a kill of started Apache process
  # warning: this command also kills the httpd process which managed the SafeKit web console
  # ps -e -o pid,comm | grep httpd | $AWK '{print "kill " $1}'| sh >/dev/null 2>&1

  return $retval
}

#---------- Apache
# Call this function for starting Apache Server
start_Apache()
{
  retval=0

  $SAFE/safekit printw "Starting Apache Server"

  # Apache - Starting 
  service httpd start   
  if [ $? -ne 0 ] ; then 
    $SAFE/safekit printw "Apache server start failed"
  else
    $SAFE/safekit printw "Apache server started"
  fi

  return $retval
}

# stdout goes into Application log
echo "Running start_both $*" 

res=0

[ -z "$OSNAME" ] && OSNAME=`uname -s`
OSNAME=`uname -s`
case "$OSNAME" in
    Linux)
	AWK=/bin/awk
	;;
    *)
	AWK=/usr/bin/awk
	;;
esac

# TODO
# remove Apache boot start 

# Clean Apache residual processes 
clean_Apache || res=$?

# Start Apache
start_Apache || res=$?

if [ $res -ne 0 ] ; then
  $SAFE/safekit printi "start_both failed"

  # uncomment to stop SafeKit when critical
  # $SAFE/safekit stop -i "start_both"
fi

exit 0

stop_both on Linux

#!/bin/sh
# Script called on the primary server for stopping application services

# For logging into SafeKit log use:
# $SAFE/safekit printi | printe "message" 

#----------------------------------------------------------
#
# 2 stop modes:
#
# - graceful stop
#   call standard application stop
#
# - force stop ($1=force)
#   kill application's processes
#
#----------------------------------------------------------

#---------- Clean Apache residual processes
# Call this function on force stop 
# to clean eventual resual Apache processes 
clean_Apache()
{
  retval=0

  # $SAFE/safekit printw "Cleaning Apache processes "

  # example of a kill of started Apache process
  # warning: this command also kills the httpd process which managed the SafeKit web console
  # ps -e -o pid,comm | grep httpd | $AWK '{print "kill " $1}'| sh >/dev/null 2>&1

  return $retval
}

#---------- Apache
# Call this function for stopping Apache
stop_Apache()
{
  retval=0

  if [ "$1" = "force" ] ; then
    # Apache force stop
    clean_Apache
    return $retval
  fi

  # Apache graceful stop
  $SAFE/safekit printw "Stopping Apache server"  
  service httpd stop
  if [ $? -ne 0 ] ; then 
    $SAFE/safekit printw "Apache server stop failed"
  else
    $SAFE/safekit printw "Apache server stopped"  
  fi

  return $retval
}

# stdout goes into Application log
echo "Running stop_both $*" 

res=0

[ -z "$OSNAME" ] && OSNAME=`uname -s`
case "$OSNAME" in
    Linux)
	AWK=/bin/awk
	;;
    *)
	AWK=/usr/bin/awk
	;;
esac

mode=
if [ "$1" = "force" ] ; then
  mode=force
  shift
fi

# Stop Apache  server 
stop_Apache $mode || res=$?

[ $res -ne 0 ] && $SAFE/safekit printi "stop_both failed"

exit 0

Redundancy at the application level

In this type of solution, only application data are replicated. And only the application is restared in case of failure.

With this solution, restart scripts must be written to restart the application.

We deliver application modules to implement redundancy at the application level. They are preconfigured for well known applications and databases. You can customize them with your own services, data to replicate, application checkers. And you can combine application modules to build advanced multi-level architectures.

This solution is platform agnostic and works with applications inside physical machines, virtual machines, in the Cloud. Any hypervisor is supported (VMware, Hyper-V...).

Solution for a new application (restart scripts to write): Windows, Linux

Redundancy at the virtual machine level

In this type of solution, the full Virtual Machine (VM) is replicated (Application + OS). And the full VM is restarted in case of failure.

The advantage is that there is no restart scripts to write per application and no virtual IP address to define. If you do not know how the application works, this is the best solution.

This solution works with Windows/Hyper-V and Linux/KVM but not with VMware. This is an active/active solution with several virtual machines replicated and restarted between two nodes.

Solution for a new application (no restart script to write): Windows/Hyper-V, Linux/KVM

Network load balancing and failover
Windows farm	Linux farm
Generic Windows farm >	Generic Linux farm >
Microsoft IIS >	-
NGINX >
Apache >
Amazon AWS farm >
Microsoft Azure farm >
Google GCP farm >
Other cloud >

Advanced clustering architectures

Several modules can be deployed on the same cluster. Thus, advanced clustering architectures can be implemented:

the farm+mirror cluster built by deploying a farm module and a mirror module on the same cluster,
the active/active cluster with replication built by deploying several mirror modules on 2 servers,
the Hyper-V cluster or KVM cluster with real-time replication and failover of full virtual machines between 2 active hypervisors,
the N-1 cluster built by deploying N mirror modules on N+1 servers.

Best high availability use cases with SafeKit

Best use cases [+]

OEM Software	Distributed Enterprise	Remote Sites

A software publisher uses SafeKit as an OEM software for high availability of its application	A distributed enterprise deploys SafeKit in many branches without specific IT skills	SafeKit is deployed in two remote sites without the need for replicated bays of disks through a SAN

Testimonials

The ideal product for a software publisher
“SafeKit is the ideal application clustering solution for a software publisher. We currently have deployed more than 80 SafeKit clusters worldwide with our critical TV broadcasting application.”
The product very easy to deploy for a reseller
“Noemis, a value added distributor of Milestone Video Surveillance, has assisted integrators to deploy the SafeKit redundancy solution on many projects such as city surveillance, datacenters, stadiums and other critical infrastructures. SafeKit is a great product, and Evidian provides a great support.”
The product to gain time for a system integrator
“Thanks to a simple and powerful product, we gained time in the integration and validation of our critical projects like the supervision of Paris metro lines (the control rooms).”

Video management, access control, building management [+]
Life safety is directly associated with the proper execution of security software. That’s why, they need redundancy and high availability. SafeKit is recognized as the simplest redundancy solution by our partners which has deployed it in:
Testimonial of Sebastien Temoin, Technical and Innovation Director, NOEMIS:

“SafeKit by Evidian is a professional solution making easy the redundancy of Milestone video management software. The solution is easy to deploy, easy to maintain and can be added on existing installation. We have assisted integrators to deploy the solution on many projects such as city surveillance, datacenters, stadiums and other critical infrastructures. SafeKit is a great product, and Evidian provides great support.”
TV broadcasting [+]

Harmonic is using SafeKit as a software OEM high availability solution and deploys it with its TV broadcasting solutions over satellites, terrestrials, cable, IPTV.

Over 80 SafeKit clusters are deployed on Windows for replication of Harmonic database and automatic failover of the critical application.

Philippe Vidal, Product Manager, Harmonic says:

“SafeKit is the ideal application clustering solution for a software publisher looking for a simple and economical high availability software. We are deploying SafeKit worldwide and we currently have more than 80 SafeKit clusters on Windows with our critical TV broadcasting application through terrestrial, satellite, cable and IP-TV. SafeKit implements the continuous and real-time replication of our database as well as the automatic failover of our application for software and hardware failures. Without modifying our application, it was possible for us to customize the installation of SafeKit. Since then, the time of preparation and implementation has been significantly reduced.”
Finance [+]

The European Society of Warranties and Guarantees in Natixis uses SafeKit as a high availability solution for its applications.

Over 30 SafeKit clusters are deployed on Unix and Windows in Natixis.
Industry [+]

Fives Syleps implements high availability of its ERP with SafeKit and deploys the solution in the food industry.

Over 20 SafeKit clusters are deployed on Linux and Windows with Oracle.

Testimonial of Fives Syleps:

“The automated factories that we equip rely on our ERP. It is not possible that our ERP is out of service due to a computer failure. Otherwise, the whole activity of the factory stops.

We chose the Evidian SafeKit high availability product because it is an easy to use solution. It is implemented on standard servers and does not require the use of shared disks on a SAN and load balancing network boxes.

It allows servers to be put in remote computer rooms. In addition, the solution is homogeneous for Linux and Windows platforms. And it provides 3 functionalities: load balancing between servers, automatic failover and real-time data replication.”

Air traffic control [+]

Air traffic control systems supplier, Copperchase, deploys SafeKit high availability in airports.

Over 20 SafeKit clusters are deployed on Windows.

Tony Myers, Director of Business Development says:

“By developing applications for air traffic control, Copperchase is in one of the most critical business activities. We absolutely need our applications to be available all the time. We have found with SafeKit a simple and complete clustering solution for our needs. This software combines in a single product load balancing, real time data replication with no data loss and automatic failover. This is why, Copperchase deploys SafeKit for air traffic control in airports in the UK and the 30 countries where we are present.”
Bank [+]

Software vendor Wellington IT deploys SafeKit high availability with its banking application for Credit Unions in Ireland and UK.

Over 25 SafeKit clusters are deployed on Linux with Oracle.

Peter Knight, Sales Manager says:

“Business continuity and disaster recovery are a major concern for our Locus banking application deployed in numerous Credit Unions around Ireland and the UK. We have found with SafeKit a simple and robust solution for high availability and synchronous replication between two servers with no data loss. With this software solution, we are not dependent on a specific and costly hardware clustering solution. It is a perfect tool to provide a software high availability option to an application of a software vendor.”
Transport [+]

Paris transport company (RATP) chose the SafeKit high availability and load balancing solution for the centralized control room of line 1 of the Paris subway.

20 SafeKit clusters are deployed on Windows and Linux.

Stéphane Guilmin, RATP, Project manager says:

“Automation of line 1 of the Paris subway is a major project for RATP, requiring a centralized command room (CCR) designed to resist IT failures. With SafeKit, we have three distinct advantages to meet this need. Firstly, SafeKit is a purely software solution that does not demand the use of shared disks on a SAN and network boxes for load balancing. It is very simple to separate our servers into separate machine rooms. Moreover, this clustering solution is homogeneous for our Windows and Linuxplatforms. SafeKit provides the three functions that we needed: load balancing between servers, automatic failover after an incident and real time data replication.”

And also, Philippe Marsol, Atos BU Transport, Integration Manager says:

“SafeKit is a simple and powerful product for application high availability. We have integrated SafeKit in our critical projects like the supervision of Paris metro Line 4 (the control room) or Marseille Line 1 and Line 2 (the operations center). Thanks to the simplicity of the product, we gained time for the integration and validation of the solution and we had also quick answers to our questions with a responsive Evidian team.”
Healthcare [+]

The software integrator Systel deploys SafeKit high-availability solution in firefighter and emergency medical call centers.

Over 30 SafeKit clusters are deployed on Windows with SQL Server.

Marc Pellas, CEO says:

“SafeKit perfectly meets the needs of a software vendor. Its main advantage is that it brings in high availability through a software option that is added to our own multi-platform software suite. This way, we are not dependent on a specific and costly hardware clustering solution that is not only difficult to install and maintain, but also differs according to client environments. With SafeKit, our firefighter call centers are run with an integrated software clustering solution, which is the same for all our customers, is user friendly and for which we master the installation up to after-sales support.”
Government [+]

ERP high availability and load balancing of the French army (DGA) are made with SafeKit.

14 SafeKit clusters are deployed on Windows and Linux.

Alexandre Barth, Systems administrator says:

“Our production team implemented the SafeKit solution without any difficulty on 14 Windows and Linux clusters. Our critical activity is thus secure, with high-availability and load balancing functions. The advantages of this product are easy deployment and administration of clusters, on the one hand, and uniformity of the solution in the face of heterogeneous operating systems, on the other hand.”

Key differentiators of a mirror cluster with replication and failover

Evidian SafeKit mirror cluster with real-time file replication and failover
3 products in 1 More info >	The SafeKit high availability software saves on Windows and Linux the cost of : external shared or replicated storage, load balancing boxes, enterprise editions of OS and databases SafeKit includes all clustering features: synchronous real-time file replication, monitoring of server / network / software failures, automatic application restart, virtual IP address switched in case of failure to reroute clients
Very simple configuration More info >	The cluster configuration is very simple and made by means of application modules. New services and new replicated directories can be added to an existing application module to complete a high availability solution All the configuration of clusters is made using a simple centralized web administration console There is no domain controller or active directory to configure as with Microsoft cluster
Synchronous replication More info >	The real-time replication is synchronous with no data loss on failure This is not the case with asynchronous replication
Fully automated failback More info >	After a failure when a server reboots, the replication failback procedure is fully automatic and the failed server reintegrates the cluster without stopping the application on the only remaining server This is not the case with most replication solutions particularly with replication at the database level. Manual operations are required for resynchronizing a failed server. The application may even be stopped on the only remaining server during the resynchonization of the failed server
Replication of any type of data More info >	The replication is working for databases but also for any files which shall be replicated This not the case for replication at the database level
File replication vs disk replication More info >	The replication is based on file directories that can be located anywhere (even in the system disk) This is not the case with disk replication where special application configuration must be made to put the application data in a special disk
File replication vs shared disk More info >	The servers can be put in two remote sites This is not the case with shared disk solutions
Remote sites and virtual IP address More info >	All SafeKit clustering features are working for 2 servers in remote sites. Replication requires an extended LAN type network (latency = performance of synchronous replication, bandwidth = performance of resynchronization after failure). If both servers are connected to the same IP network through an extended LAN between two remote sites, the virtual IP address of SafeKit is working with rerouting at level 2 If both servers are connected to two different IP networks between two remote sites, the virtual IP address can be configured at the level of a load balancer with the "healh check" of SafeKit.
Quorum and split brain More info >	The solution works with only 2 servers and for the quorum (network isolation between both sites), a simple split brain checker to a router is offered to support a single execution of the critical application This is not the case for most clustering solutions where a 3^rd server is required for the quorum
Active/active cluster More info >	The secondary server is not dedicated to the restart of the primary server. The cluster can be active-active by running 2 different mirror modules This is not the case with a fault-tolerant system where the secondary is dedicated to the execution of the same application synchronized at the instruction level
Uniform high availability solution More info >	SafeKit implements a mirror cluster with replication and failover. But it imlements also a farm cluster with load balancing and failover. Thus a N-tiers architecture can be made highly available and load balanced with the same solution on Windows and Linux (same installation, configuration, administration with the SafeKit console or with the command line interface). This is unique on the market This is not the case with an architecture mixing different technologies for load balancing, replication and failover
RTO / RPO More info >	SafeKit implements quick application restart in case of failure: around 1 mn or less Quick application restart is not ensured with full virtual machines replication. In case of hypervisor failure, a full VM must be rebooted on a new hypervisor with a recovery time depending on the OS reboot as with VMware HA or Hyper-V cluster

Key differentiators of a farm cluster with load balancing and failover

Evidian SafeKit farm cluster with load balancing and failover
No load balancer or dedicated proxy servers or special multicast Ethernet address More info >	The solution does not require load balancers or dedicated proxy servers above the farm for imlementing load balancing. SafeKit is installed directly on the application servers in the farm. The load balancing is based on a standard virtual IP address/Ethernet MAC address and is working with physical servers or virtual machines on Windows and Linux without special network configuration This is not the case with network load balancers This is not the case with dedicated proxies on Linux This is not the case with a specific multicast Ethernet address on Windows
All clustering features More info >	The solution includes all clustering features: virtual IP address, load balancing on client IP address or on sessions, monitoring of server / network / software failures, automatic application restart with a quick revovery time and a replication option with a mirror module This is not the case with other load balancing solutions. They are able to make load balancing but they do not include a full clustering solution with restart scripts and automatic application restart in case of failure. They do not offer a replication option The cluster configuration is very simple and made by means of application modules. There is no domain controller or active directory to configure on Windows. The solution works on Windows and Linux
Remote sites and virtual IP address More info >	If servers are connected to the same IP network through an extended LAN between remote sites, the virtual IP address of SafeKit is working with load balancing at level 2 If servers are connected to different IP networks between remote sites, the virtual IP address can be configured at the level of a load balancer with the help of the SafeKit health check. Thus you can implement load balancing but also all the clustering features of SafeKit, in particular monitoring and automatic recovery of the critical application on application servers
Uniform high availability solution More info >	SafeKit imlements a farm cluster with load balancing and failover. But it implements also a mirror cluster with replication and failover. Thus a N-tiers architecture can be made highly available and load balanced with the same solution on Windows and Linux (same installation, configuration, administration with the SafeKit console or with the command line interface). This is unique on the market This is not the case with an architecture mixing different technologies for load balancing, replication and failover

Key differentiators of the SafeKit high availability technology

Software clustering vs hardware clustering More info >
A simple software cluster with the SafeKit package just installed on two servers	Complex hardware clustering with external storage or network load balancers
Shared nothing vs a shared disk cluster More info >
SafeKit is a shared-nothing cluster: easy to deploy even in remote sites	A shared disk cluster is complex to deploy
Application High Availability vs Full Virtual Machine High Availability More info >
Application HA supports hardware failure and software failure with a quick recovery time (RTO around 1 mn or less). Application HA requires to define restart scripts per application and folders to replicate (SafeKit application modules).	Full virtual machines HA supports only hardware failure with a VM reboot and a recovery time depending on the OS reboot. No restart scripts to define with full virtual machines HA (SafeKit hyperv.safe or kvm.safe modules). Hypervisors are active/active with just multiple virtual machines.
High availability vs fault tolerance More info >
No dedicated server with SafeKit. Each server can be the failover server of the other one. Software failure with restart in another OS environment. Smooth upgrade of application and OS possible server by server (version N and N+1 can coexist)	Secondary server dedicated to the execution of the same application synchronized at the instruction level. Software exception on both servers at the same time. Smooth upgrade not possible
Synchronous replication vs asynchronous replication More info >
SafeKit implements real-time synchronous replication with no data loss in case of failure	With asynchronous replication, there is data loss on failure
Byte-level file replication vs block-level disk replication More info >
SafeKit implements real-time byte-level file replication and is simply configured with application directories to replicate even in the system disk	Block-level disk replication is complex to configure and requires to put application data in a special disk
Heartbeat, failover and quorum to avoid 2 master nodes More info >
To avoid 2 masters, SafeKit proposes a simple split brain checker configured on a router	To avoid 2 masters, other clusters require a complex configuration with a third machine, a special quorum disk, a special interconnect
Virtual IP address primary/secondary, network load balancing, failover More info >
No dedicated proxy servers and no special network configuration are required in a SafeKit cluster for virtual IP addresses	Special network configuration is required in other clusters for virtual IP addresses. Note that SafeKit offers a health check adapted to load balancers

Real-time file replication and failover
Windows mirror	Linux mirror
Generic Windows mirror >	Generic Linux mirror >
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PostgreSQL >
Firebird >
Windows Hyper-V >	-
-	Linux KVM >
-	Docker >
-	Kubernetes >
-	Elasticsearch >
Milestone XProtect >	-
Genetec SQL Server >	-
Hanwha Wisenet Wave > Hanwha Wisenet SSM >	-
Nedap AEOS >	-
Siemens SIMATIC WinCC > Siemens SIMATIC PCS 7 > Siemens Siveillance > Siemens Desigo CC > Siemens SiPass > Siemens SIPORT >	-
Bosch AMS > Bosch BIS > Bosch BVMS >	-
Amazon AWS mirror >
Microsoft Azure mirror >
Google GCP mirror >
Other cloud >

Apache: The Simplest Load Balancing Cluster with Failover

Evidian SafeKit

How the Evidian SafeKit software simply implements Apache load balancing and failover?

The solution for Apache

A generic product

A complete solution

Partners, the success with SafeKit

Building Management Software (BMS)

Video Management Software (VMS)

Electronic Access Control Software (EACS)

SCADA Software (Industry)

How the SafeKit farm cluster works with Apache?

Virtual IP address in a farm cluster

Load balancing in a network filter

Stateful or stateless applications

SafeKit free trial + farm module for Apache + quick installation guide

Prerequisites

Package installation on Windows

Module installation on Windows

Package installation on Linux

Module installation on Linux

1. Launch the SafeKit console

2. Configure node addresses

3. Choose the module

4. Configure the module

5. Verify successful configuration

6. Start the farm cluster on node 1 and node 2

7. Wait for the transition to UP (green) / UP (green)

8. Testing

Module log

Application log

Advanced configuration

Support

Internal files of a SafeKit / Apache load balancing cluster with failover

Internal files of the Windows apache_farm.safe module

Internal files of the Linux apache_farm.safe module

How the SafeKit mirror cluster works?

Step 1. Real-time replication

Step 2. Automatic failover

Step 3. Automatic failback

Step 4. Back to normal

Choose between redundancy at the application level or at the virtual machine level

Redundancy at the application level

Redundancy at the virtual machine level

Typical usage with SafeKit

Why a replication of a few Tera-bytes?

Why a replication < 1,000,000 files?

Why a failover < 25 replicated VMs?

Why a LAN/VLAN network between remote sites?

SafeKit Modules for Plug&Play Redundancy and High Availability Solutions

Network load balancing and failover

Advanced clustering architectures

Real-time file replication and failover

Demonstrations of Redundancy and High Availability Solutions

SafeKit Webinar

Microsoft SQL Server Cluster

Apache Cluster

Hyper-V Cluster

SafeKit Customers in all Business Activities

Best use cases [+]

Testimonials

Video management, access control, building management [+]

TV broadcasting [+]

Finance [+]

Industry [+]

Air traffic control [+]

Bank [+]

Transport [+]

Healthcare [+]

Government [+]

SafeKit High Availability Differentiators against Competition

Evidian SafeKit mirror cluster with real-time file replication and failover

Evidian SafeKit farm cluster with load balancing and failover

SafeKit Technical Documentation

User's Guide

Application Modules

Release Notes

Presales documentation

SafeKit Training

Introduction