DNS round robin and Apache Server

Laura

Hi all !
We have a web application that is hosted on Apache HTTP server.

Now we decided to make the application more scalable so we'll replace
the single Apache server with a farm of 3 Apache Servers.

So now I need to load-balance the client requests between the 3
Apache Servers.

Is it enough if I configure DNS round-robin so that, given a domain
name, it will distribute the load between servers ? The main problem
is that I don't know if DNS round robin is able to use session
affinity, so that calls from one IP address are routed always to the
same Apache server. (If not HTTP session state will be lost.....)

If not, can you point out other alternatives ? (Hardware load-
balancer?)
By the way, the farm of Apache Servers runs on a Windows Server Box.
Thanks a lot
Francesco

Matheesha Weerasinghe

Hello Laura,

> Hi all !
> We have a web application that is hosted on Apache HTTP server.
> Now we decided to make the application more scalable so we'll replace
> the single Apache server with a farm of 3 Apache Servers.
>
> So now I need to load-balance the client requests between the 3
> Apache Servers.
>

Is it worth investigating if Network Load Balancing (NLB) that is provided
with Windows Server as standard meets the needs? Please note I have not used
it myself but have heard it used for IIS.



HTH

M@

Matheesha Weerasinghe

Hello Laura,

> Hi all !
> We have a web application that is hosted on Apache HTTP server.
> Now we decided to make the application more scalable so we'll replace
> the single Apache server with a farm of 3 Apache Servers.
>
> So now I need to load-balance the client requests between the 3
> Apache Servers.
>

Is it worth investigating if Network Load Balancing (NLB) that is provided
with Windows Server as standard meets the needs? Please note I have not used
it myself but have heard it used for IIS.



HTH

M@

Herb Martin

"Laura" <> wrote in message
news:1181809154.589891.176360@j4g2000prf.googlegro ups.com...
> Hi all !
> We have a web application that is hosted on Apache HTTP server.
>
> Now we decided to make the application more scalable so we'll replace
> the single Apache server with a farm of 3 Apache Servers.
>
> So now I need to load-balance the client requests between the 3
> Apache Servers.
>
> Is it enough if I configure DNS round-robin so that, given a domain
> name, it will distribute the load between servers ?

In general this will give you (loose) load balancing.

> The main problem
> is that I don't know if DNS round robin is able to use session
> affinity, so that calls from one IP address are routed always to the
> same Apache server. (If not HTTP session state will be lost.....)

No, Round Robin will NOT do that but normally this you will get
something like this due to requesting DNS Server and requesting
DNS clients caching the results.

E.g., a client gets a resolution from your server (perhaps indirectly
from the client's own DNS server) and tends to keep that result
in cache at both the client and the server (for modern Windows
clients and practically all DNS servers anyway.)

> If not, can you point out other alternatives ? (Hardware load-
> balancer?)

NLB from Microsoft is built into the product (you must add/configure
it.)

NLB (Network Load Balancing) provides load balancing, explicit
affinity on either a single IP or Class-C basis, and also offers fault
tolerance.

Round Robin does NOT provide for fault tolerance.

> By the way, the farm of Apache Servers runs on a Windows Server Box.

You should also question a design that requires such affinity. Normally
all state data for such clients should be stored on a backend database
(perhaps with Server Clustering) OR on the web clients (e.g., using
cookies).


--
Herb Martin, MCSE, MVP

(phone on web site)

Herb Martin

"Laura" <> wrote in message
news:1181809154.589891.176360@j4g2000prf.googlegro ups.com...
> Hi all !
> We have a web application that is hosted on Apache HTTP server.
>
> Now we decided to make the application more scalable so we'll replace
> the single Apache server with a farm of 3 Apache Servers.
>
> So now I need to load-balance the client requests between the 3
> Apache Servers.
>
> Is it enough if I configure DNS round-robin so that, given a domain
> name, it will distribute the load between servers ?

In general this will give you (loose) load balancing.

> The main problem
> is that I don't know if DNS round robin is able to use session
> affinity, so that calls from one IP address are routed always to the
> same Apache server. (If not HTTP session state will be lost.....)

No, Round Robin will NOT do that but normally this you will get
something like this due to requesting DNS Server and requesting
DNS clients caching the results.

E.g., a client gets a resolution from your server (perhaps indirectly
from the client's own DNS server) and tends to keep that result
in cache at both the client and the server (for modern Windows
clients and practically all DNS servers anyway.)

> If not, can you point out other alternatives ? (Hardware load-
> balancer?)

NLB from Microsoft is built into the product (you must add/configure
it.)

NLB (Network Load Balancing) provides load balancing, explicit
affinity on either a single IP or Class-C basis, and also offers fault
tolerance.

Round Robin does NOT provide for fault tolerance.

> By the way, the farm of Apache Servers runs on a Windows Server Box.

You should also question a design that requires such affinity. Normally
all state data for such clients should be stored on a backend database
(perhaps with Server Clustering) OR on the web clients (e.g., using
cookies).


--
Herb Martin, MCSE, MVP

(phone on web site)

Laura

On 14 Giu, 17:11, "Herb Martin" <> wrote:
> "Laura" <> wrote in message
>
> news:1181809154.589891.176360@j4g2000prf.googlegro ups.com...
>
> > Hi all !
> > We have a web application that is hosted on Apache HTTP server.
>
> > Now we decided to make the application more scalable so we'll replace
> > the single Apache server with a farm of 3 Apache Servers.
>
> > So now I need to load-balance the client requests between the 3
> > Apache Servers.
>
> > Is it enough if I configure DNS round-robin so that, given a domain
> > name, it will distribute the load between servers ?
>
> In general this will give you (loose) load balancing.
>
> > The main problem
> > is that I don't know if DNS round robin is able to use session
> > affinity, so that calls from one IP address are routed always to the
> > same Apache server. (If not HTTP session state will be lost.....)
>
> No, Round Robin will NOT do that but normally this you will get
> something like this due to requesting DNS Server and requesting
> DNS clients caching the results.
>
> E.g., a client gets a resolution from your server (perhaps indirectly
> from the client's own DNS server) and tends to keep that result
> in cache at both the client and the server (for modern Windows
> clients and practically all DNS servers anyway.)
>
> > If not, can you point out other alternatives ? (Hardware load-
> > balancer?)
>
> NLB from Microsoft is built into the product (you must add/configure
> it.)
>
> NLB (Network Load Balancing) provides load balancing, explicit
> affinity on either a single IP or Class-C basis, and also offers fault
> tolerance.
>
> Round Robin does NOT provide for fault tolerance.
>
> > By the way, the farm of Apache Servers runs on a Windows Server Box.
>
> You should also question a design that requires such affinity. Normally
> all state data for such clients should be stored on a backend database
> (perhaps with Server Clustering) OR on the web clients (e.g., using
> cookies).
>
> --
> Herb Martin, MCSE, MVPhttp://www.LearnQuick.Com
> (phone on web site)

Thanks for your useful replies !!!!
regards
Francesco

Laura

On 14 Giu, 17:11, "Herb Martin" <> wrote:
> "Laura" <> wrote in message
>
> news:1181809154.589891.176360@j4g2000prf.googlegro ups.com...
>
> > Hi all !
> > We have a web application that is hosted on Apache HTTP server.
>
> > Now we decided to make the application more scalable so we'll replace
> > the single Apache server with a farm of 3 Apache Servers.
>
> > So now I need to load-balance the client requests between the 3
> > Apache Servers.
>
> > Is it enough if I configure DNS round-robin so that, given a domain
> > name, it will distribute the load between servers ?
>
> In general this will give you (loose) load balancing.
>
> > The main problem
> > is that I don't know if DNS round robin is able to use session
> > affinity, so that calls from one IP address are routed always to the
> > same Apache server. (If not HTTP session state will be lost.....)
>
> No, Round Robin will NOT do that but normally this you will get
> something like this due to requesting DNS Server and requesting
> DNS clients caching the results.
>
> E.g., a client gets a resolution from your server (perhaps indirectly
> from the client's own DNS server) and tends to keep that result
> in cache at both the client and the server (for modern Windows
> clients and practically all DNS servers anyway.)
>
> > If not, can you point out other alternatives ? (Hardware load-
> > balancer?)
>
> NLB from Microsoft is built into the product (you must add/configure
> it.)
>
> NLB (Network Load Balancing) provides load balancing, explicit
> affinity on either a single IP or Class-C basis, and also offers fault
> tolerance.
>
> Round Robin does NOT provide for fault tolerance.
>
> > By the way, the farm of Apache Servers runs on a Windows Server Box.
>
> You should also question a design that requires such affinity. Normally
> all state data for such clients should be stored on a backend database
> (perhaps with Server Clustering) OR on the web clients (e.g., using
> cookies).
>
> --
> Herb Martin, MCSE, MVPhttp://www.LearnQuick.Com
> (phone on web site)

Thanks for your useful replies !!!!
regards
Francesco

Herb Martin

"Laura" <> wrote in message
news:1181918682.115239.218140@w5g2000hsg.googlegro ups.com...

>> > If not, can you point out other alternatives ? (Hardware load-
>> > balancer?)
>>
>> NLB from Microsoft is built into the product (you must add/configure
>> it.)
>>
>> NLB (Network Load Balancing) provides load balancing, explicit
>> affinity on either a single IP or Class-C basis, and also offers fault
>> tolerance.
>>
>> Round Robin does NOT provide for fault tolerance.
>>
>> > By the way, the farm of Apache Servers runs on a Windows Server Box.
>>
>> You should also question a design that requires such affinity. Normally
>> all state data for such clients should be stored on a backend database
>> (perhaps with Server Clustering) OR on the web clients (e.g., using
>> cookies).
>>
>> --
>> Herb Martin, MCSE, MVPhttp://www.LearnQuick.Com
>> (phone on web site)
>
> Thanks for your useful replies !!!!


Happy to help. Pass on the help to someone else in need, and be sure to
ask if you have additional questions.


--
Herb Martin, MCSE, MVP

(phone on web site)

Herb Martin

"Laura" <> wrote in message
news:1181918682.115239.218140@w5g2000hsg.googlegro ups.com...

>> > If not, can you point out other alternatives ? (Hardware load-
>> > balancer?)
>>
>> NLB from Microsoft is built into the product (you must add/configure
>> it.)
>>
>> NLB (Network Load Balancing) provides load balancing, explicit
>> affinity on either a single IP or Class-C basis, and also offers fault
>> tolerance.
>>
>> Round Robin does NOT provide for fault tolerance.
>>
>> > By the way, the farm of Apache Servers runs on a Windows Server Box.
>>
>> You should also question a design that requires such affinity. Normally
>> all state data for such clients should be stored on a backend database
>> (perhaps with Server Clustering) OR on the web clients (e.g., using
>> cookies).
>>
>> --
>> Herb Martin, MCSE, MVPhttp://www.LearnQuick.Com
>> (phone on web site)
>
> Thanks for your useful replies !!!!


Happy to help. Pass on the help to someone else in need, and be sure to
ask if you have additional questions.


--
Herb Martin, MCSE, MVP

(phone on web site)