Dr. Dobb's | Load Balancing Your Web Site (Web Techniques, May 1998)

Load Balancing Your Web Site (Web Techniques, May 1998)

January 01, 2002
URL:http://drdobbs.com/load-balancing-your-web-site-web-techniq/184414169

www.foo.dom.    IN  CNAME  www1.foo.dom
                IN  CNAME  www2.foo.dom
                IN  CNAME  www3.foo.dom
                IN  CNAME  www4.foo.dom
                IN  CNAME  www5.foo.dom
                IN  CNAME  www6.foo.dom

Web Techniques: Figure 1

Figure 1

A DNS-based Web server cluster.

1   ;;
2   ;;  named.boot -- BIND daemon boot configuration
3   ;;
4
5       :
6       :
7   ;type     domain      source-file
8   primary   foo.dom     db.foo
9   primary   rr.foo.dom  db.foo.rr
10       :
11       :

;NOS = ceil(RPM * SPR * (1/60) * (100/80))
MBR = ceil((SPS * NOS * (100/70)) / 16) * 16

Web Techniques: Figure 2

Figure 2

A reverse-proxy-based Web server cluster.

1   ;;
2   ;;  db.foo -- BIND DNS zone file for the foo.dom domain
3   ;;
4
5   @  IN  SOA   world.foo.dom.  root.world.foo.dom. (
6                1998021502 ; SERIAL
7                604800     ; REFRESH: Secondaries refresh after 1 week
8                3600       ; RETRY:   Secondaries retry after 1 hour
9                604800     ; EXPIRE:  Maximum TTL of Data is 1 week
10               86400      ; MINTTL:  Minimum TTL of Data is 1 day
11                       )
12
13           IN  NS      world.foo.dom.
14
15   ;;
16   ;;  the resource record for www.foo.dom which
17   ;;  maps to the Round-Robin domain
18   ;;
19   www     IN  CNAME   www.rr.foo.dom.

maxusers 256
options  SOMAXCONN=256
options  NMBCLUSTERS=4096
options  CHILD_MAX=512
options  OPEN_MAX=512

Web Techniques: Figure 3

Figure 3

A reverse-proxy-based Web server cluster with dedicated back-end subnet.


1   ;;
2   ;;  db.foo.rr -- BIND DNS zone file for the rr.foo.dom domain
3   ;;
4
5   ;;
6   ;;  the start of authority (SOA) resource record which
7   ;;  forces a minimal time-to-live (TTL) for this zone file
8   ;;
9   @  IN  SOA world.foo.dom.  root.world.foo.dom. (
10             1998021501 ; SERIAL
11             3600       ; REFRESH: Secondaries refresh after 1 hour
12             600        ; RETRY:   Secondaries retry after 10 minutes
13             3600       ; EXPIRE:  Maximum TTL of Data is 1 hour
14             1800       ; MINTTL:  Minimum TTL of Data is 30 minutes
15                       )
16
17           IN  NS      world.foo.dom.
18
19   ;;
20   ;;  the multiple canonical name (CNAME) resource record
21   ;;  which implies BIND's Round-Robin (RR) feature
22   ;;
23   www     IN  CNAME   www1.rr.foo.dom.
24           IN  CNAME   www2.rr.foo.dom.
25           IN  CNAME   www3.rr.foo.dom.
26           IN  CNAME   www4.rr.foo.dom.
27           IN  CNAME   www5.rr.foo.dom.
28           IN  CNAME   www6.rr.foo.dom.
29
30   ;;
31   ;;  the address (A) resource records for the
32   ;;  final NAME -> IP mapping
33   ;;
34   www1    IN  A       192.168.1.1
35   www2    IN  A       192.168.1.2
36   www3    IN  A       192.168.1.3
37   www4    IN  A       192.168.1.4
38   www5    IN  A       192.168.1.5
39   www6    IN  A       192.168.1.6

(a)
-DHARD_SERVER_LIMIT=256
-DDYNAMIC_MODULE_LIMIT=0
-DBUFFERED_LOGS

(b)
MinSpareServers        256
StartServers           256
MaxSpareServers        256
MaxClients             256

MaxRequestsPerChild    1000
KeepAlive              on
KeepAliveTimeout       15
MaxKeepAliveRequests   64
Timeout                400
IdentityCheck          off
HostnameLookups        off
<Files ~ "\.(html|cg)$>
HostnameLookups on
</Files>
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>