FlashConnect allows one or more database servers to connect to one or more FlashConnect enabled Web servers. Using server pools other than the default server pool is optional. However, if other server pools are used, the default server pool does not need to be used.
In this example, requests to Web Server 1 can be directed to Database Server 1 or Database Server 2, while requests to Web Server 2 can only be directed to Database Server 2.
These pools enable the distribution of an application across several systems.
The system administrator specifies which server pool a system supports using the WWW-START command or via server pools configuration.
The programmer specifies which server pool is used to service a request by setting the w3ServerPool variable.
FlashConnect assigns the connection to any database server that supports the requested server pool. If no server pool is specified, the default server pool is used.
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WARNING |
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CAUTION |
The database server pool name can be a maximum of 15 alphanumeric characters and must include at least one alpha character in the name. |
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NOTE |
w3ServerPool is a synonym for w3HostName. In this document, all w3HostName references have been changed to w3ServerPool. |
For server pool debugging assistance, see Debugging Server Pools.
The Web servers are directed to different database servers as displayed in this example:
The following example shows which database servers are available to each Web server when a request to the server pool is made.
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Requested Pool |
Accounting |
Payroll |
Sales |
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Web Server 1 |
Database Server 1 or 2 |
Database Server 2 |
Database Server 1 or 2 |
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Web Server 2 |
Database Server 2 |
Database Server 2 or 3 |
Database Server 2 or 3 |
Specify which system should process a request and which server pool to use in processing that request. Configure server pools using the FlashConnect Server Pool Maintenance Web page.
Then use the WWW-MANAGER command to implement the configuration at startup. Create a macro containing all of the desired commands, and call that macro from within the user-coldstart macro. The macro should log to the www account, then process commands, and then log back to the dm account. The following w3Config entries are used to establish the connection for the previous examples. Note that the Min, Max, MaxFree, MinFree, Freq, Port, and HB Period are arbitrarily set for this example.
Database Server 1
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Min |
Max |
MaxFree |
MinFree |
Freq |
Port |
HB Period |
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Server pool: Accounting |
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WEBSERVER1 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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Server pool: Sales |
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WEBSERVER1 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
Database Server 2
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Min |
Max |
MaxFree |
MinFree |
Freq |
Port |
HB Period |
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Server pool: Accounting |
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WEBSERVER2 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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WEBSERVER1 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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Server pool: Payroll |
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WEBSERVER1 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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WEBSERVER2 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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Server pool: Sales |
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WEBSERVER1 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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WEBSERVER2 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
Database Server 3
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Min |
Max |
MaxFree |
MinFree |
Freq |
Port |
HB Period |
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Server pool: Payroll |
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WEBSERVER1 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
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Server pool: Sales |
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WEBSERVER2 |
1 |
3 |
2 |
1 |
60 |
1505 |
120 |
The following commands manually start the same server pools as the above example:
Database Server 1
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WWW-START 1 WEBSERVER1 1505 ACCOUNTING WWW-START 1 WEBSERVER1 1505 SALES |
Database Server 2
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WWW-START 1 WEBSERVER1 1505 ACCOUNTING WWW-START 1 WEBSERVER1 1505 PAYROLL WWW-START 1 WEBSERVER1 1505 SALES WWW-START 1 WEBSERVER2 1505 ACCOUNTING WWW-START 1 WEBSERVER2 1505 PAYROLL WWW-START 1 WEBSERVER2 1505 SALES |
Database Server 3
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WWW-START 1 WEBSERVER2 1505 PAYROLL WWW-START 1 WEBSERVER2 1505 SALES |
FlashConnect assigns the connection to any database server that supports that server pool. Use the FlashConnect variable w3ServerPool to specify which pool the FlashConnect enabled Web server should use. In the following examples, Apps represents an item in the w3Apps file.
Using the information in the Web Server 1 row in the table above:
to specify Web Server 1 for the Accounting server pool to Database Server 1 or 2, use the URL:
http://WebServer1/cgi-bin/fcisapi.dll?w3exec=Apps &w3ServerPool=Accounting
to specify Web Server 1 for the Payroll server pool to Database Server 2, use the URL:
http://WebServer1/cgi-bin/fcisapi.dll?w3exec=Apps &w3ServerPool=Payroll
Using the information in the Web Server 2 row in the table above:
to specify Web Server 2 for the Accounting server pool to Database Server 2, use the URL:
http://WebServer2/cgi-bin/fcisapi.dll?w3exec=Apps &w3ServerPool=Accounting
to specify Web Server 2 for the Payroll server pool to Database Server 2 or 3, use the URL:
http://WebServer2/cgi-bin/fcisapi.dll?w3exec=Apps &w3ServerPool=Payroll
When providing the same service on multiple database servers, the load can be automatically balanced between systems using server pools and w3Monitor. This is possible because:
connections from multiple database servers can be assigned to the same server pool on one or more Web servers.
FCService uses server pool entries to any database server supporting that server pool.
w3Monitor creates and destroys connections as needed.
See w3Monitor Application in the FlashConnect Programmer’s Guide for additional information.
To implement automatic load balancing:
Specify the relationship (which system should process a request and which server pool to use in processing that request). See Specifying the Relationship.
Assign the connection (to any database server which supports that server pool). See Assigning the Connection.
Set up w3Monitor on each database server to maintain a minimum of one or more free connections to the Web server.
How it Works:
For example, there are two database servers (A and B) supporting one Web server. Two connections to the default server pool are made from each database server to the Web server (Table 2). w3Monitor is set up on each database server to maintain a minimum of one free connection to the Web server.
Table 1: Two database Servers Support One Web Server
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Web Server Connection Number |
Host |
Assigned |
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1. |
Database A |
No |
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2. |
Database A |
No |
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3. |
Database B |
No |
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4. |
Database B |
No |
The first two user requests are assigned to connections 1 and 2, both to Database A. At this time, the w3Monitor running on Database A automatically adds one more connection (number 5), as reflected in Table 3.
Table 2: w3Monitor Automatically Adds a Connection
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Web Server Connection Number |
Host |
Assigned |
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1. |
Database A |
Yes |
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2. |
Database A |
Yes |
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3. |
Database B |
No |
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4. |
Database B |
No |
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5. |
Database A |
No |
The third and fourth user requests are assigned to connections 3 and 4, both to Database B. At this time, the w3Monitor running on Database B automatically adds one more connection (number 6) as shown in Table 3.
Table 3: w3Monitor Automatically Adds another Connection
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Web Server Connection Number |
Host |
Assigned |
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1. |
Database A |
Yes |
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2. |
Database A |
Yes |
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3. |
Database B |
Yes |
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4. |
Database B |
Yes |
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5. |
Database A |
No |
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6. |
Database B |
No |
From this point forward, as additional connections are requested, they are alternately assigned to each database server. w3Monitor creates additional connections as needed until the configuration limits are reached, thus balancing the load.
As connections are dropped, they are reassigned in connection number order. For example, if connection 1 and 3 are both available, connection 1 is used before connection 3 is used. At the same time, depending on how the w3Monitor is configured, as the load is shed from one database server, connections are dropped to help maintain load balance as the load diminishes.
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NOTE |
When additional connections are needed, w3Monitor may create more than one connection at a time, slightly changing the balancing pattern from the pattern shown here. |
Usually WWW-MANAGER is used to start and stop both the server pools and w3Monitor. However, if manual control is needed, or more visibility of w3Monitor’s action is needed, both the server pools and w3Monitor can be manually controlled.
If more visibility of w3Monitor’s activities is needed, w3Monitor can also run from a terminal (for example, by logging to the WWW account from a terminal and typing W3MONITOR-START).
w3Monitor only manages enabled server pools. The WWW-MANAGER, WWW-POOL and WWW-START commands are used to start a server pool, while WWW-STOP and WWW-MANAGER are used to stop a server pool.
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NOTE |
For information about configuring server pools, see Configuring FlashConnect Server Pools in the FlashConnect Installation Guide. |
See Also