137 lines
4.3 KiB
Transact-SQL
137 lines
4.3 KiB
Transact-SQL
--
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-- A stored procedure to reallocate a user's previous address, otherwise
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-- provide a free address.
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--
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-- Using this SP reduces the usual set dialogue of queries to a single
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-- query:
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--
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-- BEGIN TRAN; "SELECT FOR UPDATE"; UPDATE; COMMIT TRAN; -> EXEC sp
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--
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-- The stored procedure is executed on an database instance within a single
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-- round trip which often leads to reduced deadlocking and significant
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-- performance improvements especially on multi-master clusters, perhaps even
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-- by an order of magnitude or more.
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--
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-- To use this stored procedure the corresponding queries.conf statements must
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-- be configured as follows:
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--
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-- allocate_begin = ""
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-- allocate_find = "\
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-- EXEC fr_allocate_previous_or_new_framedipaddress \
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-- @v_pool_name = '%{control:${pool_name}}', \
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-- @v_username = '%{User-Name}', \
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-- @v_callingstationid = '%{Calling-Station-Id}', \
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-- @v_nasipaddress = '%{NAS-IP-Address}', \
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-- @v_pool_key = '${pool_key}', \
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-- @v_lease_duration = ${lease_duration} \
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-- "
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-- allocate_update = ""
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-- allocate_commit = ""
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--
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CREATE INDEX UserName_CallingStationId ON radippool(pool_name,UserName,CallingStationId)
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GO
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CREATE OR ALTER PROCEDURE fr_allocate_previous_or_new_framedipaddress
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@v_pool_name VARCHAR(64),
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@v_username VARCHAR(64),
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@v_callingstationid VARCHAR(64),
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@v_nasipaddress VARCHAR(15),
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@v_pool_key VARCHAR(64),
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@v_lease_duration INT
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AS
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BEGIN
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-- MS SQL lacks a "SELECT FOR UPDATE" statement, and its table
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-- hints do not provide a direct means to implement the row-level
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-- read lock needed to guarentee that concurrent queries do not
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-- select the same Framed-IP-Address for allocation to distinct
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-- users.
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--
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-- The "WITH cte AS ( SELECT ... ) UPDATE cte ... OUTPUT INTO"
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-- patterns in this procedure body compensate by wrapping
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-- the SELECT in a synthetic UPDATE which locks the row.
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DECLARE @r_address_tab TABLE(id VARCHAR(15));
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DECLARE @r_address VARCHAR(15);
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BEGIN TRAN;
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-- Reissue an existing IP address lease when re-authenticating a session
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--
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WITH cte AS (
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SELECT TOP(1) FramedIPAddress
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FROM radippool WITH (xlock rowlock readpast)
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WHERE pool_name = @v_pool_name
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AND expiry_time > CURRENT_TIMESTAMP
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AND NASIPAddress = @v_nasipaddress AND pool_key = @v_pool_key
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)
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UPDATE cte
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SET FramedIPAddress = FramedIPAddress
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OUTPUT INSERTED.FramedIPAddress INTO @r_address_tab;
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SELECT @r_address = id FROM @r_address_tab;
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-- Reissue an user's previous IP address, provided that the lease is
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-- available (i.e. enable sticky IPs)
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--
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-- When using this SELECT you should delete the one above. You must also
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-- set allocate_clear = "" in queries.conf to persist the associations
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-- for expired leases.
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--
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-- WITH cte AS (
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-- SELECT TOP(1) FramedIPAddress
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-- FROM radippool WITH (xlock rowlock readpast)
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-- WHERE pool_name = @v_pool_name
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-- AND NASIPAddress = @v_nasipaddress AND pool_key = @v_pool_key
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-- )
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-- UPDATE cte
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-- SET FramedIPAddress = FramedIPAddress
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-- OUTPUT INSERTED.FramedIPAddress INTO @r_address_tab;
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-- SELECT @r_address = id FROM @r_address_tab;
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-- If we didn't reallocate a previous address then pick the least
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-- recently used address from the pool which maximises the likelihood
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-- of re-assigning the other addresses to their recent user
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--
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IF @r_address IS NULL
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BEGIN
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WITH cte AS (
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SELECT TOP(1) FramedIPAddress
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FROM radippool WITH (xlock rowlock readpast)
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WHERE pool_name = @v_pool_name
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AND expiry_time < CURRENT_TIMESTAMP
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ORDER BY
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expiry_time
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)
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UPDATE cte
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SET FramedIPAddress = FramedIPAddress
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OUTPUT INSERTED.FramedIPAddress INTO @r_address_tab;
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SELECT @r_address = id FROM @r_address_tab;
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END
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-- Return nothing if we failed to allocated an address
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--
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IF @r_address IS NULL
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BEGIN
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COMMIT TRAN;
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RETURN;
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END
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-- Update the pool having allocated an IP address
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--
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UPDATE radippool
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SET
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NASIPAddress = @v_nasipaddress,
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pool_key = @v_pool_key,
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CallingStationId = @v_callingstationid,
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UserName = @v_username,
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expiry_time = DATEADD(SECOND,@v_lease_duration,CURRENT_TIMESTAMP)
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WHERE framedipaddress = @r_address;
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COMMIT TRAN;
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-- Return the address that we allocated
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SELECT @r_address;
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END
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GO
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