Installation
At installation time the queue creation script is executed
IF EXISTS (
SELECT *
FROM {1}.sys.objects
WHERE object_id = OBJECT_ID(N'{0}')
AND type in (N'U'))
RETURN
EXEC sp_getapplock @Resource = '{0}_lock', @LockMode = 'Exclusive'
IF EXISTS (
SELECT *
FROM {1}.sys.objects
WHERE object_id = OBJECT_ID(N'{0}')
AND type in (N'U'))
BEGIN
EXEC sp_releaseapplock @Resource = '{0}_lock'
RETURN
END
BEGIN TRY
CREATE TABLE {0} (
Id uniqueidentifier NOT NULL,
CorrelationId varchar(255),
ReplyToAddress varchar(255),
Recoverable bit NOT NULL,
Expires datetime,
Headers nvarchar(max) NOT NULL,
Body varbinary(max),
RowVersion bigint IDENTITY(1,1) NOT NULL
);
CREATE NONCLUSTERED INDEX Index_RowVersion ON {0}
(
[RowVersion] ASC
)
CREATE NONCLUSTERED INDEX Index_Expires ON {0}
(
Expires
)
INCLUDE
(
Id,
RowVersion
)
WHERE
Expires IS NOT NULL
END TRY
BEGIN CATCH
EXEC sp_releaseapplock @Resource = '{0}_lock';
THROW;
END CATCH;
EXEC sp_releaseapplock @Resource = '{0}_lock'
The subscriptions table is also created:
IF EXISTS (
SELECT *
FROM {1}.sys.objects
WHERE object_id = OBJECT_ID(N'{0}')
AND type in (N'U'))
RETURN
EXEC sp_getapplock @Resource = '{0}_lock', @LockMode = 'Exclusive'
IF EXISTS (
SELECT *
FROM {1}.sys.objects
WHERE object_id = OBJECT_ID(N'{0}')
AND type in (N'U'))
BEGIN
EXEC sp_releaseapplock @Resource = '{0}_lock'
RETURN
END
BEGIN TRY
CREATE TABLE {0} (
QueueAddress NVARCHAR(200) NOT NULL,
Endpoint NVARCHAR(200),
Topic NVARCHAR(200) NOT NULL,
PRIMARY KEY CLUSTERED
(
Endpoint,
Topic
)
)
END TRY
BEGIN CATCH
EXEC sp_releaseapplock @Resource = '{0}_lock';
THROW;
END CATCH;
EXEC sp_releaseapplock @Resource = '{0}_lock'
Creating table structure in production
There are some special considerations for creating the queue tables in production environments.
NServiceBus installers
When using NServiceBus installers the queue tables are created automatically before the endpoint is started.
the user account under which the installation of the host is performed must have CREATE TABLE and VIEW DEFINITION permissions on the database where the queues are to be created. The account under which the service runs does not have to have these permissions. Standard read/write/delete permissions (e.g. db_datawriter and db_datareader roles) are enough.
Scripted
Using NServiceBus installers does not allow review of the actual T-SQL statements that are going be executed. For that reason, some prefer to store the actual scripts in a version control system.
The script above is parametrized at execution time with the queue name so it cannot be used as-is. Alternatively, the scripts could be generated from the development or staging environments, then directly executed on a production environment by DBAs to replicate that table structure.
To capture the script for later execution use SQL Server Management Studio. Connect to the server (e.g. development or staging) and right-click the database with the queue tables. From "Tasks" menu choose "Generate Scripts..." and generate the scripts for relevant tables.
Store these scripts so they can be executed as part of the production deployment.
Runtime
The following are the T-SQL statements used by the transport at runtime.
Peek message
Checks if there are messages in the queue.
SELECT count(*) Id
FROM (SELECT TOP {1} * FROM {0} WITH (READPAST)) as count_table;
Purge expired
Purges expired messages from the queue.
DELETE FROM {0}
WHERE RowVersion
IN (SELECT TOP (@BatchSize) RowVersion
FROM {0} WITH (READPAST)
WHERE Expires < GETUTCDATE())
Purge at startup
Used by an endpoint to optionally purge all message on startup.
DELETE FROM {0}
Receive message
The T-SQL statements for sending and receiving messges execute with NOCOUNT ON option. However, this does not affect the original value of this setting. The original value is saved at the beginning and restored after executing the statement.
Retrieves a message from the queue.
DECLARE @NOCOUNT VARCHAR(3) = 'OFF';
IF ( (512 & @@OPTIONS) = 512 ) SET @NOCOUNT = 'ON';
SET NOCOUNT ON;
WITH message AS (
SELECT TOP(1) *
FROM {0} WITH (UPDLOCK, READPAST, ROWLOCK)
ORDER BY RowVersion)
DELETE FROM message
OUTPUT
deleted.Id,
deleted.CorrelationId,
deleted.ReplyToAddress,
CASE WHEN deleted.Expires IS NULL
THEN 0
ELSE CASE WHEN deleted.Expires > GETUTCDATE()
THEN 0
ELSE 1
END
END,
deleted.Headers,
deleted.Body;
IF (@NOCOUNT = 'ON') SET NOCOUNT ON;
IF (@NOCOUNT = 'OFF') SET NOCOUNT OFF;
The CorrelationId, ReplyToAddress and Recoverable columns are required for backwards compatibility with version 1 of the NServiceBus.SqlServer package. When receiving messages sent by endpoints that use later versions, the values of correlation ID and reply-to address should be read from the headers (NServiceBus. and NServiceBus.) instead. The value Recoverable can be ignored as it is always true/1.
Send message
Places a message on the queue.
DECLARE @NOCOUNT VARCHAR(3) = 'OFF';
IF ( (512 & @@OPTIONS) = 512 ) SET @NOCOUNT = 'ON'
SET NOCOUNT ON;
INSERT INTO {0} (
Id,
CorrelationId,
ReplyToAddress,
Recoverable,
Expires,
Headers,
Body)
VALUES (
@Id,
@CorrelationId,
@ReplyToAddress,
1,
CASE WHEN @TimeToBeReceivedMs IS NOT NULL
THEN DATEADD(ms, @TimeToBeReceivedMs, GETUTCDATE()) END,
@Headers,
@Body);
IF (@NOCOUNT = 'ON') SET NOCOUNT ON;
IF (@NOCOUNT = 'OFF') SET NOCOUNT OFF;
The CorrelationId, ReplyToAddress and Recoverable columns are required for backwards compatibility with version 1 of the NServiceBus.SqlServer package. When sending messages to endpoints that use later versions, the values of the correlation ID and reply-to address columns should be set to NULL and the actual values provided in the headers (NServiceBus. and NServiceBus.). The value Recoverable should always be true/1.
Subscribe to a topic
Subscribe and endpoint to a topic.
MERGE {0} WITH (HOLDLOCK, TABLOCK) AS target
USING(SELECT @Endpoint AS Endpoint, @QueueAddress AS QueueAddress, @Topic AS Topic) AS source
ON target.Endpoint = source.Endpoint
AND target.Topic = source.Topic
WHEN MATCHED AND target.QueueAddress <> source.QueueAddress THEN
UPDATE SET QueueAddress = @QueueAddress
WHEN NOT MATCHED THEN
INSERT
(
QueueAddress,
Topic,
Endpoint
)
VALUES
(
@QueueAddress,
@Topic,
@Endpoint
);
Unsubscribe from a topic
Unsubscribe an endpoint from a topic.
DELETE FROM {0}
WHERE
Endpoint = @Endpoint and
Topic = @Topic
Find all subscribers
Get a list of all endpoints that subscribe to a topic.
SELECT DISTINCT QueueAddress
FROM {0}
WHERE Topic IN ({1})
Missing index warning
Used to log a warning if a required index is missing. See also Upgrade from version 2 to 3.
SELECT COUNT(*)
FROM sys.indexes
WHERE name = 'Index_Expires'
AND object_id = OBJECT_ID('{0}')
Check column type
Used to log a warning if the message headers data type is non-unicode. See also Supporting unicode characters in headers.
SELECT t.name
FROM sys.columns c
INNER JOIN sys.types t ON c.system_type_id = t.system_type_id
WHERE c.object_id = OBJECT_ID('{0}')
AND c.name = 'Headers'
Create Delayed Queue Table
Performs delayed queue creation.
IF EXISTS (
SELECT *
FROM {1}.sys.objects
WHERE object_id = OBJECT_ID(N'{0}')
AND type in (N'U'))
RETURN
EXEC sp_getapplock @Resource = '{0}_lock', @LockMode = 'Exclusive'
IF EXISTS (
SELECT *
FROM {1}.sys.objects
WHERE object_id = OBJECT_ID(N'{0}')
AND type in (N'U'))
BEGIN
EXEC sp_releaseapplock @Resource = '{0}_lock'
RETURN
END
BEGIN TRY
CREATE TABLE {0} (
Headers nvarchar(max) NOT NULL,
Body varbinary(max),
Due datetime NOT NULL,
RowVersion bigint IDENTITY(1,1) NOT NULL
);
CREATE NONCLUSTERED INDEX [Index_Due] ON {0}
(
[Due]
)
END TRY
BEGIN CATCH
EXEC sp_releaseapplock @Resource = '{0}_lock';
THROW;
END CATCH;
EXEC sp_releaseapplock @Resource = '{0}_lock'
Move Due Delayed Messages
Moves due messages from the delayed queue table to the input queue table.
;WITH message AS (
SELECT TOP(@BatchSize) *
FROM {0} WITH (UPDLOCK, READPAST, ROWLOCK)
WHERE Due < GETUTCDATE())
DELETE FROM message
OUTPUT
NEWID(),
NULL,
NULL,
1,
NULL,
deleted.Headers,
deleted.Body
INTO {1} (Id, CorrelationId, ReplyToAddress, Recoverable, Expires, Headers, Body);
SELECT TOP 1 GETUTCDATE() as UtcNow, Due as NextDue
FROM {0}
ORDER BY Due";
Store Delayed Message
Stores a message in the delayed queue table.
DECLARE @NOCOUNT VARCHAR(3) = 'OFF';
IF ( (512 & @@OPTIONS) = 512 ) SET @NOCOUNT = 'ON'
SET NOCOUNT ON;
DECLARE @DueAfter DATETIME = GETUTCDATE();
SET @DueAfter = DATEADD(ms, @DueAfterMilliseconds, @DueAfter);
SET @DueAfter = DATEADD(s, @DueAfterSeconds, @DueAfter);
SET @DueAfter = DATEADD(n, @DueAfterMinutes, @DueAfter);
SET @DueAfter = DATEADD(hh, @DueAfterHours, @DueAfter);
SET @DueAfter = DATEADD(d, @DueAfterDays, @DueAfter);
INSERT INTO {0} (
Headers,
Body,
Due)
VALUES (
@Headers,
@Body,
@DueAfter);
IF(@NOCOUNT = 'ON') SET NOCOUNT ON;
IF(@NOCOUNT = 'OFF') SET NOCOUNT OFF;