I am trying to open a web URL through SQL Server 2012, we have tried SQLCLR but its outdadted, we tried to run a batch file and it would get stuck in the executing process
EXEC xp_cmdshell 'c:\PATH.bat'
that's the code we used to open the batch file and then it gets stuck in executing query and i waited 5 minutes still nothing popped up
we have checked through file permissions and everything is allowed, its the 4th time ive tried to this and i couldnt manage can someone please show me an alternate solution ?
While there are pros and cons to accessing a URL from within SQL Server, SQLCLR is most definitely not outdated. Even if you have no custom Assemblies, it is still being used internally for several things:
Hierarchy, Geometry, Geography datatypes
Replication
Several built-in functions such as FORMAT, TRY_PARSE, etc
etc
For more info on what SQLCLR actually is and can do, please see the series of articles I am writing on this topic on SQL Server Central: Stairway to SQLCLR (free registration is required to read content on that site, but it's worth it :-). Level 1 ("What is SQLCLR?") is a fairly comprehensive look at what SQLCLR both is and is not.
If you want a command line utility then you might be able to get away with using curl.
If you want a pre-made SQLCLR function that can handle this so that you don't need to worry about the learning curve of doing such an operation in SQLCLR, then that is available in the SQL# library that I created (but it is not in the Free version; only available in the Full / paid version).
IF you are going to be making this URL / Web Sevice call from within a Trigger (whether it is a SQLCLR Trigger or T-SQL Trigger calling a SQLCLR object), then you need to be very careful since Triggers execute within a system-created Transaction (if no explicit Transaction already exists). What this means is that the actual committing of the Transaction (i.e. the true saving of the change to the DB) will wait until the external call completes. The two problems you run into here are:
The Web Service does not respond super quickly (and it needs to respond super quickly)
There are more concurrent requests made to the specific URI such that .NET waits until there is an opening. This is controlled by ServicePointManager.DefaultConnectionLimit, which can be accessed via the HttpWebRequest object (I think there is a ServicePoint property). The default limit is 2, so any more than 1 - 3 calls to the Web Service per second (generally speaking) can cause blocking, even if the Web Service has the ability to respond quickly. 1 - 3 calls per second might not seem like much, but if using this approach in an audit Trigger scenario on multiple tables, it becomes quite easy to reach this limit. So you need to increase the limit to something much higher than 2, and per each call as it is stored in the App Domain which sometimes gets unloaded due to memory pressure.
For more info and considerations, please see my related answers to similar questions here on S.O.:
SQL Server 2012 make HTTP 'GET' Request from a stored procedure
SQL CLR awaitable not getting executed
SQL CLR for Event Driven Communication
Logging not Persisting When Exception Occurs in Method Executed in a Trigger
Also, this S.O. question is very similar in terms of wanting to get near real-time notification of DML changes, and might apply to your goal:
SqlDependency vs SQLCLR call to WebService
Related
I have two apps. One inserts into AzureSQL DB and other reads. I want second app to cache query results and invalidate cache only when something changed in table/query results. In standalone SQL Server it was possible by SQLDependency (or SQLCacheDependency) mechanism. As far as I understood, in AzureSQL this mechanism is unavailable. It requires ServiceBroker component to be enabled, and there's no such component in Azure SQL.
I apoligize if I reapeat already asked questions, but all answers come from 2012 or so. Were there any changes? It's 2017.
And the questions is, what is the mechanism to inform application (say, ASP.NET) about changes in AzureSQL?
PS: I know there's related feature "ChangesTracking", but it is about inserting records about some other changes in speical table. That is "within" database. I need to inform app outside of DB.
To my understanding, SQLDependency works by using DependencyListener, that is an implementation of RepositoryListener and relays on ServiceBroker, as you stated AzureSQL does not support ServiceBroker. But you could use the PollingListener implementation of RepositoryListener to verify a change.
"The PollingListener will run until cancelled and will simply compare the result of the query against until change is detected. Once it is detected, a callback method will be called"
(Source1)
(Source 2)
We have a requirement for notifying external systems of changes in data in various tables in a SQL Server database. The choice of which data to monitor is somewhat under the control of the user (gets to choose from a list of what we support). The recipients of the notifications may be on a locally connected network (i.e., in the same data center) or they may be remote.
We currently handle this by application code within our data access layer that detects changes and queues notifications on a Service Broker queue which is monitored by a Windows service that performs the actual notification. Not quite real time but close enough.
This has proven to have some maintenance problems so we are looking at using one of the change detection mechanisms that are built into SQL Server. Unfortunately none of the ones I have looked at (I think I looked at them all) seem to fit very well:
Change Data Capture and Change Tracking: Major problem is that they require polling the captured information to determine changes that are to be passed on to recipients. I suspect that will introduce too much overhead.
Notification Services: Essentially uses SQL Server as a web server, which is a horrible waste of licenses. It also requires access through at least two firewalls in the network, which is unacceptable from a security perspective.
Query Notification: Seems the most likely candidate but does not seem to lend itself particularly well to dynamically choosing the data elements to watch. The need to re-register the query after each notification is sent means that we would keep SQL Server busy with managing the registrations
Event Notification: Designed to notify on database or instance level events, not really applicable to data change detection.
About the best idea I have come up with is to use CDC and put insert triggers on the change data tables. The triggers would queue something to a Service Broker queue that would be handled by some other code to perform the notifications. This is essentially what we do now except using a SQL Server feature to do the change detection. I'm not even sure that you can add triggers to those tables but I thought I'd get feedback before spending a lot of time with a POC.
That seems like an awful roundabout way to get the job done. Is there something I have missed that will make the job easier or have I misinterpreted one of these features?
Thanks and I apologize for the length of this question.
Why don't you use update and insert triggers? A trigger can execute clr code, which is explained enter link description here
I'm working on a bug in a legacy Windows Mobile 5 app, which uses SQL CE Replication to sync a SQL CE database with a SQL Server 2005 or 2008 database (using Merge replication).
There is some behavior in the application which I don't believe is related to the bug, but I was curious what the side-effects of it might be. The code ends up calling "ReinitializeSubscription(true)" on the SqlCeReplication object before it calls Synchronize. The "true" flag just tells the reinit to upload any changes before reinitializing, which is fine. I don't believe there is a concrete reason to reinit the sub each time, but that's what it does...
What is the impact of calling ReinitializeSubscription on the SqlCeReplication object before each Synchronize call? Is it just a performance hit, or is it actually doing something different with the data synchronization, compared to not calling ReinitializeSubscription before Synchronize?
Unless you are experiencing major client íssues, do not reinit each time you sync, that will download the entire client database (after uploading changes), and consume time and bandwidth, and give a poor user experience (unless you data set is very small and you have high bandwidth, of course)
I have an application that consists of a database and several services. One of these services adds information to the database (triggered by a user).
Another service periodically queries the databases for changes and uses the new data as input for processing.
Until now I used a configurable timer that queries the database every 30 seconds or so. I read about Sql 2005 featuring Notification of changes. However, in Sql 2008 this feature is deprecated.
What is the best way of getting notified of changes that occurred in the database directly in code? What are the best practices?
Notification Services was deprecated, but you don't want to use that anyway.
You might consider Service Broker messages in some scenarios; the details depend on your app.
In most cases, you can probably use SqlDependency or SqlCacheDependency. The way they work is that you include a SqlDependency object with your query when you issue it. The query can be a single SELECT or a complex group of commands in a stored procedure.
Sometime later, if another web server or user or web page makes a change to the DB that might cause the results of the previous query to change, then SQL Server will send a notification to all servers that have registered SqlDependency objects. You can either register code to run when those events arrive, or the event can simply clear an entry in the Cache.
Although you need to enable Service Broker to use SqlDependency, you don't need to interact with it explicitly. However, you can also use it as an alternative mechanism; think of it more as a persistent messaging system that guarantees message order and once-only delivery.
The details of how to use these systems are a bit long for a forum post. You can either Google for them, or I also provide examples in my book (Ultra-Fast ASP.NET).
Yes, this blog post explains that Notification Services is now deprecated, and also what the replacements or alternatives are, going forward.
For your purposes - getting notified of changes that occurred in the dataase - it sounds like you want SQL Server Change Tracking. But the notification is a pull model - your app has to do the query on the change table.
I failed to figure out if SqlDependency continues to work with Notification Services deprecated.
There are a number of different ways of tracking changes in the database: either by triggers that maintain temporal structures such as backlogs, tracking logs (aka 'audit tables') or using the change-tracking facilities in SQL 2008 as references in another answer. Irrespective of whatever mechanism you use, you have the problem of notifying your homegrown service of the change. For this, you can use the Service Broker and event-based activation. From what you describe, it seems like having the application wait on an event from the queue.
http://msdn.microsoft.com/en-us/library/ms171581.aspx
If you don't wish to have the service hang around and sleep on the queue, you can investigate into firing the service into life 'on-demand' by using the external activation mechanism in service broker.
You can use the System.Data.SqlClient.SqlDependency (which works with Service Broker on) to subscribe to changes in a table.
I'm having the trouble finding the wording, but is it possible to provide a SQL query to a MS SQL server and retrieve the results asynchronously?
I'd like to submit the query from a web request, but I'd like the web process to terminate while the SQL server continues processing the query and dumps the results into a temp table that I can retrieve later.
Or is there some common modifier I can append to the query to cause it to background process the results (like "&" in bash).
More info
I manage a site that allows trusted users to run arbitrary select queries on very large data sets. I'm currently using a Java Daemon to examine a "jobs" table and run the results, I was just hopeful that there might be a more native solution.
Based on your clarification, I think you might consider a derived OLAP database that's designed for those types of queries. Since they seem to be strategic to the business.
This really depends on how you are communicating with the DB. With ADO.NET you can make a command execution run asynchronously. If you were looking to do this outside the scope of some library built to do it you could insert a record into a job table and then have SQL Agent poll the table and then run your work as a stored procedure or something.
In all likelihood though I would guess your web request is received by asp.net and you could use the ADO.NET classes.
See this question
Start stored procedures sequentially or in parallel
In effect, you would have the web page start a job. The job would execute asynchronously.
Since http is connectionless, the only way to associate the retrieval with the query would be with sessions. THen you'd have all these answers waiting around for someone to claim them, and no way to know if the connection (that doesn't exist) has been broken.
In a web page, it's pretty much use-it-or-lose-it.
Some of the other answers might work with a lot of effort, but I don't get the sense that you're looking for an edge-case, high-tech option.
It's a complicated topic to be able to execute a stored procedure and then asynchronously retrieve the result. It's not really for the faint of heart and my first recommendation would be to reexamine your design and be certain that you in fact need to asynchronously process your request in the data tier.
Depending on what precisely you are doing you should look at 2 technologies... SQL Service Broker which basically allows you to queue requests and receive responses asyncrhonously. It was introduced in SQL 2005 and sounds like it may be the best bet from the way you phrased your question.
Take a look at the tutorial for same database service broker conversations on MSDN: http://msdn.microsoft.com/en-us/library/bb839495(SQL.90).aspx
For longer running or larger processing tasks I'd potentially look at something like Biztalk or Windows Workflow. These frameworks (they're largely the same, they came from the same team at MS) allow you to start an asynchronous workflow that may not return for hours, days, weeks, or even months.