I've build a small C# application that has been able to get all values I wanted, specifically this is about products, from a webservice API. I have just switched to a larger database (via webservice API access) and now finding out that I get blocked while iterating through the requests, since I've gone from 25 products to 1000 products.
Well, honestly I'm guessing this is the case, but the database is the same built in both my trails, so what has changed is just the amount.
Might mention that I'm new to the whole conect of using webservices/API:s.
I have not tried anything specific yet. I guess one could use a timer between the requests, to have the server rest in between.
Currently I'm iterating through the list of all products, getting their URI, then each URI to get the specifics about each product.
In the best of worlds, I would like to either find a solution whichs allows me to make the numer of reqests lesser than what it is today, or to find a way to let the service rest from making requests. I.e. compare to SQL SELECT * FROM dbTable, make one request, use it
Anyone have any good suggestions. Thanks :)
Thanks to Jeremy, I understand that my backgroundinfo was incomplete. My programs purpose is to fetch all the data from a webshop (products) and distribute them to other systems. So this process of iterating through them will happen ever so often, to detect changes made to the products.
Related
Let's say that I have REST API app and I enable inserting through it some items to database, I would like to make sure that a lot of people at the same time can call that REST API to insert some objects but I also want to be sure that there will never be inserted more than x items of given type.
What would be optimal strategy for that? Let's say that there are 2 options, app is hosted only on a single node and second option is that it is distributed and can have multiple nodes on different servers but with the same database.
If it is hosted on one machine then I assume that I can have shared semaphore, easy but requests will be blocking each other all the time.
On distributed option I assume that there would have to be transaction od db level but how it could look like if performance is inportant?
I assume that this is generic and problem of well known class of problems so maybe you can give me any hints where can I read about it?
Thanks for help!
What I want to do is this: create an ASP.NET MVC web app that periodically looks for new or updated data from an external API (eg, a new order created or modified in an inventory management system), and then sends this data to another system. Similar sort of thing to this - I have tried using it, but I've found it's a bit too limited for some of the things I wanted to do.
I am currently trying to figure out the best way to go about this. I imagine that it will work like this:
Periodically (using a timer?) pull the data from one system's API, and cache the id and DateUpdated fields (in a local database I assume) for each item.
If there are any changes against the cached data, then convert the item to appropriate format if needed and post to the second API.
I would be connecting to a few different third party systems, which for the most part do not support web hooks etc, so I assume polling and caching is the only option.
Am I on the right track? Haven't been able to find a lot of resources on this sort of thing, so would appreciate any advice.
I am calling third party rest api.this rest api returns more then 2 thousand records that takes much time to
retrieve this information.I want to show these records in asp.net page.
Records display in page successfully but problem is its takes much time to display/retrieve this information.
I call this api against dropdown change so api call might be again and again.means it is not one time call and
also i cann't cache this information because in server end may be information will change.
So How I reduce download time or any trick(paging is not supported),Any suggestion?
Thanks in advance
Well there's always a workaround for any given problem even when it doesn't come to your mind at first sight.
I had one situation like this, and this is what we did:
First, keep in mind that real-time consistency is just something that cannot be achieved without writing extensive code. For example, if a user requests data from your service and then that data is rendered on the page, potentially the user could be seeing out-of-data data if at that precise time the source is updated.
So we need to accept the data will be consistent eventually
Then consider the following, replicate the data in your database using an external service periodically
Expose this local data allowing paging and consume it from your client code
As any design decision, there are trade-offs that you should evaluate to take your final choice, these were problems we had with a design like this:
Potentially phe data will not be consistent when the user requests it. You can poll the data to the server every xxx minutes depending on how often it changes (Note: usually we as developers, we are not happy with this kind of data inconsistency, we would like to see everything on real-time, but the truth, is that the end users, most of the time can live with this kind of latency because that's the way they use to work in real-life, consult with your end-users to gather their point of views about this. You can read more about this from Eric Evans in the Blue Book)
You have to write extra code to maintain the data locally
Sadly when you are dealing with a third party service with these conditions, there are few options to choose from, I recommend you to evaluate them all with your end-users explaining their trade-offs to choose the solution that best fits your needs
Alternatives:
Since I already said the data will not be consistency all the time, then perhaps you could consider caching the call to the service =)
Usually the easiest way is always the best way to face something like this, since you didn't mention it in your post I will comment here. Have you tried to simply request to the third party organization to allow paging?. Get in touch with your third party partner and talk about this.
If you can, evaluate another source (other third party companies providing a similar service)
So How I reduce download time or any trick(paging is not supported),Any suggestion?
If the API doesn't support paging, there's not much you could do from a consumer perspective than probably caching the data to avoid the expensive HTTP call.
There's no miracle. There's no client.MaxDownloadTimeMs property that you could set to 5 for example and get your huge data in less than 5 milliseconds.
Your only option would be to cache the data for some amount of time. If the third party api has a call you can make which is more generic than your dropdown change you could call that before the page loads to get all possible drop down values and store the results for a certain period of time. Then just return the appropriate data each time.
Also, look to see if the third party api has any options for gzipping (compressing) the data before sending it down to you. I have created several API's and have created this type of option for large datasets.
Ok, this is very "generic" question. We currently have a SQL Server database for which we need to develop an application in ASP.NET with will contain all the business logic in C# Web Services.
The thing is that, architecturally speaking, I'm not sure how to design the web service and the data management. There are many things to consider :
We need have very rapid access to data. Right now, we have over a million "sales" and "purchases" record from which we need to often calculate and load the current stock for a given day according to a serie of parameter. I'm not sure how we should preload the data and keep the data in the Web Service. Doing a stock calculation within a SQL query will be very lengthy. They currently have a stock calculation application that preloads all sales and purchases for the day and afterwards calculate the stock on the code-side.
We want to develop powerful reporting tools. We want to implement a "pivot table" but not sure how to implement it and have good performances.
For the reasons above, I'm not sure how to design the data model.
How would you manage the display of the current stock, considering that "stock" is actually purchases - sales and that you have to consider all rows to calculate it ? Would you cache "stock" data in the database to optimize performances, even though its redundant data ?
Anybody can give me any guidelines on how to start, or from their personnal experiences (what have you done in the past ?)
I'm not sure if it's possible to make a bounty even though the question is new (I'd put 300 rep on it, since I really need something). If you know how, let me know.
Thanks
The first suggestion is to not use legacy ASMX web services. Use WCF, which Microsoft says should be used for all new web service development.
Second, are you sure you can't optimize the database, or else place it on faster hardware, or nearer to the web server?
I don't know that you're going to get that much data in memory at once. If you could, then you could use a DataSet and use LINQ to DataSets for queries against it.
I hope I hope I'm misunderstanding what you wrote, but if by
contain all the business logic in C# Web Services
you mean something like this then you're already headed in the anti-pattern direction. Accessing your data from an ASP.NET application over web-services would just cause you to incur the serialization/deserialization penalty for pretty much no gain.
A better approach would be to organize services you want to make available into a common layer that your applications are built on and access them directly from your ASP.NET application and maybe also expose them as Web Services to allow external sources to consume this data.
You could also look into exposing data that is expensive to compute using a data warehouse that is updated at regular intervals (once or a couple of times/day). This would help with getting better read performance out of data (as long as you're willing to accept data being a bit stale).
Is that the kind of information you're looking for?
I've been implementing MS Search Server 2010 and so far its really good. Im doing the search queries via their web service, but due to the inconsistent results, im thinking about caching the result instead.
The site is a small intranet (500 employees), so it shouldnt be any problems, but im curious what approach you would take if it was a bigger site.
I've googled abit, but havent really come over anything specific. So, a few questions:
What other approaches are there? And why are they better?
How much does it cost to store a dataview of 400-500 rows? What sizes are feasible?
Other points you should take into consideration.
Any input is welcome :)
You need to employ many techniques to pull this off successfully.
First, you need some sort of persistence layer. If you are using a plain old website, then the user's session would be the most logical layer to use. If you are using web services (meaning session-less) and just making calls through a client, well then you still need some sort of application layer (sort of a shared session) for your services. Why? This layer will be home to your database result cache.
Second, you need a way of caching your results in whatever container you are using (session or the application layer of web services). You can do this a couple of ways... If the query is something that any user can do, then a simple hash of the query will work, and you can share this stored result among other users. You probably still want some sort of GUID for the result, so that you can pass this around in your client application, but having a hash lookup from the queries to the results will be useful. If these queries are unique then you can just use the unique GUID for the query result and pass this along to the client application. This is so you can perform your caching functionality...
The caching mechanism can incorporate some sort of fixed length buffer or queue... so that old results will automatically get cleaned out/removed as new ones are added. Then, if a query comes in that is a cache miss, it will get executed normally and added to the cache.
Third, you are going to want some way to page your result object... the Iterator pattern works well here, though probably something simpler might work... like fetch X amount of results starting at point Y. However the Iterator pattern would be better as you could then remove your caching mechanism later and page directly from the database if you so desired.
Fourth, you need some sort of pre-fetch mechanism (as others suggested). You should launch a thread that will do the full search, and in your main thread just do a quick search with the top X number of items. Hopefully by the time the user tries paging, the second thread will be finished and your full result will now be in the cache. If the result isn't ready, you can just incorporate some simple loading screen logic.
This should get you some of the way... let me know if you want clarification/more details about any particular part.
I'll leave you with some more tips...
You don't want to be sending the entire result to the client app (if you are using Ajax or something like an IPhone app). Why? Well because that is a huge waste. The user likely isn't going to page through all of the results... now you just sent over 2MB of result fields for nothing.
Javascript is an awesome language but remember it is still a client side scripting language... you don't want to be slowing the user experience down too much by sending massive amounts of data for your Ajax client to handle. Just send the prefetched result your client and additional page results as the user pages.
Abstraction abstraction abstraction... you want to abstract away the cache, the querying, the paging, the prefetching... as much of it as you can. Why? Well lets say you want to switch databases or you want to page directly from the database instead of using a result object in cache... well if you do it right this is much easier to change later on. Also, if using web services, many many other applications can make use of this logic later on.
Now, I probably suggested an over-engineered solution for what you need :). But, if you can pull this off using all the right techniques, you will learn a ton and have a very good base in case you want to extend functionality or reuse this code.
Let me know if you have questions.
It sounds like the slow part of the search is the full-text searching, not the result retrieval. How about caching the resulting resource record IDs? Also, since it might be true that search queries are often duplicated, store a hash of the search query, the query, and the matching resources. Then you can retrieve the next page of results by ID. Works with AJAX too.
Since it's an intranet and you may control the searched resources, you could even pre-compute a new or updated resource's match to popular queries during idle time.
I have to admit that I am not terribly familiar with MS Search Server so this may not apply. I have often had situations where an application had to search through hundreds of millions of records for result sets that needed to be sorted, paginated and sub-searched in a SQL Server though. Generally what I do is take a two step approach. First I grab the first "x" results which need to be displayed and send them to the browser for a quick display. Second, on another thread, I finish the full query and move the results to a temp table where they can be stored and retrieved quicker. Any given query may have thousands or tens of thousands of results but in comparison to the hundreds of millions or even billions of total records, this smaller subset can be manipulated very easily from the temp table. It also puts less stress on the other tables as queries happen. If the user needs a second page of records, or needs to sort them, or just wants a subset of the original query, this is all pulled from the temp table.
Logic then needs to be put into place to check for outdated temp tables and remove them. This is simple enough and I let the SQL Server handle that functionality. Finally logic has to be put into place for when the original query changes (significant perimeter changes) so that a new data set can be pulled and placed into a new temp table for further querying. All of this is relatively simple.
Users are so used to split second return times from places like google and this model gives me enough flexibility to actually achieve that without needing the specialized software and hardware that they use.
Hope this helps a little.
Tim's answer is a great way to handle things if you have the ability to run the initial query in a second thread and the logic (paging / sorting / filtering) to be applied to the results requires action on the server ..... otherwise ....
If you can use AJAX, a 500 row result set could be called into the page and paged or sorted on the client. This can lead to some really interesting features .... check out the datagrid solutions from jQueryUI and Dojo for inspiration!
And for really intensive features like arbitrary regex filters and drag-and-drop column re-ordering you can totally free the server.
Loading the data to the browser all at once also lets you call in supporting data (page previews etc) as the user "requests" them ....
The main issue is limiting the data you return per result to what you'll actually use for your sorts and filters.
The possibilities are endless :)