I have a WCF service which is called in 4 different places in my system. It returns approx 500 records from the database each time it's called.
I would like to use a cache in place of making the call to WCF every time because data in the DB will remain unchanged.
Is there anything built into WCF for this or do I have to create my own solution?
There are several classes in .NET to allow you to cache objects in memory and there are also open source solutions which will do this for you.
If you wish to code this yourself one class you can use is MemoryCache
An open source solution can be found here: Redis.IO
In addition to Jon's answer, you can also use SQL Cache Dependency.
If your WCF Web HTTP service depends on data stored in a SQL database,
you may want to cache the service's response and invalidate the cached
response when data in the SQL database table changes.
Related
I have a few (small size) tables, saved in Table Storage which I use only for reading from.
When my service starts, I'd like to read all tables, save the data in a data structure (i.e. List), and read from that List from there on.
Is there a way to do that, or must I read from the Table Storage each time I need data?
If there is a way, where should the List be declared, and where should it be initialized?
Thanks.
Azure cache may be the best route, but there is an obvious cost.
Could you declare the WCF service as a singleton and store the data as a static property?
You could use the Windows Azure Cache service to store the data. See http://www.windowsazure.com/en-us/home/tour/caching/
If your list is not too big, you could use the Windows Azure caching component http://www.windowsazure.com/en-us/home/tour/caching/ . During the initialization process of your service, read the information from your tables, and stored it there. You are also asking where the list should declared and initialized. Are you also hosting your service on Windows Azure? Is this a web service runnig on IIS, or a windows service? Are you using WCF to expose your service?
I see others are suggesting static properties (good choice) and Azure Chache. Anyway it is good to cache the data if it is not often updated, and not read it every time from the Table Storage.
I want to give my two cents:
I would not use Azure Cahce if the data is small enough (1MB is small enough for me). Static property would do the work. But there is also something new to .NET 4.0 and obviously missing from most of programmes view. It's the System.Runtime.Caching namespace. I haven't presonally used it yet, but it seems to be a good for small local caches. You could use the MemoryCache object and store your data in-memory. And, of course program like against any other type of chache - in the getter of a property, check if data exists in the chache. If exists - return it. If does not exists - retrieve from tables, store in chache, and then return it.
I have a process using Microsoft Sync Framework 2.0 across a WCF Service (IIS Hosted) to synchronize a SQL 2008 Standard database (server) and SQL CE 3.5 (client). All was working perfectly, until a single user started receiving OutOfMemory Exceptions. As it turns out, this user has a dataset that is significantly larger than any other user.
The dataset in question is 800,000 rows, with a total size when exported to CSV from SSMS of 174MB. Most users are in the 20-30MB range, which works fine.
I am using the DbServerSyncProvider, and SqlCeClientSyncProvider.
I have implemented batching as described in other articles and posted, to no avail. As I understand it, the batching mechanism in the DbServerSyncProvider is just how many revisions of the data to retrieve in one pull. Even with an anchor difference of 1, I still result in the same sized dataset.
I am using transferMode="Streamed" on my service, and I have applied the fix for Streamed when hosting in IIS.
I have tried upping the maxReceivedMessageSize, first from 20MB to 200MB, then to 2GB, and finally to 10GB, all with no success. This was done on both the server and client.
My WCF Trace logs show the Execute of GetChanges, but never logs anything under Process action.
I have read about the SqlSyncProvider, and how it allows batching by memory size. I can't find much information about using this through a WCF Service, though, and before I attempt to rewrite my client and server using this, I wanted to check if I was being an idiot on something and whether the SqlSyncProvider could solve my issue, along with being able to transfer across a WCF Service.
Thanks in advance...
The out of memory is most likely caused by the way Datasets are serialized.
If you want to re-write using the SqlSyncProvider, check out the section Code Specific to N-Tier on this link: http://msdn.microsoft.com/en-us/library/dd918908.aspx#Y3096. That should give you an idea on writing the WCF service component for the SqlSyncProvider.
You may also check out the sample SQL Server and SQL Compact N-Tier with WCF
If you want to retain your existing providers, you can play around using DatasetSurrogates. Check out a sample here: Sync Framework WCF-based Synchronization for Offline scenario – Using custom dataset serialization
We've got a smart client that talks to a SQL Server database via WCF, displaying the entities in the database, and allowing the user to edit those entities.
Some of the WCF calls return a large data set. Since this data set doesn't change very often, I'm considering some sort of write-through cache on the client, and only getting the deltas from the WCF service.
That is: the client both reads from the service and writes to the service.
I'm not looking for disconnected/offline operation, but since the majority of the data doesn't change very often, I'd probably implement this with a local data store.
I don't want the local store to get too stale, and I don't think I'm too concerned about conflict resolution, because updates will always go straight to the WCF service -- think of it as a write-through cache.
Would Microsoft's Sync Framework be good for this? Could I use a local SQL-CE cache and perform the updates over WCF? The service end has a SQL Server 2005/2008 backend, but I don't want to talk to it directly. Does Sync Framework integrate well with WCF?
Are there other solutions out there? Should I roll something myself?
I don't think you have to couple it to WCF at all. FeedSync allows you to publish directly to an RSS feed.
The only that I'm not too sure about is if it would be suitable for a "large dataset" though. Since you don't need two way replication, if your dataset is extremely large, you might want to write your own WCF implementation to optimize it; especially for the initial population.
We are developing a project that involves about 10 different WCF services with several endpoints each. One of the services keeps a few big tables of data cached in memory.
We have found we need access to that data from another service. Rather than keeping 2 copies of the cache, I'd like to be able to share those tables across all services.
I have done some research and found some articles about using an IExtension attached to the servicehosts to store the shared data.
Provided that all the services are running under the same web site, will that work? And is it the right approach? Or should I be looking elsewhere?
If the data that you're caching is required by more than one service, it sounds like - from a Service Oriented Architecture perspective, anyway - that it doesn't belong in either of services you have calling it.
If the data being cached isn't really related to either service, but is something that both services need, then perhaps it belongs in it's own seperate service. Have you considered encapsulating your cache in a third service, and performing a service-to-service call to retrieve the data you need? Benefits include...
It solves your original dilemma, avoiding the need to read the whole cache from the database several times;
It encapsulates the cache in one place for easy maintainance/change later.
It allows you to abstract the implementation of the cache away from the other services by putting another service interface in the way.
All in all, I'd suggest that's the best approach. The only downside is the extra overhead of making the service-to-service call, but that surely outperforms having to read the whole cache from the database.
Alternatively, if the data in your cache is very closely related to BOTH of the services that are calling the cache, i.e. both services add/change the data in the cache, etc. then perhaps the two existing services should be combined into a single service.
If what I'm saying is making some sense, then then principle of SOA I'm drawing on is Service Autonomy.
Provided all your services are part of the same application there doesn't seem to be any reason why you can't share the cache directly via a shared object reference. The simplest way of doing this is via a static field.
If you choose this approach, one thing to be very careful about is thread safety. If your cache is concurrently accessed via two WCF sessions, you must ensure that the two sessions are not going to interfere with each other by both changing the cache at the same time. If the cache is read-only, your need to do this is lessened, but you still might need to synchronrise initialisation of the cache.
Ok, I have a pretty complex silverlight app that gets its data from a WCF service (asp.net hosted service layer) which in turn calls into a data layer that calls stored procedures in a SQL 2005 DB to extract the needed data. So the round trip goes like this:
Silverlight App --> WCF Service --> Data Layer --> DB --> Data Layer --> WCF Service transforms Data Entity into corresponding DTO (Data Transfer Object) or List<> thereof --> Silverlight App
Much of the data is highly relational (so it needs to exist in the DB), but it will change infrequently. It seems that I have several choices of locations to cache this "semi-constant" data:
I can cache it in the data layer. My data layer is already set up to use the SQLDependency class and cache the results from a stored procedure call. I think that this is or can be an application level cache.
I can cache the resulting DTO in an application level (or session level depending on the call) cache within the WCF service itself.
2(a) I could even take this a step further by serializing the XML for the resulting DTO(s) into a file on the WCF service side so that I could (a) check memory cache, then (b) check file cache and (c) hit the data layer
I could do something similar to 2(a) with isolated storage on the client side within the SL app. I could serialize the data to the local isolated storage with a hash (or a moddate or something) and then just make a call to check that.
One more thing to add: I am hosting this WCF service in IIS7 with dynamic compression turned on so that the (often very large and easily compressed) XML response gets gzip-ed. Ideally, it would seem, I would like IIS to cache this gzip-ed result to avoid all the extra processing. I think that it may do this already but I am not sure.
I am pretty sure that the final answer to this is some flavor of "it depends", but I would love to hear how others are approaching this. A good tactical recipe of Do X, Test Performance with tool Y, the do Z if needed would be great to have.
A few links (I will add to this as I research this):
WCF Caching Approach
If you have data that are user that will change quite rarely and need fast response, going for a custom mechanism bases on local storage is a great advantage quite faster than having to wait for a server roundtrip.
Dino Sposito published an interesting article about local storage and caching on MSDN Magazine there you can find as well an approach to catch assemblies (imagine just loading the minimum package required and just go loadin the rest of assemblies in background, ... performance rocket, more complexity on your code :)).
As you said is matter to go putting in a balance and decide.
HTH
Braulio
My approach would be this:
Determine if there is actually a problem with performance (isn't it alreade acceptable to my users?)
Measure the performance at each teir (how long does it take the database to come up with data? how long does it take the service to respond with data? how much time does it take from the service to the client?)
Based on the measurements I would then determine where to do my caching. Remember that, the closer to your data storage you do caching, the easier it is, but the closer to the client you do caching, the better the performance gain (usually).
Also remember that caching should not be the first thing to do to improve performance. You should also look into other performance gains as well. Are the stored procedures slow? Is there a lot of overhead in the WCF messages? Is there some inefficient processing in the service? Do I realy need all that data in one message?
HTH,
Jonathan
I think #2 is your best bet for maintainability and architecture. IIS provides caching, why not use it?
You don't want to have to reference System.Web from a data layer. Client side is not the best option either, because you'd have to write a bunch of additional code to keep the data synchronized.
Is System.Web caching even available to WCF when it's not running in ASP.NET compatible mode? Probably best not to depend on it and write your own.
On the other hand, look into Microsoft's Velocity project, which looks like it will produce a very interesting caching technology not dependant on ASP.NET.
We just recently implemented #3, the client-side caching using Isolated Storage.
In our app we have lot of drop downs and custom fields which the app used to get from the server every time it loads. Moving these data to IS really helped. The app now makes a call to check if there were any changes on the server, and if not - loads the data from the IS, otherwise ( which is pretty rare ) refreshes IS.
That eliminated a lot of WCF calls and data transfers, the SL pages' loading time is shorter, and the app in general became more scalable because of the reduced network traffic and db access.
Yes, there are some coding involved, but the benefits for the end users are essential.
Andrew
If you use RIA Services, then a simple approach is to have two separate edmx definitions. One for cached entities, one for transactional ones.
One domain context can reference the entities on another domaincontext via AddReference see.
The cached entities could be loaded immediately after user has authenticated. For simplicity, transactional data should not load until cached entities have loaded.
Depending on the size of the cache, you may also wish to consider serializing these values to local storage.