I'm looking to add some background processing to my ASP.NET MVC 5 application, more specifically executing some long-ish (5-10 seconds) running tasks with HostingEnvironment.QueueBackgroundWorkItem. Now, the problem that I'm having is that code is running "out of band" and is not tied to the request any more - Autofac disposes of some of the injected dependencies.
Here is some of the code:
[HttpPost, ActionName("Execute")]
public ActionResult ExecutePost(Guid taskguid, FormCollection values)
{
if (taskguid == default(Guid))
{
return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
}
var model = _taskListService.GetTaskByGuid(taskguid);
if (TryUpdateModel(model.TaskObject as MissingCrossReferenceTask))
{
model.TaskObject.DependencyContainer = _dependencyContainer;
model.TaskObject.TaskListId = model.Id;
HostingEnvironment.QueueBackgroundWorkItem(ct => ExecuteTask(ct, model));
return RedirectToAction("Index", "Dashboard");
}
return View(model);
}
In the code above DependencyContainer is an object that contains a number of dependencies that are injected by Autofac (EF Repositories and Services)
private void ExecuteTask(CancellationToken ct, TaskList model)
{
model.TaskObject.Execute();
}
Inside of that execute method of the MissingCrossReferenceTask (which is in a separate assembly from the ASP.NET MVC project:
public bool Execute()
{
long tableId = DependencyContainer.CrossReferenceService.GetCrossReferenceTable(TableName).Id;
string currentValue = DependencyContainer.CrossReferenceService.GetValue(FromValue, tableId);
...
}
The first line throws an exception: ObjectDisposedExcetion {"The ObjectContext instance has been disposed and can no longer be used for operations that require a connection."}
Now, I don't know the Autofac well enough to figure out the best way around this. Is it somehow possible to re-inject the reference directly in ExecuteTask method? If so - how?
I would extremely appreciate any help of this. It has been driving me insane for a few days now...
Thanks,
Nick Goloborodko
I guess submitting the question has forced me to look at the problem from a slightly different angle.
I think I have found a way around this (in other words - it now works as I'd like it to). I'm still not sure if this approach is the best in my situation or if there are any unseen problems with it - I would much appreciate any comments around this topic!
I have solved the issue in the following way:
private void ExecuteTask(CancellationToken ct, TaskList model)
{
MvcApplication app = this.HttpContext.ApplicationInstance as MvcApplication;
using (var container = app.ContainerProvider.ApplicationContainer.BeginLifetimeScope(WebLifetime.Application))
{
model.TaskObject.DependencyContainer = container.Resolve<DependencyContainer>();
model.TaskObject.Execute();
}
}
(adopted from a solution posted on this page: http://aboutcode.net/2010/11/01/start-background-tasks-from-mvc-actions-using-autofac.html)
Hope this may save a bit of time to someone else in the future!
Related
what is the best way to capture page views by person without slowing down performance on the site. I see that stackoverflow show page views all over the place. Are they doing an insert into a db everytime i click on a page?
In asp.net-mvc, Is there any recommended way to track page view per user (my site has a login screen) so i can review which pages people are going to and how often
First off.. if what you really care about is how are customers using my site then you most likely want to look into Google Analytics or a similar service.
But if you want a quick and dirty page view record and you are using ASP.Net MVC 3 then as Chris Fulstow mentioned you're going to want to use a mix of global action filters and caching. Here is an example.
PageViewAttribute.cs
public class PageViewAttribute : ActionFilterAttribute
{
private static readonly TimeSpan pageViewDumpToDatabaseTimeSpan = new TimeSpan(0, 0, 10);
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
var calledMethod = string.Format("{0} -> {1}",
filterContext.ActionDescriptor.ControllerDescriptor.ControllerName,
filterContext.ActionDescriptor.ActionName);
var cacheKey = string.Format("PV-{0}", calledMethod);
var cachedResult = HttpRuntime.Cache[cacheKey];
if(cachedResult == null)
{
HttpRuntime.Cache.Insert(cacheKey, new PageViewValue(), null, DateTime.Now.Add(pageViewDumpToDatabaseTimeSpan) , Cache.NoSlidingExpiration, CacheItemPriority.Default,
onRemove);
}
else
{
var currentValue = (PageViewValue) cachedResult;
currentValue.Value++;
}
}
private static void onRemove(string key, object value, CacheItemRemovedReason reason)
{
if (!key.StartsWith("PV-"))
{
return;
}
// write out the value to the database
}
// Used to get around weird cache behavior with value types
public class PageViewValue
{
public PageViewValue()
{
Value = 1;
}
public int Value { get; set; }
}
}
And in your Global.asax.cs
public class MvcApplication : HttpApplication
{
public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new PageViewAttribute());
}
}
For pre-ASP.Net MVC 3 ONLY you are going to have to apply the same attribute manually to all of your actions.
[PageView]
public ActionResult CallOne()
{
}
[PageView]
public ActionResult CallTwo()
{
}
The best way would probably be a global action filter that intercepts requests to all actions on all controllers, then increments a counter in the database for the current user and page. To save hitting the database too hard, you could cache these values and invalidate them every few minutes, depending on how much traffic you're dealing with.
We use the open source Piwik: http://piwik.org/, which is setup on it's own server. One line of Javascript in the _Layout page makes a call to Piwik after the page has loaded (put the JS at the end) and does not affect page load performance at all.
In addition to just counts, you'll get a ton of info about where your users are coming from, browser, screen resolutions, installed plugins. Plus you can track conversions and use the same tool to track marketing campaigns, etc.
<soapbox>
I cannot think of a situation where you'd be better off implementing this in MVC or in your web app in general. This stuff simply does not belong in your web app and is a meta-concern that should be separated out. This approach has enabled us to track analytics for all of our apps (32 of them: mvc 2/3, webforms, php...) in a unified manner.
If you really don't want to use another tool for this purpose, I would recommend tapping into your IIS log and getting your stats from there. Again, to get any real decision making power out of it, you'll need to put a good analyzer on it. I recommend Splunk: http://www.splunk.com/
</soapbox>
I wanted to post an updated version of Shane's answer for those who are interested. Some things to consider:
You have to set the action attribute up as a service when decorating your
methods using syntax like the following :
[ServiceFilter(typeof(PageViewAttribute))]
As far as I can tell, HttpRuntime.Cache.Insert isn't a thing in .NET Core, so I used a simple implementation of IMemoryCache (You may need to add this line to your startup.cs in order to use the interface):
services.AddMemoryCache();
Because we are injecting IMemoryCache into a class that is not a controller, we need to register our attribute as a service in startup.cs, like so:
services.AddScoped<[PageViewAttribute]>(); - without brackets!
Whatever object you return when creating a cacheKey will be assigned to the 'value' parameter of the OnRemove method.
Below is the code.
public override void OnActionExecuting(ActionExecutingContext filterContext)
{
var controllerActionDescriptor = filterContext.ActionDescriptor as ControllerActionDescriptor;
var arguments = filterContext.ActionArguments;
ActionId = arguments["id"].ToString();
var calledMethod = string.Format("{0} -> {1}",
controllerActionDescriptor.ControllerName,
controllerActionDescriptor.ActionName);
var cacheKey = string.Format("PV-{0}", calledMethod);
var cachedResult = _memoryCache.Get(cacheKey);
if (cachedResult == null)
{
//Get cacheKey if found, if not create cache key with following settings
_memoryCache.GetOrCreate(cacheKey, cacheKey =>
{
cacheKey.AbsoluteExpirationRelativeToNow
= pageViewDumpToDatabaseTimeSpan;
cacheKey.SetValue(1);
cacheKey.RegisterPostEvictionCallback(onRemove);
return cacheKey.Value;
});
}
else
{
_memoryCache.Get(cacheKey);
}
}
//Called when Memory entry is removed
private void onRemove(object key, object value, EvictionReason reason, object state)
{
if (!key.ToString().StartsWith("PV-"))
{
return;
}
// write out the value to the database
SaveToDataBase(key.ToString(), (int)value);
}
As a point of reference, this was done for a .NET Core 5 MVC App.
Regards.
I have a task that runs in a different thread and requires the session. I've done:
public GenerateDocList(LLStatistics.DocLists.DocList docs)
{
this.docs = docs;
context = HttpContext.Current;
}
and
public void StartTask()
{
//this code runs in a separate thread
HttpContext.Current = context;
/* rest of the code */
}
Now the thread has knowledge of the session and it works for a while but at some point in my loop HttpContext.Current.Session becomes null. Any ideas what can I do about this?
public static LLDAC.DAL.DBCTX LLDB
{
get
{
LLDAC.DAL.DBCTX currentUserDBContext = HttpContext.Current.Session["LLDBContext"] as LLDAC.DAL.DBCTX;
if (currentUserDBContext == null)
{
currentUserDBContext = new LLDAC.DAL.DBCTX();
HttpContext.Current.Session.Add("LLDBContext", currentUserDBContext);//this works only for a few loop iterations
}
return currentUserDBContext;
}
}
In general, this is a very fragile pattern for a multi-threaded operation. Long-running tasks (which I assume this is) are best suited to instance methods in a class rather than static methods such that the class can maintain any dependent objects. Also, since the session state is not thread safe and can span multiple requests you are getting into some very risky business by cashing your DB context in the session at all.
If you are convinced this is best done with static methods and stored in the session, you may be able to do something like this:
public static HttpSessionState MySession { get; set; }
public GenerateDocList(LLStatistics.DocLists.DocList docs)
{
this.docs = docs;
MySession = HttpContext.Current.Session;
}
Then:
public static LLDAC.DAL.DBCTX LLDB
{
get
{
LLDAC.DAL.DBCTX currentUserDBContext = MySession["LLDBContext"] as LLDAC.DAL.DBCTX;
if (currentUserDBContext == null)
{
currentUserDBContext = new LLDAC.DAL.DBCTX();
if (MySession == null)
{
thow new InvalidOperaionException("MySession is null");
}
MySession.Add("LLDBContext", currentUserDBContext);
}
return currentUserDBContext;
}
}
Note that you could still run into issues with the session since other threads could still modify the session.
A better solution would probably look something like this:
public class DocListGenerator : IDisposable
{
public LLDAC.DAL.DBCTX LLDB { get; private set; }
public DocListGenerator()
{
LLDB = new LLDAC.DAL.DBCTX();
}
public void GenerateList()
{
// Put loop here.
}
public void Dispose()
{
if (LLDB != null)
{
LLDB.Dispose();
}
}
}
Then your calling code looks like this:
public void StartTask()
{
using (DocListGenerator generator = new DocListGenerator()
{
generator.GenerateList();
}
}
If you really want to cache something, you could cache your instance like this:
HttpContext.Current.Sesssion.Add("ListGenerator", generator);
However, I still don't think that is a particularly good idea since your context could still be disposed or otherwise altered by a different thread.
Using anything related to the HttpContext.Current on anything besides the main Request thread is generally going to get you into trouble in ASP.net.
The HttpContext is actually backed on a thread belonging to a Thread Pool and the thread may very well get reused on another request.
This is actually a common issue with using the new Async/Await keywords in ASP.net as well.
In order to help you, it would help to know why you're attempting this in the first place?
Is this a single server or a web farm with multiple load balanced servers?
Are you hosting it yourself, or is it the site hosted by a provider?
What is the SessionState implementation (SQL Server, State Server, In-Process, or something custom like MemCached, Redis, etc...)
What version of ASP .net?
Why are you starting a new thread instead of just doing the processing on the request thread?
If you really can't (or shouldn't) use session. Then you could use something like a correlation ID.
Guid correlationID = Guid.NewGuid();
HttpContext.Current.Session["DocListID"] = correlationID;
DocList.GoOffAndGenerateSomeStuffOnANewThread(correlationID);
... when process is done, store the results somewhere using the specified ID
// Serialize the result to SQL server, the file system, cache...
DocList.StoreResultsSomewhereUnderID();
... later on
DocList.CheckForResultsUnderID(HttpContext.Current.Session["DocListID"]);
first I want to say that I hope this doesn't look like I am lazy but I have some trouble understanding a piece of code from the following project.
http://kigg.codeplex.com/
I was going through the source code and I noticed something that would be usefull for my own little project I am making. In their BaseController they have the following code:
private static readonly Type CurrentUserKey = typeof(IUser);
public IUser CurrentUser
{
get
{
if (!string.IsNullOrEmpty(CurrentUserName))
{
IUser user = HttpContext.Items[CurrentUserKey] as IUser;
if (user == null)
{
user = AccountRepository.FindByClaim(CurrentUserName);
if (user != null)
{
HttpContext.Items[CurrentUserKey] = user;
}
}
return user;
}
return null;
}
}
This isn't an exact copy of the code I adjusted it a little to my needs. This part of the code I still understand. They store their IUser in HttpContext.Items. I guess they do it so that they don't have to call the database eachtime they need the User object.
The part that I don't understand is how they maintain this object in between requests. If I understand correctly the HttpContext.Items is a per request cache storage.
So after some more digging I found the following code.
internal static IDictionary<UnityPerWebRequestLifetimeManager, object> GetInstances(HttpContextBase httpContext)
{
IDictionary<UnityPerWebRequestLifetimeManager, object> instances;
if (httpContext.Items.Contains(Key))
{
instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key];
}
else
{
lock (httpContext.Items)
{
if (httpContext.Items.Contains(Key))
{
instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key];
}
else
{
instances = new Dictionary<UnityPerWebRequestLifetimeManager, object>();
httpContext.Items.Add(Key, instances);
}
}
}
return instances;
}
This is the part where some magic happens that I don't understand. I think they use Unity to do some dependency injection on each request? In my project I am using Ninject and I am wondering how I can get the same result.
I guess InRequestScope in Ninject is the same as UnityPerWebRequestLifetimeManager? I am also wondering which class/method they are binding to which interface? Since the HttpContext.Items get destroyed each request how do they prevent losing their user object?
Anyway it's kinda a long question so I am grateful for any push in the right direction.
In Ninject, you pick your tech-specific extension (Ninject.Web or Ninject.Web.Mvc) and use InRequestScope to manage stuff in 'the .Items context'. They get Disposed at the end of the request and fresh ones will be Resolved as needed on subsequent requests.
It definitely wont be as much code or as complex as some of the stuff you're citing IMO :D
I'm seeing this code in a project and I wonder if it is safe to do:
(ASP.NET MVC 2.0)
class MyController
{
void ActionResult SomeAction()
{
System.Threading.Thread newThread = new System.Threading.Thread(AsyncFunc);
newThread.Start();
}
void AsyncFunc()
{
string someString = HttpContext.Request.UrlReferrer.Authority + Url.Action("Index", new { controller = "AnotherAction" } );
}
}
Is the controller reused, possibly changing the content of HttpContext.Request and Url, or is this fine (except for not using the thread pool).
Thanks for info!
Even if this is valid and works fine now, it just seems risky. The API and/or underlying implementation could always change in a future version, which might cause this code to break.
A much better practice is to pass any required data to the new thread in SomeAction when it is being spawned. For example, by using ParameterizedThreadStart as demonstrated in Passing Parameters to Threads.
I have an ASP.NET MVC app which depends on a lot of settings (name-value pairs), I am planning to store this information in a database table called SiteSettings. Is there an easy way in which I can get these settings using NHibernate. And what are the best practices when saving settings for a web application. And by settings I mean the settings which control the flow of processes in the web application and which are governed by business rules. These are not the typical connection string kind of settings. I was unable to get much information on the web on this topic. Maybe I am not searching on the right keywords, Any help will be greatly appreciated.
I can't answer in the context of nhibernate (which I'm not using) or best practices (I came up with this on my own recently). However, it works well for me, and will probably work for you.
I have a table (Biz_Config) in the database to store business preferences. (I've created a web.config section for what I call IT preferences.)
I have a class that is in charge of managing the biz preferences. The constructor grabs the entire table (one row per setting) and copies these into a dictionary, and it has methods to access (such as bizconfig.get("key")) and update this dictionary, also updating the table at the same time. It also has a few shortcut properties for specific dictionary values, especially where the value has to be cast (I have a few important numbers). It works quite well.
In order to be more efficient and not instantiate it every time I need a setting, and also to access it easily from my controllers and views, I created a static class, Globals, that is in charge of getting things out of the session or application variables. For the biz config object, it checks the application variable and, if null, creates a new one. Otherwise it just returns it. Globals is part of my helpers namespace, which is included in my web.config to be available to my views. So I can easily call:
<% Globals.Biz_Config.Get("key") %>
I hope this helps. If you'd like code, I can dig that up for you.
James
If you have a set of key/value pairs, you probably want to use a <map>. See the official NHibernate documentation or Ayende's post about 'NHibernate Mapping - <map/>'.
I have come up with a solution which is quite similar to the one suggested by James. I have an SiteSettingsService class which manages the settings for the whole site, it has a simple dependency on an interface called ISiteServiceRepository. This might not be the most elegant solution, But it is working perfectly for me. I have also configured the SiteSettingsService class as a Singleton using StructureMap. So, it saves me unnecessary instantiantion every time I need any settings.
//ISiteServiceRepository, an implementation of this uses NHibernate to do just two things
//i)Get all the settings, ii)Persist all the settings
using System.Collections.Generic;
using Cosmicvent.Mcwa.Core.Domain.Model;
namespace Cosmicvent.Mcwa.Core.Domain {
public interface ISiteServiceRepository {
IList<Setting> GetSettings();
void PersistSettings(IDictionary<string, string> settings);
}
}
//The main SiteSettingsService class depends on the ISiteServiceRepository
using System;
using System.Collections.Generic;
using Cosmicvent.Mcwa.Core.Domain;
using Cosmicvent.Mcwa.Core.Domain.Model;
namespace Cosmicvent.Mcwa.Core.Services {
public class SiteSettingsService : ISiteSettingsService {
private readonly ISiteServiceRepository _siteServiceRepository;
private IDictionary<string, string> _settings;
public SiteSettingsService(ISiteServiceRepository siteServiceRepository) {
_siteServiceRepository = siteServiceRepository;
//Fill up the settings
HydrateSettings();
}
public int ActiveDegreeId {
get {
return int.Parse(GetValue("Active_Degree_Id"));
}
}
public string SiteTitle {
get { return GetValue("Site_Title"); }
}
public decimal CounsellingFee {
get { return decimal.Parse(GetValue("Counselling_Fee")); }
}
public decimal TuitionFee {
get { return decimal.Parse(GetValue("Tuition_Fee")); }
}
public decimal RegistrationFee {
get { return decimal.Parse(GetValue("Registration_Fee")); }
}
public void UpdateSetting(string setting, string value) {
if (!string.IsNullOrEmpty(setting) && !string.IsNullOrEmpty(value)) {
SetValue(setting, value);
PersistSettings();
}
}
//Helper methods
private void HydrateSettings() {
_settings = new Dictionary<string, string>();
IList<Setting> siteRepoSettings = _siteServiceRepository.GetSettings();
if (siteRepoSettings == null) {
throw new ArgumentException("Site Settings Repository returned a null dictionary");
}
foreach (Setting setting in siteRepoSettings) {
_settings.Add(setting.Name.ToUpper(), setting.Value);
}
}
private string GetValue(string key) {
key = key.ToUpper();
if (_settings == null) {
throw new NullReferenceException("The Site Settings object is Null");
}
if (!_settings.ContainsKey(key)) {
throw new KeyNotFoundException(string.Format("The site setting {0} was not found", key));
}
return _settings[key];
}
private void SetValue(string key, string value) {
key = key.ToUpper();
if (_settings == null) {
throw new NullReferenceException("The Site Settings object is Null");
}
if (!_settings.ContainsKey(key)) {
throw new KeyNotFoundException(string.Format("The site setting {0} was not found", key));
}
_settings[key] = value;
}
private void PersistSettings() {
_siteServiceRepository.PersistSettings(_settings);
}
}
}
Hope this helps future developers facing similar problems. Any suggestions for improving this are more than welcome.