"Marten does need to know what the event types are before you issue queries against the event data"
But I do for example
session.Events.FetchStream(streamId)
and
session.Events.Load<MembersJoined>()
and they works fine
thanks
I have found that, in practice, if your application commits events to Marten prior to reading any streams, you don't have to register any events.
If, however, you wind up reading streams prior to committing anything, you need to configure your events first. My application conditionally rebuilds projections on startup prior to accepting input, so it wound up causing this problem.
How to configure Marten for your events
When configuring Marten, pass in an IEnumerable<Type> of all your event types. For instance, my registration looks like this:
cfg.Events.AddEventTypes(
typeof(EventBase)
.Assembly
.GetTypes()
.Where(typeof(EventBase).IsAssignableFrom)
);
I recommend using a base class for all events as it makes things like this super simple.
Having configured Marten with those events, you are now free to query streams as you need to.
Related
So this is something I've been racking my brain about a bit, consider the following scenario:
I'm working on my project, I build it, and in my bundle is a lazyloaded module: module-a-[oldhash].js, that will get lazyloaded at some point in time.
Everything is fine and dandy.
I do some more work on my project, create a new bundle, deploy, and now my content hash has changed: module-a-[newhash].js. I deploy, go to my page, my service worker calls skipWaiting, but my page still tries to request module-a-[oldhash].js, which now no longer exists.
How do I go about this? The only way that I can think of handling this, is show an 'update available' message that posts a skipWaiting message to the service worker, and reloads the page on controllerchange event. But I'm curious if theres no way to achieve to same thing without having to include such a notification/toast pattern and a reload.
Additionally, its my understanding that this would only pose a problem with lazyloaded resources
Is my understanding of these problems correct? What are some common patterns for dealing with this?
Pretty much everything you describe there is correct. I'll just point out that this is a problem that extends beyond the use of a service worker. It can easily happen with long-lived single page apps that attempt to lazy-load a URL that has been replaced server-side with a new deployment.
There's some general information about the problem and potential solutions collected on at this Paying Attention while Loading Lazily site and associated video.
In general, the best practice is to:
Always assume that lazy-loading might fail (for whatever reason) and handle those failures gracefully. One approach might be to ask a user to reload the page upon encountering a failure.
Using a cache-first service worker can help protect against lazy-loading failures, at the expense of delaying updates until the newly installed service worker moves from waiting to active. As you mentioned, the best practice tends to be to show something in your UI letting a user know that updates are available, and once they opt-in to accepting those updates, postMessage() to the service worker telling it to call skipWaiting(). And finally, listening for the controllerchange event and calling window.location.reload() when that's fired.
I am using Revulytics SDK to track feature usage and came across the below problem.
I am sending feature usage after properly setting up the SDK configuration etc, using the EventTrack() method like this:
GenericReturn grTest = telemetryObj.EventTrack("FeatureUsage", textBoxName.Text.ToString(), null, false);
This returns OK and usually, I can see the usage data in the dashboard. However, after multiple tests, the data I am sending does not show up on the dashboard.
Can anyone hint me how to debug this? Thanks for any help!
I hit a similar issue when first working with this SDK.
I was able to address this as soon as I understood the following:
There are event quotas for the incoming events;
Event names are used for making the distinction.
So when I was sending dummy test data, it made it there, but when I sent some demo data for stakeholders, it was not showing up.
I think the same happens here. You're getting the event name form textbox.text... Pretty sure that varies every time you run the code.
Here are the things to keep in mind when testing your code:
the server has a mechanism to discard / consider events;
implicitly, it allows first xx events depending on the quota;
if you are sending more than xx events, they will not show up in reports.
So, you must control which events to discard and which to consider (there are a couple of levels you can configure, and based of them you can get the events in various types of reports).
Find the "Tracked Events Whitelist Management". You will be able to control these things form there.
This blog helped me (it is not SDK documentation): https://www.revulytics.com/blog/getting-started-with-usage-intelligence-part2-event-tracking
Good luck!
I am using Redis for asp.net MVC output cache. Some of my views take a fair bit of processing, currently I have an overnight process that generates the required data for the views and puts it in Redis cache so the views can render much quicker, however the data is only in the cache for the purpose of the initial render of the view and then the view is cached by output cache config.
It would be MUCH better if I could just render the view and put that directly into the cache from the overnight console program. How would I do this? I gather I would need to insert to Redis with the same key that ASP.NET MVC would give and call whatever internal render method that asp.net MVC uses?
I don't need instructions for inserting to Redis, rather what is the render method I need to call and how are the key names constructed for asp.net MVC OutputCache.
I am using asp.net MVC 5, however, bonus kudos if you can also answer for Core to futureproof the answer!
Please no suggestions of generating static files, that's not what I want, Thanks.
How are the key names constructed for asp.net mvc outputcache?
This part is easy to answer if you consult the source code for OutputCacheAttribute. The keys depend on the settings (e.g. the keys will have more data in them if you have set VaryByParam). You can determine the keys by checking how the attribute populates uniqueID for you use case. Notice that the keys are concatenated and then hashed (since they could get very long) and then base64-encoded. Here is the relevant code:
internal string GetChildActionUniqueId(ActionExecutingContext filterContext)
{
StringBuilder uniqueIdBuilder = new StringBuilder();
// Start with a prefix, presuming that we share the cache with other users
uniqueIdBuilder.Append(CacheKeyPrefix);
// Unique ID of the action description
uniqueIdBuilder.Append(filterContext.ActionDescriptor.UniqueId);
// Unique ID from the VaryByCustom settings, if any
uniqueIdBuilder.Append(DescriptorUtil.CreateUniqueId(VaryByCustom));
if (!String.IsNullOrEmpty(VaryByCustom))
{
string varyByCustomResult = filterContext.HttpContext.ApplicationInstance.GetVaryByCustomString(HttpContext.Current, VaryByCustom);
uniqueIdBuilder.Append(varyByCustomResult);
}
// Unique ID from the VaryByParam settings, if any
uniqueIdBuilder.Append(GetUniqueIdFromActionParameters(filterContext, SplitVaryByParam(VaryByParam)));
// The key is typically too long to be useful, so we use a cryptographic hash
// as the actual key (better randomization and key distribution, so small vary
// values will generate dramtically different keys).
using (SHA256Cng sha = new SHA256Cng())
{
return Convert.ToBase64String(sha.ComputeHash(Encoding.UTF8.GetBytes(uniqueIdBuilder.ToString())));
}
}
You'll notice later the uniqueID is used as a key into the internal cache:
ChildActionCacheInternal.Add(uniqueId, capturedText, DateTimeOffset.UtcNow.AddSeconds(Duration));
What is the render method I need to call?
Short answer: ExecuteResult.
Long answer: Holy crap, you are asking a lot here. Essentially you wish to instantiate some objects within the console process and call methods which will faithfully recreate the output that would have been created if you called it from within the AppDomain where the web site usually runs.
Web applications often rely on initialization and state that is created when the application starts up (e.g. setting up the composition root/IoC, or setting up Automapper, that sort of thing), so you'd have to run the initialization of your web site. A specific view may rely on contextual information such as the URL, cookies, and querystring parameters; it may rely on configuration; it may call internal services, which also rely on configuration, as well as the AppDomain account being set up a certain way; it may need to use things like client certificates which may be set up in the service account's personal store, etc.
Here is the general procedure of what the console app would have to do:
Instantiate the site's global object, calling its constructor, which may attempt to wire up events to the pipeline.
You will need to mock the pipeline and handle any events raised by the site. You will also need to raise events in a manner that simulates the way the ASP.NET pipeline works.
You will need to implement any quirks in the ASP.NET pipeline, e.g. in addition to raising events you will also need to call handlers that aren't subscribed to the events if they have certain predefined names, such as Application_Start.
You will need to emulate the HTTP request by constructing or mocking pipeline objects, such as HttpContext.
You will need to fire request-specific events at your code in the correct order to simulate HTTP traffic.
You will need to run your routing logic to determine the appropriate controller to instantiate, then instantiate it.
You will need to read metadata from your action methods to determine which filters to apply, then instantiate them, and allow them to subscribe to yet more events, which you must publish.
In the end you will need to get the ActionResult object that results from the action method and call its ExecuteResult method.
I don't think this is a feasible approach, but I'd like to hear back from you if you succeed at it.
What you really ought to do
Your console application should simply fire HTTP requests at your application to populate the cache in a manner consistent with actual end user usage. This is how everyone else does it.
If you wish to replace the cached page before it has expired, you can invalidate the cache by restarting the app pool, or by using a dependency.
If you are worried about your response time statistics, change the manner in which you measure them so that you exclude any time window where this refresh is occuring.
If you are worried about impacts to a Google crawl, you can modify the host load schedule and set it to 0 during your reset window.
If you really don't want to exercise the site
If you insist that you don't want to exercise the site to create the cache, I suggest you make the views lighter weight, and look at caching at lower layers in your application.
For example, if the reason your views take so long to render is that they must run complicated queries with a lot of joins, consider implementing a database cache in the form of a denormalized table. You can run SQL Agent jobs to populate the denormalized table on a nightly basis, thus refreshing your cache. This way the view can be lightweight and you won't have to cache it on the web server.
For another example, if your web application calls RESTful services that take a long time to run, consider implementing cache-control headers in your service, and modify your REST client to honor them, so that repeated requests for the same representation won't actually require a service call. See Caching your REST API.
Hopefully the title is clear, I couldn't find a better name but if someone can improve it please update it, thanks.
I would like the Firebase database to write on a node if a certain condition is met. For example, if one node receives an input from a client (say an angular app) then another node in the database should write certain data, something like a callback that is fired when a node receives some data.
I know there are 4 rule types (.read .write .validate .indexOn), what I am thinking of is some kind of .callback rule that is fired and writes on a node after some other node has received an input.
Obviously this can be achieved via a server side script but Firebase is about a server-less approach so I am trying to understand what are its current limits and what I can do with it.
Thanks for your responses
firebaser here
Running the multi-location update client-side or on a server-side process that you control are currently the only ways to accomplish this.
There is currently no way to trigger updates based on modifications to the database on Firebase servers. It is no big secret that we've been working on such functionality for a while now, but we have made no announcement as to when that will be available.
Also see Can I host a listener on Firebase?, which (I realize now) is probably a duplicate.
I want to trigger an API call to fetch some supplemental data and display it alongside my react final form. What's the best way to do this?
I've started by using OnChange from react-final-form-listeners to listen for a field change and make an API call, but I don't really know how to store this data somewhere and display it within the react-final-form framework. Using a functional component and a State hook, it would be relatively trivial, because I would just set the state of a variable and then display it somewhere in the same component. Is this a sign that I should be storing these kinds of things in redux? Can I use hooks instead?
I forked one of the examples and added what I am trying to do:
https://codesandbox.io/embed/react-final-form-field-arrays-k9pqm
You're talking a little too abstractly about your goal here, but sure, you could keep the loaded data in state with a useState() hook. If I were you, I'd want to debounce it, and keep track of whether or not the Promise from your API call was the Promise from the last call or not.