I have multiple React components wrapped with Query component react-apollo. Each fires its query once being rendered by React.
Sometimes I would like to manage Query execution based on the result of another query. So one Query will need to wait until another has returned a result, update local state, and later fire the other queries, which input/variables is based on the first query result.
Is there a best practice for this kind of orchestration using Apollo?
Or should I manage it myself with the use of the skip property on the Query component?
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I have an application that needs to update the UI with the results of an Amplify Datastore query. I am making the query as soon as the component mounts/renders, but the results of the query are empty even though I know there is available data. If I add a timeout of 1 second or greater before making the query, then the query returns the expected data. My hunch is that this is because the query is returning an empty set of data before the response from the delta sync table, which shows there is data to be fetched, is returned.
Is there any type of event provided by Datastore that would allow me to wait until the data store is initialized or has data to query before making the query?
I understand that I could use the .observe functionality of datastore for a similar effect, but this is currently not an option.
First, if you do not use the Datastore start method then sync from the backend starts when the first query is submitted. Queries are run against the local store so data won't be there yet.
Second, Datastore publishes events on the amplify hub so that you can monitor changes, such as a set of data being synced, Datastore being ready and even Datastore being ready and all data synced locally.
See the documentation on Datastore.start
and the documentation for Datastore events for more information.
I have a requirement to capture session level details like session start time, end time, src success row, failedrows etc.. in a audit table. As all those details are available in prebuilt session variables i need to store these in a table. As of now what i am doing is, taking an assignment task in a workflow and assigning all these prebuilt session variables values for a particular session to wrkflow variables and passing these workflow variables to mapping variables using another non reusable session (the mapping which loads the table) using pre variable assignment option.It is working fine for workflow which is having one session. But if i have to implement this for a workflow having more no of sessions this process will be tedious as i have to create assignment task for each of these sessions and need to create non resuable session which calls a mapping to load into audit table.
So i am wondering is there any alternative solution to get this job done? I am thinking of a solution in which if we can able to captures audit details of all session in a file and pass this file as a input to a mapping to load this data at once into table. Is this possible? any solution?
Check this out: ETL Operational framework
It covers and end-to-end solution that should fit your needs and be quite easy to extend if you have multiple sessions - all you'd need to do is apply similar Post session commands before running the final session that loads the stats to database.
I'm implementing a CQRS/ES solution with Akka.Net and Akka.Net.Persistence with a SQL Server Journal. So far everything seems to work great with the default sql-server plugin.
Last thing to verify was the ability to be able to reload/replay events from a specific AR, e.g. to rebuild a read model or to fill a newly implemented projection for a read model. The way I would go about this is reading the events from de DB and putting them on the eventbus or directly into the mailbox of the "projection actor".
I can't seem to find any examples of manually reloading events and besides querying the Journal table myself (executing sql query) and using the built-in serializer I'm basically stuck with this.
Is there anyone trying to do, more or less, the same thing?
Depending on your needs there are few ways:
Using PersistentView - it's a dedicated actor, which is correlated with some specific persistent actor, and it's able to receive it's events to build some different state from them. It's readonly. Pros: it's keeping itself up to date with events produced by peristent actor (however some delay between updates applies). Cons: it's related with a single actor, it cannot be used to aggregate event's from many of them.
Using journal query (SQL journals only) - it allows you to query journal using some specific filters. Pros: it can be used across multiple aggregates. Cons: it's not automatically kept up to date, you need to send subsequent queries to get updates. I'm not sure, if it has official documentation, but flow itself is described here.
PS: some of the journal implementations have their own dedicated serializers, but not SQL-based ones. And belive me, you never want to rely on default serializer for persisting events.
We are considering moving from Backbone to Ember. There are a few issues through I can't get answers to from the docs.
1) Ember-Data caches it's data. Our application is multi-user so other users need to be able to see new records created by everyone. Is there a way around this? I read on another post that when a query string is passed, ember data does not cache data, is this true? If it is, can I then just always send query string and nothing will be cached?
2) Ember data has a single model in the router that appears to be instantiated at route load time. I can see that your can request data from multiple sources by returning an object with many this.store.find calls. Say I have a select element and when you select an option, another select gets populated with items based on the first select (which requires a call back to the server). How would that work, how can I get model data on demand (not at route load time)?
I'm not sure if it answers your question but you can always call
model.reload()
to refetch data from server so you can work with up to date data.
You may want to consider Faye (http://faye.jcoglan.com/), which would let you have a pub/sub setup that could update your store by listening to topics of interest. This uses WebSocket for the streaming interface. You could then put new objects into the store, remove or update existing objects which the server could publish to the client.
I have a product catalog with a few hundred categories in it and I am dynamically creating an SqlDependency for each category in the catalog. The SqlCommands that these dependencies will be based on, will differ only on the categoryID. The problem that I have is that I want all these dependencies to perform different actions depending on the SqlDependency that fired them. How can I do that? Do I have to create a different OnChange event for each SqlDependency? Is there a way all these dependencies to fire the same OnChange event and this event to know which dependency fired it or receive a parameter which will be passed during the dependency creation?
This problem arised trying to create a Sql Dependency mechanism that will work with AppFabric Cache.
Thank you in advance.
See if you can look into the cache tables that asp.net is creating for you and the triggers that are being created on the original tables. Once you see what is going on, you can create the tables and triggers yourself and can implement the caching through your own asp.net code. It really is not that hard. Then, not when a table is updated(when you use SQLDependency), but relevant rows in that table are updated, you can refresh the relevant cache or write your own code to perform the whatever unique actions you want. Better off doing it yourself when you learn how to!