I could not find detailed info on on the behaviour of Tracker.autorun in Meteor.
E.g. inside of the autorun function what happens (and why):
if I get the same reactive var twice
if I get Meteor.user() and Meteor.userId()
what about reactive vars got in functions nested inside the autorun function
what about multiple different reactive vars
I found a great article about the topic: Meteor Tracker Manual
The Tracker functions (so called computations) are updated whenever the client is idle (this is called Flush-Cycle). If any reactive variable within a computation did change since the last flush it is rerun. This implies that for my questions 1, 2 & 4 this means the computation is only called once. Even if many different variables are updated.
For the nested function question I wrote a test. As it seems even very deeply nested reactive variables are tracked. So one has to be really careful which functions to call within a Tracker function. Since they may contain reactive vars which are then tracked too.
Related
We have 20 functions that must run everyday. Each of these functions do something different based on inputs from the previous function.
We tried calling all the functions in one function, but it hits the timeout error as these 20 functions take more than 9 minutes to execute.
How can we trigger these multiple functions sequentially, or avoid timeout error for one function that executes each of these functions?
There is no configuration or easy way to get this done. You will have to set up a fair amount of code and infrastructure to get this done.
The most straightforward solution involves chaining together calls using pubsub type functions. You can send a message to a pubsub topic that will trigger the next function to run. The payload of the message to send can be the parameters that the function should use to determine how it should operate. If the payload is too big, or some more complex sources of data are required to make that decision, you can use a database to store intermediate data that the next function can query and use.
Since we don't have any more specific details about how your functions actually work, nothing more specific can be said. If you run into problems with a specific detail of this scheme, please post again describing that specifically you're trying to do and what's not working the way you expect.
There is a variant to the Doug solution. At the end of the function, instead of publishing a message into pubsub, simply write a specific log (for example " end").
Then, go to stackdriver logging, search for this specific log trace (turn on advanced filters) and configure a sink into a PubSub topic of this log entry. Thereby, every time that the log is detected, a PubSub message is published with the log content.
Finally, plug your next function on this PubSub topic.
If you need to pass values from function to another one, you can simply add these values in the log trace at the end of the function and parse it at the beginning of the next one.
Chaining functions is not an easy things to do. Things are coming, maybe Google Cloud Next will announce new products for helping you in this task.
If you simply want the functions to execute in order, and you don't need to pass the result of one directly to the next, you could wrap them in a scheduled function (docs) that spaces them out with enough time for each to run.
Sketch below with 3 minute spacing:
exports.myScheduler = functions.pubsub
.schedule('every 3 minutes from 22:00 to 23:00')
.onRun(context => {
let time = // check the time
if (time === '22:00') func1of20();
else if (time === '22:03') func2of20();
// etc. through func20of20()
}
If you do need to pass the results of each function to the next, func1 could store its result in a DB entry, then func2 starts by reading that result, and ends by overwriting with its own so func3 can read when fired 3 minutes later, etc. — though perhaps in this case, the other solutions are more tailored to your needs.
Does dart handle the case in which two different calls of an asynchronous function try to add two (or more) objects to a List at the same time? If it does not is there a way for me to handle this?
I do not need those two new objects to be inserted in a particular order because I take care of that later on, I only wandered what happens in that unlikely but still possible case
If you're wondering if there's any kind of locking necessary to prevent race conditions in the List data structure itself, no. As pskink noted in a comment, each Dart isolate runs in its own thread, and as the "isolate" name implies, memory is not shared. Two operations therefore cannot both be actively updating a List at the same time. Once all asynchronous operations complete, your List will contain all of the added items but not with any guaranteed ordering.
If you need to prevent asynchronous operations from being interleaved, you could use package:pool.
First let's understand the app:
The sample app mocks grabbing data from 2 sources: an array of available objects, and an array of objects being used.
The app also displays new objects (available ones not being used).
Finally, it also allows you to use (register) one of the new objects
Requirements:
The app needs to display the list of New objects first
The app needs to minimize the number of API calls to the bare minimum and only make calls when strictly necessary
Calls to produce changes in API data (register) should be reactive and display changes in UI immediately
The code I have implemented meets these 3 requirements. However, I'm really unhappy with this implementation, and I'm sure that's not the way the Vuex store is supposed to be used.
For starters, my implementation only works for the specific order in which the components are displayed in the screen:
<new name="New" :selected="true"></new>
<available name="Available"></available>
<using name="Using"></using>
If I, for example, want to move <available> to the last tab, the code will break.
This happens because I haven't been able to simply call dispatch('getNews') once and have everything else fall into place, without at the same time duplicating one or to API calls, and thus not meeting the requirements...
I tried using dispatch('...').then().then() but I haven't been able to make it work and meet the requirements.
I would greatly appreciate anyone with experience in similar situations with Vuex tell me how they'd do this.
Bonus if you can do it without adding extra mutations.
I have a cloud function that is called onWrite for /searches/{id}. It was stuck in an infinite loop, similar to what happened here and here. Difference being, as far as I can tell, writing wasn't happening.
This same cloud function was working just fine minutes ago. I did make minor changes, but nothing is writing to the database as far as I can tell.
There is the distinct possibility that somehow writing was happening and I am mistaken. But, checking my live database, there were no changes to any of the records (currently, there is just one, so it is easy to monitor...).
The events that were being called also were marked with ids that never showed up in my database. E.g., one event.resource outputted as 'projects/_/instances/sequel-tracker/refs/searches/00235180-bb4d-11e7-a598-412f4ffc71ff' in the console, but my one record in /searches has a different ID.
Each event in the infinite loop seems to have a different ref path.
Any guesses on what could be happening?
I have a web application that talks to R using plr when doing adaptive testing.
I would need to find a way to store static data persistently between calls.
I have an expensive calculation creating an item bank than a lot of cheap ones getting the next item after each response submission. However currently I can't find a way to store the result of the expensive calculation persistently.
Putting it into the db seems to be a lot of overhead.
library(catR)
data(tcals)
itembank <- createItemBank(tcals) --this is the expensive call
nextItem(itembank, 0) # item 63 is selected
I tried to save and load the result, like this, but it doesn't seem to work, the result of the second NOTICE is 'itembank'.
save(itembank, file="pltrial.Rdata")
pg.thrownotice(itembank)
aaa=load("pltrial.Rdata")
pg.thrownotice(aaa)
I tried saving and loading the workspace as well, but didn't succeed with that either.
Any idea how to do this?
The load function directly loads objects into your workspace. You don't have to assign the return value (which is just the names of the objects loaded, as you discovered). If you do a ls() after loading, you should find your itembank object sitting there.