apt – How to solve “Unable to download updates: failed to refresh cache: http://it.archive.ubuntu.com/ubuntu disco Release?

The software updater doesn’t work good and the system also keeps asking me to report a problem, I believe this error is the reason but what do I have to do to solve it? Updater also says that i should upgrade to 20.04 lts because my 19.04 version is no longer updated, but then i click on “upgrade” and nothing happens. Let me know if i have to paste something specific.

The full error message is:

Unable to download updates: failed to refresh cache: E: The repository 
'http://it.archive.ubuntu.com/ubuntu disco Release' does not have a Release file. 

computer architecture – A cache has 64K lines where each line can store 8 blocks of the memory at a time

A cache has 64K lines where each line can store 8 blocks of the memory at a time. If the size of the memory is 2GB and block size is 4 Bytes, then which cache line is supposedly be holding the memory block with number “256” if cache supports Direct Mapping. Also compute total number of blocks this memory has and total number of blocks the cache in question can store at a time.

magento2.3.1 – Magento2: Redis Cache issue on Product page gallery image not showing

We are facing issue with Magento2 with Redis Cache on Product page gallery image not showing.
Images are showing on Category listing and all pages but on product view page images not showing.

We are using Redis 4.0 ver and using cloudfront with magento2 and we have 2 storeview.
In Arabic default store view image are displaying but in English storeview images are not showing.

In admin product images are assign in all products.
When click on image URL, it’s showing pub/media/catalog/product/cache/1851fb9fe6a1abd654a28e505b3e92be/7/0/7006005_test.jpg

image cache folder(1851fb9fe6a1abd654a28e505b3e92be) is showing wrong path on english store view

Algorithm to figure our deps in a graph that can resolve deps from cache (dictionary) of walked paths

I have a graph like this that starts from one top node and has cycles:

enter image description here

I need to write an algorithm to figure if node1 depends on node2. The most primitive algorithm I’ve written simply starts with node1 and recursively follows all available edges looking for node2 starting from node1. It’s very inefficient because I traverse the graph over and over again. I’m wondering if there’s an algorithm I can look at that caches nodes and dependencies it already walked through so that I don’t go through paths I’ve walked once and can figure if there’s a dependency or not from cache?

For example, if I’m given node D and the question is whether it depends on node F, I’ll walk D->E->F, and when next time I get the question if node E depends on F, I’ll get that from cache without walking the graph.

Thanks for any ideas and suggestions!

computer architecture – How does the cache / memory know where to return results of read requests to?

The pipeline of a modern processor has many stages that may issue read
requests to main memory, e.g. in fetching the next command or loading
some memory location into a register. How is the result of a read
request returned to the right pipeline stage, given that there are more than one possible recipients?
Since most CPUs access main memory via a cache hierarchy, the question
becomes: how does the L1 cache know which part of the pipeline to
return a result to?

I imagine that access to the L1 cache is queued, but each access
presumably needs a ‘return address’. How is this typically handled?

sharepoint online – Client-side page cache issue

I am a SharePoint developer with a relative good knowledge of SharePoint administration.
I am facing a weird behavior on a customer tenant, which I cannot reproduce on my Dev tenant.

(As a background information which does matter, we have an app which is currently working mostly in the classic SharePoint pages/layout)

The issue being encountered is the editform.aspx page (for any list or library) is showing the n-1 data. Let’s say I access the site the first time, I edit item ID 4, it will edit that item. Now if I want to edit item ID 5, it will show up the editform with data from ID 4. If I edit the item ID 54, the editform will show data from ID 5. And so on, and so forth.

This behavior does not seem to happen in case we do not ever open a modern list view, or a modern page which contains some logic I have not yet figured out.

I managed to deep dive a bit into the browser developer tools to find the following bit of information:

  • The editform.aspx is called with a “preload” request, and a service/web worker (odspserviceworkerproxy.aspx) is being used on the site, providing a cached page.
    If I temporarily disable the worker for the session using the browser developer tools and try again to edit items, the correct data comes back every time.
  • This odspserviceworkerproxy.aspx seems to be a standard helper from Microsoft included in all modern sites. It seems to be automatically installed, registered and started on the browser every time a modern list or view is displayed.
  • The service stores information in the browser in an IndexedDB named “ODSP_DB – <Tenant URL>”, and has a table named “ODSP_DB_TABLE”.
  • The table stores different kind of information, but it also stores a “_odsp_<encoded page url>” key with a JSON object as a value. This JSON object has a property “app” with a value of “sts-page-response-cache”
  • Whenever the service sees a page to display is available in this internal cache, it seems to be using the cached data to render, while the real live page is gathered in the background to update this local cache.
  • This internal local cache can hold an unknown amount of pages in cache, but the service seems to focus on the 15 most accessed pages
  • And most importantly, it seems it does not care about the dynamic data in the URL, like the ID of the item being edited, causing the previous form being accessed to be rendered instead.

I am unsure whether this behavior is caused by a recent SharePoint Online update as my customer said it started about 3 weeks ago or so, or if a specific feature (native SharePoint site or site collection feature, or a custom developed one) can be responsible for that behavior. I thought of the Publishing one, but it did not seem to make a change on my side.

I checked the SharePoint Admin section as well as the Office365 Admin section, but I could not find anything to configure client-side caching through this service worker.

As previously said, I am partially unable to reproduce that behavior on my tenant. I can get list views pages into the local cached DB, but the editform.aspx never reaches the cache and I can always edit the correct items I need.

I am wondering if anybody has a clue, a hint or if I am the only one facing such issue.

8 – How can I reset render cache on an entity for current user in hook_entity_view_alter()?

I have Commerce products for which I’m showing or hiding the add-to-cart link, if that product is or isn’t in the current cart. In my code:

function mymodule_commerce_product_view_alter(array &$build, EntityInterface $entity, EntityViewDisplayInterface $display) {
    $myservice = Drupal::service('myservice');
    if ($myservice->isProductInCurrentCart($entity->id()) {
        $build('add_to_cart_link')('#access') = FALSE;

That works fine, however, when the product entities are rendered, they retain their cache and will continue to display, or not display, the add-to-cart link until the cache is cleared.

In my view_alter hook, how can I clear the cache for the current user for that entity before it’s rendered? Can I set a cache tag?