I have a regional object store. I would like to be able to tell a particular object that I want you deleted in 5 days time from now.
How do you suggest I implement?
I don't really want to keep track of the object in a database, and based on time send delete commands as a separate process. Is there any tag that could be set to get deletion to occur at a later time (from now, not a specific time in the past)?
There's no functionality built into Google Cloud Storage to do this.
You can configure Lifecycle Management to delete objects according to a number of criteria (including age) - but deleting at a particular date in the future isn't one of the supported conditions and in fact there's no guarantee that a lifecycle condition will run the same day the condition becomes true. Instead you would have to implement this functionality yourself (e.g., in a Compute Engine or App Engine implementation).
Related
I'm planning on using rxdb + hasura/postgresql in the backend. I'm reading this rxdb page for example, which off the bat requires sync-able entities to have a deleted flag.
Q1 (main question)
Is there ANY point at which I can finally hard-delete these entities? What conditions would have to be met - eg could I simply use "older than X months" and then force my app to only ever displays data for less than X months?
Is such a hard-delete, if possible, best carried out directly in the central db, since it will be the source of truth? Would there be any repercussions client-side that I'm not foreseeing/understanding?
I foresee the number of deleted's growing rapidly in my app and i don't want to have to store all this extra data forever.
Q2 (bonus / just curious)
What is the (algorithmic) basis for needing a 'deleted' flag? Is it that it's just faster to check a flag rather than to check for the omission of an object from, say, a very large list. I apologize if it's kind of a stupid question :(
Ultimately it comes down to a decision that's informed by your particular business/product with regards to how long you want to keep deleted entities in your system. For some applications it's important to always keep a history of deleted things or even individual revisions to records stored as a kind of ledger or history. You'll have to make a judgement call as to how long you want to keep your deleted entities.
I'd recommend that you also add a deleted_at column if you haven't already and then you could easily leverage something like Hasura's new Scheduled Triggers functionality to run a recurring job that fully deletes records older than whatever your threshold is.
You could also leverage Hasura's permissions system to ensure that rows that have been deleted aren't returned to the client. There is documentation and examples for ways to work with soft deletes and Hasura
For your second question it is definitely much faster to check for the deleted flag on records than to have to try and diff the entire dataset looking for things that are now missing.
my challenge:
we receive files every day with about 200.000 records. We keep the files for approx 1 year, to support re-processing, etc..
For the sake of the discussion assume it is some sort of long lasting fulfilment process, with a provisioning-ID that correlates records.
we need to identify flexible patterns in these files, and trigger events
typical questions are:
if record A is followed by record B which is followed by record C, and all records occured within 60 days, then trigger an event
if record D or record E was found, but record F did NOT follow within 30 days, then trigger an event
if both records D and record E were found (irrespective of the order), followed by ... within 24 hours, then trigger an event
some pattern require lookups in a DB/NoSql or joins for additional information either to select the record, or to put into the event.
"Selecting a record" can be simple "field-A equals", but can also be "field-A in []" or "filed-A match " or "func identify(field-A, field-B)"
"days" might also be "hours" or "in previous month". Hence more flexible then just "days". Usually we have some date/timestamp in the record. The maximum is currently "within 6 months" (cancel within setup phase)
The created events (preferably JSON) needs to contain data from all records which were part of the selection process.
We need an approach that allows to flexibly change (add, modify, delete) the pattern, optionally re-processing the input files.
Any thoughts on how to tackle the problem elegantly? May be some python or java framework, or does any of the public cloud solutions (AWS, GCP, Azure) address the problem space especially well?
thanks a lot for your help
After some discussions and readings, we'll try first Apache Flink with the FlinkCEP library. From the docs and blog entries it seems to be able to do the job. It also seems AWS's choice, running on their EMR cluster. We didn't find any managed service on GCP nor Azure providing the functionalities. Of course we can always deploy and manage it ourselves. Unfortunately we didn't find a Python framework
I am trying to implement a method where a post(s) will be deleted after a given time frame. In my case 10 weeks.
How would I go about implementing a feature? I've read that Firebase does not support server-sided scripting. So how could I go about it? When users uploads a post, I do have a timestamp node attached. Is it a case of comparing the post's timestamp to a timestamp of 10 weeks? And then removing the post? Or is there another, more efficient way to achieve such a thing?
If I was to implement the aforementioned method, this would mean I'd require an observer/method to first analyse ALL posts, then do the comparison and then execute the second phase, depending on the timestamp - removeValue or simply return. And I wouldn't I need to use NotificatonCenter so I can call this code throughout my whole app?
Any input/advice would be appreciated.
I found time as the best value as event version.
I can merge perfectly independent events of different event sources on different servers whenever needed without being worry about read side event order synchronization. I know which event (from server 1) had happened before the other (from server 2) without the need for global sequential event id generator which makes all read sides to depend on it.
As long as the time is a globally ever sequential event version , different teams in companies can act as distributed event sources or event readers And everyone can always relay on the contract.
The world's simplest notification from a write side to subscribed read sides followed by a query pulling the recent changes from the underlying write side can simplify everything.
Are there any side effects I'm not aware of ?
Time is indeed increasing and you get a deterministic number, however event versioning is not only serves the purpose of preventing conflicts. We always say that when we commit a new event to the event store, we send the new event version there as well and it must match the expected version on the event store side, which must be the previous version plus exactly one. If there will be a thousand or three millions of ticks between two events - I do not really care, this does not give me the information I need. And if I have missed one event on the go is critical to know. So I would not use anything else than incremental counter, with events versioned per aggregate/stream.
I keep seeing questions floating through that make reference to a column in a database table named something like DateLastUpdated. I don't get it.
The only companion field I've ever seen is LastUpdateUserId or such. There's never an indicator about why the update took place; or even what the update was.
On top of that, this field is sometimes written from within a trigger, where even less context is available.
It certainly doesn't even come close to being an audit trail; so that can't be the justification. And if there is and audit trail somewhere in a log or whatever, this field would be redundant.
What am I missing? Why is this pattern so popular?
Such a field can be used to detect whether there are conflicting edits made by different processes. When you retrieve a record from the database, you get the previous DateLastUpdated field. After making changes to other fields, you submit the record back to the database layer. The database layer checks that the DateLastUpdated you submit matches the one still in the database. If it matches, then the update is performed (and DateLastUpdated is updated to the current time). However, if it does not match, then some other process has changed the record in the meantime and the current update can be aborted.
It depends on the exact circumstance, but a timestamp like that can be very useful for autogenerated data - you can figure out if something needs to be recalculated if a depedency has changed later on (this is how build systems calculate which files need to be recompiled).
Also, many websites will have data marking "Last changed" on a page, particularly news sites that may edit content. The exact reason isn't necessary (and there likely exist backups in case an audit trail is really necessary), but this data needs to be visible to the end user.
These sorts of things are typically used for business applications where user action is required to initiate the update. Typically, there will be some kind of business app (eg a CRM desktop application) and for most updates there tends to be only one way of making the update.
If you're looking at address data, that was done through the "Maintain Address" screen, etc.
Such database auditing is there to augment business-level auditing, not to replace it. Call centres will sometimes (or always in the case of financial services providers in Australia, as one example) record phone calls. That's part of the audit trail too but doesn't tend to be part of the IT solution as far as the desktop application (and related infrastructure) goes, although that is by no means a hard and fast rule.
Call centre staff will also typically have some sort of "Notes" or "Log" functionality where they can type freeform text as to why the customer called and what action was taken so the next operator can pick up where they left off when the customer rings back.
Triggers will often be used to record exactly what was changed (eg writing the old record to an audit table). The purpose of all this is that with all the information (the notes, recorded call, database audit trail and logs) the previous state of the data can be reconstructed as can the resulting action. This may be to find/resolve bugs in the system or simply as a conflict resolution process with the customer.
It is certainly popular - rails for example has a shorthand for it, as well as a creation timestamp (:timestamps).
At the application level it's very useful, as the same pattern is very common in views - look at the questions here for example (answered 56 secs ago, etc).
It can also be used retrospectively in reporting to generate stats (e.g. what is the growth curve of the number of records in the DB).
there are a couple of scenarios
Let's say you have an address table for your customers
you have your CRM app, the customer calls that his address has changed a month ago, with the LastUpdate column you can see that this row for this customer hasn't been touched in 4 months
usually you use triggers to populate a history table so that you can see all the other history, if you see that the creationdate and updated date are the same there is no point hitting the history table since you won't find anything
you calculate indexes (stock market), you can easily see that it was recalculated just by looking at this column
there are 2 DB servers, by comparing the date column you can find out if all the changes have been replicated or not etc etc ect
This is also very useful if you have to send feeds out to clients that are delta feeds, that is only the records that have been changed or inserted since the data of the last feed are sent.