> On 31 May 2017, at 12:15, Guillaume Delhumeau <guillaume.delhum...@xwiki.com> > wrote: > > Help me to decide! > > TL;DR: > > * I need to know if performing a query on the database for each user who > want to receive an email with all the notifications, is a scalability issue > (in a job context). > * If it's not an issue, I can implement the "naïve" solution which requires > less development. > > Full message: > > Status: > * notifications are displayed on the top menu when you browse the wiki. > * notifications are displayed differently for each individual user > according to their preferences (filters on event type, on locations, > etc...). > * similar notifications are grouped together into "composite notifications". > * there is only a few notifications displayed (5 by default). > > Objective: > * send an email periodically (every hour, every day, every week) according > to the user preferences with ALL events that happened during the last > period of time, but still according to the user preferences.
Don’t forget the realtime email notification use case too! Thanks -Vincent > Inspiration: > * the watchlist gets ALL events that happened during the last period of time > * then, for each user, remove the events which the user is not interested in > * Benefit: only one query to get the events from the database for all users > > Problems: > * in the notifications, I have introduced a NotificationFilter role the > make possible to inject some SQL in the query to get the events according > to the user preferences. I call this "pre-filters". > ** it means we generate a unique request for each individual user, so if we > send a mail to 1000 users, we will have 1000 requests to the database. > > I wonder if it's a non-problem or a big scability issue. Because even if > the whole job that send emails take ~10 minutes, it does not matter. It's > not a realtime thing. > > For the records, NotificationFilter have "post-filters" too, that perform > check on the event itself (for example checking the permissions, etc...). > > Alternatives: > * just like the watchlist, perform a very generic query on the database to > get all the events that happened during the last period of time > * then for each user, use only the "post-filters" to remove events the user > don't care of > > Problem: > * it means the pre-filters that make sense in the notification use-case > cannot be used for emails. Developers must be aware of this. > * it requires some refactoring of the code that group similar notifications. > > Question: > Should I go with the "naive" solution, ie for each user get all > notifications and send a mail, or should I go with the "only 1 query to the > database for all users" version? > > Thanks, > > -- > Guillaume Delhumeau (guillaume.delhum...@xwiki.com) > Research & Development Engineer at XWiki SAS > Committer on the XWiki.org project
