author here:
> replica 0
It's an example for the article and the intention was to remove the complexity of primary/replica shards.
Let's say "shard" is an unit and no matter about primary or replica.
In fact with replica to 1, the behaviour would be the same but in the diagram it will have twice more shards.
What we wanted to show is IF one node goes down and up after few times AND a rollover occurs just after then this node will handle all those new shards and so handle all the write. here we have a spread write issue
> introduction of a job which runs each day
this job has many purposes:
1) because of rollover, our indexes are now suffixed by -000001 then -000002 etc...our applications no matter of the rollover post and get doc by the alias in front of these indexes suffixed by -000001... So if you don't create the index for the next day in a daily basis index design, your application will push at 00:00:01 a new index with the alias name and it won't be in rollover "mode".
2) because we are using ILM feature, we need to define the ILM rollover alias in the template and it changes each day because our indexes name are "index_$date"
3) performance issues: we have a lot of traffic and if we do not create index before for the next day, we will except a lot of unassigned shards, cluster yellow etc...
in fact, yes, it's a common use-case (daily based index) but maybe not with rollover + ilm
> introduction of a job which runs each day this job has many purposes: 1) because of rollover, our indexes are now suffixed by -000001 then -000002 etc...our applications no matter of the rollover post and get doc by the alias in front of these indexes suffixed by -000001... So if you don't create the index for the next day in a daily basis index design, your application will push at 00:00:01 a new index with the alias name and it won't be in rollover "mode". 2) because we are using ILM feature, we need to define the ILM rollover alias in the template and it changes each day because our indexes name are "index_$date" 3) performance issues: we have a lot of traffic and if we do not create index before for the next day, we will except a lot of unassigned shards, cluster yellow etc...
in fact, yes, it's a common use-case (daily based index) but maybe not with rollover + ilm