Delay operator

[darach]

Describe the problem you are trying to solve

As a developer/operator of a complex system or service undergoing transformation
or migration to a service oriented architecture, a facility to inject delays into streams
would be a useful migration/debugging aid for complex system and service migrations.

Describe the solution you'd like

Provide delay operator that can be configured with a configurable default delay
in nanoseconds, or a per event delay via metadata ( also in nanoseconds ). Events
are delayed either by the default delay, or the per-event delay provided in metadata.

define qos::delay operator mimic_xdc_latency
with
  delay = 30000000 # 30 millis
end;

create operator mimic_xdc_latency;

select event from in into mimic_xdc_latency;
select event from mimic_xdc_latency into out;

Notes

A more advanced implementation would offer variance of the delayed time to
a distribution ( eg: pareto ) by some mechanism, but even the basic design
highlighted would be super useful for migration/capacity planning and impact
analysis for existing systems/services where tremor is in production.

[mfelsche]

Nice idea. And a metadata value that controls the actual delay would also be nice.

[darach]

I clarified the metadata variant in the description - the description wasn't clear enough on per event delay being metadata driven. Thanks @mfelsche !

[tobehardest]

Does this problem still need to be solved? I'd like to try it out if I can.

[Licenser]

Due to the lack of communication on the other issue you asked to be assigned we're holding off on assigning this for now.