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I was trying yesterday to debug an issue that was appeared to be affecting the PubSub Agent — yes, I re-started it at the request of their sysadmin.

The issue was that it was showing data that appeared to have no relationship with the data appearing from all of the other measurement locations. I tried blocking it off using IPTables, MySQL restrictions, etc.

This afternoon, I figured out the problem.

Yesterday, I had been using this query to diagnose the problem:

select
       *
from
    data
where
    agent_id = 11
    and date between subdate(now(),interval 30 minute) and now()
order by
    date DESC

And everytime I looked, there was new data. I couldn’t seem to stop the agent from delivering data. Then I had a flash.

select
       count(*)
from
    data
where
    agent_id = 11
    and date > now()

157,000 rows of data. From the future.

Thankfully I know the guy who is responsible for keeping the PubSub servers running, and he is going to adjust the time, etc. But he makes no promises about how long the agent machine will stay running.

I apologize for the bad data.

Technorati Tags: GrabPERF, PubSub, Web Performance, The Future