Comment 0 for bug 1554993

I've observed that a service which is OKAY can flap to CRITICAL sometimes. Depending on when the request is made, the "group by" returns 'null' and grafana panel interpret it as CRITICAL.

request/response:
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SELECT last("value") FROM "haproxy_backend_status" WHERE "hostname" =~ /node-110/ AND time > now() - 5m GROUP BY time(1m)

{"results":[{"series":[{"name":"haproxy_backend_status","columns":["time","last"],"values":[[1457193600000,1],[1457193660000,1],[1457193720000,1],[1457193780000,1],[1457193840000,1],[1457193900000,null]]}]}]}

Solution
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add fill(previous) to avoid null results