title: Influxdb - group by time(1m) - missing data
body: <p>I have some data that is coming in from the network every minute from collectd and being entered into my influx database.  Since its via the network it never comes in right on the one minute mark and has some jitter...</p>
  
  <p>I am trying to reconcile this irregular data to one minute intervals but I am seeing some missing gaps, please see example below.</p>
  
  <pre><code>&gt; precision rfc3339
  &gt;
  &gt; select value from snmp_ecio where host = 'my_host_a' and time &gt; now() - 10m
  name: snmp_ecio
  time                            value
  ----                            -----
  2017-01-22T00:25:59.987735Z     -0.1
  2017-01-22T00:27:00.003208Z     -0.1
  2017-01-22T00:28:00.047265Z     -0.2
  2017-01-22T00:29:00.142676Z     -0.1
  2017-01-22T00:30:00.048707Z     -0.3
  2017-01-22T00:31:00.211728Z     -0.1
  2017-01-22T00:31:59.980621Z     -0.1
  2017-01-22T00:32:59.795329Z     -0.1
  2017-01-22T00:34:03.206552Z     -0.1
  2017-01-22T00:35:00.01463Z      -0.1
  
  &gt; select mean(value) from snmp_ecio where host = 'my_host_a' and time &gt; now() - 10m group by time(1m)
  name: snmp_ecio
  time                    mean
  ----                    ----
  2017-01-22T00:25:00Z    -0.1
  2017-01-22T00:26:00Z
  2017-01-22T00:27:00Z    -0.1
  2017-01-22T00:28:00Z    -0.2
  2017-01-22T00:29:00Z    -0.1
  2017-01-22T00:30:00Z    -0.3
  2017-01-22T00:31:00Z    -0.1
  2017-01-22T00:32:00Z    -0.1
  2017-01-22T00:33:00Z
  2017-01-22T00:34:00Z    -0.1
  2017-01-22T00:35:00Z    -0.1
  </code></pre>
  
  <p>Has anyone experienced this issue or can point me in the right direction?</p>
  
  <p>Thanks!</p>