openweather plugin ?

[Donato]

Hi akbooer,
i hope all is well.

I've a question about datayours and the aggregation e schemas parameters.
I've these configurations :

1. aggregation :
   [Power_Calcolata_Kwatt]
   pattern = .Variable
   xFilesFactor = 0
   aggregationMethod = average

2. schemas:
   [Power_Calcolata_Kwatt]
   pattern = .Variable
   retentions = 1m:1d,5m:90d,10m:180d,1h:2y,1d:10y

In the cache history of openluup console for example i see these values :

2024-06-27 09:17:57 46.73
2024-06-27 09:17:25 16.55

and in the whisper file (it contains a point every minute) i see :

1719472620, 46.73 (17119472620 is 09.17 time for my zone)

It seems that is considered the last value and not the average of two value registered at 9.17 time.

Is it correct ?

tnks

donato

[akbooer]

Hi Donato

Hope that things are going well for you.

Yes, this is expected behaviour. Your shortest aggregation interval is one minute, so any updates faster than that only retain the latest value.

There are two possible options:

1. Use a schema with an even shorter initial interval, for example 10s.
2. Write a custom aggregator which collects and averages values before writing to the variable.

I think I gave you the means to do option 2 a while ago, by allowing user-defined actions… but it’s so long ago, I’ve forgotten what we called that! The newest versions of openLuup actually allows you to add a user defined function to any variable to modify the value before it is written, so you could also do it that way.

[Donato]

Hi akbooer,

tnks now things is going well for me too.

You wrote for me the following L_DataUser.lua that I'm using :

local function run (metric, value, time) 

  local target = "Variable"
  local names = {"kwdaily", "kwhourly", "kwmaxhourly"}

  local metrics = {metric}
  for i, name in ipairs (names) do
    local x,n = metric: gsub (target, name)
    metrics[#metrics+1] = n>0 and x or nil
  end

  local i = 0
 
  return function ()
    i = i + 1
    return metrics[i], value, time
  end
end

return {run = run}

that write for every value of "Variablex" variable to other whisper files with different aggregation and schemas.

[akbooer]

Ah yes, that's how we did it!

So, the question is how do you want to proceed? Option #1 is by far the easiest, unless other considerations preclude this. It would allow configuration on a per-file basis.

What is it that concerns you, that you're really trying to avoid? Are variations within a one-minute interval too much for you? Or is the issue that for the longer durations (one hour, one day) you are not averaging over those correctly?

[Donato]

In my installation sensors measure at least a value every 20/30s (in my case is electric power) and I'd like to register the average value every minute (if possible).
Can I change the retention schemas of the actual whisper files without loosing the actual data or do I have to start from zero?

Over hour and daily period the aggregation is different for the whisper files created by L_DataUser routine :

[Power_Daily_DataWatcher]
pattern = .kwdaily
xFilesFactor = 0
aggregationMethod = sum
[Power_Hourly_DataWatcher]
pattern = .kwhourly
xFilesFactor = 0
aggregationMethod = sum
[Power_MaxHourly_DataWatcher]
pattern = .kwmaxhourly
xFilesFactor = 0
aggregationMethod = max

For the "Variable" whisper files seems correct the average calculation for 5m, 10m, 1h .. etc based on :

retentions = 1m:1d,5m:90d,10m:180d,1h:2y,1d:10y

and the value registered every minute.

[akbooer]

So it would be enough to make all the variables handled by L_DataUser.lua output one minute averages, under the assumption that there is at least one per minute?

[Donato]

Yes, but all the variables with the name "Variable" (local target = "Variable")

[akbooer]

Yes, indeed.

[akbooer]

@Donato

I think this will do what you need:

local target = "Variable"
local names = {"kwdaily", "kwhourly", "kwmaxhourly"}
local avg_time = 60   -- average over 60 seconds
local caches = {}

local function average (metric, value, time) 
  local stale = time - avg_time
  local cache = caches[metric] or {}      -- find the right cache
  caches[metric] = cache
  cache[time] = value                     -- update latest value
  local n,sum = 0,0
  for t,v in pairs(cache) do
    if t <= stale then                    -- clear stale values from the cache
      cache[t] = nil
    else                                  -- add to total
      n = n + 1
      sum = sum + v
    end  
  end
  return sum / n
end

local function run (metric, value, time) 
  local metrics = {metric}
  if metric: match(target) then 
    value = average(metric, value, time)
    for i, name in ipairs (names) do
      local x,n = metric: gsub (target, name)
      metrics[#metrics+1] = n>0 and x or nil
    end
  end

  local i = 0
 
  return function ()
    i = i + 1
    return metrics[i], value, time
  end
end

return {run = run}

[Donato]

Hi akbooer,

excuse me for late answer. Tnks for your precious support as usual.
I'll test your code asap.
A question for my clarity: does the routine register only a value every minute in the whisper file (average of values in a minute) ? Are the different values in a minute momentarily memorized in a DY cache ?

tnks

[akbooer]

No, a new 60 second average is calculated, and emitted, on every new measurement.

However, there is still an issue that the averaging window for the internal cache may not be aligned with the one that DataYours is using.

Also, how accurately is the acquisition machine timestamp synchronised with the one doing the averaging and storage?

It’s actually not a trivial problem for these reasons, but there are different options, so do try it, investigate the results, and report back!

Good luck,

AK