Retry get last value in Price Change alarms about boilr

[algazarra]

Considering a price change alarm, how often does boilr ask for last price?

[dllud]

After some discussion, I and @andrefbsantos concluded that compensating for the incurred delay, i.e. turning the change into an average change, would be a bad failsafe. Instead Boilr will show the elapsed time when a Price Change alarm fires.

Giving an example. Bob sets a Price Change alarm for pair FOO/BAR in BazExchange with a 10% change and a 10 minutes time frame. His smartphone looses internet connection and can only fetch data 20 minutes later. Meanwhile, FOO/BAR had a 12% change during the first 10 minutes and a 6% change in the following ten.

When Bob phone finally connects it detects a 18% change. If Boilr was calculating averages it would see a 9% change for each 10 minutes and no alarm would fire. However, the retrieved data hints to the possibility of a > 10% change during some 10 min period while the phone was offline. Therefore we prefer to fire the alarm and show something like this:

FOO/BAR had 18% change in BazExchange during 20 minutes.

As @andrefbsantos puts it

Giving useless information is better than omitting information that might be useful.

[dllud]

@cicardia Boilr asks for last price after the user-defined time frame has elapsed. For instance, if you set the time frame for 1 day, Boilr only fetches the last price once per day. You could infer this from the first comment.