wait_info/wait_info.go

   1 // github.com/sjmudd/wait_info - routines for managing when we
   2 // collect information from MySQL.
   3 package wait_info
   4
   5 import (
   6         "github.com/sjmudd/pstop/lib"
   7         "time"
   8 )
   9
  10 // over-schedule the next wait by this time _iff__ the last scheduled time is in the past.
  11 const extra_delay = 200 * time.Millisecond
  12
  13 // used to record when we need to collect information from MySQL
  14 type WaitInfo struct {
  15         last_collected   time.Time
  16         collect_interval time.Duration
  17 }
  18
  19 // returns the configured wait interval between collecting data.
  20 func (wi *WaitInfo) WaitInterval() time.Duration {
  21         return wi.collect_interval
  22 }
  23
  24 // record we have just collected data now.
  25 func (wi *WaitInfo) CollectedNow() {
  26         wi.SetCollected(time.Now())
  27 }
  28
  29 // Change the desired collection interval to a new value
  30 func (wi *WaitInfo) SetWaitInterval(required_interval time.Duration) {
  31         wi.collect_interval = required_interval
  32 }
  33
  34 // Set the time we last collected information
  35 func (wi *WaitInfo) SetCollected(collect_time time.Time) {
  36         wi.last_collected = collect_time
  37         lib.Logger.Println("WaitInfo.SetCollected() last_collected=", wi.last_collected)
  38 }
  39
  40 // Return when we last collection happened
  41 func (wi WaitInfo) LastCollected() time.Time {
  42         return wi.last_collected
  43 }
  44
  45 // return the amount of time to wait before doing the next collection
  46 func (wi WaitInfo) TimeToWait() time.Duration {
  47         now := time.Now()
  48         lib.Logger.Println("WaitInfo.TimeToWait() now: ", now)
  49
  50         next_time := wi.last_collected.Add(wi.collect_interval)
  51         lib.Logger.Println("WaitInfo.TimeToWait() next_time: ", next_time)
  52         if next_time.Before(now) {
  53                 lib.Logger.Println("WaitInfo.TimeToWait() next_time scheduled time in the past, so schedule", extra_delay, "after", now)
  54                 next_time = now
  55                 next_time.Add(extra_delay) // add a deliberate tiny delay
  56                 lib.Logger.Println("WaitInfo.TimeToWait() next_time: ", next_time, "(corrected)")
  57         }
  58         wait_time := next_time.Sub(now)
  59         lib.Logger.Println("WaitInfo.TimeToWait() returning wait_time:", wait_time)
  60
  61         return wait_time
  62 }
  63
  64 // return a channel which will be written to at the next 'scheduled' time.
  65 func (wi WaitInfo) WaitNextPeriod() <-chan time.Time {
  66         return time.After(wi.TimeToWait())
  67 }