Remove time.Ticker and adjust polling mechanism

diff --git a/main.go b/main.go
index 3981b1b..927a151 100644 (file)
--- a/main.go
+++ b/main.go
@@ -22,6 +22,7 @@ import (
        "github.com/sjmudd/pstop/lib"
        "github.com/sjmudd/pstop/state"
        "github.com/sjmudd/pstop/version"
+       "github.com/sjmudd/pstop/wait_info"
 )
 
 const (
@@ -150,7 +151,9 @@ func main() {
        }
 
        var state state.State
-       interval := time.Second
+       var wi wait_info.WaitInfo
+       wi.SetWaitInterval(time.Second)
+
        sigChan := make(chan os.Signal, 1)
        done := make(chan struct{})
        defer close(done)
@@ -158,8 +161,6 @@ func main() {
 
        signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
 
-       ticker := time.NewTicker(interval) // generate a periodic signal
-
        state.Setup(dbh)
 
        finished := false
@@ -171,8 +172,9 @@ func main() {
                case sig := <-sigChan:
                        fmt.Println("Caught a signal", sig)
                        done <- struct{}{}
-               case <-ticker.C:
+               case <-wi.WaitNextPeriod():
                        state.Collect()
+                       wi.CollectedNow()
                        state.Display()
                case event := <-termboxChan:
                        // switch on event type
@@ -187,15 +189,11 @@ func main() {
                                }
                                switch event.Ch {
                                case '-': // decrease the interval if > 1
-                                       if interval > time.Second {
-                                               ticker.Stop()
-                                               interval -= time.Second
-                                               ticker = time.NewTicker(interval)
+                                       if wi.WaitInterval() > time.Second {
+                                               wi.SetWaitInterval(wi.WaitInterval() - time.Second)
                                        }
                                case '+': // increase interval by creating a new ticker
-                                       ticker.Stop()
-                                       interval += time.Second
-                                       ticker = time.NewTicker(interval)
+                                       wi.SetWaitInterval(wi.WaitInterval() + time.Second)
                                case 'h': // help
                                        state.SetHelp(!state.Help())
                                case 'q': // quit
@@ -216,6 +214,5 @@ func main() {
                }
        }
        state.Cleanup()
-       ticker.Stop()
        lib.Logger.Println("Terminating " + lib.MyName())
 }

diff --git a/wait_info/wait_info.go b/wait_info/wait_info.go
new file mode 100644 (file)
index 0000000..24b8b77
--- /dev/null
+++ b/wait_info/wait_info.go
@@ -0,0 +1,64 @@
+package wait_info
+
+import (
+       "github.com/sjmudd/pstop/lib"
+       "time"
+)
+
+const extra_delay = 200 * time.Millisecond
+
+// used to record when we need to wa
+type WaitInfo struct {
+       last_collected   time.Time
+       collect_interval time.Duration
+}
+
+// return the configured wait interval
+func (wi *WaitInfo) WaitInterval() time.Duration {
+       return wi.collect_interval
+}
+
+// recognise we've done a collection
+func (wi *WaitInfo) CollectedNow() {
+       wi.SetCollected(time.Now())
+}
+
+// change the configured wait interval
+func (wi *WaitInfo) SetWaitInterval(required_interval time.Duration) {
+       wi.collect_interval = required_interval
+}
+
+// set the time the last collection happened
+func (wi *WaitInfo) SetCollected(collect_time time.Time) {
+       wi.last_collected = collect_time
+       lib.Logger.Println("WaitInfo.SetCollected() last_collected=", wi.last_collected)
+}
+
+// return the time the last collection happened
+func (wi WaitInfo) LastCollected() time.Time {
+       return wi.last_collected
+}
+
+// return the amount of time to wait before doing the next collection
+func (wi WaitInfo) TimeToWait() time.Duration {
+       now := time.Now()
+       lib.Logger.Println("WaitInfo.TimeToWait() now: ", now)
+
+       next_time := wi.last_collected.Add(wi.collect_interval)
+       lib.Logger.Println("WaitInfo.TimeToWait() next_time: ", next_time)
+       if next_time.Before(now) {
+               lib.Logger.Println("WaitInfo.TimeToWait() next_time scheduled time in the past, so schedule", extra_delay, "after", now)
+               next_time = now
+               next_time.Add(extra_delay) // add a deliberate tiny delay
+               lib.Logger.Println("WaitInfo.TimeToWait() next_time: ", next_time, "(corrected)")
+       }
+       wait_time := next_time.Sub(now)
+       lib.Logger.Println("WaitInfo.TimeToWait() returning wait_time:", wait_time)
+
+       return wait_time
+}
+
+// behave like time.After()
+func (wi WaitInfo) WaitNextPeriod() <-chan time.Time {
+       return time.After(wi.TimeToWait())
+}