From 8bf472bb75aa7cbb747aa4876517f97db948babe Mon Sep 17 00:00:00 2001
From: Samir Patel <48686912+54mir@users.noreply.github.com>
Date: Mon, 14 Jun 2021 10:48:52 -0500
Subject: [PATCH] add duty cycle config flag

---
 api.go           | 10 ++++++++--
 ctl/server.go    |  3 +++
 server/config.go |  6 ++++++
 server/server.go |  2 +-
 4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/api.go b/api.go
index 0ff042165..c9766e27c 100644
--- a/api.go
+++ b/api.go
@@ -1061,15 +1061,21 @@ func (api *API) calculateUsage() {
 }
 
 // Periodically calculates disk usage
-func (api *API) RefreshUsageCache() {
+func (api *API) RefreshUsageCache(dutyCycle float64) {
 	trigger := make(chan bool)
 	defer close(trigger)
+
+	if dutyCycle <= 0 {
+		dutyCycle = 20
+	}
+	multiplier := int(math.Ceil(100/dutyCycle)) - 1
+
 	api.usageCache = &usageCache{
 		data:             make(map[string]NodeUsage),
 		refreshInterval:  time.Hour,
 		resetTrigger:     trigger,
 		lastCalcDuration: 0,
-		waitMultiplier:   time.Duration(5),
+		waitMultiplier:   time.Duration(multiplier),
 	}
 	for {
 		start := time.Now()
diff --git a/ctl/server.go b/ctl/server.go
index 6c885d213..98472ea95 100644
--- a/ctl/server.go
+++ b/ctl/server.go
@@ -110,4 +110,7 @@ func BuildServerFlags(cmd *cobra.Command, srv *server.Command) {
 	flags.DurationVar((*time.Duration)(&srv.Config.Postgres.WriteTimeout), "postgres.write-timeout", time.Duration(srv.Config.Postgres.WriteTimeout), "Timeout for writes on a postgres connection. (set 0 to disable)")
 	flags.Uint32Var(&srv.Config.Postgres.MaxStartupSize, "postgres.max-startup-size", srv.Config.Postgres.MaxStartupSize, "Maximum acceptable size of a postgres startup packet, in bytes. (set 0 to disable)")
 	flags.Uint16Var(&srv.Config.Postgres.ConnectionLimit, "postgres.connection-limit", srv.Config.Postgres.ConnectionLimit, "Maximum number of simultaneous postgres connections to allow. (set 0 to disable)")
+
+	// Disk and Memory usage cache for ui/usage endpoint
+	flags.Float64Var(&srv.Config.UsageDutyCycle, "usage-duty-cycle", srv.Config.UsageDutyCycle, "Sets the percentage of time that is spent recalculating the disk and memory usage cache. 100.0 for always-running, must be > 0.")
 }
diff --git a/server/config.go b/server/config.go
index f59040271..e744b86e2 100644
--- a/server/config.go
+++ b/server/config.go
@@ -224,6 +224,9 @@ type Config struct {
 
 	// LookupDBDSN is an external database to connect to for `ExternalLookup` queries.
 	LookupDBDSN string `toml:"lookup-db-dsn"`
+
+	// The percentage of time spent recalculating the disk and memory usage cache.
+	UsageDutyCycle float64 `toml:"usage-duty-cycle"`
 }
 
 // MustValidate checks that all ports in a Config are unique and not zero.
@@ -359,6 +362,9 @@ func NewConfig() *Config {
 	c.Etcd.PeerCertFile = ""
 	c.Etcd.PeerKeyFile = ""
 
+	// Disk and Memory Usage
+	c.UsageDutyCycle = 20.0
+
 	return c
 }
 
diff --git a/server/server.go b/server/server.go
index febdb13ee..11ff5bf1b 100644
--- a/server/server.go
+++ b/server/server.go
@@ -277,7 +277,7 @@ func (m *Command) Start() (err error) {
 		}
 	}
 
-	go m.API.RefreshUsageCache()
+	go m.API.RefreshUsageCache(m.Config.UsageDutyCycle)
 
 	_ = testhook.Opened(pilosa.NewAuditor(), m, nil)
 	close(m.Started)