pool: Fix logic of falling back to replicated expansion in computation of ExpansionFactor.

The code was assuming that the command would succeed with empty output
if a non-EC profile was given, when in fact it fails. Re-work the code
to properly handle this case.

collectors/conn.go

@@ -16,6 +16,7 @@ package collectors
 
 import (
 	"encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/ceph/go-ceph/rados"
@@ -157,6 +158,9 @@ func (n *NoopConn) MonCommand(args []byte) ([]byte, string, error) {
 			"w": "8"
 		}`
 			return []byte(ec42Return), "", nil
+
+		default:
+			return []byte(""), "", errors.New("unknown erasure code profile")
 		}
 
 	case "osd erasure-code-profile get replicated-ruleset":

collectors/pool.go

@@ -221,7 +221,7 @@ func (p *PoolInfoCollector) collect() error {
 		p.QuotaMaxBytes.WithLabelValues(pool.Name, pool.Profile).Set(pool.QuotaMaxBytes)
 		p.QuotaMaxObjects.WithLabelValues(pool.Name, pool.Profile).Set(pool.QuotaMaxObjects)
 		p.StripeWidth.WithLabelValues(pool.Name, pool.Profile).Set(pool.StripeWidth)
-		p.ExpansionFactor.WithLabelValues(pool.Name, pool.Profile).Set(p.getExpansionCommand(pool))
+		p.ExpansionFactor.WithLabelValues(pool.Name, pool.Profile).Set(p.getExpansionFactor(pool))
 	}
 
 	return nil
@@ -262,7 +262,15 @@ func (p *PoolInfoCollector) Collect(ch chan<- prometheus.Metric) {
 	}
 }
 
-func (p *PoolInfoCollector) getExpansionCommand(pool poolInfo) float64 {
+func (p *PoolInfoCollector) getExpansionFactor(pool poolInfo) float64 {
+	if ef, ok := p.getECExpansionFactor(pool); ok {
+		return ef
+	}
+	// Non-EC pool (or unable to get profile info); assume that it's replicated.
+	return pool.ActualSize
+}
+
+func (p *PoolInfoCollector) getECExpansionFactor(pool poolInfo) (float64, bool) {
 	prefix := fmt.Sprintf("osd erasure-code-profile get")
 	cmd, err := json.Marshal(map[string]interface{}{
 		"prefix": prefix,
@@ -272,7 +280,7 @@ func (p *PoolInfoCollector) getExpansionCommand(pool poolInfo) float64 {
 
 	buf, _, err := p.conn.MonCommand(cmd)
 	if err != nil {
-		return -1
+		return -1, false
 	}
 
 	type ecInfo struct {
@@ -283,7 +291,7 @@ func (p *PoolInfoCollector) getExpansionCommand(pool poolInfo) float64 {
 	ecStats := ecInfo{}
 	err = json.Unmarshal(buf, &ecStats)
 	if err != nil || ecStats.K == "" || ecStats.M == "" {
-		return pool.ActualSize
+		return -1, false
 	}
 
 	k, _ := strconv.ParseFloat(ecStats.K, 64)
@@ -291,5 +299,5 @@ func (p *PoolInfoCollector) getExpansionCommand(pool poolInfo) float64 {
 
 	expansionFactor := (k + m) / k
 	roundedExpansion := math.Round(expansionFactor*100) / 100
-	return roundedExpansion
+	return roundedExpansion, true
 }