fix(core): Correctly handle and report errors listing pools

Fixes #18

collector/zfs.go

@@ -121,18 +121,20 @@ func (c *ZFS) Collect(ch chan<- prometheus.Metric) {
 		c.ready <- struct{}{}
 	}()
 
-	pools, err := c.getPools(c.Pools)
-	if err != nil {
-		_ = level.Error(c.logger).Log("msg", "Error finding pools", "err", err)
-		return
-	}
+	pools, poolErr := c.getPools(c.Pools)
 
 	for name, state := range c.Collectors {
 		if !*state.Enabled {
 			wg.Done()
 			continue
 		}
 
+		if poolErr != nil {
+			c.publishCollectorMetrics(ctx, name, poolErr, 0, proxy)
+			wg.Done()
+			continue
+		}
+
 		collector, err := state.factory(c.logger, c.client, strings.Split(*state.Properties, `,`))
 		if err != nil {
 			_ = level.Error(c.logger).Log("Error instantiating collector", "collector", name, "err", err)
@@ -147,7 +149,7 @@ func (c *ZFS) Collect(ch chan<- prometheus.Metric) {
 
 	// Wait for completion or timeout
 	<-ctx.Done()
-	err = ctx.Err()
+	err := ctx.Err()
 	if err == context.Canceled {
 		finalize()
 	} else if err != nil {
@@ -206,6 +208,11 @@ func (c *ZFS) execute(ctx context.Context, name string, collector Collector, ch
 	begin := time.Now()
 	err := collector.update(ch, pools, c.excludes)
 	duration := time.Since(begin)
+
+	c.publishCollectorMetrics(ctx, name, err, duration, ch)
+}
+
+func (c *ZFS) publishCollectorMetrics(ctx context.Context, name string, err error, duration time.Duration, ch chan<- metric) {
 	var success float64
 
 	if err != nil {

collector/zfs_test.go

@@ -0,0 +1,43 @@
+package collector
+
+import (
+	"context"
+	"fmt"
+	"testing"
+
+	"github.com/golang/mock/gomock"
+	"github.com/pdf/zfs_exporter/v2/zfs/mock_zfs"
+)
+
+func TestZFSCollectInvalidPools(t *testing.T) {
+	const result = `# HELP zfs_scrape_collector_duration_seconds zfs_exporter: Duration of a collector scrape.
+# TYPE zfs_scrape_collector_duration_seconds gauge
+zfs_scrape_collector_duration_seconds{collector="pool"} 0
+# HELP zfs_scrape_collector_success zfs_exporter: Whether a collector succeeded.
+# TYPE zfs_scrape_collector_success gauge
+zfs_scrape_collector_success{collector="pool"} 0
+`
+
+	ctrl, ctx := gomock.WithContext(context.Background(), t)
+	zfsClient := mock_zfs.NewMockClient(ctrl)
+	zfsClient.EXPECT().PoolNames().Return(nil, fmt.Errorf(`Error returned from PoolNames()`)).Times(1)
+
+	config := defaultConfig(zfsClient)
+	config.DisableMetrics = false
+	collector, err := NewZFS(config)
+	collector.Collectors = map[string]State{
+		`pool`: {
+			Name:       "pool",
+			Enabled:    boolPointer(true),
+			Properties: stringPointer(``),
+			factory:    newPoolCollector,
+		},
+	}
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err = callCollector(ctx, collector, []byte(result), []string{`zfs_scrape_collector_duration_seconds`, `zfs_scrape_collector_success`}); err != nil {
+		t.Fatal(err)
+	}
+}