Provide option to turn on WAL compression

Signed-off-by: Chris Marchbanks <csmarchbanks@gmail.com>

Documentation/api.md

@@ -340,6 +340,7 @@ PrometheusSpec is a specification of the desired behavior of the Prometheus clus
 | prometheusExternalLabelName | Name of Prometheus external label used to denote Prometheus instance name. Defaults to the value of `prometheus`. External label will _not_ be added when value is set to empty string (`\"\"`). | *string | false |
 | retention | Time duration Prometheus shall retain data for. Default is '24h', and must match the regular expression `[0-9]+(ms\|s\|m\|h\|d\|w\|y)` (milliseconds seconds minutes hours days weeks years). | string | false |
 | retentionSize | Maximum amount of disk space used by blocks. | string | false |
+| walCompression | Enable compression of the write-ahead log using Snappy. This flag is only available in versions of Prometheus >= 2.11.0. | *bool | false |
 | logLevel | Log level for Prometheus to be configured with. | string | false |
 | logFormat | Log format for Prometheus to be configured with. | string | false |
 | scrapeInterval | Interval between consecutive scrapes. | string | false |

example/prometheus-operator-crd/prometheus.crd.yaml

@@ -3453,6 +3453,10 @@ spec:
             version:
               description: Version of Prometheus to be deployed.
               type: string
+            walCompression:
+              description: Enable compression of the write-ahead log using Snappy.
+                This flag is only available in versions of Prometheus >= 2.11.0.
+              type: boolean
           type: object
         status:
           description: 'PrometheusStatus is the most recent observed status of the

pkg/apis/monitoring/v1/openapi_generated.go

@@ -1647,6 +1647,13 @@ func schema_pkg_apis_monitoring_v1_PrometheusSpec(ref common.ReferenceCallback)
 							Format:      "",
 						},
 					},
+					"walCompression": {
+						SchemaProps: spec.SchemaProps{
+							Description: "Enable compression of the write-ahead log using Snappy. This flag is only available in versions of Prometheus >= 2.11.0.",
+							Type:        []string{"boolean"},
+							Format:      "",
+						},
+					},
 					"logLevel": {
 						SchemaProps: spec.SchemaProps{
 							Description: "Log level for Prometheus to be configured with.",

pkg/apis/monitoring/v1/types.go

@@ -131,6 +131,9 @@ type PrometheusSpec struct {
 	Retention string `json:"retention,omitempty"`
 	// Maximum amount of disk space used by blocks.
 	RetentionSize string `json:"retentionSize,omitempty"`
+	// Enable compression of the write-ahead log using Snappy. This flag is
+	// only available in versions of Prometheus >= 2.11.0.
+	WALCompression *bool `json:"walCompression,omitempty"`
 	// Log level for Prometheus to be configured with.
 	LogLevel string `json:"logLevel,omitempty"`
 	// Log format for Prometheus to be configured with.

pkg/apis/monitoring/v1/zz_generated.deepcopy.go

@@ -715,6 +715,11 @@ func (in *PrometheusSpec) DeepCopyInto(out *PrometheusSpec) {
 		*out = new(string)
 		**out = **in
 	}
+	if in.WALCompression != nil {
+		in, out := &in.WALCompression, &out.WALCompression
+		*out = new(bool)
+		**out = **in
+	}
 	out.Rules = in.Rules
 	if in.ExternalLabels != nil {
 		in, out := &in.ExternalLabels, &out.ExternalLabels

pkg/prometheus/statefulset.go

@@ -430,6 +430,14 @@ func makeStatefulSetSpec(p monitoringv1.Prometheus, c *Config, ruleConfigMapName
 		}
 	}
 
+	if version.GTE(semver.MustParse("2.11.0")) && p.Spec.WALCompression != nil {
+		if *p.Spec.WALCompression {
+			promArgs = append(promArgs, "-storage.tsdb.wal-compression")
+		} else {
+			promArgs = append(promArgs, "-no-storage.tsdb.wal-compression")
+		}
+	}
+
 	var ports []v1.ContainerPort
 	if p.Spec.ListenLocal {
 		promArgs = append(promArgs, "-web.listen-address=127.0.0.1:9090")

pkg/prometheus/statefulset_test.go

@@ -792,3 +792,59 @@ func TestAdditionalContainers(t *testing.T) {
 		}
 	}
 }
+
+func TestWALCompression(t *testing.T) {
+	var (
+		tr = true
+		fa = false
+	)
+	tests := []struct {
+		version       string
+		enabled       *bool
+		expectedArg   string
+		shouldContain bool
+	}{
+		// Nil should not have either flag.
+		{"v1.8.2", nil, "-no-storage.tsdb.wal-compression", false},
+		{"v1.8.2", nil, "-storage.tsdb.wal-compression", false},
+		{"v1.8.2", &fa, "-no-storage.tsdb.wal-compression", false},
+		{"v1.8.2", &tr, "-storage.tsdb.wal-compression", false},
+		{"v2.10.0", nil, "--no-storage.tsdb.wal-compression", false},
+		{"v2.10.0", nil, "--storage.tsdb.wal-compression", false},
+		{"v2.10.0", &fa, "--no-storage.tsdb.wal-compression", false},
+		{"v2.10.0", &tr, "--storage.tsdb.wal-compression", false},
+		{"v2.11.0", nil, "--no-storage.tsdb.wal-compression", false},
+		{"v2.11.0", nil, "--storage.tsdb.wal-compression", false},
+		{"v2.11.0", &fa, "--no-storage.tsdb.wal-compression", true},
+		{"v2.11.0", &tr, "--storage.tsdb.wal-compression", true},
+	}
+
+	for _, test := range tests {
+		sset, err := makeStatefulSet(monitoringv1.Prometheus{
+			Spec: monitoringv1.PrometheusSpec{
+				Version:        test.version,
+				WALCompression: test.enabled,
+			},
+		}, defaultTestConfig, nil, "")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		promArgs := sset.Spec.Template.Spec.Containers[0].Args
+		found := false
+		for _, flag := range promArgs {
+			if flag == test.expectedArg {
+				found = true
+				break
+			}
+		}
+
+		if found != test.shouldContain {
+			if test.shouldContain {
+				t.Fatalf("expected Prometheus args to contain %v, but got %v", test.expectedArg, promArgs)
+			} else {
+				t.Fatalf("expected Prometheus args to NOT contain %v, but got %v", test.expectedArg, promArgs)
+			}
+		}
+	}
+}