arbitrary sidecar support

docs/user.md

@@ -242,3 +242,35 @@ metadata:
 
 Note that timezone required for `timestamp` (offset relative to UTC, see RFC
 3339 section 5.6)
+
+
+## Sidecar Support
+
+Each cluster can specify arbitrary sidecars to run. These containers could be used for
+log aggregation, monitoring, backups or other tasks. A sidecar can be specified like this:
+
+```yaml
+apiVersion: "acid.zalan.do/v1"
+kind: postgresql
+
+metadata:
+  name: acid-minimal-cluster
+spec:
+  ...
+  sidecars:
+    - name: "container-name"
+      image: "company/image:tag"
+      env:
+        - name: "ENV_VAR_NAME"
+          value: "any-k8s-env-things"
+```
+
+In addition to any environment variables you specify, the following environment variables
+are always passed to sidecars:
+
+  - `POD_NAME` - field reference to `metadata.name`
+  - `POD_NAMESPACE` - field reference to `metadata.namespace`
+  - `POSTGRES_USER` - the superuser that can be used to connect to the database
+  - `POSTGRES_PASSWORD` - the password for the superuser
+
+The PostgreSQL volume is shared with sidecars and is mounted at `/home/postgres/pgdata`.

pkg/cluster/k8sres.go

@@ -318,8 +318,9 @@ func (c *Cluster) generatePodTemplate(
 	patroniParameters *spec.Patroni,
 	cloneDescription *spec.CloneDescription,
 	dockerImage *string,
+	sidecars *[]spec.Sidecar,
 	customPodEnvVars map[string]string,
-) *v1.PodTemplateSpec {
+) (*v1.PodTemplateSpec, error) {
 	spiloConfiguration := c.generateSpiloJSONConfiguration(pgParameters, patroniParameters)
 
 	envVars := []v1.EnvVar{
@@ -525,6 +526,16 @@ func (c *Cluster) generatePodTemplate(
 		)
 	}
 
+	if sidecars != nil && len(*sidecars) > 0 {
+		for index, sidecar := range *sidecars {
+			sc, err := c.getSidecarContainer(sidecar, index, volumeMounts)
+			if err != nil {
+				return nil, err
+			}
+			podSpec.Containers = append(podSpec.Containers, *sc)
+		}
+	}
+
 	template := v1.PodTemplateSpec{
 		ObjectMeta: metav1.ObjectMeta{
 			Labels:    c.labelsSet(true),
@@ -536,7 +547,72 @@ func (c *Cluster) generatePodTemplate(
 		template.Annotations = map[string]string{constants.KubeIAmAnnotation: c.OpConfig.KubeIAMRole}
 	}
 
-	return &template
+	return &template, nil
+}
+
+func (c *Cluster) getSidecarContainer(sidecar spec.Sidecar, index int, volumeMounts []v1.VolumeMount) (*v1.Container, error) {
+	name := sidecar.Name
+	if name == "" {
+		name = fmt.Sprintf("sidecar-%d", index)
+	}
+	resources, err := c.resourceRequirements(
+		makeResources(
+			sidecar.Resources.ResourceRequest.CPU,
+			sidecar.Resources.ResourceRequest.Memory,
+			sidecar.Resources.ResourceLimits.CPU,
+			sidecar.Resources.ResourceLimits.Memory,
+		),
+	)
+	if err != nil {
+		return nil, err
+	}
+	env := []v1.EnvVar{
+		{
+			Name: "POD_NAME",
+			ValueFrom: &v1.EnvVarSource{
+				FieldRef: &v1.ObjectFieldSelector{
+					APIVersion: "v1",
+					FieldPath:  "metadata.name",
+				},
+			},
+		},
+		{
+			Name: "POD_NAMESPACE",
+			ValueFrom: &v1.EnvVarSource{
+				FieldRef: &v1.ObjectFieldSelector{
+					APIVersion: "v1",
+					FieldPath:  "metadata.namespace",
+				},
+			},
+		},
+		{
+			Name:  "POSTGRES_USER",
+			Value: c.OpConfig.SuperUsername,
+		},
+		{
+			Name: "POSTGRES_PASSWORD",
+			ValueFrom: &v1.EnvVarSource{
+				SecretKeyRef: &v1.SecretKeySelector{
+					LocalObjectReference: v1.LocalObjectReference{
+						Name: c.credentialSecretName(c.OpConfig.SuperUsername),
+					},
+					Key: "password",
+				},
+			},
+		},
+	}
+	if len(sidecar.Env) > 0 {
+		env = append(env, sidecar.Env...)
+	}
+	return &v1.Container{
+		Name:            name,
+		Image:           sidecar.DockerImage,
+		ImagePullPolicy: v1.PullIfNotPresent,
+		Resources:       *resources,
+		VolumeMounts:    volumeMounts,
+		Env:             env,
+		Ports:           sidecar.Ports,
+	}, nil
 }
 
 func getBucketScopeSuffix(uid string) string {
@@ -583,7 +659,10 @@ func (c *Cluster) generateStatefulSet(spec *spec.PostgresSpec) (*v1beta1.Statefu
 			customPodEnvVars = cm.Data
 		}
 	}
-	podTemplate := c.generatePodTemplate(c.Postgresql.GetUID(), resourceRequirements, resourceRequirementsScalyrSidecar, &spec.Tolerations, &spec.PostgresqlParam, &spec.Patroni, &spec.Clone, &spec.DockerImage, customPodEnvVars)
+	podTemplate, err := c.generatePodTemplate(c.Postgresql.GetUID(), resourceRequirements, resourceRequirementsScalyrSidecar, &spec.Tolerations, &spec.PostgresqlParam, &spec.Patroni, &spec.Clone, &spec.DockerImage, &spec.Sidecars, customPodEnvVars)
+	if err != nil {
+		return nil, fmt.Errorf("could not generate pod template: %v", err)
+	}
 	volumeClaimTemplate, err := generatePersistentVolumeClaimTemplate(spec.Volume.Size, spec.Volume.StorageClass)
 	if err != nil {
 		return nil, fmt.Errorf("could not generate volume claim template: %v", err)

pkg/spec/postgresql.go

@@ -61,6 +61,15 @@ type CloneDescription struct {
 	EndTimestamp string `json:"timestamp,omitempty"`
 }
 
+// Sidecar defines a container to be run in the same pod as the Postgres container.
+type Sidecar struct {
+	Resources   `json:"resources,omitempty"`
+	Name        string             `json:"name,omitempty"`
+	DockerImage string             `json:"image,omitempty"`
+	Ports       []v1.ContainerPort `json:"ports,omitempty"`
+	Env         []v1.EnvVar        `json:"env,omitempty"`
+}
+
 type UserFlags []string
 
 // PostgresStatus contains status of the PostgreSQL cluster (running, creation failed etc.)
@@ -124,6 +133,7 @@ type PostgresSpec struct {
 	ClusterName        string               `json:"-"`
 	Databases          map[string]string    `json:"databases,omitempty"`
 	Tolerations        []v1.Toleration      `json:"tolerations,omitempty"`
+	Sidecars           []Sidecar            `json:"sidecars,omitempty"`
 }
 
 // PostgresqlList defines a list of PostgreSQL clusters.