[installer]: add backup command to in-cluster mysql

Author: Simon Emms

install/installer/pkg/common/common.go

@@ -5,6 +5,7 @@
 package common
 
 import (
+	"bytes"
 	"crypto/sha256"
 	"encoding/json"
 	"fmt"
@@ -613,3 +614,12 @@ func NodeNameEnv(context *RenderContext) []corev1.EnvVar {
 		},
 	}}
 }
+
+// ToUnescapedJSONString returns the serialized JSON string of an object without escaping any of the characters
+func ToUnescapedJSONString(t interface{}) ([]byte, error) {
+	buffer := &bytes.Buffer{}
+	encoder := json.NewEncoder(buffer)
+	encoder.SetEscapeHTML(false)
+	err := encoder.Encode(t)
+	return buffer.Bytes(), err
+}

install/installer/pkg/components/database/incluster/helm.go

@@ -24,6 +24,17 @@ var Helm = common.CompositeHelmFunc(
 			return nil, err
 		}
 
+		backupCmd, err := common.ToUnescapedJSONString([]string{
+			"/bin/bash",
+			"-c",
+			"echo \"hello world\" > /backup/sje.txt",
+		})
+
+		backupSettings, err := helm.KeyFileValue("mysql.primary.podAnnotations.pre\\.hook\\.backup\\.velero\\.io/command", backupCmd)
+		if err != nil {
+			return nil, err
+		}
+
 		customization := helm.CustomizeAnnotation([]string{}, "mysql.primary.podAnnotations", cfg, Component, common.TypeMetaDeployment)
 		customization = helm.CustomizeLabel(customization, "mysql.primary.podLabels", cfg, Component, common.TypeMetaDeployment)
 		customization = helm.CustomizeAnnotation(customization, "mysql.primary.service.annotations", cfg, Component, common.TypeMetaService)
@@ -58,6 +69,7 @@ var Helm = common.CompositeHelmFunc(
 				// This is too complex to be sent as a string
 				FileValues: []string{
 					primaryAffinityTemplate,
+					backupSettings,
 				},
 			},
 		}, nil

install/installer/third_party/charts/mysql/values.yaml

@@ -8,6 +8,17 @@ mysql:
     # We switched to the specific version because "5.7" was broken at least once
     tag: 5.7.34-debian-10-r55
   primary:
+    # Backup settings
+    podAnnotations:
+      backup.velero.io/backup-volumes: backup
+      pre.hook.backup.velero.io/timeout: 5m
+    extraVolumes:
+      - name: backup
+        emptyDir: {}
+    extraVolumeMounts:
+      - name: backup
+        mountPath: /backup
+    # End of backup settings
     extraEnvVars:
       # We rely on this in our DB implementations: NULL (re-)sets configured columns to be initialized with CURRENT_TIMESTAMP.
       # OFF is the default as documented [here](https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html#sysvar_explicit_defaults_for_timestamp) (we also see this in GCP), but not for this chart.
@@ -19,4 +30,4 @@ mysql:
   serviceAccount:
     create: false
   volumePermissions:
-    enabled: true
+    enabled: true