Add async caching commit option in diskcache (#10742)

Add store and a forward option for a single part
uploads when an async mode is enabled with env
MINIO_CACHE_COMMIT=writeback 

It defaults to `writethrough` if unspecified.

cmd/config/cache/config.go

@@ -28,16 +28,17 @@ import (
 
 // Config represents cache config settings
 type Config struct {
-	Enabled       bool     `json:"-"`
-	Drives        []string `json:"drives"`
-	Expiry        int      `json:"expiry"`
-	MaxUse        int      `json:"maxuse"`
-	Quota         int      `json:"quota"`
-	Exclude       []string `json:"exclude"`
-	After         int      `json:"after"`
-	WatermarkLow  int      `json:"watermark_low"`
-	WatermarkHigh int      `json:"watermark_high"`
-	Range         bool     `json:"range"`
+	Enabled         bool     `json:"-"`
+	Drives          []string `json:"drives"`
+	Expiry          int      `json:"expiry"`
+	MaxUse          int      `json:"maxuse"`
+	Quota           int      `json:"quota"`
+	Exclude         []string `json:"exclude"`
+	After           int      `json:"after"`
+	WatermarkLow    int      `json:"watermark_low"`
+	WatermarkHigh   int      `json:"watermark_high"`
+	Range           bool     `json:"range"`
+	CommitWriteback bool     `json:"-"`
 }
 
 // UnmarshalJSON - implements JSON unmarshal interface for unmarshalling
@@ -152,3 +153,13 @@ func parseCacheExcludes(excludes string) ([]string, error) {
 
 	return excludesSlice, nil
 }
+
+func parseCacheCommitMode(commitStr string) (bool, error) {
+	switch strings.ToLower(commitStr) {
+	case "writeback":
+		return true, nil
+	case "writethrough":
+		return false, nil
+	}
+	return false, config.ErrInvalidCacheCommitValue(nil).Msg("cache commit value must be `writeback` or `writethrough`")
+}

cmd/config/cache/help.go

@@ -74,5 +74,11 @@ var (
 			Optional:    true,
 			Type:        "string",
 		},
+		config.HelpKV{
+			Key:         Commit,
+			Description: `set to control cache commit behavior, defaults to "writethrough"`,
+			Optional:    true,
+			Type:        "string",
+		},
 	}
 )

cmd/config/cache/lookup.go

@@ -35,6 +35,7 @@ const (
 	WatermarkLow  = "watermark_low"
 	WatermarkHigh = "watermark_high"
 	Range         = "range"
+	Commit        = "commit"
 
 	EnvCacheDrives        = "MINIO_CACHE_DRIVES"
 	EnvCacheExclude       = "MINIO_CACHE_EXCLUDE"
@@ -45,6 +46,7 @@ const (
 	EnvCacheWatermarkLow  = "MINIO_CACHE_WATERMARK_LOW"
 	EnvCacheWatermarkHigh = "MINIO_CACHE_WATERMARK_HIGH"
 	EnvCacheRange         = "MINIO_CACHE_RANGE"
+	EnvCacheCommit        = "MINIO_CACHE_COMMIT"
 
 	EnvCacheEncryptionMasterKey = "MINIO_CACHE_ENCRYPTION_MASTER_KEY"
 
@@ -53,6 +55,7 @@ const (
 	DefaultAfter         = "0"
 	DefaultWaterMarkLow  = "70"
 	DefaultWaterMarkHigh = "80"
+	DefaultCacheCommit   = "writethrough"
 )
 
 // DefaultKVS - default KV settings for caching.
@@ -90,6 +93,10 @@ var (
 			Key:   Range,
 			Value: config.EnableOn,
 		},
+		config.KV{
+			Key:   Commit,
+			Value: DefaultCacheCommit,
+		},
 	}
 )
 
@@ -210,6 +217,12 @@ func LookupConfig(kvs config.KVS) (Config, error) {
 		}
 		cfg.Range = rng
 	}
+	if commit := env.Get(EnvCacheCommit, kvs.Get(Commit)); commit != "" {
+		cfg.CommitWriteback, err = parseCacheCommitMode(commit)
+		if err != nil {
+			return cfg, err
+		}
+	}
 
 	return cfg, nil
 }