config: Add api requests max & deadline configs (#9273)

Add two new configuration entries, api.requests-max and
api.requests-deadline which have the same role of
MINIO_API_REQUESTS_MAX and MINIO_API_REQUESTS_DEADLINE.

cmd/config/api/api.go

@@ -0,0 +1,91 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package api
+
+import (
+	"encoding/json"
+	"errors"
+	"strconv"
+	"time"
+
+	"github.com/minio/minio/cmd/config"
+	"github.com/minio/minio/pkg/env"
+)
+
+const (
+	apiRequestsMax      = "requests_max"
+	apiRequestsDeadline = "requests_deadline"
+)
+
+// DefaultKVS - default storage class config
+var (
+	DefaultKVS = config.KVS{
+		config.KV{
+			Key:   apiRequestsMax,
+			Value: "0",
+		},
+		config.KV{
+			Key:   apiRequestsDeadline,
+			Value: "10s",
+		},
+	}
+)
+
+// Config storage class configuration
+type Config struct {
+	APIRequestsMax      int           `json:"requests_max"`
+	APIRequestsDeadline time.Duration `json:"requests_deadline"`
+}
+
+// UnmarshalJSON - Validate SS and RRS parity when unmarshalling JSON.
+func (sCfg *Config) UnmarshalJSON(data []byte) error {
+	type Alias Config
+	aux := &struct {
+		*Alias
+	}{
+		Alias: (*Alias)(sCfg),
+	}
+	return json.Unmarshal(data, &aux)
+}
+
+// LookupConfig - lookup api config and override with valid environment settings if any.
+func LookupConfig(kvs config.KVS) (cfg Config, err error) {
+	if err = config.CheckValidKeys(config.APISubSys, kvs, DefaultKVS); err != nil {
+		return cfg, err
+	}
+
+	// Check environment variables parameters
+	requestsMax, err := strconv.Atoi(env.Get(config.EnvAPIRequestsMax, kvs.Get(apiRequestsMax)))
+	if err != nil {
+		return cfg, err
+	}
+
+	if requestsMax < 0 {
+		return cfg, errors.New("invalid API max requests value")
+	}
+
+	requestsDeadline, err := time.ParseDuration(env.Get(config.EnvAPIRequestsDeadline, kvs.Get(apiRequestsDeadline)))
+	if err != nil {
+		return cfg, err
+	}
+
+	cfg = Config{
+		APIRequestsMax:      requestsMax,
+		APIRequestsDeadline: requestsDeadline,
+	}
+	return cfg, nil
+}

cmd/config/api/help.go

@@ -0,0 +1,37 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package api
+
+import "github.com/minio/minio/cmd/config"
+
+// Help template for storageclass feature.
+var (
+	Help = config.HelpKVS{
+		config.HelpKV{
+			Key:         apiRequestsMax,
+			Description: `set the maximum number of concurrent requests, e.g. "1600"`,
+			Optional:    true,
+			Type:        "number",
+		},
+		config.HelpKV{
+			Key:         apiRequestsDeadline,
+			Description: `set the deadline for API requests waiting to be processed e.g. "1m"`,
+			Optional:    true,
+			Type:        "duration",
+		},
+	}
+)

cmd/config/config.go

@@ -71,6 +71,7 @@ const (
 	RegionSubSys         = "region"
 	EtcdSubSys           = "etcd"
 	StorageClassSubSys   = "storage_class"
+	APISubSys            = "api"
 	CompressionSubSys    = "compression"
 	KmsVaultSubSys       = "kms_vault"
 	KmsKesSubSys         = "kms_kes"
@@ -102,6 +103,7 @@ var SubSystems = set.CreateStringSet([]string{
 	RegionSubSys,
 	EtcdSubSys,
 	CacheSubSys,
+	APISubSys,
 	StorageClassSubSys,
 	CompressionSubSys,
 	KmsVaultSubSys,
@@ -129,6 +131,7 @@ var SubSystemsSingleTargets = set.CreateStringSet([]string{
 	RegionSubSys,
 	EtcdSubSys,
 	CacheSubSys,
+	APISubSys,
 	StorageClassSubSys,
 	CompressionSubSys,
 	KmsVaultSubSys,