feat(config): support runtime configuration from environment variables (Issue 1559)

.env.example

@@ -34,3 +34,15 @@ SITE_ADDR=0.0.0.0:3000
 # Logging
 LOG_LEVEL=INFO
 LOG_PATH=
+
+# Runtime configuration
+#
+# Use `answer config export-env -C /data` after installation to produce the
+# complete canonical variable set. The two database variables below must be
+# non-empty to start without config.yaml. Keep the exported file secret because
+# the connection value can contain database credentials.
+#
+# ANSWER_DATA_DATABASE_DRIVER=
+# ANSWER_DATA_DATABASE_CONNECTION=
+#
+# See docs/runtime-configuration.md for every ANSWER_* runtime variable.

README.md

@@ -28,6 +28,11 @@ docker run -d -p 9080:80 -v answer-data:/data --name answer apache/answer:2.0.2
 
 For more information, see [Installation](https://answer.apache.org/docs/installation).
 
+Answer can also start from a complete set of runtime environment variables
+without a local `config.yaml`. See [runtime configuration from environment
+variables](docs/runtime-configuration.md) for the supported variables,
+precedence rules, and safe export workflow.
+
 ### Plugins
 
 Answer provides a plugin system for developers to create custom plugins and expand Answer’s features. You can find the [plugin documentation here](https://answer.apache.org/community/plugins).

charts/README.md

@@ -6,6 +6,12 @@ An open-source knowledge-based community software. You can use it quickly to bui
 - Kubernetes 1.20+
 ## Configuration
 
+Answer can run without a persisted `config.yaml` when the complete runtime
+configuration is supplied through environment variables. See [runtime
+configuration from environment variables](../docs/runtime-configuration.md).
+Uploads still require persistent or external storage if they must survive pod
+replacement.
+
 The following table lists the configurable parameters of the answer chart and their default values.
 
 | Parameter | Description | Default |
@@ -72,4 +78,4 @@ Publish the chart to Artifacthub and add proper installation instructions. E.G.
 $ helm repo add apache https://charts.answer.apache.org/
 $ helm repo update
 $ helm install apache/answer -n mynamespace
-```
+```

charts/values.yaml

@@ -80,7 +80,8 @@ extraContainers: []
   #     - containerPort: 5432
 
 # Persistence for the /data volume
-# Without persistence, your uploads and config.yaml will not be remembered between restarts.
+# Without persistence, uploads will not survive restarts. config.yaml can be
+# replaced by the documented ANSWER_* runtime environment variables.
 persistence:
   enabled: true
   # If set to "-", storageClassName: "", which disables dynamic provisioning
@@ -167,4 +168,4 @@ nodeSelector: {}
 
 tolerations: []
 
-affinity: {}
+affinity: {}

cmd/command.go

@@ -77,6 +77,7 @@ func init() {
 	upgradeCmd.Flags().StringVarP(&upgradeVersion, "from", "f", "", "upgrade from specific version, eg: -f v1.1.0")
 
 	configCmd.Flags().StringSliceVarP(&configFields, "with", "w", []string{}, "the fields that need to be set to the default value, eg: -w allow_password_login")
+	configCmd.AddCommand(configExportEnvCmd)
 
 	i18nCmd.Flags().StringVarP(&i18nSourcePath, "source", "s", "", "i18n source path, eg: -s ./i18n/source")
 
@@ -136,6 +137,19 @@ To run answer, use:
 				}
 			}
 
+			if conf.RuntimeEnvironmentConfigured() {
+				fmt.Println("runtime configuration found in environment, try to connect database...")
+				c, err := conf.ReadConfig(path.GetConfigFilePath())
+				if err != nil {
+					fmt.Println("read environment config failed: ", err.Error())
+					return
+				}
+				if cli.CheckDBTableExist(c.Data.Database) {
+					fmt.Println("connect to database successfully and table already exists, do nothing.")
+					return
+				}
+			}
+
 			// start installation server to install
 			install.Run(path.GetConfigFilePath())
 		},
@@ -286,6 +300,29 @@ To run answer, use:
 		},
 	}
 
+	configExportEnvCmd = &cobra.Command{
+		Use:          "export-env",
+		Short:        "Export runtime configuration in dotenv format",
+		SilenceUsage: true,
+		Long: `Export the effective runtime configuration in dotenv format.
+The output can contain database credentials and is only written to standard output
+when this command is explicitly invoked.`,
+		Args: cobra.NoArgs,
+		RunE: func(cmd *cobra.Command, _ []string) error {
+			path.FormatAllPath(dataDirPath)
+			c, err := conf.ReadConfig(path.GetConfigFilePath())
+			if err != nil {
+				return fmt.Errorf("read config failed: %w", err)
+			}
+			output, err := conf.ExportEnvironment(c)
+			if err != nil {
+				return fmt.Errorf("export config failed: %w", err)
+			}
+			_, err = fmt.Fprintln(cmd.OutOrStdout(), output)
+			return err
+		},
+	}
+
 	i18nCmd = &cobra.Command{
 		Use:   "i18n",
 		Short: "Overwrite i18n files",

docs/runtime-configuration.md

@@ -0,0 +1,88 @@
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you 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.
+-->
+
+# Runtime configuration from environment variables
+
+Answer normally reads its runtime configuration from `/data/conf/config.yaml`.
+It can also run without that file when both
+`ANSWER_DATA_DATABASE_DRIVER` and `ANSWER_DATA_DATABASE_CONNECTION` are set to
+non-empty values. This explicit requirement prevents an accidentally missing
+configuration file from silently starting Answer with the embedded SQLite
+defaults.
+
+When `config.yaml` exists, canonical `ANSWER_*` environment variables override
+the corresponding file values. `SITE_ADDR`, `SWAGGER_HOST`, and
+`SWAGGER_ADDRESS_PORT` remain supported for backward compatibility, but their
+canonical replacements take precedence when both names are set.
+
+When `config.yaml` does not exist and the two required database variables are
+present, Answer starts with the embedded configuration template and applies all
+set environment variables over it. Values omitted from the environment retain
+the embedded defaults shown below.
+
+| Environment variable | `config.yaml` field | Embedded default |
+| --- | --- | --- |
+| `ANSWER_DEBUG` | `debug` | `false` |
+| `ANSWER_SERVER_HTTP_ADDR` | `server.http.addr` | `0.0.0.0:80` |
+| `ANSWER_DATA_DATABASE_DRIVER` | `data.database.driver` | `sqlite3` |
+| `ANSWER_DATA_DATABASE_CONNECTION` | `data.database.connection` | `/data/sqlite3/answer.db` |
+| `ANSWER_DATA_DATABASE_CONN_MAX_LIFE_TIME` | `data.database.conn_max_life_time` | `0` |
+| `ANSWER_DATA_DATABASE_MAX_OPEN_CONN` | `data.database.max_open_conn` | `0` |
+| `ANSWER_DATA_DATABASE_MAX_IDLE_CONN` | `data.database.max_idle_conn` | `0` |
+| `ANSWER_DATA_CACHE_FILE_PATH` | `data.cache.file_path` | `/data/cache/cache.db` |
+| `ANSWER_I18N_BUNDLE_DIR` | `i18n.bundle_dir` | `/data/i18n` |
+| `ANSWER_SERVICE_CONFIG_UPLOAD_PATH` | `service_config.upload_path` | `/data/uploads` |
+| `ANSWER_SERVICE_CONFIG_CLEAN_UP_UPLOADS` | `service_config.clean_up_uploads` | `true` |
+| `ANSWER_SERVICE_CONFIG_CLEAN_ORPHAN_UPLOADS_PERIOD_HOURS` | `service_config.clean_orphan_uploads_period_hours` | `48` |
+| `ANSWER_SERVICE_CONFIG_PURGE_DELETED_FILES_PERIOD_DAYS` | `service_config.purge_deleted_files_period_days` | `30` |
+| `ANSWER_SWAGGERUI_SHOW` | `swaggerui.show` | `true` |
+| `ANSWER_SWAGGERUI_PROTOCOL` | `swaggerui.protocol` | `http` |
+| `ANSWER_SWAGGERUI_HOST` | `swaggerui.host` | `127.0.0.1` |
+| `ANSWER_SWAGGERUI_ADDRESS` | `swaggerui.address` | `:80` |
+| `ANSWER_UI_BASE_URL` | `ui.base_url` | empty |
+| `ANSWER_UI_API_BASE_URL` | `ui.api_base_url` | empty |
+
+Boolean values use Go boolean syntax such as `true` or `false`. Integer values
+must be base-10 integers. An invalid value stops configuration loading and names
+the invalid variable.
+
+## Exporting an installed configuration
+
+After installation, export the effective runtime configuration in dotenv format:
+
+```bash
+umask 077
+answer config export-env -C /data > answer-runtime.env
+```
+
+The command writes only the dotenv document to standard output, so it can also
+be piped to a secret-management command. The database connection can contain a
+password. Answer never emits the exported document during ordinary `init`,
+`upgrade`, or `run` operations; it is produced only by this explicit command.
+
+The exported file contains the complete canonical variable set. Store it as a
+secret, not as a ConfigMap or a source-controlled file.
+
+To start another instance against the already initialized database, inject the
+exported values and run Answer normally. `AUTO_INSTALL` is not needed and should
+not be set for this runtime-only path.
+
+Configuration statelessness does not make uploaded files persistent. Configure
+the appropriate upload storage plugin or retain storage for the upload path if
+uploads must survive pod replacement.

internal/base/conf/conf.go

@@ -21,9 +21,11 @@ package conf
 
 import (
 	"bytes"
+	"errors"
 	"os"
 	"path/filepath"
 
+	"github.com/apache/answer/configs"
 	"github.com/apache/answer/internal/base/data"
 	"github.com/apache/answer/internal/base/path"
 	"github.com/apache/answer/internal/base/server"
@@ -46,20 +48,6 @@ type AllConfig struct {
 	UI            *server.UI                    `json:"ui" mapstructure:"ui" yaml:"ui"`
 }
 
-type envConfigOverrides struct {
-	SwaggerHost        string
-	SwaggerAddressPort string
-	SiteAddr           string
-}
-
-func loadEnvs() (envOverrides *envConfigOverrides) {
-	return &envConfigOverrides{
-		SwaggerHost:        os.Getenv("SWAGGER_HOST"),
-		SwaggerAddressPort: os.Getenv("SWAGGER_ADDRESS_PORT"),
-		SiteAddr:           os.Getenv("SITE_ADDR"),
-	}
-}
-
 type PathIgnore struct {
 	Users []string `yaml:"users"`
 }
@@ -77,21 +65,32 @@ type Data struct {
 
 // SetDefault set default config
 func (c *AllConfig) SetDefault() {
-	if c.UI == nil {
-		c.UI = &server.UI{}
+	if c.Server == nil {
+		c.Server = &Server{}
 	}
-}
-
-func (c *AllConfig) SetEnvironmentOverrides() {
-	envs := loadEnvs()
-	if envs.SiteAddr != "" {
-		c.Server.HTTP.Addr = envs.SiteAddr
+	if c.Server.HTTP == nil {
+		c.Server.HTTP = &server.HTTP{}
+	}
+	if c.Data == nil {
+		c.Data = &Data{}
 	}
-	if envs.SwaggerHost != "" {
-		c.Swaggerui.Host = envs.SwaggerHost
+	if c.Data.Database == nil {
+		c.Data.Database = &data.Database{}
 	}
-	if envs.SwaggerAddressPort != "" {
-		c.Swaggerui.Address = envs.SwaggerAddressPort
+	if c.Data.Cache == nil {
+		c.Data.Cache = &data.CacheConf{}
+	}
+	if c.I18n == nil {
+		c.I18n = &translator.I18n{}
+	}
+	if c.ServiceConfig == nil {
+		c.ServiceConfig = &service_config.ServiceConfig{}
+	}
+	if c.Swaggerui == nil {
+		c.Swaggerui = &router.SwaggerConfig{}
+	}
+	if c.UI == nil {
+		c.UI = &server.UI{}
 	}
 }
 
@@ -101,15 +100,27 @@ func ReadConfig(configFilePath string) (c *AllConfig, err error) {
 		configFilePath = filepath.Join(path.ConfigFileDir, path.DefaultConfigFileName)
 	}
 	c = &AllConfig{}
-	config, err := viper.NewWithPath(configFilePath)
-	if err != nil {
-		return nil, err
+	_, statErr := os.Stat(configFilePath)
+	switch {
+	case statErr == nil:
+		config, err := viper.NewWithPath(configFilePath)
+		if err != nil {
+			return nil, err
+		}
+		if err = config.Parse(&c); err != nil {
+			return nil, err
+		}
+	case errors.Is(statErr, os.ErrNotExist) && RuntimeEnvironmentConfigured():
+		if err = yaml.Unmarshal(configs.Config, c); err != nil {
+			return nil, err
+		}
+	default:
+		return nil, statErr
 	}
-	if err = config.Parse(&c); err != nil {
+	c.SetDefault()
+	if err = c.SetEnvironmentOverrides(); err != nil {
 		return nil, err
 	}
-	c.SetDefault()
-	c.SetEnvironmentOverrides()
 	return c, nil
 }