Configuration File Support

text/0034-telemetry-policies.md

@@ -87,6 +87,7 @@ The collected data is sent to [Segment](https://segment.com/). Segment is a plat
 | `infos.log_level`                       | Value of `--log-level`/`MEILI_LOG_LEVEL`                | debug             | Every Hour |
 | `infos.max_indexing_memory`                      | Value of `--max-indexing-memory`/`MEILI_MAX_INDEXING_MEMORY` in bytes     | 336042103         | Every Hour |
 | `infos.max_indexing_threads`                   | Value of `--max-indexing-threads`/`MEILI_MAX_INDEXING_THREADS` in integer | 4             | Every Hour |
+| `infos.with_configuration_file`         | `true` if the instance is launched with a configuration file, otherwise `false` | false | Every Hour |
 | `system.distribution`                   | Distribution on which MeiliSearch is launched           | Arch Linux        | Every hour |
 | `system.kernel_version`                 | Kernel version on which MeiliSearch is launched         | 5.14.10           | Every hour |
 | `system.cores`                          | Number of cores                                         | 24                | Every hour |
@@ -179,6 +180,7 @@ This property allows us to gather essential information to better understand on
 | infos.log_level | Value of `--log-level`/`MEILI_LOG_LEVEL`  | `debug` |
 | infos.max_indexing_memory  | Value of `--max-indexing-memory`/`MEILI_MAX_INDEXING_MEMORY` in bytes     | `336042103` |
 | infos.max_indexing_threads  | Value of `--max-indexing-threads`/`MEILI_MAX_INDEXING_THREADS` in integer | `4` |
+| infos.with_configuration_file | `true` if the instance is launched with a configuration file, otherwise `false` | `false` |
 
 ##### MeiliSearch Statistics `stats`
 

text/0119-instance-options.md

@@ -120,6 +120,7 @@ The expected behavior of each flag is described in the list above.
 - [SSL require auth](#3327-ssl-require-auth)
 - [SSL resumption](#3328-ssl-resumption)
 - [SSL tickets](#3329-ssl-tickets)
+- [Config file path](#3330-config-file-path)
 
 #### 3.3.1. Database path
 
@@ -457,6 +458,16 @@ Activates SSL session resumption.
 
 Activates SSL tickets.
 
+#### 3.3.30. Config file path
+
+**Environment variable**: `MEILI_CONFIG_FILE_PATH`
+**CLI option**: `--config-file-path`
+**Default**: `./config.toml`
+
+Define the config file to load at Meilisearch launch.
+
+See [Configuration File](0185-configuration-file.md) specification details.
+
 ## 4. Technical Aspects
 
 N/A

text/0185-configuration-file.md

@@ -0,0 +1,98 @@
+# Configuration File
+
+## 1. Summary
+
+Meilisearch options can be defined in a `.toml` configuration file being loaded at launch.
+
+## 2. Motivation
+
+Teams can easily version, track, and share configuration files. It makes it easier to learn about the different options available and to define at a glance how Meilisearch is configured.
+
+## 3. Functional Specification
+
+### 3.1. Supported Formats
+
+| Format    |
+|-----------|
+| `.toml`   |
+
+### 3.2. Priority Order
+
+`Configuration file < Env variables < Command-line options`
+
+It means the options in the configuration file are overwritten by the environment variables set (if they exist) and that can be themself overwritten by the command-line options (if they exist).
+
+### 3.3. Default Configuration File
+
+By default, Meilisearch will try to read the `./config.toml` in the current working directory.
+
+We provide a default configuration file as an example [here](https://github.com/meilisearch/meilisearch/blob/main/config.toml).
+
+### 3.4. `--config-file-path`/`MEILI_CONFIG_FILE_PATH`
+
+It is possible to override the default configuration file by setting the `MEILI_CONFIG_FILE_PATH` environment variable or by specifying the `--config-file-path` option.
+
+### 3.5. Configuration File Content Definition
+
+The current consistency rule is that all environment variables and launch options are configurable by a dedicated key in the configuration file.
+
+Configuration keys are named following the `snake_case` convention from the name of a CLI option. That is, `--import-dump` must be named `import_dump` within the configuration file.
+
+There is an exception rule. The `config_file_path` key is not accepted in the configuration file and stops Meilisearch from being launched if specified.
+
+See [Instance Options](0119-instance-options.md) for more details.
+
+### 3.6. Indication of the loaded configuration file
+
+When Meilisearch is launched, the loaded configuration file is indicated by the `Config file path` key on stdout.
+
+```bash
+888b     d888          d8b 888 d8b                                            888
+8888b   d8888          Y8P 888 Y8P                                            888
+88888b.d88888              888                                                888
+888Y88888P888  .d88b.  888 888 888 .d8888b   .d88b.   8888b.  888d888 .d8888b 88888b.
+888 Y888P 888 d8P  Y8b 888 888 888 88K      d8P  Y8b     "88b 888P"  d88P"    888 "88b
+888  Y8P  888 88888888 888 888 888 "Y8888b. 88888888 .d888888 888    888      888  888
+888   "   888 Y8b.     888 888 888      X88 Y8b.     888  888 888    Y88b.    888  888
+888       888  "Y8888  888 888 888  88888P'  "Y8888  "Y888888 888     "Y8888P 888  888
+
+Config file path:       "./config.toml"
+```
+
+If Meilisearch can't find the default `config.toml` or if no other config file is specified with `MEILI_CONFIG_FILE_PATH` env var or `--config-file-path` options, `none` is indicated.
+
+### 3.7. Errors
+
+#### 3.7.1. Defining `config_file_path` in the configuration file
+
+Defining `config_file_path` in the configuration file is not valid and Meilisearch returns an error.
+
+```bash
+Error: `config_file_path` is not supported in configuration file.
+```
+
+#### 3.7.2. Defining a non-existent config file.
+
+Defining a configuration file other than the default file that does not exist returns an error when launching Meilisearch.
+
+```bash
+Error: unable to open or read the "XXX" configuration file: No such file or directory (os error 2).
+```
+
+#### 3.7.3. Defining a config file with a syntax error.
+
+Defining a configuration file wrongly formatted or containing an invalid configuration key returns an error when launching Meilisearch.
+
+```bash
+Error: unknown field `XXX` at line Y column Z
+```
+
+## 4. Technical Details
+N/A
+
+## 5. Future Possibilities
+
+- Better indicate a syntax error
+- List all loaded configuration at launch on the stdout
+- Introduce toml sections to group options under a common name. e.g. A dump section could contain a `schedule`, `dir`, `interval-sec` and `enable`. That could help navigate the toml.
+- Introduce other formats