Centralized storage

Author: andreyaksenov

doc/code_snippets/snippets/centralized_config/README.md

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+# Centralized configuration storages
+
+Sample applications demonstrating how to store configuration data in one place using Tarantool or etcd-based storage. Learn more at [Centralized configuration storages](https://www.tarantool.io/en/doc/latest/concepts/configuration/configuration_etcd/).

doc/code_snippets/snippets/centralized_config/etcd_config_storage.sh

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+#!/usr/bin/env bash
+
+# 1. Remove the 'default.etcd' directory to reset etcd to initial state.
+# 2. Start etcd by executing the 'etcd' command.
+# 3. Execute this script to enable authentication.
+etcdctl user add root:topsecret
+etcdctl role add myapp_config_manager
+etcdctl role grant-permission myapp_config_manager --prefix=true readwrite /myapp/
+etcdctl user add sampleuser:123456
+etcdctl user grant-role sampleuser myapp_config_manager
+etcdctl auth enable

doc/code_snippets/snippets/centralized_config/instances.enabled/config_etcd/README.md

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+# etcd configuration storage
+
+A sample application demonstrating how to obtain a cluster's configuration from the etcd-based configuration storage.
+
+## Running
+
+Before running this sample, start etcd and enable authentication by executing [etcd_config_storage.sh](../../etcd_config_storage.sh).
+
+To start all instances, execute the following command in the [centralized_config](../../../centralized_config) directory:
+
+```console
+$ tt start config_etcd
+```

doc/code_snippets/snippets/centralized_config/instances.enabled/config_etcd/config.yaml

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+config:
+  etcd:
+    endpoints:
+    - http://localhost:2379
+    prefix: /myapp
+    username: sampleuser
+    password: '123456'
+    http:
+      request:
+        timeout: 3

doc/code_snippets/snippets/config/instances.enabled/etcd/instances.yml renamed to doc/code_snippets/snippets/centralized_config/instances.enabled/config_etcd/instances.yml

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+# Tarantool configuration storage
+
+A sample application demonstrating how to obtain a cluster's configuration from the Tarantool-based configuration storage.
+
+## Running
+
+Before running this sample, start a Tarantool-based configuration storage: [tarantool_config_storage](../tarantool_config_storage).
+
+To start all instances, execute the following command in the [centralized_config](../../../centralized_config) directory:
+
+```console
+$ tt start config_storage
+```

doc/code_snippets/snippets/centralized_config/instances.enabled/config_storage/README.md

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+config:
+  storage:
+    endpoints:
+      - uri: '127.0.0.1:4401'
+        login: sampleuser
+        password: '123456'
+      - uri: '127.0.0.1:4402'
+        login: sampleuser
+        password: '123456'
+      - uri: '127.0.0.1:4403'
+        login: sampleuser
+        password: '123456'
+    prefix: /myapp
+    timeout: 3
+    reconnect_after: 5
+
+# Watch key changes
+app:
+  file: 'myapp.lua'

doc/code_snippets/snippets/centralized_config/instances.enabled/config_storage/config.yaml

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+net_box = require('net.box')
+local conn = net_box.connect('127.0.0.1:4401')
+local log = require('log')
+conn:watch('config.storage:/myapp/config/all', function(key, value)
+    log.info("Configuration stored by the '/myapp/config/all' key is changed")
+end)

doc/code_snippets/snippets/config/instances.enabled/etcd_full/instances.yml renamed to doc/code_snippets/snippets/centralized_config/instances.enabled/config_storage/instances.yml

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+# Setting up Tarantool configuration storage
+
+A sample application demonstrating how to set up Tarantool configuration storage.
+
+## Running
+
+To start all instances of the configuration storage, execute the following command in the [centralized_config](../../../centralized_config) directory:
+
+```console
+$ tt start tarantool_config_storage
+```