TCM data storages: etcd and Tarantool (#4123)

Resolves #4123 

Co-authored-by: Andrey Aksenov <38073144+andreyaksenov@users.noreply.github.com>

Author: p7nov

doc/reference/tooling/tcm/index.rst

@@ -42,4 +42,5 @@ to read data. LDAP authorization is supported as well.
     tcm_access_control
     tcm_audit_log
     tcm_configuration
+    tcm_backend_store
     tcm_configuration_reference

doc/reference/tooling/tcm/tcm_backend_store.rst

@@ -0,0 +1,386 @@
+.. _tcm_backend_store:
+
+Backend store
+=============
+
+..  include:: index.rst
+    :start-after: ee_note_tcm_start
+    :end-before: ee_note_tcm_end
+
+|tcm_full_name| uses an underlying data store (*backend store*) for its entities:
+users, roles, cluster connections, settings, and other objects that you manipulate in |tcm|.
+The backend store can be either an etcd or a Tarantool cluster.
+
+For better reliability and scalability, the backend store works independently from |tcm|.
+For example, it can be the same ectd or Tarantool cluster that you use as a :ref:`centralized configuration storage <configuration_etcd>`.
+This makes |tcm| stateless: all objects created or modified in its web UI are saved
+to the backend store, and nothing is stored inside the |tcm| instances themselves.
+Any number of instances can duplicate each other when connected to the same backend store.
+If you stop all instances, the store still contains their objects. You can continue
+working with them right after starting a new instance.
+
+In addition to using an external backend store, you can run |tcm| with an embedded
+etcd or Tarantool instance to use as the backend store.
+
+On this page, you will learn to connect |tcm| to backend stores of both types,
+or start |tcm| with an embedded backend store.
+
+.. _tcm_backend_store_set_up:
+
+Setting up a backend store
+--------------------------
+
+The |tcm| backend store requires the same configuration as
+:ref:`Tarantool centralized configuration storage <configuration_etcd>`.
+Follow the instructions in :ref:`centralized_configuration_storage_set_up` to
+set up a backend store.
+
+.. note::
+
+    If you already have the centralized configuration store for your Tarantool clusters,
+    you can use it as a |tcm| backend store as well.
+
+.. _tcm_backend_store_connect:
+
+Configuring backend store connection
+------------------------------------
+
+The |tcm|'s connection to its backend store is configured using the :ref:`storage.* <tcm_configuration_reference_storage>`
+configuration options. The :ref:`storage.provider <tcm_configuration_reference_storage_provider>`
+option selects the store type. It can be either ``etcd`` or ``tarantool``.
+
+.. _tcm_backend_store_connect_etcd:
+
+External etcd store
+~~~~~~~~~~~~~~~~~~~
+
+To use an etcd cluster as a |tcm| backend store, set the ``storage.provider`` option
+to ``etcd`` and specify connection parameters in ``storage.etcd.*`` options.
+A minimal etcd configuration includes the storage endpoints:
+
+.. code-block:: yaml
+
+    storage:
+      provider: etcd
+      etcd:
+        endpoints:
+          - http://127.0.0.1:2379
+
+If authentication is enabled in etcd, specify ``storage.etcd.username`` and ``storage.etcd.password``:
+
+.. code-block:: yaml
+
+    storage:
+      provider: etcd
+      etcd:
+        endpoints:
+          - http://127.0.0.1:2379
+        username: etcduser
+        password: secret
+
+The |tcm| data is stored in etcd under the prefix specified in ``storage.etcd.prefix``.
+By default, the prefix is ``/tcm``. If you want to change it or store data of
+different |tcm| instances separately in one etcd cluster, set the prefix explicitly:
+
+.. code-block:: yaml
+
+    storage:
+      provider: etcd
+      etcd:
+        endpoints:
+          - http://127.0.0.1:2379
+        prefix: /tcm2
+
+
+Other ``storage.etcd.*`` options configure various aspects of the etcd store connection,
+such as network timeouts and limits or TLS parameters.
+For the full list of the etcd |tcm| backend store options, see the
+:ref:`TCM configuration reference <tcm_configuration_reference_storage>`.
+
+.. _tcm_backend_store_connect_tarantool:
+
+External Tarantool-based store
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To use a Tarantool cluster as a |tcm| backend store, set the ``storage.provider`` option
+to ``tarantool`` and specify connection parameters in ``storage.tarantool.*`` options.
+A minimal configuration includes the one or more addresses of
+the backend store instances:
+
+.. code-block:: yaml
+
+    storage:
+      provider: tarantool
+      tarantool:
+        addr: http://127.0.0.1:3301
+
+Or:
+
+.. code-block:: yaml
+
+    storage:
+      provider: tarantool
+      tarantool:
+        addrs:
+          - http://127.0.0.1:3301
+          - http://127.0.0.1:3302
+          - http://127.0.0.1:3303
+
+If authentication is enabled in the backend store, specify ``storage.tarantool.username``
+and ``storage.tarantool.password``:
+
+.. code-block:: yaml
+
+    storage:
+      provider: tarantool
+      tarantool:
+        addr: http://127.0.0.1:3301
+        username: tarantooluser
+        password: secret
+
+The |tcm| data is stored in the Tarantool-based backend store under the prefix
+specified in ``storage.tarantool.prefix``.
+By default, the prefix is ``/tcm``. If you want to change it or store data of
+different |tcm| instances separately in one Tarantool cluster, set the prefix explicitly:
+
+.. code-block:: yaml
+
+    storage:
+      provider: tarantool
+      tarantool:
+        addr: http://127.0.0.1:3301
+        username: tarantooluser
+        password: secret
+        prefix: /tcm2
+
+
+Other ``storage.tarantool.*`` options configure various aspects of |tcm| connection
+to the Tarantool-based backend store, such as network timeouts and limits or TLS parameters.
+For the full list of the Tarantool-based |tcm| backend store options, see the
+:ref:`TCM configuration reference <tcm_configuration_reference_storage>`.
+
+.. _tcm_backend_store_embed:
+
+Embedded backend store
+----------------------
+
+For development purposes, you can start |tcm| with an embedded backend store.
+This is useful for local runs when you don't have or don't need an external backend store.
+
+An embedded |tcm| backend store is a single instance of etcd or Tarantool that
+is started automatically on the same host during the |tcm| startup. It runs
+in the background until |tcm| is stopped. The embedded backend store is persistent:
+if you start |tcm| again with the same backend store configuration, it restores
+the |tcm| data from the previous runs.
+
+.. note::
+
+    To start a clean instance of |tcm|, remove the working directory of the
+    embedded backend store specified in the ``storage.etcd.embed.workdir`` or
+    ``storage.tarantool.embed.workdir`` option.
+
+The embedded backend store parameters are configured using the ``storage.etcd.embed.*`` options
+for etcd or ``storage.tarantool.embed.*`` options for a Tarantool-based store.
+
+To start |tcm| with an embedded etcd with default settings, set ``storage.etcd.embed.enabled`` to ``true``
+and leave other ``storage.*`` options default:
+
+.. code-block:: yaml
+
+    storage.etcd.embed.enabled: true
+
+You can use the following call to get |tcm| running with embedded etcd without
+a configuration file:
+
+.. code-block:: console
+
+    $ tcm --storage.etcd.embed.enabled
+
+To start |tcm| with an embedded Tarantool storage with default settings:
+
+*   set ``storage.provider`` to ``tarantool``
+*   set ``storage.tarantool.embed.enabled`` to ``true``
+
+.. code-block:: yaml
+
+    storage:
+      provider: tarantool
+      tarantool.embed.enabled: true
+
+With command-line arguments:
+
+.. code-block:: console
+
+    $ tcm --storage.provider=tarantool --storage.tarantool.embed.enabled
+
+You can tune the embedded backend store, for example, enable and configure TLS on it
+or change its working directories or startup arguments. To set specific parameters,
+specify the corresponding ``storage.etcd.embed.*`` or ``storage.tarantool.embed.*``
+options. For the full list of configuration options of embedded backend stores, see the
+:ref:`TCM configuration reference <tcm_configuration_reference_storage>`.
+
+.. _tcm_backend_store_embed_cluster:
+
+Setting up a cluster of embedded backend stores
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To simulate the production environment, you can form a distributed multi-instance cluster
+from embedded stores of multiple |tcm| instances. To do this, configure each |tcm|
+instance's embedded store to join each other.
+
+For etcd, provide the embedded store clustering parameters ``storage.etcd.embed.*``
+and specify the endpoints in ``storage.etcd.endpoints``. The options that configure
+embedded etcd mostly match the etcd configuration options. For more information
+about these options, see the `etcd documentation <https://etcd.io/docs/latest/op-guide/configuration/>`__.
+
+Below are example configurations of three |tcm| instances that start with embedded etcd instances
+and form an etcd cluster from them:
+
+*   First instance:
+
+    .. code-block:: yaml
+
+        http.port: 8080
+        storage:
+          provider: etcd
+          etcd:
+            endpoints:
+              - http://127.0.0.1:2379
+              - http://127.0.0.1:22379
+              - http://127.0.0.1:32379
+            embed:
+              enabled: true
+              name: infra1
+              endpoints: http://127.0.0.1:2379
+              advertises: http://127.0.0.1:2379
+              initial-cluster-state: new
+              initial-cluster: infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380
+              initial-cluster-token: etcd-cluster-1
+              peer-endpoints: http://127.0.0.1:12380
+              peer-advertises: http://127.0.0.1:12380
+              workdir: node1.etcd
+
+*   Second instance:
+
+    .. code-block:: yaml
+
+        http.port: 8081
+        storage:
+          provider: etcd
+          etcd:
+            endpoints:
+              - http://127.0.0.1:2379
+              - http://127.0.0.1:22379
+              - http://127.0.0.1:32379
+            embed:
+              enabled: true
+              name: infra2
+              endpoints: http://127.0.0.1:22379
+              advertises: http://127.0.0.1:22379
+              initial-cluster-state: new
+              initial-cluster: infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380
+              initial-cluster-token: etcd-cluster-1
+              peer-endpoints: http://127.0.0.1:22380
+              peer-advertises: http://127.0.0.1:22380
+              workdir: node2.etcd
+
+*   Third instance:
+
+    .. code-block:: yaml
+
+        http.port: 8082
+        storage:
+          provider: etcd
+          etcd:
+            endpoints:
+              - http://127.0.0.1:2379
+              - http://127.0.0.1:22379
+              - http://127.0.0.1:32379
+            embed:
+              enabled: true
+              name: infra3
+              endpoints: http://127.0.0.1:32379
+              advertises: http://127.0.0.1:32379
+              initial-cluster-state: new
+              initial-cluster: infra1=http://127.0.0.1:12380,infra2=http://127.0.0.1:22380,infra3=http://127.0.0.1:32380
+              initial-cluster-token: etcd-cluster-1
+              peer-endpoints: http://127.0.0.1:32380
+              peer-advertises: http://127.0.0.1:32380
+              workdir: node3.etcd
+
+
+To set up a cluster from embedded Tarantool-based backend stores:
+
+1.  Specify the Tarantool cluster configuration in ``storage.tarantool.embed.config``
+    (as a plain text) or ``storage.tarantool.embed.config-file`` (as a YAML file).
+2.  Assign an instance name from this configuration to each instance using ``storage.tarantool.embed.args``
+    to each embedded store.
+
+Below are example configurations of three |tcm| instances that start with embedded
+Tarantool-based backend stores and form a cluster from them:
+
+*   First instance:
+
+    .. code-block:: yaml
+
+        http.port: 8080
+        storage:
+          provider: tarantool
+          tarantool:
+            addrs:
+              - http://127.0.0.1:3301
+              - http://127.0.0.1:3302
+              - http://127.0.0.1:3303
+            embed:
+              enabled: true
+              config-filename: config.yml
+              workdir: node1.tarantool
+              args:
+                - --name
+                - instance-001
+                - --config
+                - config.yml
+
+*   Second instance:
+
+    .. code-block:: yaml
+
+        http.port: 8081
+        storage:
+          provider: tarantool
+          tarantool:
+            addrs:
+              - http://127.0.0.1:3301
+              - http://127.0.0.1:3302
+              - http://127.0.0.1:3303
+            embed:
+              enabled: true
+              config-filename: config.yml
+              workdir: node2.tarantool
+              args:
+                - --name
+                - instance-002
+                - --config
+                - config.yml
+
+*   Third instance:
+
+    .. code-block:: yaml
+
+        http.port: 8082
+        storage:
+          provider: tarantool
+          tarantool:
+            addrs:
+              - http://127.0.0.1:3301
+              - http://127.0.0.1:3302
+              - http://127.0.0.1:3303
+            embed:
+              enabled: true
+              config-filename: config.yml
+              workdir: node3.tarantool
+              args:
+                - --name
+                - instance-003
+                - --config
+                - config.yml