Add TCM stateboard page (#3946)

Resolves #3632 

Co-authored-by: Kseniia Antonova <[email protected]>

Author: p7nov

doc/reference/tooling/tcm/index.rst

@@ -37,6 +37,7 @@ to read data. LDAP authorization is supported as well.
 
     tcm_connect_clusters
     tcm_cluster_config
+    tcm_cluster_monitoring
     tcm_access_control
     tcm_audit_log
     tcm_configuration

doc/reference/tooling/tcm/tcm_cluster_monitoring.rst

@@ -0,0 +1,117 @@
+..  _tcm_cluster_monitoring:
+
+Cluster monitoring
+==================
+
+|tcm_full_name| provides means for monitoring various aspects of connected clusters,
+such as:
+
+*   topology
+*   instance state
+*   memory usage
+*   data distribution
+*   Tarantool versions
+
+Cluster monitoring tools are available on the **Cluster** > **Stateboard** page.
+
+..  _tcm_cluster_monitoring_topology:
+
+Cluster topology
+----------------
+
+The cluster topology is displayed on the **Stateboard** page in one of two forms:
+a list or a graph.
+
+..  _tcm_cluster_monitoring_topology_list:
+
+List view
+~~~~~~~~~
+
+The list view of the cluster topology is used by default. In this view, each row contains
+the general information about an instance: its current state, memory usage and limit,
+and other parameters.
+
+In the list view, |tcm| additionally displays the Tarantool version information
+and instance states on circle diagrams. You can click the sectors of these diagrams
+to filter the instances with the selected versions and states.
+
+To switch to the list view, click the list button on the right of the search bar on the **Stateboard** page.
+
+..  _tcm_cluster_monitoring_topology_graph:
+
+Graph view
+~~~~~~~~~~
+
+The graph view of the cluster topology is shown in a tree-like structure where
+leafs are the cluster's instances. Each instance's state is shown by its color.
+You can move the graph vertexes to arrange them as you like, and zoom in and out,
+which is helpful for bigger clusters.
+
+To switch to the graph view, click the graph button on the right of the search bar on the **Stateboard** page.
+
+..  _tcm_cluster_monitoring_topology_group:
+
+Instance grouping
+~~~~~~~~~~~~~~~~~
+
+By default, the cluster topology is shown hierarchically as it's defined in the configuration:
+instances are grouped by their replica set, and replica sets are grouped by
+their configuration group.
+
+For better navigation across the cluster, you can adjust the instance grouping.
+For example, you can group instances by their roles or custom tags defined in the configuration.
+A typical case for such tags is adding a geographical markers to instances. In this case,
+you see if issues happen in a specific data center or server.
+
+To change the instance grouping, click **Group by** in the **Actions** menu on the **Stateboard** page.
+Then add or remove grouping criteria.
+
+..  _tcm_cluster_monitoring_topology_filters:
+
+Filtering
+~~~~~~~~~
+
+You can filter the instances shown on the **Stateboard** page using the search bar
+at the top. It has predefined filters that select:
+
+*   instances with errors or warnings
+*   leader or read-only instances
+*   instances with no issues
+*   stale instances
+
+To display all instances, delete the filter applied in the search bar.
+
+..  _tcm_cluster_monitoring_instance_details:
+
+Instance details
+----------------
+
+The general information about the state of cluster instances is shown in the
+list view of the cluster topology. Each row contains the information about the instance
+status, used and available memory, read-only status, and virtual buckets for sharded
+clusters.
+
+To view the detailed information about an instance or connect to it, click the corresponding
+row in the instances list or a vertex of the graph. On the instance page, you can
+find:
+
+*   its configuration overview
+*   current state (with warning and error messages if any)
+*   the detailed Tarantool information returned by the instance introspection functions
+    from :ref:`box.info <box_introspection-box_info>`, :ref:`box.stat <box_introspection-box_stat>`,
+    and other built-in modules.
+
+Additionally, on the instance details page there is a terminal in which you can execute
+arbitrary Lua code on the instance.
+
+..  _tcm_cluster_monitoring_urls:
+
+Additional monitoring services
+------------------------------
+
+When you :ref:`connect a cluster <tcm_connect_clusters>` to |tcm|, you can specify
+URLs of external services linked to this cluster. For example, this can be a Grafana
+server that monitors the cluster metrics.
+
+All the URLs added for a cluster are available for quick access in the **Actions**
+menu on the **Stateboard** page.