Remove sockets_used/sockets_total metrics from UIs

Part of the removal of file_handle_cache.

The Prometheus endpoint was updated but the Grafana dashboard
was not.

The FD stats are using the system's state rather than
file_handle_cache so there's no need to remove them.

Author: lhoguin

deps/rabbitmq_management/priv/www/api/index.html

@@ -2038,18 +2038,6 @@ <h2>/api/nodes</h2>
           Location of <a href="https://www.erlang.org/doc/man/sasl_app.html">sasl</a> log file.
         </td>
       </tr>
-      <tr>
-        <td><code>sockets_total</code></td>
-        <td>
-          File descriptors available for use as sockets.
-        </td>
-      </tr>
-      <tr>
-        <td><code>sockets_used</code></td>
-        <td>
-          File descriptors used as sockets.
-        </td>
-      </tr>
       <tr>
         <td><code>type</code></td>
         <td>

deps/rabbitmq_management/priv/www/js/global.js

@@ -136,7 +136,6 @@ var ALL_COLUMNS =
                         ['rate-deliver', 'deliver / get', true]]},
      'overview':
      {'Statistics': [['file_descriptors',   'File descriptors',   true],
-                     ['socket_descriptors', 'Socket descriptors', true],
                      ['erlang_processes',   'Erlang processes',   true],
                      ['memory',             'Memory',             true],
                      ['disk_space',         'Disk space',         true]],
@@ -314,21 +313,14 @@ var HELP = {
     'file-descriptors':
       '<p>File descriptor count and limit, as reported by the operating \
       system. The count includes network sockets and file handles.</p> \
-      <p>To optimize disk access RabbitMQ uses as many free descriptors as are \
-      available, so the count may safely approach the limit. \
-      However, if most of the file descriptors are used by sockets then \
-      persister performance will be negatively impacted.</p> \
+      <p>To optimize disk access RabbitMQ uses as many file descriptors as \
+      needed, so the limit must be high enough for safe operation.</p> \
       <p>To change the limit on Unix / Linux, use "ulimit -n". To change \
       the limit on Windows, set the ERL_MAX_PORTS environment variable</p> \
       <p>To report used file handles on Windows, handle.exe from \
       sysinternals must be installed in your path. You can download it \
       <a target="_blank" href="https://technet.microsoft.com/en-us/sysinternals/bb896655">here</a>.</p>',
 
-    'socket-descriptors':
-      'The network sockets count and limit managed by RabbitMQ.<br/> \
-      When the limit is exhausted RabbitMQ will stop accepting new \
-      network connections.',
-
     'memory-alarm':
       '<p>The <a target="_blank" href="https://www.rabbitmq.com/memory.html#memsup">memory \
       alarm</a> for this node has gone off. It will block \

deps/rabbitmq_management/priv/www/js/tmpl/node.ejs

@@ -92,14 +92,6 @@
 <% } %>
       </td>
     </tr>
-    <tr>
-      <th>
-        Socket descriptors <span class="help" id="socket-descriptors"></span>
-      </th>
-      <td>
-        <%= node_stat_count('sockets_used', 'sockets_total', node, FD_THRESHOLDS) %>
-      </td>
-    </tr>
     <tr>
       <th>
         Erlang processes

deps/rabbitmq_management/priv/www/js/tmpl/overview.ejs

@@ -84,9 +84,6 @@
   <% if (show_column('overview', 'file_descriptors')) { %>
     <th>File descriptors <span class="help" id="file-descriptors"></span></th>
   <% } %>
-  <% if (show_column('overview', 'socket_descriptors')) { %>
-    <th>Socket descriptors <span class="help" id="socket-descriptors"></span></th>
-  <% } %>
   <% if (show_column('overview', 'erlang_processes')) { %>
     <th>Erlang processes</th>
   <% } %>
@@ -153,11 +150,6 @@
     <% } %>
      </td>
   <% } %>
-  <% if (show_column('overview', 'socket_descriptors')) { %>
-     <td>
-        <%= node_stat_count_bar('sockets_used', 'sockets_total', node, FD_THRESHOLDS) %>
-     </td>
-  <% } %>
   <% if (show_column('overview', 'erlang_processes')) { %>
      <td>
 

deps/rabbitmq_prometheus/metrics.md

@@ -132,9 +132,7 @@ These metrics are specific to the stream protocol.
 | rabbitmq_disk_space_available_limit_bytes | Free disk space low watermark in bytes             |
 | rabbitmq_identity_info                    | RabbitMQ node & cluster identity info              |
 | rabbitmq_process_max_fds                  | Open file descriptors limit                        |
-| rabbitmq_process_max_tcp_sockets          | Open TCP sockets limit                             |
 | rabbitmq_process_open_fds                 | Open file descriptors                              |
-| rabbitmq_process_open_tcp_sockets         | Open TCP sockets                                   |
 | rabbitmq_process_resident_memory_bytes    | Memory used in bytes                               |
 | rabbitmq_resident_memory_limit_bytes      | Memory high watermark in bytes                     |
 

deps/rabbitmq_prometheus/src/collectors/prometheus_rabbitmq_core_metrics_collector.erl

@@ -69,7 +69,6 @@
     ]},
     {node_coarse_metrics, [
         {2, undefined, process_open_fds, gauge, "Open file descriptors", fd_used},
-        {2, undefined, process_open_tcp_sockets, gauge, "Open TCP sockets", sockets_used},
         {2, undefined, process_resident_memory_bytes, gauge, "Memory used in bytes", mem_used},
         {2, undefined, disk_space_available_bytes, gauge, "Disk space available in bytes", disk_free},
         {2, undefined, erlang_processes_used, gauge, "Erlang processes used", proc_used},
@@ -79,7 +78,6 @@
     ]},
     {node_metrics, [
         {2, undefined, process_max_fds, gauge, "Open file descriptors limit", fd_total},
-        {2, undefined, process_max_tcp_sockets, gauge, "Open TCP sockets limit", sockets_total},
         {2, undefined, resident_memory_limit_bytes, gauge, "Memory high watermark in bytes", mem_limit},
         {2, undefined, disk_space_available_limit_bytes, gauge, "Free disk space low watermark in bytes", disk_free_limit},
         {2, undefined, erlang_processes_limit, gauge, "Erlang processes limit", proc_total},