Add ability to gets all active connections to the database.

This adds the ability to get all active connections to the database.

Co-authored-by: Matt Hall <matt.hall@binarynoggin.com>

README.md

@@ -555,6 +555,32 @@ EctoPSQLExtras.mandelbrot(YourApp.Repo)
 
 This command outputs the Mandelbrot set, calculated through SQL.
 
+### `connections`
+
+```
+
+EctoPSQLExtras.connections(YourApp.Repo)
++----------------------------------------------+
+|  Shows all the active database connections   |
++----------+----------------+------------------+
+| username | client_address | application_name |
++----------+----------------+------------------+
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | phoenix_1_6_15   |
+| postgres | 172.20.0.1/32  | psql             |
++----------+----------------+------------------+
+```
+
+This command returns the list of all active connections to the database.
+
 ## Query sources
 
 - [https://github.com/heroku/heroku-pg-extras](https://github.com/heroku/heroku-pg-extras)

lib/ecto_psql_extras.ex

@@ -49,7 +49,8 @@ defmodule EctoPSQLExtras do
       duplicate_indexes: EctoPSQLExtras.DuplicateIndexes,
       null_indexes: EctoPSQLExtras.NullIndexes,
       vacuum_stats: EctoPSQLExtras.VacuumStats,
-      kill_all: EctoPSQLExtras.KillAll
+      kill_all: EctoPSQLExtras.KillAll,
+      connections: EctoPSQLExtras.Connections
     }
     |> Map.merge(pg_stat_statements_queries(repo))
     |> Map.merge(ssl_used_query(repo))
@@ -360,6 +361,13 @@ defmodule EctoPSQLExtras do
   """
   def ssl_used(repo, opts \\ []), do: query(:ssl_used, repo, opts)
 
+  @doc """
+  Run `connections` query on `repo`, in the given `format`.
+
+  `format` is either `:ascii` or `:raw`
+  """
+  def connections(repo, opts \\ []), do: query(:connections, repo, opts)
+
   defp format(:ascii, info, result) do
     names = Enum.map(info.columns, & &1.name)
     types = Enum.map(info.columns, & &1.type)

lib/queries/connections.ex

@@ -0,0 +1,23 @@
+defmodule EctoPSQLExtras.Connections do
+  @behaviour EctoPSQLExtras
+
+  def info do
+    %{
+      title: "Returns the list of all active database connections",
+      columns: [
+        %{name: :username, type: :string},
+        %{name: :client_address, type: :string},
+        %{name: :application_name, type: :string}
+      ]
+    }
+  end
+
+  def query(_args \\ []) do
+    """
+    /* ECTO_PSQL_EXTRAS: Returns the list of all active database connections */
+
+    SELECT usename as username, client_addr::text as client_address, application_name FROM pg_stat_activity
+      WHERE datname = current_database();
+    """
+  end
+end

test/ecto_psql_extras_test.exs

@@ -13,7 +13,7 @@ defmodule EctoPSQLExtrasTest do
     outliers_legacy: EctoPSQLExtras.OutliersLegacy
   }
 
-  @skip_queries [:kill_all]
+  @skip_queries [:kill_all, :connections]
 
   test "all queries define info" do
     for pair <- Map.merge(queries(), @optional_queries) do