Add documentation for new connection pool settings and remove some

`:retry_timeout` and `:retry` got removed because reconnecting on failure is
something the new pool intentionally doesn't do.

`:max_overflow` had to go in favor of `:max_waiting`, I didn't reuse the key because
the settings are very different in their behaviour.

`:checkin_timeout` got removed in favor of `:connection_acquisition_wait`,
I didn't reuse the key because the settings are somewhat different.

I didn't do any migrations/deprecation warnings/changelog entries because
these settings were never in stable.

config/description.exs

@@ -3161,36 +3161,37 @@
     description: "Advanced settings for `gun` connections pool",
     children: [
       %{
-        key: :checkin_timeout,
+        key: :connection_acquisition_wait,
         type: :integer,
-        description: "Timeout to checkin connection from pool. Default: 250ms.",
+        description:
+          "Timeout to acquire a connection from pool.The total max time is this value multiplied by the number of retries. Default: 250ms.",
         suggestions: [250]
       },
+      %{
+        key: :connection_acquisition_retries,
+        type: :integer,
+        description:
+          "Number of attempts to acquire the connection from the pool if it is overloaded. Default: 5",
+        suggestions: [5]
+      },
       %{
         key: :max_connections,
         type: :integer,
         description: "Maximum number of connections in the pool. Default: 250 connections.",
         suggestions: [250]
       },
-      %{
-        key: :retry,
-        type: :integer,
-        description:
-          "Number of retries, while `gun` will try to reconnect if connection goes down. Default: 1.",
-        suggestions: [1]
-      },
-      %{
-        key: :retry_timeout,
-        type: :integer,
-        description:
-          "Time between retries when `gun` will try to reconnect in milliseconds. Default: 1000ms.",
-        suggestions: [1000]
-      },
       %{
         key: :await_up_timeout,
         type: :integer,
         description: "Timeout while `gun` will wait until connection is up. Default: 5000ms.",
         suggestions: [5000]
+      },
+      %{
+        key: :reclaim_multiplier,
+        type: :integer,
+        description:
+          "Multiplier for the number of idle connection to be reclaimed if the pool is full. For example if the pool maxes out at 250 connections and this setting is set to 0.3, the pool will reclaim at most 75 idle connections if it's overloaded. Default: 0.1",
+        suggestions: [0.1]
       }
     ]
   },
@@ -3199,108 +3200,29 @@
     key: :pools,
     type: :group,
     description: "Advanced settings for `gun` workers pools",
-    children: [
+    children:
+      Enum.map([:federation, :media, :upload, :default], fn pool_name ->
         %{
-        key: :federation,
+          key: pool_name,
           type: :keyword,
-        description: "Settings for federation pool.",
+          description: "Settings for #{pool_name} pool.",
           children: [
             %{
               key: :size,
               type: :integer,
-            description: "Number workers in the pool.",
+              description: "Maximum number of concurrent requests in the pool.",
               suggestions: [50]
             },
             %{
-            key: :max_overflow,
+              key: :max_waiting,
               type: :integer,
-            description: "Number of additional workers if pool is under load.",
+              description:
+                "Maximum number of requests waiting for other requests to finish. After this number is reached, the pool will start returning errrors when a new request is made",
               suggestions: [10]
-          },
-          %{
-            key: :timeout,
-            type: :integer,
-            description: "Timeout while `gun` will wait for response.",
-            suggestions: [150_000]
-          }
-        ]
-      },
-      %{
-        key: :media,
-        type: :keyword,
-        description: "Settings for media pool.",
-        children: [
-          %{
-            key: :size,
-            type: :integer,
-            description: "Number workers in the pool.",
-            suggestions: [50]
-          },
-          %{
-            key: :max_overflow,
-            type: :integer,
-            description: "Number of additional workers if pool is under load.",
-            suggestions: [10]
-          },
-          %{
-            key: :timeout,
-            type: :integer,
-            description: "Timeout while `gun` will wait for response.",
-            suggestions: [150_000]
-          }
-        ]
-      },
-      %{
-        key: :upload,
-        type: :keyword,
-        description: "Settings for upload pool.",
-        children: [
-          %{
-            key: :size,
-            type: :integer,
-            description: "Number workers in the pool.",
-            suggestions: [25]
-          },
-          %{
-            key: :max_overflow,
-            type: :integer,
-            description: "Number of additional workers if pool is under load.",
-            suggestions: [5]
-          },
-          %{
-            key: :timeout,
-            type: :integer,
-            description: "Timeout while `gun` will wait for response.",
-            suggestions: [300_000]
-          }
-        ]
-      },
-      %{
-        key: :default,
-        type: :keyword,
-        description: "Settings for default pool.",
-        children: [
-          %{
-            key: :size,
-            type: :integer,
-            description: "Number workers in the pool.",
-            suggestions: [10]
-          },
-          %{
-            key: :max_overflow,
-            type: :integer,
-            description: "Number of additional workers if pool is under load.",
-            suggestions: [2]
-          },
-          %{
-            key: :timeout,
-            type: :integer,
-            description: "Timeout while `gun` will wait for response.",
-            suggestions: [10_000]
             }
           ]
         }
-    ]
+      end)
   },
   %{
     group: :pleroma,

docs/configuration/cheatsheet.md

@@ -448,36 +448,32 @@ For each pool, the options are:
 
 *For `gun` adapter*
 
-Advanced settings for connections pool. Pool with opened connections. These connections can be reused in worker pools.
+Settings for HTTP connection pool.
 
-For big instances it's recommended to increase `config :pleroma, :connections_pool, max_connections: 500` up to 500-1000.
+* `:connection_acquisition_wait` - Timeout to acquire a connection from pool.The total max time is this value multiplied by the number of retries.
-It will increase memory usage, but federation would work faster.
+* `connection_acquisition_retries` - Number of attempts to acquire the connection from the pool if it is overloaded. Each attempt is timed `:connection_acquisition_wait` apart.
-
+* `:max_connections` - Maximum number of connections in the pool.
-* `:checkin_timeout` - timeout to checkin connection from pool. Default: 250ms.
+* `:await_up_timeout` - Timeout to connect to the host.
-* `:max_connections` - maximum number of connections in the pool. Default: 250 connections.
+* `:reclaim_multiplier` - Multiplied by `:max_connections` this will be the maximum number of idle connections that will be reclaimed in case the pool is overloaded.
-* `:retry` - number of retries, while `gun` will try to reconnect if connection goes down. Default: 1.
-* `:retry_timeout` - time between retries when `gun` will try to reconnect in milliseconds. Default: 1000ms.
-* `:await_up_timeout` - timeout while `gun` will wait until connection is up. Default: 5000ms.
 
 ### :pools
 
 *For `gun` adapter*
 
-Advanced settings for workers pools.
+Settings for request pools. These pools are limited on top of `:connections_pool`.
 
 There are four pools used:
 
-* `:federation` for the federation jobs.
+* `:federation` for the federation jobs. You may want this pool's max_connections to be at least equal to the number of federator jobs + retry queue jobs.
-  You may want this pool max_connections to be at least equal to the number of federator jobs + retry queue jobs.
+* `:media` - for rich media, media proxy.
-* `:media` for rich media, media proxy
+* `:upload` - for proxying media when a remote uploader is used and `proxy_remote: true`.
-* `:upload` for uploaded media (if using a remote uploader and `proxy_remote: true`)
+* `:default` - for other requests.
-* `:default` for other requests
 
 For each pool, the options are:
 
-* `:size` - how much workers the pool can hold
+* `:size` - limit to how much requests can be concurrently executed.
 * `:timeout` - timeout while `gun` will wait for response
-* `:max_overflow` - additional workers if pool is under load
+* `:max_waiting` - limit to how much requests can be waiting for others to finish, after this is reached, subsequent requests will be dropped.
 
 ## Captcha
 

lib/pleroma/gun/conn.ex

@@ -13,8 +13,6 @@ def open(%URI{} = uri, opts) do
     opts =
       opts
       |> Enum.into(%{})
-      |> Map.put_new(:retry, pool_opts[:retry] || 1)
-      |> Map.put_new(:retry_timeout, pool_opts[:retry_timeout] || 1000)
       |> Map.put_new(:await_up_timeout, pool_opts[:await_up_timeout] || 5_000)
       |> Map.put_new(:supervise, false)
       |> maybe_add_tls_opts(uri)