Avoid setting recbuf/sndbuf in replica(_reader) processes

src/osiris_replica.erl

@@ -89,7 +89,8 @@
 
 -define(DEFAULT_ONE_TIME_TOKEN_TIMEOUT, 30000).
 -define(TOKEN_SIZE, 32).
--define(DEF_REC_BUF, 408300 * 5).
+%% Size of the Erlang inet driver's read buffer (userspace).
+-define(DEF_BUFFER, 408300 * 10).
 
 %%%===================================================================
 %%% API functions
@@ -779,8 +780,7 @@ setopts(ssl, Socket, Options) ->
     ssl:setopts(Socket, Options).
 
 listener_opts(tcp) ->
-    RcvBuf = application:get_env(osiris, replica_recbuf, ?DEF_REC_BUF),
-    Buffer = application:get_env(osiris, replica_buffer, RcvBuf * 2),
+    Buffer = application:get_env(osiris, replica_buffer, ?DEF_BUFFER),
     KeepAlive = application:get_env(osiris, replica_keepalive, false),
     ReuseAddr = application:get_env(osiris, replica_reuseaddr, true),
     Linger = application:get_env(osiris, replica_linger, true),
@@ -795,10 +795,13 @@ listener_opts(tcp) ->
      {backlog, 0},
      {packet, raw},
      {active, false},
-     {buffer, Buffer},
-     {recbuf, RcvBuf},
      {keepalive, KeepAlive}
-    ];
+    ]
+    %% `recbuf' is applied before `buffer': on older OTP releases setting
+    %% recbuf raises the driver buffer to match, so `buffer' must come last
+    %% to stay authoritative.
+    ++ osiris_util:optional_socket_opt(recbuf, replica_recbuf)
+    ++ [{buffer, Buffer}];
 listener_opts(ssl) ->
     Opts = listener_opts(tcp),
     SslOptions = application:get_env(osiris, replication_server_ssl_options, []),

src/osiris_replica_reader.erl

@@ -11,7 +11,6 @@
 
 -include("osiris.hrl").
 
--define(DEF_SND_BUF, 146988 * 10).
 %% replica reader, spawned remotely by replica process, connects back to
 %% configured host/port, reads entries from master and uses file:sendfile to
 %% replicate read records
@@ -386,15 +385,14 @@ close(ssl, Socket) ->
     ssl:close(Socket).
 
 connect_options() ->
-    SndBuf = application:get_env(osiris, replica_sndbuf, ?DEF_SND_BUF),
     KeepAlive = application:get_env(osiris, replica_keepalive, false),
     IPAddrFamily = osiris_util:get_replica_listener_inet_address_family(),
     [binary,
      IPAddrFamily,
      {packet, 0},
      {nodelay, true},
-     {sndbuf, SndBuf},
-     {keepalive, KeepAlive}].
+     {keepalive, KeepAlive}]
+    ++ osiris_util:optional_socket_opt(sndbuf, replica_sndbuf).
 
 setopts(tcp, Sock, Opts) ->
     inet:setopts(Sock, Opts);

src/osiris_util.erl

@@ -19,6 +19,7 @@
          get_replication_configuration_from_tls_dist/1,
          get_replication_configuration_from_tls_dist/2,
          get_replica_listener_inet_address_family/0,
+         optional_socket_opt/2,
          partition_parallel/3,
          normalise_name/1,
          get_reader_context/1,
@@ -248,6 +249,15 @@ get_replica_listener_inet_address_family() ->
         _     -> inet
     end.
 
+-spec optional_socket_opt(atom(), atom()) -> [{atom(), pos_integer()}].
+optional_socket_opt(Opt, Key) ->
+    case application:get_env(osiris, Key) of
+        {ok, Value} when is_integer(Value) andalso Value > 0 ->
+            [{Opt, Value}];
+        _ ->
+            []
+    end.
+
 inet_tls_enabled([]) ->
     false;
 inet_tls_enabled([{proto_dist, ["inet_tls"]} | _]) ->