feat: configurable client reqq (#7030)

* chore: housekeeping

* refactor: raise client reqq value

* feat: allow configuring client reqq value

* feat: expose reqq config in RPC

* test: add new key

* code review: distinguish client vs peer

* docs: fix new config name

---------

Co-authored-by: Charles Kerr <charles@charleskerr.com>

docs/Editing-Configuration-Files.md

@@ -101,6 +101,7 @@ Here is a sample of the three basic types: respectively Boolean, Number and Stri
  * **peer-limit-global:** Number (default = 200)
  * **peer-limit-per-torrent:** Number (default = 50)
  * **peer-socket-tos:** String (default = "le") Set the [DiffServ](https://en.wikipedia.org/wiki/Differentiated_services) parameter for outgoing packets. Allowed values are lowercase DSCP names. See the `tr_tos_t` class from `libtransmission/net.h` for the exact list of possible values.
+ * **reqq:** Number (default = 2000) The number of outstanding block requests a peer is allowed to queue in the client. The higher this number, the higher the max possible upload speed towards each peer.
 
 #### Peer Port
  * **peer-port:** Number (default = 51413)

docs/rpc-spec.md

@@ -554,6 +554,7 @@ Response arguments: `path`, `name`, and `id`, holding the torrent ID integer
 | `queue-stalled-enabled` | boolean | whether or not to consider idle torrents as stalled
 | `queue-stalled-minutes` | number | torrents that are idle for N minuets aren't counted toward seed-queue-size or download-queue-size
 | `rename-partial-files` | boolean | true means append `.part` to incomplete files
+| `reqq` | number | the number of outstanding block requests a peer is allowed to queue in the client
 | `rpc-version-minimum` | number | the minimum RPC API version supported
 | `rpc-version-semver` | string | the current RPC API version in a [semver](https://semver.org)-compatible string
 | `rpc-version` | number | the current RPC API version

libtransmission/peer-mgr.cc

@@ -905,7 +905,7 @@ EXIT:
     // ---
 
     // number of bad pieces a peer is allowed to send before we ban them
-    static auto constexpr MaxBadPiecesPerPeer = 5;
+    static auto constexpr MaxBadPiecesPerPeer = 5U;
 
     // how long we'll let requests we've made linger before we cancel them
     static auto constexpr RequestTtlSecs = 90;

libtransmission/peer-msgs.cc

@@ -178,7 +178,7 @@ auto constexpr KeepaliveIntervalSecs = time_t{ 100 };
 
 auto constexpr MetadataReqQ = size_t{ 64U };
 
-auto constexpr ReqQ = 512;
+auto constexpr PeerReqQDefault = 500U;
 
 // when we're making requests from another peer,
 // batch them together to send enough requests to
@@ -571,6 +571,11 @@ private:
 
     void update_block_requests();
 
+    [[nodiscard]] constexpr auto client_reqq() const noexcept
+    {
+        return session->reqq();
+    }
+
     // ---
 
     [[nodiscard]] std::optional<int64_t> pop_next_metadata_request()
@@ -702,7 +707,7 @@ private:
 
     // if the peer supports the Extension Protocol in BEP 10 and
     // supplied a reqq argument, it's stored here.
-    std::optional<size_t> reqq_;
+    std::optional<size_t> peer_reqq_;
 
     std::unique_ptr<libtransmission::Timer> pex_timer_;
 
@@ -1131,9 +1136,8 @@ void tr_peerMsgsImpl::send_ltep_handshake()
 
     // https://www.bittorrent.org/beps/bep_0010.html
     // An integer, the number of outstanding request messages this
-    // client supports without dropping any. The default in in
-    // libtorrent is 250.
-    tr_variantDictAddInt(&val, TR_KEY_reqq, ReqQ);
+    // client supports without dropping any.
+    tr_variantDictAddInt(&val, TR_KEY_reqq, client_reqq());
 
     // https://www.bittorrent.org/beps/bep_0010.html
     // A string containing the compact representation of the ip address this peer sees
@@ -1289,7 +1293,7 @@ void tr_peerMsgsImpl::parse_ltep_handshake(MessageReader& payload)
     /* get peer's maximum request queue size */
     if (auto reqq_in = int64_t{}; tr_variantDictFindInt(&*var, TR_KEY_reqq, &reqq_in))
     {
-        reqq_ = reqq_in;
+        peer_reqq_ = reqq_in;
     }
 }
 
@@ -1994,7 +1998,7 @@ bool tr_peerMsgsImpl::is_valid_request(peer_request const& req) const
         return false;
     }
 
-    if (std::size(peer_requested_) >= ReqQ)
+    if (std::size(peer_requested_) >= client_reqq())
     {
         logtrace(this, "rejecting request ... reqq is full");
         return false;
@@ -2045,7 +2049,7 @@ size_t tr_peerMsgsImpl::max_available_reqs() const
     static auto constexpr Floor = size_t{ 32 };
     static size_t constexpr Seconds = RequestBufSecs;
     size_t const estimated_blocks_in_period = (rate.base_quantity() * Seconds) / tr_block_info::BlockSize;
-    auto const ceil = reqq_.value_or(250);
+    auto const ceil = peer_reqq_.value_or(PeerReqQDefault);
 
     return std::clamp(estimated_blocks_in_period, Floor, ceil);
 }

libtransmission/rpcimpl.cc

@@ -1695,6 +1695,11 @@ char const* sessionSet(tr_session* session, tr_variant::Map const& args_in, tr_v
         tr_sessionSetPeerLimitPerTorrent(session, *val);
     }
 
+    if (auto const val = args_in.value_if<int64_t>(TR_KEY_reqq); val && val > 0)
+    {
+        session->set_reqq(*val);
+    }
+
     if (auto const val = args_in.value_if<bool>(TR_KEY_pex_enabled))
     {
         tr_sessionSetPexEnabled(session, *val);
@@ -1955,6 +1960,7 @@ char const* sessionStats(tr_session* session, tr_variant::Map const& /*args_in*/
     case TR_KEY_queue_stalled_enabled: return session.queueStalledEnabled();
     case TR_KEY_queue_stalled_minutes: return session.queueStalledMinutes();
     case TR_KEY_rename_partial_files: return session.isIncompleteFileNamingEnabled();
+    case TR_KEY_reqq: return session.reqq();
     case TR_KEY_rpc_version: return RpcVersion;
     case TR_KEY_rpc_version_minimum: return RpcVersionMin;
     case TR_KEY_rpc_version_semver: return RpcVersionSemver;

libtransmission/session.h

@@ -398,6 +398,7 @@ public:
         size_t peer_limit_global = TR_DEFAULT_PEER_LIMIT_GLOBAL;
         size_t peer_limit_per_torrent = TR_DEFAULT_PEER_LIMIT_TORRENT;
         size_t queue_stalled_minutes = 30U;
+        size_t reqq = 2000U;
         size_t seed_queue_size = 10U;
         size_t speed_limit_down = 100U;
         size_t speed_limit_up = 100U;
@@ -465,6 +466,7 @@ public:
                 { TR_KEY_ratio_limit, &ratio_limit },
                 { TR_KEY_ratio_limit_enabled, &ratio_limit_enabled },
                 { TR_KEY_rename_partial_files, &is_incomplete_file_naming_enabled },
+                { TR_KEY_reqq, &reqq },
                 { TR_KEY_scrape_paused_torrents_enabled, &should_scrape_paused_torrents },
                 { TR_KEY_script_torrent_added_enabled, &script_torrent_added_enabled },
                 { TR_KEY_script_torrent_added_filename, &script_torrent_added_filename },
@@ -693,6 +695,16 @@ public:
         return settings().peer_limit_per_torrent;
     }
 
+    [[nodiscard]] constexpr auto reqq() const noexcept
+    {
+        return settings().reqq;
+    }
+
+    constexpr void set_reqq(size_t reqq) noexcept
+    {
+        settings_.reqq = reqq;
+    }
+
     // bandwidth
 
     [[nodiscard]] tr_bandwidth& getBandwidthGroup(std::string_view name);

tests/libtransmission/rpc-test.cc

@@ -168,7 +168,7 @@ TEST_F(RpcTest, sessionGet)
     EXPECT_TRUE(tr_variantDictFindDict(&response, TR_KEY_arguments, &args));
 
     // what we expected
-    auto const expected_keys = std::array<tr_quark, 59>{
+    static auto constexpr ExpectedKeys = std::array{
         TR_KEY_alt_speed_down,
         TR_KEY_alt_speed_enabled,
         TR_KEY_alt_speed_time_begin,
@@ -204,6 +204,7 @@ TEST_F(RpcTest, sessionGet)
         TR_KEY_queue_stalled_enabled,
         TR_KEY_queue_stalled_minutes,
         TR_KEY_rename_partial_files,
+        TR_KEY_reqq,
         TR_KEY_rpc_version,
         TR_KEY_rpc_version_minimum,
         TR_KEY_rpc_version_semver,
@@ -242,8 +243,8 @@ TEST_F(RpcTest, sessionGet)
 
     auto missing_keys = std::vector<tr_quark>{};
     std::set_difference(
-        std::begin(expected_keys),
-        std::end(expected_keys),
+        std::begin(ExpectedKeys),
+        std::end(ExpectedKeys),
         std::begin(actual_keys),
         std::end(actual_keys),
         std::inserter(missing_keys, std::begin(missing_keys)));
@@ -253,8 +254,8 @@ TEST_F(RpcTest, sessionGet)
     std::set_difference(
         std::begin(actual_keys),
         std::end(actual_keys),
-        std::begin(expected_keys),
-        std::end(expected_keys),
+        std::begin(ExpectedKeys),
+        std::end(ExpectedKeys),
         std::inserter(unexpected_keys, std::begin(unexpected_keys)));
     EXPECT_EQ(decltype(unexpected_keys){}, unexpected_keys);