stats: move message sending logic to RawSender

`RawSender` is inspired by `UDPSender` from `vthiery/cpp-statsd-client`
and separating it out of `StatsdClient` is needed to implement queueing
and batching support in upcoming commits.

This is the start of migrating our Statsd codebase to `cpp-statsd-client`.

src/Makefile.am

@@ -314,6 +314,7 @@ BITCOIN_CORE_H = \
   stacktraces.h \
   streams.h \
   stats/client.h \
+  stats/rawsender.h \
   support/allocators/mt_pooled_secure.h \
   support/allocators/pool.h \
   support/allocators/pooled_secure.h \
@@ -527,6 +528,7 @@ libbitcoin_server_a_SOURCES = \
   shutdown.cpp \
   spork.cpp \
   stats/client.cpp \
+  stats/rawsender.cpp \
   timedata.cpp \
   torcontrol.cpp \
   txdb.cpp \

src/stats/client.cpp

@@ -1,4 +1,5 @@
 // Copyright (c) 2014-2017 Statoshi Developers
+// Copyright (c) 2017-2023 Vincent Thiery
 // Copyright (c) 2020-2024 The Dash Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
@@ -35,8 +36,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include <stats/client.h>
 
-#include <compat.h>
-#include <netbase.h>
+#include <stats/rawsender.h>
 #include <util/system.h>
 
 #include <cmath>
@@ -60,10 +60,8 @@ bool StatsdClient::ShouldSend(float sample_rate)
     return sample_rate > std::uniform_real_distribution<float>(0.f, 1.f)(insecure_rand);
 }
 
-StatsdClient::StatsdClient(const std::string& host, const std::string& nodename, uint16_t port, const std::string& ns,
-                           bool enabled) :
-    m_port{port},
-    m_host{host},
+StatsdClient::StatsdClient(const std::string& host, const std::string& nodename, uint16_t port,
+                           const std::string& ns, bool enabled) :
     m_nodename{nodename},
     m_ns{ns}
 {
@@ -72,31 +70,19 @@ StatsdClient::StatsdClient(const std::string& host, const std::string& nodename,
         return;
     }
 
-    if (auto netaddr = LookupHost(m_host, /*fAllowLookup=*/true); netaddr.has_value()) {
-        if (!netaddr->IsIPv4()) {
-            LogPrintf("ERROR: Host %s on unsupported network, cannot init StatsdClient\n", m_host);
-            return;
-        }
-        if (!CService(*netaddr, port).GetSockAddr(reinterpret_cast<struct sockaddr*>(&m_server.first), &m_server.second)) {
-            LogPrintf("ERROR: Cannot get socket address for %s, cannot init StatsdClient\n", m_host);
-            return;
-        }
-    } else {
-        LogPrintf("Unable to lookup host %s, cannot init StatsdClient\n", m_host);
+    std::optional<std::string> error_opt;
+    m_sender = std::make_unique<RawSender>(host, port, error_opt);
+    if (error_opt.has_value()) {
+        LogPrintf("ERROR: %s, cannot initialize StatsdClient.\n", error_opt.value());
+        m_sender.reset();
         return;
     }
 
-    SOCKET hSocket = ::socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
-    if (hSocket == INVALID_SOCKET) {
-        LogPrintf("ERROR: Cannot create socket (socket() returned error %s), cannot init StatsdClient\n",
-                  NetworkErrorString(WSAGetLastError()));
-        return;
-    }
-    m_sock = std::make_unique<Sock>(hSocket);
-
-    LogPrintf("StatsdClient initialized to transmit stats to %s:%d\n", m_host, m_port);
+    LogPrintf("StatsdClient initialized to transmit stats to %s:%d\n", host, port);
 }
 
+StatsdClient::~StatsdClient() {}
+
 /* will change the original string */
 void StatsdClient::cleanup(std::string& key)
 {
@@ -133,7 +119,7 @@ bool StatsdClient::timing(const std::string& key, int64_t ms, float sample_rate)
 
 bool StatsdClient::send(std::string key, int64_t value, const std::string& type, float sample_rate)
 {
-    if (!m_sock) {
+    if (!m_sender) {
         return false;
     }
 
@@ -147,17 +133,22 @@ bool StatsdClient::send(std::string key, int64_t value, const std::string& type,
 
     cleanup(key);
 
-    std::string buf{strprintf("%s%s:%d|%s", m_ns, key, value, type)};
+    RawMessage msg{strprintf("%s%s:%d|%s", m_ns, key, value, type)};
     if (sample_rate < 1.f) {
-        buf += strprintf("|@%.2f", sample_rate);
+        msg += strprintf("|@%.2f", sample_rate);
     }
 
-    return send(buf);
+    if (auto error_opt = m_sender->Send(msg); error_opt.has_value()) {
+        LogPrintf("ERROR: %s.\n", error_opt.value());
+        return false;
+    }
+
+    return true;
 }
 
 bool StatsdClient::sendDouble(std::string key, double value, const std::string& type, float sample_rate)
 {
-    if (!m_sock) {
+    if (!m_sender) {
         return false;
     }
 
@@ -171,22 +162,13 @@ bool StatsdClient::sendDouble(std::string key, double value, const std::string&
 
     cleanup(key);
 
-    std::string buf{strprintf("%s%s:%f|%s", m_ns, key, value, type)};
+    RawMessage msg{strprintf("%s%s:%f|%s", m_ns, key, value, type)};
     if (sample_rate < 1.f) {
-        buf += strprintf("|@%.2f", sample_rate);
+        msg += strprintf("|@%.2f", sample_rate);
     }
 
-    return send(buf);
-}
-
-bool StatsdClient::send(const std::string& message)
-{
-    assert(m_sock);
-
-    if (::sendto(m_sock->Get(), message.data(), message.size(), /*flags=*/0,
-                 reinterpret_cast<struct sockaddr*>(&m_server.first), m_server.second) == SOCKET_ERROR) {
-        LogPrintf("ERROR: Unable to send message (sendto() returned error %s), host=%s:%d\n",
-                  NetworkErrorString(WSAGetLastError()), m_host, m_port);
+    if (auto error_opt = m_sender->Send(msg); error_opt.has_value()) {
+        LogPrintf("ERROR: %s.\n", error_opt.value());
         return false;
     }
 

src/stats/client.h

@@ -1,4 +1,5 @@
 // Copyright (c) 2014-2017 Statoshi Developers
+// Copyright (c) 2017-2023 Vincent Thiery
 // Copyright (c) 2020-2023 The Dash Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
@@ -7,12 +8,13 @@
 #define BITCOIN_STATS_CLIENT_H
 
 #include <random.h>
-#include <threadsafety.h>
-#include <util/sock.h>
+#include <sync.h>
 
 #include <memory>
 #include <string>
 
+class RawSender;
+
 static constexpr bool DEFAULT_STATSD_ENABLE{false};
 static constexpr uint16_t DEFAULT_STATSD_PORT{8125};
 static const std::string DEFAULT_STATSD_HOST{"127.0.0.1"};
@@ -29,6 +31,7 @@ class StatsdClient
 public:
     explicit StatsdClient(const std::string& host, const std::string& nodename, uint16_t port,
                             const std::string& ns, bool enabled);
+    ~StatsdClient();
 
 public:
     bool inc(const std::string& key, float sample_rate = 1.f);
@@ -45,12 +48,6 @@ public:
     bool sendDouble(std::string key, double value, const std::string& type, float sample_rate);
 
 private:
-    /**
-        * (Low Level Api) manually send a message
-        * which might be composed of several lines.
-        */
-    bool send(const std::string& message);
-
     void cleanup(std::string& key);
     bool ShouldSend(float sample_rate);
 
@@ -58,11 +55,8 @@ private:
     mutable Mutex cs;
     mutable FastRandomContext insecure_rand GUARDED_BY(cs);
 
-    std::unique_ptr<Sock> m_sock{nullptr};
-    std::pair<struct sockaddr_storage, socklen_t> m_server{{}, sizeof(struct sockaddr_storage)};
+    std::unique_ptr<RawSender> m_sender{nullptr};
 
-    const uint16_t m_port;
-    const std::string m_host;
     const std::string m_nodename;
     const std::string m_ns;
 };

src/stats/rawsender.cpp

@@ -0,0 +1,74 @@
+// Copyright (c) 2017-2023 Vincent Thiery
+// Copyright (c) 2024 The Dash Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <stats/rawsender.h>
+
+#include <netaddress.h>
+#include <netbase.h>
+#include <util/sock.h>
+
+RawSender::RawSender(const std::string& host, uint16_t port, std::optional<std::string>& error) :
+    m_host{host},
+    m_port{port}
+{
+    if (host.empty()) {
+        error = "No host specified";
+        return;
+    }
+
+    if (auto netaddr = LookupHost(m_host, /*fAllowLookup=*/true); netaddr.has_value()) {
+        if (!netaddr->IsIPv4()) {
+            error = strprintf("Host %s on unsupported network", m_host);
+            return;
+        }
+        if (!CService(*netaddr, port).GetSockAddr(reinterpret_cast<struct sockaddr*>(&m_server.first), &m_server.second)) {
+            error = strprintf("Cannot get socket address for %s", m_host);
+            return;
+        }
+    } else {
+        error = strprintf("Unable to lookup host %s", m_host);
+        return;
+    }
+
+    SOCKET hSocket = ::socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+    if (hSocket == INVALID_SOCKET) {
+        error = strprintf("Cannot create socket (socket() returned error %s)", NetworkErrorString(WSAGetLastError()));
+        return;
+    }
+    m_sock = std::make_unique<Sock>(hSocket);
+
+    LogPrintf("Started RawSender sending messages to %s:%d\n", m_host, m_port);
+}
+
+RawSender::~RawSender()
+{
+    LogPrintf("Stopping RawSender instance sending messages to %s:%d. %d successes, %d failures.\n",
+              m_host, m_port, m_successes, m_failures);
+}
+
+std::optional<std::string> RawSender::Send(const RawMessage& msg)
+{
+    if (!m_sock) {
+        m_failures++;
+        return "Socket not initialized, cannot send message";
+    }
+
+    if (::sendto(m_sock->Get(), reinterpret_cast<const char*>(msg.data()),
+#ifdef WIN32
+                 static_cast<int>(msg.size()),
+#else
+                 msg.size(),
+#endif // WIN32
+                 /*flags=*/0, reinterpret_cast<struct sockaddr*>(&m_server.first), m_server.second) == SOCKET_ERROR) {
+        m_failures++;
+        return strprintf("Unable to send message to %s (sendto() returned error %s)", this->ToStringHostPort(),
+                         NetworkErrorString(WSAGetLastError()));
+    }
+
+    m_successes++;
+    return std::nullopt;
+}
+
+std::string RawSender::ToStringHostPort() const { return strprintf("%s:%d", m_host, m_port); }

src/stats/rawsender.h

@@ -0,0 +1,84 @@
+// Copyright (c) 2017-2023 Vincent Thiery
+// Copyright (c) 2024 The Dash Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_STATS_RAWSENDER_H
+#define BITCOIN_STATS_RAWSENDER_H
+
+#include <compat.h>
+#include <sync.h>
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <vector>
+
+class Sock;
+
+struct RawMessage : public std::vector<uint8_t>
+{
+    using parent_type = std::vector<value_type>;
+    using parent_type::parent_type;
+
+    explicit RawMessage(const std::string& data) : parent_type{data.begin(), data.end()} {}
+
+    parent_type& operator+=(value_type rhs) { return append(rhs); }
+    parent_type& operator+=(std::string::value_type rhs) { return append(rhs); }
+    parent_type& operator+=(const parent_type& rhs) { return append(rhs); }
+    parent_type& operator+=(const std::string& rhs) { return append(rhs); }
+
+    parent_type& append(value_type rhs)
+    {
+        push_back(rhs);
+        return *this;
+    }
+    parent_type& append(std::string::value_type rhs)
+    {
+        push_back(static_cast<value_type>(rhs));
+        return *this;
+    }
+    parent_type& append(const parent_type& rhs)
+    {
+        insert(end(), rhs.begin(), rhs.end());
+        return *this;
+    }
+    parent_type& append(const std::string& rhs)
+    {
+        insert(end(), rhs.begin(), rhs.end());
+        return *this;
+    }
+};
+
+class RawSender
+{
+public:
+    RawSender(const std::string& host, uint16_t port, std::optional<std::string>& error);
+    ~RawSender();
+
+    RawSender(const RawSender&) = delete;
+    RawSender& operator=(const RawSender&) = delete;
+    RawSender(RawSender&&) = delete;
+
+    std::optional<std::string> Send(const RawMessage& msg);
+
+    std::string ToStringHostPort() const;
+
+private:
+    /* Socket used to communicate with host */
+    std::unique_ptr<Sock> m_sock{nullptr};
+    /* Socket address containing host information */
+    std::pair<struct sockaddr_storage, socklen_t> m_server{{}, sizeof(struct sockaddr_storage)};
+
+    /* Hostname of server receiving messages */
+    const std::string m_host;
+    /* Port of server receiving messages */
+    const uint16_t m_port;
+
+    /* Number of messages sent */
+    uint64_t m_successes{0};
+    /* Number of messages not sent */
+    uint64_t m_failures{0};
+};
+
+#endif // BITCOIN_STATS_RAWSENDER_H