Merge #14060: ZMQ: add options to configure outbound message high water mark, aka SNDHWM

a4edb168b635b6f5c36324e44961cd42cf9bbbaa ZMQ: add options to configure outbound message high water mark, aka SNDHWM (mruddy)

Pull request description:

  ZMQ: add options to configure outbound message high water mark, aka SNDHWM

  This is my attempt at https://github.com/bitcoin/bitcoin/pull/13315

Tree-SHA512: a4cc3bcf179776899261a97c8c4f31f35d1d8950fd71a09a79c5c064879b38e600b26824c89c4091d941502ed5b0255390882f7d44baf9e6dc49d685a86e8edb

6 files changed, 32 insertions, 9 deletions

diff --git a/src/zmq/zmqabstractnotifier.cpp b/src/zmq/zmqabstractnotifier.cpp
index 82e5ee5cc9..6a9661e3e8 100644
--- a/src/zmq/zmqabstractnotifier.cpp
+++ b/src/zmq/zmqabstractnotifier.cpp
@@ -5,6 +5,7 @@
 #include <zmq/zmqabstractnotifier.h>
 #include <util/system.h>
 
+const int CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM;
 
 CZMQAbstractNotifier::~CZMQAbstractNotifier()
 {
diff --git a/src/zmq/zmqabstractnotifier.h b/src/zmq/zmqabstractnotifier.h
index 5081c6cd02..887dde7b27 100644
--- a/src/zmq/zmqabstractnotifier.h
+++ b/src/zmq/zmqabstractnotifier.h
@@ -15,7 +15,9 @@ typedef CZMQAbstractNotifier* (*CZMQNotifierFactory)();
 class CZMQAbstractNotifier
 {
 public:
-    CZMQAbstractNotifier() : psocket(nullptr) { }
+    static const int DEFAULT_ZMQ_SNDHWM {1000};
+
+    CZMQAbstractNotifier() : psocket(nullptr), outbound_message_high_water_mark(DEFAULT_ZMQ_SNDHWM) { }
     virtual ~CZMQAbstractNotifier();
 
     template <typename T>
@@ -28,6 +30,12 @@ public:
     void SetType(const std::string &t) { type = t; }
     std::string GetAddress() const { return address; }
     void SetAddress(const std::string &a) { address = a; }
+    int GetOutboundMessageHighWaterMark() const { return outbound_message_high_water_mark; }
+    void SetOutboundMessageHighWaterMark(const int sndhwm) {
+        if (sndhwm >= 0) {
+            outbound_message_high_water_mark = sndhwm;
+        }
+    }
 
     virtual bool Initialize(void *pcontext) = 0;
     virtual void Shutdown() = 0;
@@ -39,6 +47,7 @@ protected:
     void *psocket;
     std::string type;
     std::string address;
+    int outbound_message_high_water_mark; // aka SNDHWM
 };
 
 #endif // BITCOIN_ZMQ_ZMQABSTRACTNOTIFIER_H
diff --git a/src/zmq/zmqnotificationinterface.cpp b/src/zmq/zmqnotificationinterface.cpp
index df4e51ca20..6826cf62d6 100644
--- a/src/zmq/zmqnotificationinterface.cpp
+++ b/src/zmq/zmqnotificationinterface.cpp
@@ -59,6 +59,7 @@ CZMQNotificationInterface* CZMQNotificationInterface::Create()
             CZMQAbstractNotifier *notifier = factory();
             notifier->SetType(entry.first);
             notifier->SetAddress(address);
+            notifier->SetOutboundMessageHighWaterMark(static_cast<int>(gArgs.GetArg(arg + "hwm", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM)));
             notifiers.push_back(notifier);
         }
     }
@@ -102,11 +103,11 @@ bool CZMQNotificationInterface::Initialize()
         CZMQAbstractNotifier *notifier = *i;
         if (notifier->Initialize(pcontext))
         {
-            LogPrint(BCLog::ZMQ, "  Notifier %s ready (address = %s)\n", notifier->GetType(), notifier->GetAddress());
+            LogPrint(BCLog::ZMQ, "zmq: Notifier %s ready (address = %s)\n", notifier->GetType(), notifier->GetAddress());
         }
         else
         {
-            LogPrint(BCLog::ZMQ, "  Notifier %s failed (address = %s)\n", notifier->GetType(), notifier->GetAddress());
+            LogPrint(BCLog::ZMQ, "zmq: Notifier %s failed (address = %s)\n", notifier->GetType(), notifier->GetAddress());
             break;
         }
     }
@@ -128,7 +129,7 @@ void CZMQNotificationInterface::Shutdown()
         for (std::list<CZMQAbstractNotifier*>::iterator i=notifiers.begin(); i!=notifiers.end(); ++i)
         {
             CZMQAbstractNotifier *notifier = *i;
-            LogPrint(BCLog::ZMQ, "   Shutdown notifier %s at %s\n", notifier->GetType(), notifier->GetAddress());
+            LogPrint(BCLog::ZMQ, "zmq: Shutdown notifier %s at %s\n", notifier->GetType(), notifier->GetAddress());
             notifier->Shutdown();
         }
         zmq_ctx_term(pcontext);
diff --git a/src/zmq/zmqpublishnotifier.cpp b/src/zmq/zmqpublishnotifier.cpp
index 718597e57c..15d4ac1b89 100644
--- a/src/zmq/zmqpublishnotifier.cpp
+++ b/src/zmq/zmqpublishnotifier.cpp
@@ -76,8 +76,18 @@ bool CZMQAbstractPublishNotifier::Initialize(void *pcontext)
             return false;
         }
 
-        int rc = zmq_bind(psocket, address.c_str());
-        if (rc!=0)
+        LogPrint(BCLog::ZMQ, "zmq: Outbound message high water mark for %s at %s is %d\n", type, address, outbound_message_high_water_mark);
+
+        int rc = zmq_setsockopt(psocket, ZMQ_SNDHWM, &outbound_message_high_water_mark, sizeof(outbound_message_high_water_mark));
+        if (rc != 0)
+        {
+            zmqError("Failed to set outbound message high water mark");
+            zmq_close(psocket);
+            return false;
+        }
+
+        rc = zmq_bind(psocket, address.c_str());
+        if (rc != 0)
         {
             zmqError("Failed to bind address");
             zmq_close(psocket);
@@ -120,7 +130,7 @@ void CZMQAbstractPublishNotifier::Shutdown()
 
     if (count == 1)
     {
-        LogPrint(BCLog::ZMQ, "Close socket at address %s\n", address);
+        LogPrint(BCLog::ZMQ, "zmq: Close socket at address %s\n", address);
         int linger = 0;
         zmq_setsockopt(psocket, ZMQ_LINGER, &linger, sizeof(linger));
         zmq_close(psocket);
diff --git a/src/zmq/zmqpublishnotifier.h b/src/zmq/zmqpublishnotifier.h
index 0f5b43d726..278fdb94d2 100644
--- a/src/zmq/zmqpublishnotifier.h
+++ b/src/zmq/zmqpublishnotifier.h
@@ -12,7 +12,7 @@ class CBlockIndex;
 class CZMQAbstractPublishNotifier : public CZMQAbstractNotifier
 {
 private:
-    uint32_t nSequence; //!< upcounting per message sequence number
+    uint32_t nSequence {0U}; //!< upcounting per message sequence number
 
 public:
 
diff --git a/src/zmq/zmqrpc.cpp b/src/zmq/zmqrpc.cpp
index 4f88bf4eb9..0e0b745375 100644
--- a/src/zmq/zmqrpc.cpp
+++ b/src/zmq/zmqrpc.cpp
@@ -22,7 +22,8 @@ UniValue getzmqnotifications(const JSONRPCRequest& request)
             "[\n"
             "  {                        (json object)\n"
             "    \"type\": \"pubhashtx\",   (string) Type of notification\n"
-            "    \"address\": \"...\"       (string) Address of the publisher\n"
+            "    \"address\": \"...\",      (string) Address of the publisher\n"
+            "    \"hwm\": n                 (numeric) Outbound message high water mark\n"
             "  },\n"
             "  ...\n"
             "]\n"
@@ -38,6 +39,7 @@ UniValue getzmqnotifications(const JSONRPCRequest& request)
             UniValue obj(UniValue::VOBJ);
             obj.pushKV("type", n->GetType());
             obj.pushKV("address", n->GetAddress());
+            obj.pushKV("hwm", n->GetOutboundMessageHighWaterMark());
             result.push_back(obj);
         }
     }