MB-67175: Add termination reason to log description

Extend the description with the termination reason if it is
set:

    2025-10-16T11:13:31.741832+02:00 INFO Removing connection
    {"conn_id":925,
     "bucket":"travel-sample",
     "dcp":"producer",
     "dcp_name":"eq_dcpq:DCPT:INIT_309d2c13b63794168603c93e5ee53d84:travel-sample:inventory:airline:11100504861856972217:##4:3",
     "description":{
         "peer":{
             "ip":"127.0.0.1",
             "port":44664},
         "socket":{
             "ip":"127.0.0.1",
             "port":11210},
         "termination_reason":"Client closed connection: EOF",
         "user":{
             "name":"@Projector",
             "system":true}}}

Previously the description was set when the connection was created and
only updated as part of authentication (and in those contexts it
wouldn't be used from other threads). DCP connections will log the
description from other threads than the connections front end thread
so with this change we need to protect the data with a lock.

Change-Id: I2fd4d730bbf55d42696d994fa3ba89d1422299c4
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/235358
Tested-by: Trond Norbye <[email protected]>
Reviewed-by: Jim Walker <[email protected]>

Author: trondn

daemon/connection.cc

@@ -436,22 +436,26 @@ cb::engine_errc Connection::remapErrorCode(cb::engine_errc code) {
 }
 
 void Connection::updateDescription() {
-    description = {
+    nlohmann::json desc = {
             {"peer", peername},
             {"socket", sockname},
     };
     if (isAuthenticated()) {
-        nlohmann::json user{{"name", getUser().getSanitizedName()}};
+        nlohmann::json me{{"name", getUser().getSanitizedName()}};
         if (isInternal()) {
-            user["system"] = true;
+            me["system"] = true;
         }
         if (getUser().domain == cb::sasl::Domain::External) {
-            user["ldap"] = true;
+            me["ldap"] = true;
         }
-        description["user"] = std::move(user);
+        desc["user"] = std::move(me);
     } else {
-        description["user"] = nullptr;
+        desc["user"] = nullptr;
     }
+    if (!terminationReason.empty()) {
+        desc["termination_reason"] = terminationReason;
+    }
+    description = desc;
 }
 
 void Connection::setBucketIndex(int index, Cookie* cookie) {
@@ -1340,6 +1344,9 @@ void Connection::setTerminationReason(std::string reason) {
         terminationReason.append(";");
         terminationReason.append(reason);
     }
+    description.withLock([this](auto& json) {
+        json["termination_reason"] = terminationReason;
+    });
 }
 
 void Connection::setAgentName(std::string_view name) {

daemon/connection.h

@@ -17,6 +17,7 @@
 
 #include <cbsasl/server.h>
 #include <daemon/protocol/mcbp/command_context.h>
+#include <folly/Synchronized.h>
 #include <mcbp/protocol/unsigned_leb128.h>
 #include <memcached/connection_iface.h>
 #include <memcached/dcp.h>
@@ -96,8 +97,10 @@ class Connection : public ConnectionIface, public DcpMessageProducersIface {
         return uint32_t(socketDescriptor);
     }
 
-    const nlohmann::json& getDescription() const override {
-        return description;
+    nlohmann::json getDescription() const override {
+        nlohmann::json desc;
+        description.copyInto(desc);
+        return desc;
     }
 
     /**
@@ -1098,7 +1101,7 @@ class Connection : public ConnectionIface, public DcpMessageProducersIface {
     } authContextLifetime;
 
     /// The description of the connection
-    nlohmann::json description;
+    folly::Synchronized<nlohmann::json, std::mutex> description;
 
     /// The reason why the session was terminated
     std::string terminationReason;

include/memcached/connection_iface.h

@@ -67,7 +67,7 @@ class ConnectionIface {
      * Note that the description may be modified in the context of the front end
      * thread as part of authentication so the description should not be cached.
      */
-    virtual const nlohmann::json& getDescription() const = 0;
+    virtual nlohmann::json getDescription() const = 0;
 
     /**
      * Get the username this connection is authenticated as (should only be

include/test/dummy_connection.h

@@ -40,8 +40,8 @@ class DummyConnection : public ConnectionIface {
     }
     void setPriority(ConnectionPriority value) override {
     }
-    const nlohmann::json& getDescription() const override {
-        return description;
+    nlohmann::json getDescription() const override {
+        return {{"dummy", true}};
     }
     const cb::rbac::UserIdent& getUser() const override {
         return user;
@@ -51,6 +51,5 @@ class DummyConnection : public ConnectionIface {
 
 protected:
     cb::rbac::UserIdent user{"dummy", cb::rbac::Domain::Local};
-    nlohmann::json description{{"dummy", true}};
 };
 } // namespace cb::test

programs/engine_testapp/mock_cookie.cc

@@ -25,9 +25,8 @@ void MockConnection::scheduleDcpStep() {
 void MockConnection::setUserScheduleDcpStep(std::function<void()> func) {
     userScheduleDcpStep = std::move(func);
 }
-const nlohmann::json& MockConnection::getDescription() const {
-    static nlohmann::json description{{"peer", "you"}, {"socket", "me"}};
-    return description;
+nlohmann::json MockConnection::getDescription() const {
+    return {{"peer", "you"}, {"socket", "me"}};
 }
 const cb::rbac::UserIdent& MockConnection::getUser() const {
     return user;

programs/engine_testapp/mock_cookie.h

@@ -43,7 +43,7 @@ class MockConnection : public ConnectionIface {
         priority = value;
     }
 
-    const nlohmann::json& getDescription() const override;
+    nlohmann::json getDescription() const override;
     const cb::rbac::UserIdent& getUser() const override;
 
     void setUser(const std::string& newUser) {