HPCC-24916 Roxie topology update thread reads off end of buffer

Also contains some test code designed to help investigate topology/autoscaling
in the future.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>

roxie/ccd/ccdstate.cpp

@@ -2775,6 +2775,19 @@ private:
             {
                 toXML(topology, reply);
             }
+            else if (stricmp(queryName, "control:toposerver")==0)
+            {
+                if (control->hasProp("@freeze"))
+                {
+                    freezeTopology(control->getPropBool("@freeze"));
+                }
+                else
+                {
+                    reply.append("<Toposerver>");
+                    getTopology()->report(reply);
+                    reply.append("</Toposerver>");
+                }
+            }
             else if (stricmp(queryName, "control:trace")==0)
             {
                 traceLevel = control->getPropInt("@level", 0);

roxie/udplib/udptopo.cpp

@@ -97,6 +97,7 @@ public:
     virtual const ChannelInfo &queryChannelInfo(unsigned channel) const override;
     virtual const std::vector<unsigned> &queryChannels() const override;
     virtual bool implementsChannel(unsigned channel) const override;
+    virtual void report(StringBuffer &ret) const override;
 
 private:
     std::map<unsigned, SocketEndpointArray> agents;  // indexed by channel
@@ -106,6 +107,9 @@ private:
     std::map<unsigned, unsigned> mySubChannels;
     std::vector<unsigned> channels;
     std::vector<unsigned> replicationLevels;
+#ifdef _DEBUG
+    StringAttr rawData;
+#endif
 };
 
 SocketEndpoint myAgentEP;
@@ -115,6 +119,9 @@ CTopologyServer::CTopologyServer()
 }
 
 CTopologyServer::CTopologyServer(const char *topologyInfo)
+#ifdef _DEBUG
+    : rawData(topologyInfo)
+#endif
 {
     std::istringstream ss(topologyInfo);
     std::string line;
@@ -210,6 +217,16 @@ bool CTopologyServer::implementsChannel(unsigned channel) const
     else
         return true;   // Kinda-sorta - perhaps not true if separated servers from agents, but even then child queries may access channel 0
 }
+
+void CTopologyServer::report(StringBuffer &ret) const
+{
+#ifdef _DEBUG
+    ret.append(rawData);
+#else
+    UNIMPLEMENTED;
+#endif
+}
+
 const SocketEndpointArray CTopologyServer::nullArray;
 
 // Class TopologyManager (there is a single instance) handles interaction with topology servers
@@ -225,6 +242,8 @@ public:
 
     bool update();
     unsigned numServers() const { return topoServers.length(); }
+    void freeze(bool frozen);
+
 private:
     Owned<const ITopologyServer> currentTopology;
     SpinLock lock;
@@ -233,12 +252,15 @@ private:
     const unsigned maxReasonableResponse = 32*32*1024;  // At ~ 32 bytes per entry, 1024 channels and 32-way redundancy that's a BIG cluster!
     StringBuffer md5;
     StringBuffer topoBuf;
+    bool frozen = false;    // used for testing
 };
 
 static TopologyManager topologyManager;
 
 bool TopologyManager::update()
 {
+    if (frozen)
+        return false;
     bool updated = false;
     ForEachItemIn(idx, topoServers)
     {
@@ -273,8 +295,9 @@ bool TopologyManager::update()
                         else
                         {
                             MemoryBuffer mb;
-                            char *mem = (char *)mb.reserveTruncate(responseLen);
+                            char *mem = (char *)mb.reserveTruncate(responseLen+1);
                             topo->read(mem, responseLen);
+                            mem[responseLen] = '\0';
                             if (responseLen>=md5.length() && mem[0]=='=')
                             {
                                 if (md5.length()==0 || memcmp(mem, md5.str(), md5.length())!=0)
@@ -311,6 +334,11 @@ bool TopologyManager::update()
     return updated;
 }
 
+void TopologyManager::freeze(bool _frozen)
+{
+    frozen = _frozen;
+}
+
 const ITopologyServer &TopologyManager::getCurrent()
 {
     SpinBlock b(lock);
@@ -350,6 +378,11 @@ extern UDPLIB_API const ITopologyServer *getTopology()
     return &topologyManager.getCurrent();
 }
 
+extern UDPLIB_API void freezeTopology(bool frozen)
+{
+    topologyManager.freeze(frozen);
+}
+
 extern UDPLIB_API unsigned getNumAgents(unsigned channel)
 {
     Owned<const ITopologyServer> topology = getTopology();

roxie/udplib/udptopo.hpp

@@ -103,10 +103,12 @@ interface ITopologyServer : public IInterface
     virtual const ChannelInfo &queryChannelInfo(unsigned channel) const = 0;
     virtual const std::vector<unsigned> &queryChannels() const = 0;
     virtual bool implementsChannel(unsigned channel) const = 0;
+    virtual void report(StringBuffer &ret) const = 0;
 };
 
 extern UDPLIB_API unsigned getNumAgents(unsigned channel);
 extern UDPLIB_API const ITopologyServer *getTopology();
+extern UDPLIB_API void freezeTopology(bool frozen);
 
 struct RoxieEndpointInfo
 {