QPID-4428: HA add UUID tag to avoid using an out of date queue/exchange.

Imagine a cluster with primary A and backups B and C. A queue Q is created on A
and replicated to B, C. Now A dies and B takes over as primary. Before C can
connect to B, a client destroys Q and creates a new queue with the same name.
When B connects it sees Q and incorrectly assumes it is the same Q that it has
already replicated. Now C has an inconsistent replica of Q.

The fix is to tag queues/exchanges with a UUID so a backup can tell if a queue
is not the same as the one it has already replicated, even if the names are the
same.  This all also applies to exchanges.

- Minor imrovements to printing UUIDs in a FieldTable.
- Fix comparison of void Variants, added operator !=

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk/qpid@1409241 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 12 insertions, 2 deletions

diff --git a/cpp/include/qpid/framing/FieldValue.h b/cpp/include/qpid/framing/FieldValue.h
index 458de62fdf..e964da495a 100644
--- a/cpp/include/qpid/framing/FieldValue.h
+++ b/cpp/include/qpid/framing/FieldValue.h
@@ -175,11 +175,19 @@ class FixedWidthValue : public FieldValue::Data {
         return v;
     }
     uint8_t* rawOctets() { return octets; }
-    uint8_t* rawOctets() const { return octets; }
+    const uint8_t* rawOctets() const { return octets; }
 
     void print(std::ostream& o) const { o << "F" << width << ":"; };
 };
 
+class UuidData : public FixedWidthValue<16> {
+  public:
+    UuidData();
+    UuidData(const unsigned char* bytes);
+    bool convertsToString() const;
+    std::string getString() const;
+};
+
 template <class T, int W>
 inline T FieldValue::getIntegerValue() const
 {
@@ -356,7 +364,7 @@ class Var16Value : public FieldValue {
 class Var32Value : public FieldValue {
   public:
     QPID_COMMON_EXTERN Var32Value(const std::string& v, uint8_t code);
-};
+ };
 
 class Struct32Value : public FieldValue {
   public:
@@ -453,6 +461,7 @@ class ListValue : public FieldValue {
 
 class UuidValue : public FieldValue {
   public:
+    QPID_COMMON_EXTERN UuidValue();
     QPID_COMMON_EXTERN UuidValue(const unsigned char*);
 };
 
diff --git a/cpp/include/qpid/types/Variant.h b/cpp/include/qpid/types/Variant.h
index 3493559777..e6bfd6bc0a 100644
--- a/cpp/include/qpid/types/Variant.h
+++ b/cpp/include/qpid/types/Variant.h
@@ -177,6 +177,7 @@ QPID_TYPES_EXTERN std::ostream& operator<<(std::ostream& out, const Variant& val
 QPID_TYPES_EXTERN std::ostream& operator<<(std::ostream& out, const Variant::Map& map);
 QPID_TYPES_EXTERN std::ostream& operator<<(std::ostream& out, const Variant::List& list);
 QPID_TYPES_EXTERN bool operator==(const Variant& a, const Variant& b);
+QPID_TYPES_EXTERN bool operator!=(const Variant& a, const Variant& b);
 #endif
 }} // namespace qpid::types