[#2438] add MySqlLeaseMgr::isJsonSupported()

src/lib/dhcpsrv/lease_mgr.h

@@ -724,6 +724,12 @@ public:
     /// string if no limits are exceeded
     virtual std::string checkLimits6(isc::data::ConstElementPtr const& user_context) const = 0;
 
+    /// @brief Checks if JSON support is enabled in the database.
+    /// Abstract method.
+    ///
+    /// @return true if there is JSON support, false otherwise
+    virtual bool isJsonSupported() const = 0;
+
     /// @brief Return backend type
     ///
     /// Returns the type of the backend (e.g. "mysql", "memfile" etc.)

src/lib/dhcpsrv/memfile_lease_mgr.cc

@@ -2069,6 +2069,10 @@ Memfile_LeaseMgr::checkLimits6(ConstElementPtr const& /* user_context */) const
     isc_throw(NotImplemented, "Memfile_LeaseMgr::checkLimits4() not implemented");
 }
 
+bool
+Memfile_LeaseMgr::isJsonSupported() const {
+    return true;
+}
+
 }  // namespace dhcp
 }  // namespace isc
-

src/lib/dhcpsrv/memfile_lease_mgr.h

@@ -530,6 +530,12 @@ public:
     /// string if no limits are exceeded
     std::string checkLimits6(isc::data::ConstElementPtr const& user_context) const override;
 
+    /// @brief Checks if JSON support is enabled in the database.
+    /// Memfile implementation assumes JSON support is always enabled.
+    ///
+    /// @return true if there is JSON support, false otherwise
+    bool isJsonSupported() const override;
+
 private:
 
     /// @name Internal methods called while holding the mutex in multi threading

src/lib/dhcpsrv/mysql_lease_mgr.cc

@@ -329,6 +329,7 @@ tagged_statements = { {
     // TODO: remove single quotes from the following two SELECTs when the functions are implemented
     {MySqlLeaseMgr::CHECK_LEASE4_LIMITS, "SELECT 'checkLease4Limits(?)'"},
     {MySqlLeaseMgr::CHECK_LEASE6_LIMITS, "SELECT 'checkLease6Limits(?)'"},
+    {MySqlLeaseMgr::IS_JSON_SUPPORTED, "SELECT isJsonSupported()"},
 } };  // tagged_statements
 
 }  // namespace
@@ -3278,6 +3279,28 @@ MySqlLeaseMgr::wipeLeases6(const SubnetID& /*subnet_id*/) {
     isc_throw(NotImplemented, "wipeLeases6 is not implemented for MySQL backend");
 }
 
+bool
+MySqlLeaseMgr::isJsonSupported() const {
+    // Get a context.
+    MySqlLeaseContextAlloc get_context(*this);
+    MySqlLeaseContextPtr ctx = get_context.ctx_;
+
+    // Create bindings.
+    MySqlBindingCollection in_bindings;
+    MySqlBindingCollection out_bindings({
+        MySqlBinding::createBool()
+    });
+
+    // Execute the select.
+    bool json_supported(false);
+    ctx->conn_.selectQuery(IS_JSON_SUPPORTED, in_bindings, out_bindings,
+                           [&json_supported] (MySqlBindingCollection const& result) {
+        json_supported = result[0]->getBool();
+    });
+
+    return json_supported;
+}
+
 // Miscellaneous database methods.
 
 std::string

src/lib/dhcpsrv/mysql_lease_mgr.h

@@ -638,6 +638,12 @@ public:
     /// @return number of leases removed.
     virtual size_t wipeLeases6(const SubnetID& subnet_id);
 
+    /// @brief Checks if JSON support is enabled in the database.
+    /// MySQL implementation.
+    ///
+    /// @return true if there is JSON support, false otherwise
+    bool isJsonSupported() const override;
+
     /// @brief Return backend type
     ///
     /// Returns the type of the backend (e.g. "mysql", "memfile" etc.)
@@ -726,6 +732,7 @@ public:
         SUBNET_RANGE_LEASE6_STATS,   // Fetched IPv6 lease stats for a subnet range.
         CHECK_LEASE4_LIMITS,         // Check if allocated IPv4 leases are inside the set limits.
         CHECK_LEASE6_LIMITS,         // Check if allocated IPv6 leases are inside the set limits.
+        IS_JSON_SUPPORTED,           // Checks if JSON support is enabled in the database.
         NUM_STATEMENTS               // Number of statements
     };
 

src/lib/dhcpsrv/pgsql_lease_mgr.cc

@@ -2425,6 +2425,11 @@ PgSqlLeaseMgr::wipeLeases6(const SubnetID& /*subnet_id*/) {
     isc_throw(NotImplemented, "wipeLeases6 is not implemented for PostgreSQL backend");
 }
 
+bool
+PgSqlLeaseMgr::isJsonSupported() const {
+    isc_throw(NotImplemented, "PgSqlLeaseMgr::isJsonSupported() not implemented");
+}
+
 std::string
 PgSqlLeaseMgr::getName() const {
     // Get a context

src/lib/dhcpsrv/pgsql_lease_mgr.h

@@ -613,6 +613,12 @@ public:
     /// @return number of leases removed.
     virtual size_t wipeLeases6(const SubnetID& subnet_id);
 
+    /// @brief Checks if JSON support is enabled in the database.
+    /// PostgreSQL implementation.
+    ///
+    /// @return true if there is JSON support, false otherwise
+    bool isJsonSupported() const override;
+
     /// @brief Return backend type
     ///
     /// Returns the type of the backend (e.g. "mysql", "memfile" etc.)

src/lib/dhcpsrv/tests/lease_mgr_unittest.cc

@@ -369,6 +369,13 @@ public:
         isc_throw(NotImplemented, "ConcreteLeaseMgr::checkLimits6() not implemented");
     }
 
+    /// @brief Checks if JSON support is enabled in the database.
+    ///
+    /// @return true if there is JSON support, false otherwise
+    bool isJsonSupported() const override {
+        isc_throw(NotImplemented, "ConcreteLeaseMgr::isJsonSupported() not implemented");
+    }
+
     /// @brief Returns backend type.
     ///
     /// Returns the type of the backend (e.g. "mysql", "memfile" etc.)

src/lib/dhcpsrv/tests/mysql_lease_mgr_unittest.cc

@@ -1072,4 +1072,13 @@ TEST_F(MySqlLeaseMgrTest, leaseStatsQueryAttribution6MultiThreading) {
     testLeaseStatsQueryAttribution6();
 }
 
+/// @brief Checks that no exceptions are thrown when inquiring about JSON
+/// support and prints an informative message.
+TEST_F(MySqlLeaseMgrTest, isJsonSupported) {
+    bool json_supported;
+    ASSERT_NO_THROW(json_supported = LeaseMgrFactory::instance().isJsonSupported());
+    std::cout << "JSON support is " << (json_supported ? "" : "not ") <<
+                 "enabled in the database." << std::endl;
+}
+
 }  // namespace

src/lib/mysql/mysql_binding.cc

@@ -131,6 +131,11 @@ MySqlBinding::createFloat(const float value) {
     return (createInteger<float>(value));
 }
 
+MySqlBindingPtr
+MySqlBinding::createBool() {
+    return (createInteger<uint8_t>(static_cast<uint8_t>(false)));
+}
+
 MySqlBindingPtr
 MySqlBinding::createBool(const bool value) {
     return (createInteger<uint8_t>(static_cast<uint8_t>(value)));

src/lib/mysql/mysql_binding.h

@@ -447,6 +447,12 @@ public:
                 createInteger<float> (static_cast<float>(value.get())));
     }
 
+    /// @brief Creates binding having a bool type for receiving data.
+    ///
+    /// @return Pointer to the created binding holding an @c uint8_t
+    /// value representing the boolean value.
+    static MySqlBindingPtr createBool();
+
     /// @brief Creates binding having a bool type for sending data.
     ///
     /// @param value Boolean value to be sent to the database.