MXS-1779 Add initial support for classification URL

This commit introduces the plumbing support for obtaining
classification information of a statement using the REST-API.
It introduces a URL like

    /v1/maxscale/query_classifier/classify?sql=SELECT+1

that in the response will return a JSON object with the
information. Subsequent commits will provide the actual
information.

include/maxscale/config.h

@@ -110,6 +110,7 @@ extern const char CN_AUTH_READ_TIMEOUT[];
 extern const char CN_AUTH_WRITE_TIMEOUT[];
 extern const char CN_AUTO[];
 extern const char CN_CACHE_SIZE[];
+extern const char CN_CLASSIFY[];
 extern const char CN_CONNECTION_TIMEOUT[];
 extern const char CN_DUMP_LAST_STATEMENTS[];
 extern const char CN_DATA[];

include/maxscale/json_api.h

@@ -36,6 +36,7 @@ MXS_BEGIN_DECLS
 #define MXS_JSON_API_MODULES     "/maxscale/modules/"
 #define MXS_JSON_API_QC_STATS    "/maxscale/qc_stats/"
 #define MXS_JSON_API_QC          "/maxscale/query_classifier/"
+#define MXS_JSON_API_QC_CLASSIFY "/maxscale/query_classifier/classify"
 #define MXS_JSON_API_USERS       "/users/"
 
 /**

server/core/config.cc

@@ -91,6 +91,7 @@ const char CN_AUTH_READ_TIMEOUT[] = "auth_read_timeout";
 const char CN_AUTH_WRITE_TIMEOUT[] = "auth_write_timeout";
 const char CN_AUTO[] = "auto";
 const char CN_CACHE_SIZE[] = "cache_size";
+const char CN_CLASSIFY[] = "classify";
 const char CN_CONNECTION_TIMEOUT[] = "connection_timeout";
 const char CN_DATA[] = "data";
 const char CN_DEFAULT[] = "default";

server/core/internal/query_classifier.hh

@@ -56,4 +56,14 @@ std::unique_ptr<json_t> qc_as_json(const char* zHost);
  */
 bool qc_alter_from_json(json_t* pJson);
 
+/**
+ * Classify statement
+ *
+ * @param zHost      The MaxScale host.
+ * @param statement  The statement to be classified.
+ *
+ * @return A json object containing information about the statement.
+ */
+std::unique_ptr<json_t> qc_classify_as_json(const char* zHost, const std::string& statement);
+
 MXS_END_DECLS

server/core/query_classifier.cc

@@ -1376,3 +1376,21 @@ bool qc_alter_from_json(json_t* pJson)
 
     return rv;
 }
+
+
+std::unique_ptr<json_t> qc_classify_as_json(const char* zHost, const std::string& statement)
+{
+    json_t* pParams = json_object();
+
+    // TODO: Fill object with classification information.
+
+    json_t* pAttributes = json_object();
+    json_object_set_new(pAttributes, CN_PARAMETERS, pParams);
+
+    json_t* pSelf = json_object();
+    json_object_set_new(pSelf, CN_ID, json_string(CN_CLASSIFY));
+    json_object_set_new(pSelf, CN_TYPE, json_string(CN_CLASSIFY));
+    json_object_set_new(pSelf, CN_ATTRIBUTES, pAttributes);
+
+    return std::unique_ptr<json_t>(mxs_json_resource(zHost, MXS_JSON_API_QC_CLASSIFY, pSelf));
+}

server/core/resource.cc

@@ -677,6 +677,13 @@ HttpResponse cb_qc(const HttpRequest& request)
     return HttpResponse(MHD_HTTP_OK, qc_as_json(request.host()).release());
 }
 
+HttpResponse cb_qc_classify(const HttpRequest& request)
+{
+    string sql = request.get_option("sql");
+
+    return HttpResponse(MHD_HTTP_OK, qc_classify_as_json(request.host(), sql).release());
+}
+
 HttpResponse cb_thread(const HttpRequest& request)
 {
     int id = atoi(request.last_uri_part().c_str());
@@ -950,6 +957,8 @@ public:
 
         m_get.push_back(SResource(new Resource(cb_maxscale, 1, "maxscale")));
         m_get.push_back(SResource(new Resource(cb_qc, 2, "maxscale", "query_classifier")));
+        m_get.push_back(SResource(new Resource(cb_qc_classify, 3,
+                                               "maxscale", "query_classifier", "classify")));
         m_get.push_back(SResource(new Resource(cb_all_threads, 2, "maxscale", "threads")));
         m_get.push_back(SResource(new Resource(cb_thread, 3, "maxscale", "threads", ":thread")));
         m_get.push_back(SResource(new Resource(cb_logs, 2, "maxscale", "logs")));