MXS-1220: Add to_string to HttpRequest

Allowing requests to be converted to raw HTTP requests allows them to be
propagated to other instances of MaxScale. This should allow multiple
MaxScales to perform the same action in a coherent manner.

A simple clustering mechanism needs to be added to make MaxScale aware of
other instances.

server/core/admin.cc

@@ -105,6 +105,8 @@ int Client::process(string url, string method, const char* upload_data, size_t *
     HttpRequest request(m_connection, url, method, json);
     HttpResponse reply(MHD_HTTP_NOT_FOUND);
 
+    MXS_DEBUG("Request:\n%s", request.to_string().c_str());
+
     if (url == "/")
     {
         // Respond to pings with 200 OK

server/core/httprequest.cc

@@ -16,6 +16,7 @@
 
 #include <ctype.h>
 #include <string.h>
+#include <sstream>
 
 using std::string;
 using std::deque;
@@ -128,3 +129,78 @@ bool HttpRequest::validate_api_version()
 
     return rval;
 }
+
+namespace
+{
+struct ValueFormatter
+{
+    std::stringstream ss;
+    const char* separator;
+    const char* terminator;
+
+    ValueFormatter(const char* sep, const char* term):
+        separator(sep), terminator(term)
+    {
+    }
+};
+}
+
+static int value_combine_cb(void *cls,
+                          enum MHD_ValueKind kind,
+                          const char *key,
+                          const char *value)
+{
+    ValueFormatter& cnf = *(ValueFormatter*)cls;
+
+    cnf.ss << key;
+
+    if (value)
+    {
+        cnf.ss << cnf.separator << value;
+    }
+
+    cnf.ss << cnf.terminator;
+
+    return MHD_YES;
+}
+
+std::string HttpRequest::to_string() const
+{
+    std::stringstream req;
+    req << m_verb << " " << m_resource;
+
+    ValueFormatter opts("=", "&");
+    MHD_get_connection_values(m_connection, MHD_GET_ARGUMENT_KIND,
+                              value_combine_cb, &opts);
+
+    std::string optstr = opts.ss.str();
+    size_t len = optstr.length();
+
+    if (len)
+    {
+        req << "?";
+
+        if (optstr[len - 1] == '&')
+        {
+            optstr.erase(len - 1);
+        }
+    }
+
+    req << optstr << " " << "HTTP/1.1" << "\r\n";
+
+    ValueFormatter hdr(": ", "\r\n");
+    MHD_get_connection_values(m_connection, MHD_HEADER_KIND,
+                              value_combine_cb, &hdr);
+
+    std::string hdrstr = hdr.ss.str();
+
+    if (hdrstr.length())
+    {
+        req << hdrstr;
+    }
+
+    req << "\r\n";
+
+    req << m_json_string;
+    return req.str();
+}

server/core/maxscale/httprequest.hh

@@ -43,6 +43,7 @@ static int value_iterator(void *cls,
 
     return MHD_YES;
 }
+
 static int value_sum_iterator(void *cls,
                               enum MHD_ValueKind kind,
                               const char *key,
@@ -252,11 +253,25 @@ public:
         return  m_resource_parts.size() > 0 ? m_resource_parts[m_resource_parts.size() - 1] : "";
     }
 
+    /**
+     * @brief Return the value of the Host header
+     *
+     * @return The value of the Host header
+     */
     const char* host() const
     {
         return m_hostname.c_str();
     }
 
+    /**
+     * @brief Convert request to string format
+     *
+     * The returned string should be logically equivalent to the original request.
+     *
+     * @return The request in string format
+     */
+    std::string to_string() const;
+
     /**
      * @brief Drop the API version prefix
      *