HTTP post to create InfluxDB database with libcurl - c++

Question

I'm trying to make an http post with libcurl library to create an InfluxDB database, as indicated in their website:
curl -i -XPOST http://localhost:8086/query --data-urlencode "q=CREATE DATABASE mydb"
It looks like my code is not working. It doesnt give me any errors but db is not created. But instead if i try to add some points to an existing database, with the same function, it works. I think i miss the correct way of adding "q=CREATE DATABASE mydb" part. How should i change my code?
int main(int argc, char *argv[]){
char *url = "http://localhost:8086/query";
char *data = "q=CREATE DATABASE mydb";
/* should i change data string to json?
data = "{\"q\":\"CREATE DATABASE mydb\" }" */
bool res = createInfluxDB(url, data);
/*control result*/
return(0);
}
bool createInfluxDB(char *url, char *data) {
CURL *curl;
curl = curl_easy_init();
if(curl) {
CURLcode res;
/* What Content-type should i use?*/
struct curl_slist* headers = curl_slist_append(headers, "Content-Type: application/json");
/*--data-urlencode*/
char *urlencoded = curl_easy_escape(curl, data, int(strlen(data)));
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_POST, 1L);
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, urlencoded);
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)strlen(urlencoded));
res = curl_easy_perform(curl);
/*omitted controls*/
curl_free(urlencoded);
curl_slist_free_all(headers);
curl_easy_cleanup(curl);
}
return(true);
}

Answer 1

After analyzing packets with http post request (which was returning Bad Request) i arrived to the point that i shouldn't add query parameters as data. But instead it should be part of url. So after changing code like that, it works!
int main(int argc, char *argv[]){
char *url = "http://localhost:8086/query?q=CREATE+DATABASE+mydb";
bool res = createInfluxDB(url);
/*control result*/
return(0);
}
bool createInfluxDB(char *url) {
CURL *curl;
curl = curl_easy_init();
if(curl) {
CURLcode res;
struct curl_slist* headers = curl_slist_append(headers, "Content-Type: application/x-www-form-urlencoded");
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_POST, 1L);
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
res = curl_easy_perform(curl);
/*omitted controls*/
curl_slist_free_all(headers);
curl_easy_cleanup(curl);
}
return(true);
}

Answer 2

EDITED ANSWER:
You still got a missnamed var in a if statment:
if (urlencode) free(...
That should be
if (urlencoded) free(...
Then in your headers you set the application type as json and I don't think that's what you want.
Something like "application/x-www-form-urlencoded" may be better.
struct curl_slist* headers = curl_slist_append(headers, "Content-Type: application/x-www-form-urlencoded");
ORIGNIAL ANSWER:
A workaround could be in your
char *data = curl_easy_escape(curl, json, int(strlen(json)));
That overload data with a json var that doesn't exist ?
Something like this may work better:
data = curl_easy_escape(curl, data, int(strlen(data)));