Getting started

Beginning

All Akumuli functions starts with aku prefix (macros starts with the same uppercase prefix). You need to call aku_initialize first, before you call any other function.

Creating new database

apr_status_t result = aku_create_database("test", "/tmp", "/tmp", 8, 
                                          nullptr, nullptr, nullptr, nullptr);

if (result != APR_SUCCESS) { exit(1); }

This function will create new database instance on disk. First argument of the call is database name, second - path to directory, third - path to volumes directory. In this case database will be called test and all data will be placed in /tmp directory (it must be created beforehand). Fourth parameter is more interesting, this is database size. In this example size is eight, this means that eight volumes will be created. Each volume is 4Gb and resulting database size will be 32Gb. After call in tmp directory will be created 8 files with "volume" extension, each is 4Gb is size. Disk space allocated beforehand, during call to aku_create_database.

Last four parameter can be used to specify optional configuration parameters, we don't need this at this moment.

This call returns APR status, it can be compared to APR_SUCCESS constant and examined with libapr function apr_strerror to get human readable error message.

Now we can open this database and do something useful with it.

aku_FineTuneParams = {
  0, 1000, 0x1000000, nullptr
};
aku_Database* db = aku_open_database("/tmp/test.akumuli", params);
// check error!
aku_Status status = aku_open_status(db);
if (status != AKU_SUCCESS) {
  aku_close_database(db);
  exit(1);
}

Function aku_open_database can open database that already exists. Structure params must contain some useful parameters, we interested in second one - 1000, this is window size. After call to aku_open_database we can check it's state with aku_open_status this function return status code for the open operation. Variable db will always contain pointer to database instance, no matter what, even if file doesn't exists. In this case we can check for error using aku_open_error function.