Persisting LR Data Using MySQL

In the beginning it was horrible: not knowing what kind of C compiler LoadRunner is using, I experience with several header files from cygwin and mingw, which I know, deep inside, won’t work.

But RTFM saved the day, by merging the header files to $LR/include MySQL C code can be compiled by only tweaking one 64 bits reference.

Below is the final code to commit unique users, I totally rely on MySQL’s ACID to do the right thing. Hopefully I put my belief at the right place.

int commit_user() {
int rc = 0;
char *exec;
int good = 0;
int available = 1;

db_connection = mysql_init(NULL);
if (db_connection == NULL) {
lr_error_message("Insufficient memory");
return -1;
}

// Connect to the database
if (mysql_real_connect(db_connection, server, user, password, database, port, NULL, 0) == NULL) {
lr_error_message("error on connect: %s", mysql_error(db_connection));
mysql_close(db_connection);
return -1;
}
lr_output_message("Connection to DB is established");

while (!good) {
available = 1;

while (available) {
 exec = lr_eval_string("SELECT EXISTS (select login from LATLogin WHERE login = '{pUserName}');");
 if (mysql_query(db_connection, exec)!= 0) {
  lr_error_message("%s;error on query: %s", exec, mysql_error(db_connection));
  mysql_close(db_connection);
  return -1;
 }
 lr_output_message("exec: %s", exec);

 if ((query_result = mysql_store_result(db_connection)) == NULL) {
  lr_error_message("%s;error on store: %s", exec, mysql_error(db_connection));
  mysql_close(db_connection);
  return -1;
 }

 result_row = mysql_fetch_row(query_result);
 available = atoi(result_row[0]);
 lr_output_message("available=%d", available);

 if (available) { //exists
  lr_advance_param("pDataFileUserName");
  lr_output_message("Advance pDataFileUserName = %s", lr_eval_string("{pDataFileUserName}"));
  while (strcmp(lr_eval_string("{pDataFileUserName}"), lr_eval_string("{pUserName}")) == 0) {
   lr_advance_param("pDataFileUserName");
   lr_output_message("Advance pDataFileUserName = %s", lr_eval_string("{pDataFileUserName}"));
  }
  lr_save_string(lr_eval_string("{pDataFileUserName}"), "pUserName");
 }
 mysql_free_result(query_result);
}

exec = lr_eval_string("INSERT INTO LATLogin VALUES('{pUserName}');");
if (mysql_query(db_connection, exec)!= 0) {
 rc = mysql_errno(db_connection);

 if (rc == 1062) {
  lr_output_message("%s is too late, duplicate exists", exec);

  //when pUserName exists, probably some else took it already
  lr_advance_param("pDataFileUserName");
  lr_output_message("Advance pDataFileUserName = %s", lr_eval_string("{pDataFileUserName}"));
  while (strcmp(lr_eval_string("{pDataFileUserName}"), lr_eval_string("{pUserName}")) == 0) {
   lr_advance_param("pDataFileUserName");
   lr_output_message("Advance pDataFileUserName = %s", lr_eval_string("{pDataFileUserName}"));
  }
  lr_save_string(lr_eval_string("{pDataFileUserName}"), "pUserName");
 }
 else {
  lr_error_message("%s, error(%d): %s", exec, mysql_errno(db_connection), mysql_error(db_connection));
  mysql_close(db_connection);
  return -1;
 }
}
else {
 lr_output_message("exec: %s", exec);
 good = 1;
 user_removed = 0;
}
}
mysql_close(db_connection);
lr_output_message("Connection to DB is closed");
return 0;
}

The final result: running 90 virtual users (I ran out of login), each running 20 seconds transactions.
GetUniqueUserName

• 75% of population: 0.028 +/- 0.02
• 90Percentile: 0.043

The generator machine CPU consumption is hovering around 25% - I give this method of persisting LR data a stamp of approval.

Next Stop: SQLite

Actually no, I was thinking about something more ambitious (MySQL). The fact that I have to hunt down other C library files, forces me to consider SQLite. Just drop sqlite3.dll to $LR/bin, sqlite3.h to $LR/include and trim off the 64 bit references in sqlite3.h to make it works.

But simpler solution doesn’t make my life easier, since writing SQLite code (or any db code), in C, that doesn’t leak memory or crashes the db, is fairly hard.

But finally, I get this:

rc = sqlite3_open("test.db", &db);
if (rc) {
 lr_output_message("Can't open database: %s", sqlite3_errmsg(db));
 sqlite3_close(db);
 return -1;
}
exec = "NO RESULT QUERY SUCH AS: DELETE, INSERT”; 
isPrepared = 0;
while (!isPrepared) {
 rc = sqlite3_prepare(db, exec, -1, &stmt, 0);
 if (rc == SQLITE_OK) { //SQLITE_OK == 0
  isPrepared = 1;
  isExecuted = 0;
  while (!isExecuted) {
   rc = sqlite3_step(stmt);
   /* uncomment this section when exec is a query that return result
   while ((rc == SQLITE_ROW)||(rc == SQLITE_BUSY) ) {
    if (rc == SQLITE_BUSY ) {
     lr_output_message("SQLITE_BUSY - wait for 0.1 seconds");
     lr_think_time(0.1); // TODO: tweak the wait time to your need
    }
    else {
     // extract data
     rc = sqlite3_step(stmt);
    }
   }
   */
   if (rc == SQLITE_DONE) {
    isExecuted = 1;
    sqlite3_finalize(stmt);
   }
   else if (rc == SQLITE_BUSY) { // DB is locked
    lr_output_message("SQLITE_BUSY - wait for 0.1 seconds");
    lr_think_time(0.1); // TODO: tweak the wait time to your need
   }
   else { // real bad stuff usually happens here
    lr_output_message("Cannot execute step, rc = %d", rc);
    lr_output_message("sqlite3_errmsg: %s", sqlite3_errmsg(db));
    lr_output_message("sqlite3_extended_errcode, rc = %d", sqlite3_extended_errcode(db));
    sqlite3_finalize(stmt);
    sqlite3_close(db);
    return -1;
   }
  }
 }
 else if (rc == SQLITE_BUSY) { // DB is locked
  lr_output_message("SQLITE_BUSY - wait for 0.1 seconds");
  lr_think_time(0.1); // TODO: tweak the wait time to your need
 }
 else { // real bad stuff usually happens here
  lr_output_message("Could not prepare statement, rc=%d", rc);
  lr_output_message("sqlite3_errmsg: %s", sqlite3_errmsg(db));
  lr_output_message("sqlite3_extended_errcode, rc = %d", sqlite3_extended_errcode(db));
  sqlite3_close(db);
  return -1;
 }
}
sqlite3_close(db);

Functionally the script works, at 50 virtual users, each running 20 seconds transactions, even the GetUniqueUserName transaction is fairly fast:

• 75% of population: 0.269 +/- 0.731
• 90Percentile: 0.655

But, it doesn’t work at 60 virtual users, it also locks the controller. Not good, need to look into MySQL solution.

Each VUser Must Use Unique Login ID

This is a problem: the web app that I am testing is using the login id as session id. Since I am furnished with data, that has multiple non-unique logins, I have to make sure that all of virtual users are using unique login id.

Several solutions come to mind, but I decided to give LoadRunner VTS a whirl.

Perusing VTS2.doc I quickly hone in lrvtc_send_if_unique function:

VTCERR lrvtc_send_if_unique(char *columnName, char *message)

But this function is pretty much useless since the VTCERR equals 1 no matter if the insertion is successful or not. Trying its cousin instead:

VTCERR vtc_send_if_unique(PVCI pvci, char *columnName, char *message, unsigned short *outRc)

This function returns successful insertion status in outRc parameter (1 = Pass, 0 = Fail).

lr_start_transaction("GetUniqueUserName");
status = 0;
while (status == 0) {
 lr_save_string(lr_eval_string("{pDATAFILEUserName}"), "pUserName");

 pvci = lrvtc_connect(lr_eval_string("{pVTSServer}"), 8888, 0);
 rc = vtc_send_if_unique(pvci, "pUserName1", lr_eval_string("{pUserName}"), &status);
 lr_output_message("Insert if unique, rc = %d, status: = %d", rc, status);
 lrvtc_disconnect();
  
 if (status == 0)  //try another login in the data file if fail
  lr_advance_param("pDATAFILEUserName ");
 else
  user_removed = 0; // just another flag
}
lr_end_transaction("GetUniqueUserName", LR_AUTO);

The login removal process is a trickier than the insert process, since VTS doesn’t have a function to look up a value in a column, a value has to be looked up (one by one):

int removePreviousUserName() { // to eliviate the nasty side effect of exit when error
 int rc = 0;
 unsigned short  status;
 int EOT = 0;
 int i;
 int user_removed = 0;

 lr_start_transaction("RemovePreviousUserName");
 i=lastrowID;

 while (!EOT) {
  i++;
  pvci = lrvtc_connect(lr_eval_string("{pVTSServer}"), 8888, 0);
  
  rc = lrvtc_query_column("pUserName1", i);
  lr_output_message("query row %d, rc = %d", i, rc);

  if (rc!=0)
   EOT = 1;
  else {
   if (stricmp(lr_eval_string("{pUserName}"), lr_eval_string("{pUserName1}")) == 0)  {
    lr_output_message("Del msg (%s) at row %d", lr_eval_string("{pUserName1}"), i);
    rc = vtc_clear_message(pvci, "pUserName1", i, &status);
    lr_output_message("Del msg, rc = %d, Status = %d", rc, status);
    lastrowID = i;
    EOT = 1; // exit anyway
    user_removed = 1;
   }
  }
  lrvtc_disconnect();
 }
 lr_end_transaction("RemovePreviousUserName", LR_AUTO);
 return user_removed;
}

A little explanation about lastrowID, when a data is deleted from VTS, a value can never be re-inserted into that row again via vtc_send_if_unique function. So, there are lots of empty rows at the lower index after the value is deleted. Thus there is no point for the script to start the search for a login to delete from row 1; instead it should start the search from the last deletion point.

Functionally the script works, but VTS system is not capable of handling multiple virtual users. At 10 virtual users, each running 20 seconds transactions, VTS is throwing numerous -10003 errors, that causes slow GetUniqueUserName transaction:

• 75% of population: 2.201 +/- 2.912
• 90 Percentile: 6.506

2.2 seconds on the average to insert unique value? I don’t think so. I need a better solution.