Running remote Unix commands from LoadRunner

If you need to run a Unix command on a remote server with a LoadRunner script (running on Windows), then there is a neat program called plink that you will find very useful.

If you use any variety of Unix, you will probably already by using PuTTY; well plink is is distributed with PuTTY, and allows you to run remote Unix commands from your DOS prompt.

In this example, I have used it to collect disk I/O metrics from a remote Solaris server.

You may need to refer to some background material for the different components that are used for this example.

• Solaris Tips
• AWK
• Running command-line programs from LoadRunner

To capture the %busy metric for each disk, I can run iostat -xc. This gives the following output:

                 extended device statistics                      cpu
device    r/s    w/s   kr/s   kw/s wait actv  svc_t  %w  %b  us sy wt id
md0       0.5    0.6    8.5    0.8  0.0  0.0   19.9   0   0   1  1  0 98
md1       6.3    6.8   50.3   54.5  0.0  0.3   24.0   0   0
md3       0.2    0.7   12.7   12.6  0.0  0.0   11.0   0   1
md5       0.0    0.0    2.7    0.3  0.0  0.0    8.0   0   0
md6       0.0    0.0    0.0    0.0  0.0  0.0    3.6   0   0
md10      0.3    0.6    4.2    0.8  0.0  0.0   21.3   0   0
md11      3.1    6.8   25.1   54.5  0.0  0.3   25.6   0   0
md13      0.1    0.7    6.4   12.6  0.0  0.0    8.7   0   0

Using AWK to just grab the device name and the %b column can be done by running iostat -xc | awk ‘NR >2 {print $1, $9}’, which gives:

md0 0
md1 0
md3 1
md5 0
md6 0
md10 0
md11 0
md13 0

Putting this in a LoadRunner script that will save the %b value for each device using lr_user_data_point() looks like this:

/*
 * This script retrieves Disk IO stats from a Solaris server and plots them in the Controller using lr_user_data_point().
 */

#define BUFFER_SIZE 10240 // 10 KB

extern char* strtok(char *token, const char *delimiter); // Explicit declaration required for functions that do not return an int.

Action()
{
    long fp; // file/stream pointer
    int count; // number of characters that have been read from the stream.
    char buffer[BUFFER_SIZE]; // allocate memory for the output of the command.
    char * row_token; // for each row in the output of the command.
    char field_name[100]; // for the first column in the row.
    int field_value; // for the second column in the row.
    char lrudp_name[100]; // buffer to hold the LR user data point name.
    int rc; // return code for sscanf.

    lr_start_transaction("Monitor Disk IO");

    // The command we want to run is: plink -ssh -l username -pw password hostname command
    lr_save_string("stuart", "UserName");
    lr_save_string("asdf7890", "Password");
    lr_save_string("sdb526.sysdomain.local", "Server");
    lr_save_string("iostat -xc | awk 'NR >2 {print $1, $10}'", "Command"); // run iostat, and retrieve the "device" and "%b" column from the output.
    lr_save_string(lr_eval_string("C:\\Progra~1\\PuTTY\\plink -ssh -l {UserName} -pw {Password} {Server} \"{Command}\" 2>&1 0< nul:"), "CompleteCommand"); // Note: plink refuses to work without stdin redirected
    fp = popen(lr_eval_string("{CompleteCommand}"), "r"); 
    if (fp == NULL) {
        lr_error_message("Error opening stream.");
        return -1;
    }

    count = fread(buffer, sizeof(char), BUFFER_SIZE, fp); // read up to 10KB
    if (feof(fp) == 0) {
        lr_error_message("Did not reach the end of the input stream when reading. Try increasing BUFFER_SIZE.");
        return -1;
    }
    if (ferror(fp)) {
        lr_error_message ("I/O error during read."); 
        return -1;
    } 
    if (count == 0) {
        lr_error_message("Something went wrong when running command. No output returned.");
        return -1;
    }
    buffer[count] = NULL;

    /*
    The command should return data formatted like this:

    md0 0
    md1 0
    md3 1
    md5 0
    md6 0
    md10 0
    md11 0
    md13 0

    Iterate through each row, and save the name and value.
    */
    row_token = (char*) strtok(buffer, "\n"); // Split the buffer at each newline character 
    if (row_token == NULL) { 
        lr_error_message ("Something went wrong. No token found"); 
        return -1; 
    }
    while (row_token != NULL) { // While there are still rows in the buffer...
        rc = sscanf(row_token, "%s %d", field_name, &field_value); // Grab the field name and value.
        if (rc != 2) {
            lr_error_message("Incorrect number of items read from the row.");
            return -1;
        }

        // Create a user data point, so this value can be graphed in the LoadRunner Controller (and in LoadRunner Analysis).
        sprintf(lrudp_name, "disk_busy_%s", field_name);
        lr_user_data_point(lrudp_name, field_value);

        row_token = (char*) strtok(NULL, "\n");
    }

    /*
    Output will be 
        Notify: Data Point "disk_busy_md0" value = 0.0000.
        Notify: Data Point "disk_busy_md1" value = 0.0000.
        Notify: Data Point "disk_busy_md3" value = 1.0000.
        Notify: Data Point "disk_busy_md5" value = 0.0000.
        Notify: Data Point "disk_busy_md6" value = 0.0000.
        Notify: Data Point "disk_busy_md10" value = 0.0000.
        Notify: Data Point "disk_busy_md11" value = 0.0000.
        Notify: Data Point "disk_busy_md13" value = 0.0000.
    */

    pclose(fp);

    lr_end_transaction("Monitor Disk IO", LR_AUTO);

    return 0;
}

I hope you find this useful - both for the general concept of using LoadRunner to invoke commands (or shell scripts) on a remote Unix host and retrieve the output, and for the ability to monitor disk IO on Solaris without using SiteScope.