Cacti – Data Input Methods

# Data Input Methods

Data Input Methods allow Cacti to retrieve data to insert into RRD files based upon a mapping controlled by Data Templates and their corresponding Data Sources. These resulting Data Templates and Data Sources can then be used to create Graph Templates and Graphs. Cacti includes a number of build in Data Input Methods for SNMP data and for Script, Script Server and SNMP Data Queries.

Outside of the built in Data Input Methods, the Cacti Administrator can create virtually any Data Input Method based upon a Scripts, or a PHP Script Server script. The Script based Data Input Method allows Cacti to virtually collect data from anywhere, though the built in SNMP and Script Server methods provide the greatest scalability in Cacti. Both Data Queries, and PHP Script Server topics will be covered in later sections of the documentation.

## Creating a Data Input Method

To create a new Data Input Method, from the Cacti Console, select Data Collection > Data Input Methods. Once on that screen, click the plus (+) glyph on the right which will allow you to add a new Data Input Method. You will be presented with a few fields to populate on the following screen.

###### Table 11-1. Field Description: Data Input Methods

Name | Description
--- | ---
Name | Give the data query a name that you will use to identify it
Input Type | Select the type of Data Input Method you are trying to create
Input String | This field is only used when the Input Type is set to Script/Command

The `Name` specified will be used throughout Cacti to identify the human readable name given to the Data Input Method. Careful consideration should be made to help uniquely identify the Data Source. Having very similar names can lead to confusion when utilizing them as your Cacti system grows.

Valid options for `Input Type` are Script/Command, and Script Server. As mentioned previously, Cacti provides built in Data Input Methods for SNMP data gathering and for SNMP, Script, and Script Server based Data Queries. Though present in the Cacti database, they are hidden from user view.

When the type is set to `Script/Command`, the `Input String` specifies the full path to the script including any per Data Source input variables. Data Source input variables must be enclosed in greater than and less than characters. For instance, if you are passing an IP address to a script, your input string might look something like: `/path/to/script.pl <ip>` When the user creates a Data Source based on this Data Input Method, they will be prompted for an IP address to pass onto the script.

When you are finished filling in all necessary fields, click the Create button to continue. Upon saving the new Data Input Method, you will be presented with two new sections to complete. Those sections will instruct Cacti what to pass to the Script, known as `Input Fields` otherwise known as `Input Parameters` and how to handle the output data, which we refer to as `Output Fields`.

The `Input Fields` box is used to define any fields that require information from the user or from various data within the Cacti Database such as the hostname, ip address, host id, etc. Any input fields referenced to in the input string must be defined here.

The `Output Fields` box is used to define each field that you expect back from the script and will be eventually stored in both the database and RRD files.

All Data Input Methods must have at least one output field defined, but may have more than one depending on the type.

### Data Input Fields

To define a new field, click the plus sign (+) next to the input or output field boxes. You will be presented with some or all of the fields below depending on whether you are adding an input or output field.

###### Table 11-2. Field Description: Data Input Fields

Name | Description
--- | ---
Field/Field Name | You will be presented a drop down list of the unused braced input fields from the command
Friendly Name | Enter a more descriptive name for this field
Regular Expression Match (Input Only) | Enter a valid regular expression as to how to modify the output
Allow Empty Input (Input Only) | Can the input value of this field blank or not
Special Type Code (Input Only) | Pull the input data from the Cacti database and don't prompt the user for this input value
Update RRDfile (Output Only) | Checked if you intend this output data to be stored in an RRDfile

The `Field Name` must contain no spaces or other non-alphanumeric characters (except '-' or '_').

If you want to enforce a certain regular expression pattern when the user enters a value into `Regular Expression Match (Input Only)` for this Data Input Field, it must follow POSIX syntax as it will be passed to PHP's preg() functions.

If the Data Input Field needs to reference another field internally, you can enter this into the `Special Type Code`. For instance, if your field requires an IP address from the user, you can enter 'management_ip' here and Cacti will fill this field in with the current IP address of the selected host.

###### Table 11-3. Special Type Codes

Field Name | Description
--- | ---
hostname | The hostname
management_ip | The ip
snmp_community | The SNMP community
snmp_username | The SNMP username
snmp_password | The SNMP version

If you enable the `Update RRDfile`, Cacti will insert the return value from this field into the RRDfile. This box needs to be checked for at least one output field per data input source, but can be left blank to have Cacti store the value only in the database instead.

When you are finished filling in all necessary fields, click the Create button to continue. You will be redirected back to the Data Input Method edit page. From here you can continue to add additional fields, or click Save on this screen when finished.

## Making Your Scripts Work With Cacti

The simplest way to extend Cacti's data gathering functionality is through external scripts. Cacti comes with a number of scripts out of the box which are located in the `scripts/` directory. These scripts are used by the Data Input Methods that are present in a new installation of Cacti.

To have Cacti call an external script to gather data you must create a new Data Input Method, making sure to specify Script/Command for the Input Type field. See the previous section, Creating a Data Input Method for more information about how to create a Data Input Method. To gather data using your Data Input Method, Cacti simply executes the shell command specified in the Input String field. Because of this, you can have Cacti run any shell command or call any script which can be written in almost any language.

What Cacti is concerned with is the output of the script. When you define your Data Input Method, you are required to define one or more output fields. The number of output fields that you define here is important to your script's output. For a Data Input Method with only one output field, your script should output its value in the following format:

    <value_1>

So if I wrote a script that outputs the number of running processes, its output might look like the following:

`67`

Data Input Methods with more than one output field are handled a bit differently when writing scripts. Scripts that output more than one value should be formatted like the following:

    <fieldname_1>:<value_1> <fieldname_2>:<value_2> ... <fieldname_n>:<value_n>

Lets say that I write a script that outputs the 1, 5, and 10 minute load average of a Unix machine. In Cacti, I name the output fields '1min', '5min', and '10min', respectively. Based on these two things, the output of the script should look like the following:

`1min:0.40 5min:0.32 10min:0.01`

One last thing to keep in mind when writing scripts for Cacti is that they will be executed as the user the data gatherer runs as. Sometimes a script may work correctly when executed as root, but fails due to permissions problems when executed as a less privileged user.

## Walkthrough: My First Data Input Method

### Data Input Method returning a single value

Lets start with a simple script, that takes a hostname or IP address as input parameter, returning a single value. You may find this one as

`<path_cacti>/scripts/ping.pl`:

    #!/usr/bin/perl

    # take care for tcp:hostname or TCP:ip@
    $host = $ARGV[0];
    $host =~ s/tcp:/$1/gis;

    # old Linux version use "icmp_seq"
    # newer use "icmp_req" instead
    open(PROCESS, "ping -c 1 $host | grep 'icmp_[s|r]eq' | grep time |");
    $ping = <PROCESS>;
    close(PROCESS);
    $ping =~ m/(.*time=)(.*) (ms|usec)/;

    if ($2 == "") {
        print "U";              # avoid cacti errors, but do not fake RRDTool stats
    }elsif ($3 eq "usec") {
        print $2/1000;  # re-calculate in units of "ms"
    }else{
        print $2;
    }

To define this script as a Data Input Method to Cacti, please go to Data Input Methods and click Add. You should see:

Please fill in Name, select Script/Command as Input Type and provide the command that should be used to retrieve the data. You may use `<path_cacti>` as a symbolical name for the path_to_your_Cacti_installation. Those commands will be executed from crontab; so pay attention to providing full path to binaries if required (e.g. `/usr/bin/perl` instead of `perl`). Enter all Input Parameters in `<>` brackets. Click create to see:

Now lets define the Input Fields. Click Add as given above to see:

The drop down Field [Input] contains one single value only. This is taken from the Input String `<host>` above. Fill Friendly Name to serve your needs. The Special Type Code allows you to provide parameters from the current Device to be queried. In this case, the hostname will be taken from the current device. Click create to see:

At least, define the Output Fields. Again, click Add as described above:

Provide a short Field [Output] name and a more meaningful Friendly Name. As you will want to save those data, select Update RRDfile. Create to see:

Click Save and you're done.

#### Creating the Data Template

Now you want to tell Cacti, how to store the data retrieved from this script. Please go to Data Templates and click Add. You should see:

Fill in the Data Templates Name with a reasonable text. This name will be used to find this Template among others. Then, please fill in the Data Source Name. This is the name given to the host-specific Data Source. The variable |host_description| is taken from the actual Device. This is to distinguish Data Sources for different devices. The Data Input Method is a drop down containing all known scripts and the like. Select the Data Input Method you just created. The Associated RRA's is filled by default. At the moment there's no need to change this. The lower part of the screen looks like:

The Internal Data Source Name may be defined at your wish. There's no need to use the same name as the Output Field of the Data Input Method, but it may look nicer. Click create to see:

Notice the new drop down Output Field. As there is only one Output Field defined by our Data Input Method, you'll see only this. Here's how to connect the Data Source Name (used in the RRDfile) to the Output Field of the Script. Click Save and you're done.

#### Creating the Graph Template

Now you want to tell Cacti, how to present the data retrieved from this script. Please go to Graph Templates and click Add. You should see:

Fill in Name and Title. The variable `|host_description|` will again be filled from the Device's definition when generating the Graph. Keep the rest as is and Create. See:

Now click the plus (+) glyph to Add the first item to be shown on the Graphs:

Select the correct Data Source from the drop down, fill in a color of your liking and select AREA as a Graph Item Type. You want to fill in a Text Format that will be shown underneath the Graph as a legend. Again, Create:

Notice, that not only an entry was made under Graph Template Items, but under Graph Item Inputs as well. Don't bother with that now. Lets fill some more nice legends, see:

Notice, that the Data Source is filled in automagically. Select LEGEND as Graph Item Type (it is not really a Graph Item Type in RRDTool-speak, but a nice time-saver), and click Create to see:

Wow! Three items filled with one action!

#### Apply the Graph Template to a Device

Now go to the Devices and select the one of your choice. See the Associated Graph Templates in the middle of this page:

Select your newly created Graph Template from the Add Graph Template drop down. Click the plus (+) glyph to see:

By default, the Graph Template is added and shown as Is Being Graphed. The reason for this is that Cacti now automatically creates Graphs automatically, unless disabled. If the Graph Template shows Not Being Graphed, you can create the Graph by pressing the Create Graphs at the top of the Devices page. Click this link to see:

Check the box that belongs to the new template and Create. See the results:

This will automatically

- Create the needed Graph Description from the Graph Template. As you may notice from the success message, this Graph takes the hosts name in it: router - Test ping (router is the hosts name of this example).
- Create the needed Data Source Description from the Data Template. Again, you will find the Hosts name replaced for |host_description|
- Create the needed RRDfile with definitions from the Data Template. The name of this file is derived from the Host and the Data Template in conjunction with an auto-incrementing number.
- Create an entry to the poller_item to instruct Cacti to gather data on each polling cycle.

You'll have to wait at least two polling cycles to find data in the Graph. Find your Graph by going to Graph Management, filtering for your host and selecting the appropriate Graph (there are other methods as well). This may look like:

## Walkthrough: Script with more Output Parameters

The script below will be implemented in perl. Please note that any supported language is supported using Cacti from direct command execution to scripts written in perl, python, php, bash, etc.

    #!/usr/bin/perl -w

    # --------------------------------------------------
    # ARGV[0] = &lt;hostname&gt;     required
    # ARGV[1] = &lt;snmp port&gt;    required
    # ARGV[2] = &lt;community&gt;    required
    # ARGV[3] = &lt;version&gt;      required
    # --------------------------------------------------
    use Net::SNMP;

    # verify input parameters
    my $in_hostname         = $ARGV[0] if defined $ARGV[0];
    my $in_port             = $ARGV[1] if defined $ARGV[1];
    my $in_community        = $ARGV[2] if defined $ARGV[2];
    my $in_version          = $ARGV[3] if defined $ARGV[3];

    # usage notes
    if (
        ( ! defined $in_hostname ) ||
        ( ! defined $in_port ) ||
        ( ! defined $in_community ) ||
        ( ! defined $in_version )
    ) {
        print "usage:\n\n
            $0 &lt;host&gt; &lt;port&gt; &lt;community&gt; &lt;version&gt;\n\n";
        exit;
    }

    # list all OIDs to be queried
    my $udpInDatagrams      = ".1.3.6.1.2.1.7.1.0";
    my $udpOutDatagrams     = ".1.3.6.1.2.1.7.4.0";

    # get information via SNMP
    # create session object
    my ($session, $error) = Net::SNMP->session(
        -hostname      => $in_hostname,
        -port          => $in_port,
        -version       => $in_version,
        -community     => $in_community,
        # please add more parameters if there's a need for them:
        #   [-localaddr     => $localaddr,]
        #   [-localport     => $localport,]
        #   [-nonblocking   => $boolean,]
        #   [-domain        => $domain,]
        #   [-timeout       => $seconds,]
        #   [-retries       => $count,]
        #   [-maxmsgsize    => $octets,]
        #   [-translate     => $translate,]
        #   [-debug         => $bitmask,]
        #   [-username      => $username,]    # v3
        #   [-authkey       => $authkey,]     # v3
        #   [-authpassword  => $authpasswd,]  # v3
        #   [-authprotocol  => $authproto,]   # v3
        #   [-privkey       => $privkey,]     # v3
        #   [-privpassword  => $privpasswd,]  # v3
        #   [-privprotocol  => $privproto,]   # v3
    );

    # on error: exit
    if (!defined($session)) {
        printf("ERROR: %s.\n", $error);
        exit 1;
    }

    # perform get requests for all wanted OIDs
    my $result = $session->get_request(
        -varbindlist      => [$udpInDatagrams, $udpOutDatagrams]
    );

    # on error: exit
    if (!defined($result)) {
        printf("ERROR: %s.\n", $session->error);
        $session->close;
        exit 1;
    }

    # print results
    printf("udpInDatagrams:%s udpOutDatagrams:%s", # <<< cacti requires this format!
        $result->{$udpInDatagrams},
        $result->{$udpOutDatagrams},
    );

    $session->close;

It should produce following output, when executed from command line:

    [prompt]> perl udp_packets.pl localhost 161 public 1
    udpInDatagrams:10121 udpOutDatagrams:11102

Where “public” would be replaced by your community string. Those input parameters again are controlled by the `Input Fields` in Cacti and the output from the script will be mapped to `Output Fields`. If you wish to return multiple output values, they must be space delimited name value pairs in the form of nameA:valueA nameB:valueB ...

### The Data Input Method

To define this script as a Data Input Method to Cacti, please go to Data Input Methods and click the plus (+) glyph.

You should see:

Enter the name of the new Data Input Method, select Script/Command and type in the command to call the script. Please use the full path to the command interpreter. Instead of entering the specific parameters, type `<symbolic variable name>` for each parameter the script needs. Save:

Now add each of the input parameters in the Input Fields section, one after the other. All of them are listed in sequence, starting with `<host>`:

`<port>`

`<community>`

`<version>`

We've used some of Cacti builtin parameters. When applied to a host, those variables will be replaced by the hosts actual settings. Then, this command will be stored in the poller_command table. Now Save your work to see

After having entered all Input Fields, let's now turn to the Output Fields, respectively. Add the first one, udpInDatagrams:

Now udpOutDatagrams:

Be careful to avoid typos. The strings entered here must exactly match those spitted out by the script. Double check Output Fields! Now, results should be like

Finally Save and be proud!

### The Data Template

The previous step explained how to call the script that retrieves the data. Now it's time to tell Cacti, how to store them in RRD files. You will need a single Data Template only, even if two different output fields will be stored. RRD files are able to store more than one output fields; RRDTool's name for those is Data Source. So we will create

1. one single Data Template representing one RRDfile
2. two output fields/data sources

The first step is quite the same as Create the Data Template for a simple Data Input Method. For sure, we provide a different name, Example - UDP Packets. Now, let's enter the first Data Source. Again, its like above. But we now provide the name of udpInPackets, enter a Maximum value of 100,000 and select the Data Source Type of COUNTER.

Then save and find with the exception that the Output Field will be set to None Selected. Therefore, before adding the second Data Source Item, make sure you select the Output Field of udpInDatagrams and press the Save button to create the association.

Then, add the second Data Source by pressing the plus (+) glyph and providing data for udpOutPackets. Pay attention to select the correct Output Field defined by the Data Input Method as we did with the udpInDatagrams.

To deactivate maximum checking, enter 'U', else the desired number. Do not forget to select the correct Data Source Type and the Output Field as before.

### The Graph Template

Most of this task of creating a Graph Template has already been covered in our example. You will basically create a new Graph Template, provide a Line or an Area Fill followed by a Legend for both the udpInDatagrams and udpOutDatagrams. The result of those actions will be the image below:

After you have created your Graph Template you can proceed to Add the Graph Template to your Device, and either allow the automation to create the Graph for you, or to manually add it from the New Graphs menu pick.

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