Introduction

While working with customers who wanted to extend NMIS and make it even more of a Network Management System (e.g. to support parts of their operational processes and integrate more closely with their ITIL service management processes), we found that it could become difficult for them to maintain the customisations of the extended data collection. To better support NMIS users we have simplified the way "Tables" in NMIS are defined and extended as well as how they are shown in the Menus.

This article will briefly describe how this capability works and how it supports operational agility.

Prerequisites

• NMIS version 8.3.18G or newer for custom tables
• NMIS version 8.6.2G or newer for input validation
• Shell access to the NMIS server and suitable user privileges to edit the NMIS configuration files
  (which usually means being  a member of the group "nmis" or having root privileges)

Custom Tables in NMIS

What are NMIS Tables?

To use NMIS various data is required, this data represents various policies, configuration, credentials or a combination of all of those.  In the past NMIS users have added tables as they needed, this required some Perl coding.  To support faster and more easily modified tables in NMIS the table definitions are now defined outside of the code base, making the tables themselves configuration items.  So like the chicken and the egg, you need to start with something.

Typical Tables used in NMIS

The following tables are used in NMIS internally:
(Note that this also includes the 'meta-table' Tables.nmis, which defines what other tables NMIS presents, to allow dynamic definition of tables.)

Table Configuration

For each known type of table there is a separate "table configuration" file, all of which are named Table-<yourtable>.nmis (e.g.  for table Users.nmis  the configuration file is called Table-Users.nmis).
Both the actual tables and their configuration files live in the conf directory, ie.  /usr/local/nmis8/conf.

These table configuration files consist of declaration stanzas and little bits of code, which is evaluated at run time.

Let's look at an example; this is what "Table-SampleTable.nmis" could look like:

%hash = (
  SampleTable => [
    { Email => { header => 'Email Address', display => 'key,header,text', value => [""] }},
    { Name => { header => 'Name', display => 'header,text', value => [""] }},
    { Age => { header => 'Age', display => 'header,text', value => [""],
               validate => { "int" => [ 0, undef ] }}},
    { Married => { header => 'Married', display => 'popup', value => ["true", "false"] }}, 
    { Children => { header => 'Children', display => 'popup', value => [0,1,2,3,4,5,6,7,8,9,10,11,12,"Many"] }},
  ]
);

SampleTable => [

{ 

  Email => { 

    header => 'Email Address', 

    display => 'key,header,text', 

    value => [""] 

  }

},

{ 

  Married => { 

    header => 'Married', 

    display => 'popup',

    value => ["true", "false"] 

  }

}, 

Display Options

Display controls how the field from the table configuration will be displayed and where it will be displayed, it is a comma separated list of values as shown in the examples above.

Possible values for display are:

Validation Options (8.6.2G and newer)

From NMIS version 8.6.2G onwards, a basic data validation mechanism is available for all NMIS tables. Not all properties are setup for validation yet, but the most critical ones are validation-enabled.

Validation is specificed by including a validate section in your property definition, e.g. for Age in the example above. A validation section can contain at most one rule for each supported validation type, but usually will contain just one rule altogether.

Management of Tables

Adding a New Table to NMIS

The following steps are required to add a new table:

1. Create a table configuration
2. Add the table to Tables.nmis
3. Create permissions in Access.nmis
4. Link to any other data

Create a Table Configuration

Create a file in /usr/local/nmis8/conf/, in our case /usr/local/nmis8/conf/Table-SampleTable.nmis, and add the appropriate configuration.

Add the table to Tables.nmis

Using the GUI or from the Unix prompt add the new table to Tables.nmis.

To add using GUI, access the menu item "System -> System Configuration -> Tables", a dialog will appear, and click on "add" next "Action >" in the top right of the widget.

Enter the properties for the table, the "Table Name" must match the name in the "Table Configuration", in our case SampleTable, the "Display Name" is what you want it to appear in the menu, and Description helps you remember what the table is for.

Refresh the NMIS Dashboard and your new table will exist in the menu but you will not be able to access it yet because there are no permissions defined for the table.

Create permissions in Access.nmis

You need to tell NMIS what Access permissions to add this with, we have created a script to add the tables with the default permissions which is as described in the table below, the command to run to add the permissions is.

/usr/local/nmis8/admin/add_table_auth.pl SampleTable

You should get some output like this:

Checking NMIS Authorisation for SampleTable
INFO: Authorisation NOT defined for SampleTable RW Access, ADDING IT NOW
INFO: Authorisation NOT defined for SampleTable View Access, ADDING IT NOW

The script can be run multiple times, it will not add the table twice.

The following table is the default permissions your table will be added with, if you want to change them, you can do that through the Access menu item at "System -> System Configuration -> Access Policy".

* This step is intentionally done using the Unix shell, as we want to ensure that people adding privileges are truly NMIS admins and not someone sneaking up and using a browser window.

View the Table and Add Something

If you haven't already, refresh the NMIS Dashboard and access the new table through the menu, in this example "System -> System Configuration -> Sample Table". It will likely have an error message like "Error on loading table SampleTable" this is because there was not data.  

Linking Data Between Tables

Creating new tables isn't that thrilling but if we could start linking data between them, e.g. a select (drop down) in the Nodes table could contain information from a new custom table, then we would have a much more useful system for adding properties.  Custom tables allow us to do this, as an example lets add a look up (displayed as a drop down) to our SampleTable called "Business Service".

To add a "Business Service" to our Sample table we will need to edit the Table Configuration and add some additional code to use the NMIS API (for looking up the values for "Business Service".

use NMIS;
use Auth;
my $C = loadConfTable();
# variables used for the security mods
my $AU = Auth->new(conf => $C); # Auth::new will reap init values from NMIS::config
# Calling program needs to do auth, then set the ENVIRONMENT before this is called.
$AU->SetUser($ENV{'NMIS_USER'});

%hash = (
  SampleTable => [
    { Email => { header => 'Email Address', display => 'key,header,text', value => [""] }},
    { Name => { header => 'Name', display => 'header,text', value => [""] }},
    { Age => { header => 'Age', display => 'header,text', value => [""] }},
    { Married => { header => 'Married', display => 'popup',value => ["true", "false"] }}, 
    { businessService => { header => 'Business Service', display => 'header,pop', value => [ sort keys %{loadGenericTable('BusinessServices')} ] }},
  ]
);

These lines setup the NMIS API

use NMIS;
use Auth;
my $C = loadConfTable();
# variables used for the security mods
my $AU = Auth->new(conf => $C); # Auth::new will reap init values from NMIS::config
# Calling program needs to do auth, then set the ENVIRONMENT before this is called.
$AU->SetUser($ENV{'NMIS_USER'});

Then this line added to the %hash section gives up the lookup value. loadGenericTable('TableName') is what grabs the values to be displayed in the drop down for us..

 { businessService => { header => 'Business Service',display => 'header,pop',value => [ sort keys %{loadGenericTable('BusinessServices')} ] }},

Refresh our widget and you will see the new empty value.

Edit that record and you can see a select box made up of the linked data.

Yes it really is that easy.

Troubleshooting

If you want to troubleshoot what is happening with a table when it is not working, you can look in the nmis log file, which is /usr/local/nmis8/logs/nmis.log, for example, refresh the table and then using the log tool select "NMIS_Log", or from unix "tail -50 /usr/local/nmis8/logs/nmis.log".

You might see an error like below, this is a Perl error and can be read the same way as reading a Perl compile or runtime error.  Everything after the <br> is the error.  The information before the <br> includes the callstack.

16-Mar-2013 13:48:26,tables.pl::loadCfgTable#140NMIS::loadGenericTable#293NMIS::loadFileOrDBTable#288func::loadTable#869func::readFiletoHash#976<br>ERROR convert /usr/local/nmis8/conf/Table-Nodes.nmis to hash table, Global symbol "$example" requires explicit package name at (eval 46) line 34, <$handle> line 70. 

In this example 'Global symbol "$example" requires explicit package name at (eval 46) line 34' is saying there is a compile time error at line 46 of the evaluated code, in this case the variable $example has not been declared inline with Perl "strict".

The callstack looks like this: 

NMIS::loadGenericTable (line 293)
  called:  NMIS::loadFileOrDBTable (line 288)
  called:  func::loadTable (line 869)
  called:  func::readFiletoHash (line 976)

Feedback

We would love you get your feedback, please let us know if you had any problems or would like more information at contact@opmantek.com