For more in-depth information about writing and assigning Puppet classes, see Language: Classes. Each manifest includes the examplecloud class declaration, as shown in the following example:. The declarations for the examplecloud class in the previous example ensure the following:.
A certain configuration file which is sourced from a location other than the Puppet master is installed. Exit Print View. Search Scope:. The syntax error can be fixed by the following code snippet. Improve this answer. Ah sorry, I didn't copy over my code correctly!
Likewise, I didn't complete my anwser before hitting "Answer". I've updated it with the real answer Maybe not the root error as you obsviously obfuscated the example. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. You need:. It has two parameters, one of which is optional it defaults to the title of the resource , and the collection of resources it declares is just a single file resource.
A quick note: If your VM is running Puppet 2. Exactly like defining a class? Since the user might declare any number of instances of a defined type, you have to make sure that the implementation will never declare the same resource twice. The following snippet shows an example of a class with a single parameter:. Note that we still supply an optional default value in our Hiera lookup to be used in case Hiera is not available.
The approach demonstrated in the previous code example has several major advantages over alternatives:. In many cases, a default of undef is a perfectly valid and simple value.
There are many situations for which you might want to test or experiment with one or many modules. This is common when deciding whether a module from the Puppet Forge is suitable for a site.
Another case for which sane defaults are useful is during testing. This can complicate the setup for your test cases because your Hiera data will not be available in this context. Puppet allows fairly complex generation of parameter defaults.
The default can be a function call, nested function, selector, or a complex data structure. Although you can embed selectors and other complex logic in your parameter defaults, doing so makes the input section difficult to comprehend. The data in modules pattern moves complex logic outside the parameter default block without losing the benefits of parameterization. Until recent versions of Puppet, a parameter default could not contain the value of another parameter.
To work around this, people often used confusing intermediary variables to test the value of the original variable. This limitation has been removed in Puppet 5, and parameters can now use the value of any parameter declared before them. So you can now simplify all of the mess in the preceding example to this much more readable form:.
A good parameter name has a few properties:. A good rule of thumb is to name the parameter after whatever will consume its value. For example, if your parameter will supply a DocumentRoot value for an Apache configuration file, the most intuitive name for your parameter will be documentroot.
If your parameter provides a source for a package resource, the most intuitive name will be source or source prefixed with the package name when necessary to disambiguate multiple sources. For example, the following parameter names would be fairly obvious to someone familiar with Apache:.
The design of input validation is important to consider and can be very environment specific. It is important to assess both the goals of validating input and the risks associated with invalid input. Data supplied to your module will usually come from a trusted source such as from Hiera data from an internal data repository. In these cases, the goal of input validation is not so much about security as it is to generate useful failure messages when the input is malformed.
When the data comes from an external source, the goal is to protect against not just invalid input, but also dangerous input. Input validation should be designed to provide useful troubleshooting information, and you should avoid overly restrictive validation. For example, unqualified paths are valid in most parts of an Apache configuration, and are interpreted relative to the ServerRoot directive. Facts are simply data provided about the node, which can be used to customize the catalog.
However, there is a risk of privilege escalation if a nonprivileged user can alter the fact values supplied to the Puppet catalog, which is implemented by the privileged Puppet agent process. You can protect against privilege escalation by preventing unprivileged users from modifying the environment or configuration used to determine fact values. When using exported resources or other forms of shared node data, facts from one compromised node can be used to attack other nodes on the network.
In these cases, input should absolutely be validated to help protect nodes from one another. The best way to protect against privilege escalation in an exported resources environment is to limit sharing to strictly validated values that can be tested for sanity before use. For example, ensure that only carefully validated hostnames are used in the load-balancer configuration built from exported resources. Although all business and service-specific data will come from other data sources, it can be helpful to provide data within a module.
In a moment, we will examine two popular patterns for providing data in modules. Regardless of the source of default data for a component module, the values should be component-specific defaults, not site-specific defaults or business logic.
Module data default values should be true no matter where the module is deployed. You should use parameters from your roles and profiles to override these defaults when necessary to implement site-specific needs. The params. For those familiar with Chef, the params. This pattern was necessary for now obsolete Puppet versions, but it has been replaced by the data in modules pattern of Puppet 4 and higher. With this pattern, the logic to select the appropriate default values was moved out of the main class to, as you might guess, the params.
Please copy these values It also relies on fully qualified resource references to data outside the class scope. This enables the author to keep functions in code, and data in text files.
Hiera data in modules far exceeds the features of the params. As you can see, the manifest now contains only actionable code. There are no data values embedded in the code. So, where do these values come from? A component module should have a small hierarchy of data files containing platform-specific and default values, as illustrated in the following:. Each of the data files shown in Examples through contains the exact same information in plain text. This code pattern provides a clear separation of code and data and is significantly easier to read and maintain than the inheritence pattern of params.
This section covers managing the relationships between cooperating and dependent classes. Module dependencies allow you to make use of classes, defined types, functions, and resource types and providers from other modules without reinventing the wheel within your own module.
Use class relationships to indicate any ordering or notification requirements described in the next section. Classes organize data and establish relationships between resources.
Building resource relationships this way then becomes a huge maintainability win. If we add a new resource to our module, we simply place it in the appropriate class and Puppet automatically establishes relationships between it and the rest of our resources, as demonstrated in Example Although this is suitable for simple cases, the number of relationships can grow exponentially as related files and services are added to the module.
Class relationships are also a huge win if we need to be able to uninstall an application. Removing an application from a node requires reversing the resource relationships so that things can be removed in the opposite order of installation.
You can use these example relationships as a guide for how to break your module into classes. If you find a lot of relationships between two sets of resources, consider using classes and class-based relationships instead. It is not incorrect to create a module with three child classes for three resources. You can then add new things to the module without breaking existing relationships. Containment causes relationships with a parent class to flow down to the contained classes.
In this example, the class java has a before relationship with the class tomcat and the resource Notify[tomcat]. Although the child classes are defined in the Tomcat module, the relationships with tomcat apply only to resources declared directly in the tomcat class and not to the resources in any of its child classes. In Example , the following relationships exist:. Unfortunately, the Tomcat class contains only Notify['tomcat'] , whereas the following relationships remain freestanding:.
The contain keyword includes a class and creates a relationship between the included class and its parent class. Example presents our previous module but this time using containment. By using contain , Example now has the following relationships:. Notice that Class['tomcat'] now has a relationship with its child Class['tomcat::package'] , whereas this relationship did not exist in Example Although the contain function automatically includes the class being contained, it can be combined with resource-style class declarations, as is illustrated in Example Doing so is parse-order dependent, so you must declare the classes before you contain them remember: you safely include a class previously declared with parameters, but not vice versa.
Regardless, this approach is currently the best-practice solution to handling containment and is the officially documented approach to building good modules, as the preceding example shows. The anchor pattern is the original solution to the class containment problem.
Anchors themselves perform no actions, but they do offer an anchor with which to establish class relationships inside a module. They also pass along notify signals so that notification works between modules as expected. The contain keyword was added to Puppet in version 3. If you are writing modules for modern releases of Puppet, we recommend that you use the contain function in your classes rather than the anchor pattern. Although this seems to be simpler than our containment example, it carries extra complexity to ensure that our resource relationships behave the way we expect.
The tomcat class shown above contains a subtle bug: Anchor['tomcat::begin'] does not have a notify relationship with Anchor['tomcat::service']. As a result, notifications sent to the Tomcat module would not cause the Tomcat service to restart.
This might be an issue if, for example, you updated Java to patch a vulnerability using Puppet, and the Tomcat service continued running under the old release of Java because its service never received a notification to restart. There are some cases for which you might want to intentionally avoid containing resources. Consider the following case for which we need to insert the deployment of one application after its dependent module has been installed and configured but before the service from its dependent service has been started:.
This example will work only if Class['tomcat::service'] is not contained inside of Class['tomcat']. Otherwise, a dependency loop would be created, like so:. Internally, the rest of the Tomcat module might have a notify relationship with Class['tomcat::service'] and a relationship loop will not be created. We could create such a module using this basic layout:. This works because resource relationships do not require that one resource be evaluated immediately after another when a relationship is defined.
The relationship simply sets general ordering requirements and allows for other resources to be inserted into the order. Puppet maintains the relationship ordering internally using a dependency graph. When using an approach such as this, remember that you lose the ability for the un-contained resources to generate notifications for the parent class; anything that wants to subscribe to Class['tomcat::service'] must do so explicitly now.
Intermodule relationships like this are typically domain-logic handled in your profiles rather than hardcoded into your modules. This approach is useful when complex relationships are necessary between arbitrary modules. Declare classes using contain or include , with fully qualified variable references inside the class.
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