geopm::PluginFactory(3) – abstract factory for plugins

Namespaces

The PluginFactory class template is a member of the namespace geopm, but the full name, geopm::PluginFactory<class T>, has been abbreviated in this manual. Similarly, the std:: namespace specifier has been omitted from the interface definitions for the following standard types: std::vector, std::string, std::set, and std::function, to enable better rendering of this manual.

Synopsis

#include <geopm/PluginFactory.hpp>

Link with -lgeopm (MPI) or -lgeopm (non-MPI)

void PluginFactory<T>::register_plugin(const string &plugin_name,
                                       function<unique_ptr<T>()> make_plugin,
                                       const map<string, string> &dictionary);

unique_ptr<T> PluginFactory<T>::make_plugin(const string &plugin_name) const;

vector<string> PluginFactory<T>::plugin_names(void) const;

const map<string, string>& PluginFactory<T>::dictionary(const string &plugin_name) const;

Description

GEOPM can be extended though Agent, IOGroup, and Comm plugins. This man page describes the steps for adding a plugin. Refer to geopm::Agent(3), and geopm::IOGroup(3) for more details about these interfaces. Any C++ class that derives from one of these plugin base classes and is compiled into a shared object file can be loaded at application launch time through the GEOPM plugin interface. This allows users and system administrators to extend the features and behavior of the monitor and control process that GEOPM executes without recompiling the GEOPM runtime.

There are several steps to implementing and integrating a plugin into GEOPM. First, the base class interface must be completely implemented by the new class. In addition to the virtual methods required by the interface, there are several recommended static class methods, described below, that should also be implemented by the derived class to aid in registration with the plugin factory. Finally, the plugin must be registered with the appropriate factory at plugin load time. This process is discussed in more detail in the following sections. The factory singletons for Agent, IOGroup, and Comm plugins are available through their respective single accessor functions: geopm::agent_factory(), geopm::iogroup_factory(), and geopm::comm_factory().

A good starting point for implementing a new Agent or IOGroup plugin is to modify the examples found in the Agent tutorial and the IOGroup tutorial. This code is located in the GEOPM source under tutorial/agent and tutorial/iogroup respectively.

Terms

Below are some definitions of terms that are used to describe different parts of the GEOPM runtime. Understanding these terms will help to interpret the documentation about how to extend the GEOPM runtime. These are arranged from from highest levels of abstraction down to the lowest levels of abstraction.

launcher:

Wrapper of system application launch (e.g. srun or aprun) that executes the GEOPM runtime with the application.

report:

Text file containing summary of aggregated stats collected during application run.

trace:

Time series of signals collected over application run in a pipe separated ASCII table.

agent:

Implementation used by GEOPM to interpret sampled data and enforce the appropriate controls.

policy:

Array of floating-point settings for Agent-specific control parameters in SI units.

sample:

Array of floating-point values providing Agent-specific runtime statistics in SI units.

endpoint:

Interface between resource manager and GEOPM runtime. This feature is still under development and is only available when GEOPM is compiled with the --enable-beta flag.

profile:

Interface for annotating compute application; provides PlatformIO region signals.

controller:

Thread on each compute node that loads plugins and runs GEOPM algorithm.

level:

Attribute of an Agent describing the number of edges between it and the nearest leaf Agent in the communication tree (a leaf Agent is level zero).

signal:

Named parameter in SI units that can be measured using PlatformIO.

control:

Named parameter in SI units that can be set using PlatformIO.

Factory Class Methods

register_plugin()

Add a plugin to this factory. The plugin_name parameter will be used to request plugins of the registered type. The make_plugin parameter is a function that returns a new object of the registered type. The dictionary is an optional string-to-string dictionary containing static information about the registered type.

make_plugin()

Creates an object of the registered type. If the type was not previously registered, an exception will be thrown. The plugin_name parameter will be used to look up the constructor function used to create the object. Returns a unique_ptr to the created object. The caller owns the created object.

plugin_names()

Returns a list of all valid plugin names that have been registered with this factory.

dictionary()

Returns an optional dictionary of static metadata about a registered type. If the type was not registered, an exception is thrown. The plugin_name parameter is used to look up the desired dictionary.

Building A Plugin Shared Object

A GEOPM plugin is a shared object file that is loaded at runtime by the controller through the dlopen(3) interface. Each file provides a new implementation for one of the three extensible classes: IOGroup, Agent, and Comm. Each implementation is identified by a unique name string referred to as the plugin_name. An exception will be thrown if more than one plugin of the same name and same type are loaded. The plugin_name is standardized to be all lower case letters. The shared object file names must conform to the pattern:

libgeopm<CLASS>_<NAME>.so.2.0.0

Here <NAME> is the plugin_name and <CLASS> is one of the three strings identifying the plugin type: "iogroup", "agent", or "comm". The current GEOPM ABI version is 1.0.0, and the file name must end with this string. Plugins must be marked to have exactly the same ABI version as the GEOPM library they are intended to be loaded by. Do not link the plugin shared object against any of the GEOPM libraries; this will cause a circular link dependency. Compile the shared object with flags appropriate for a dynamically loaded library, e.g. for g++ and icpx you must provide the -fPIC and -shared options.

Plugin Search Path And Load Order

The GEOPM_PLUGIN_PATH is a colon-separated list of directories that contain plugin shared object files to be loaded by the GEOPM runtime. Any symlink that resides in a directory specified by this variable will be ignored. See geopm(7) for details about GEOPM_PLUGIN_PATH. Note that an Exception will be thrown by the register_plugin() method if an attempt is made to register a plugin with the same name as a previously registered plugin.

In the case of IOGroup plugins, the most recently loaded plugin to register a signal or control name provides the implementation at runtime, even if an earlier IOGroup plugin had provided a signal or control with the same name. The plugins in the GEOPM_PLUGIN_PATH are loaded in reverse (right to left) order so that plugins earlier in the search path from left to right are preferred when looking up signal and control implementations. The default search path (<PREFIX>/lib/geopm) will have the lowest priority.

For example, if GEOPM_PLUGIN_PATH is set using the exports below, the plugins in $HOME/plugin/iogroup will be used with the highest priority to provide signal and control names, followed by the plugins in $GEOPM_HOME/tutorial/iogroup. Plugins in the default path will only be used if no higher priority implementation is found. A more detailed example of plugin load order can be found in tutorial/plugin_load.

export GEOPM_PLUGIN_PATH=$GEOPM_HOME/tutorial/iogroup
export GEOPM_PLUGIN_PATH=$HOME/plugin/iogroup:$GEOPM_PLUGIN_PATH

Warning

It is imperative that any dynamically loaded library that is a dependency of a plugin is available in the environment of the systemd initiated geopmd service. If dependent libraries are not available on the root user’s LD_LIBRARY_PATH, the plugin will fail to load. For this reason, it is recommended that any plugins are compiled with system installed gcc/g++ compilers.

Plugin Load Constructor Function

The shared object file must provide a function that is decorated with the constructor compiler directive. The __attribute__((constructor)) enables the registration of plugins when the shared object is loaded by a call to dlopen(3). Please see the gcc documentation for the constructor attribute.

Plugin Class Static Methods

It is recommended that each class deriving from one of the GEOPM plugin classes implement two static helper methods called plugin_name() and make_plugin(). These functions can be used to provide the inputs to PluginFactory::register_plugin(). Note that the first argument to register_plugin() is a string, i.e. the result of calling plugin_name(), whereas the make_plugin() function itself is passed as the second argument. The make_plugin() function should take no arguments and returns a unique_ptr to an object of the derived class. The plugin_name() function should take no arguments and return a string specifying the name of the plugin. The process for registering IOGroup and Comm plugins is identical other than the factory singleton name and is shown in the example below. In the case of Agent plugins, additional metadata is passed in the form of a dictionary as the third argument to register_plugin(). This dictionary is used by Agent class helper methods to look up information about the sample and policy names required by the Agent.

EXAMPLE: REGISTER IOGROUP PLUGIN

Please see the IOGroup tutorial for more information. This code is located in the GEOPM source under tutorial/iogroup.

// This example shows how to register an IOGroup plugin
#include <geopm/IOGroup.hpp> // geopm::IOGroup,
                             // geopm::iogroup_factory
#include <geopm/Helper.hpp>  // geopm::make_unique

// Header providing class ExampleIOGroup interface
#include "ExampleIOGroup.hpp"

// Called during dlopen() to register plugin
static void __attribute__((constructor))
register_plugin_example_iogroup(void)
{
    geopm::PluginFactory<geopm::IOGroup> &iof =
        geopm::iogroup_factory();
    iof.register_plugin(ExampleIOGroup::plugin_name(),
                        ExampleIOGroup::make_plugin);
}

// Static method used by the factory to create objects
std::unique_ptr<IOGroup> ExampleIOGroup::make_plugin(void)
{
    return geopm::make_unique<ExampleIOGroup>();
}

// Static method providing unique plugin name
std::string ExampleIOGroup::plugin_name(void)
{
    return "example";
}

EXAMPLE: REGISTER AGENT PLUGIN

Please see the Agent tutorial for more information. This code is located in the GEOPM source under tutorial/agent.

// This example shows how to register an Agent plugin
#include <geopm/Agent.hpp>  // geopm::Agent,
                            // geopm::agent_factory
#include <geopm/Helper.hpp> // geopm::make_unique

// Header providing class ExampleAgent interface
#include "ExampleAgent.hpp"

// Called during dlopen() to register plugin
static void __attribute__((constructor))
register_plugin_example_agent(void)
{
    geopm::PluginFactory<geopm::Agent> &af =
        geopm::agent_factory();
    af.register_plugin(ExampleAgent::plugin_name(),
                       ExampleAgent::make_plugin,
                       geopm::Agent::make_dictionary(
                           ExampleAgent::policy_names(),
                           ExampleAgent::sample_names()));
}

// Static method used by the factory to create objects
std::unique_ptr<geopm::Agent> ExampleAgent::make_plugin(void)
{
    return geopm::make_unique<ExampleAgent>();
}

// Static method providing unique plugin name
std::string ExampleAgent::plugin_name(void)
{
    return "example";
}

See Also

geopm(7), geopm::Agent(3), geopm::IOGroup(3), dlopen(3)