Plugins¶

What a plugin can do¶

• Add a new class to AiiDA’s entry point groups, including:: calculations, parsers, workflows, data types, verdi commands, schedulers, transports and importers/exporters from external databases. This typically involves subclassing the respective base class AiiDA provides for that purpose.

• Install new commandline and/or GUI executables

• Depend on, and build on top of any number of other plugins (as long as their requirements do not clash)

What a plugin should not do¶

An AiiDA plugin should not:

• Change the database schema AiiDA uses

• Use protected functions, methods or classes of AiiDA (those starting with an underscore _)

• Monkey patch anything within the aiida namespace (or the namespace itself)

Failure to comply will likely prevent your plugin from being listed on the official AiiDA plugin registry.

If you find yourself in a situation where you feel like you need to do any of the above, please open an issue on the AiiDA repository and we can try to advise on how to proceed.

What is an entry point?¶

The setuptools package (used by pip) has a feature called entry points, which allows to associate a string (the entry point identifier) with any python object defined inside a python package. Entry points are defined in the setup.py file, for example:

...
entry_points={
"aiida.data": [
# entry point = path.to.python.object
"mycode.mydata = aiida_mycode.data.mydata:MyData",
]
}
...


Here, we add a new entry point mycode.mydata to the entry point group aiida.data. The entry point identifier points to the MyData class inside the file mydata.py, which is part of the aiida_mycode package.

When installing a python package that defines entry points, the entry point specifications are written to a file inside the distribution’s .egg-info folder. setuptools provides a package pkg_resources for querying these entry point specifications by distribution, by entry point group and/or by name of the entry point and load the data structure to which it points.

Why entry points?¶

AiiDA defines a set of entry point groups (see AiiDA entry point groups below). By inspecting the entry points added to these groups by AiiDA plugins, AiiDA can offer uniform interfaces to interact with them. For example:

• verdi plugin list aiida.workflows provides an overview of all workflows installed by AiiDA plugins. Users can inspect the inputs/outputs of each workflow using the same command without having to study the documentation of the plugin.

• The DataFactory, CalculationFactory and WorkflowFactory methods allow instantiating new classes through a simple short string (e.g. quantumespresso.pw). Users don’t need to remember exactly where in the plugin package the class resides, and plugins can be refactored without users having to re-learn the plugin’s API.

AiiDA entry point groups¶

Below, we list the entry point groups defined and searched by AiiDA. You can get the same list as the output of verdi plugin list.

aiida.calculations¶

Entry points in this group are expected to be subclasses of aiida.orm.JobCalculation. This replaces the previous method of placing a python module with the class in question inside the aiida/orm/calculation/job subpackage.

Example entry point specification:

entry_points={
"aiida.calculations": [
"mycode.mycode = aiida_mycode.calcs.mycode:MycodeCalculation"
]
}


aiida_mycode/calcs/mycode.py:

from aiida.orm import JobCalculation
class MycodeCalculation(JobCalculation):
...


from aiida.plugins import CalculationFactory
calc = CalculationFactory('mycode.mycode')


aiida.parsers¶

AiiDA expects a subclass of Parser. Replaces the previous approach consisting in placing a parser module under aiida/parsers/plugins.

Example spec:

entry_points={
"aiida.calculations": [
"mycode.mycode = aiida_mycode.parsers.mycode:MycodeParser"
]
}


aida_mycode/parsers/myparser.py:

from aiida.parsers import Parser
class MycodeParser(Parser)
...


Usage:

from aiida.plugins import ParserFactory
parser = ParserFactory('mycode.mycode')


aiida.data¶

Group for Data subclasses. Previously located in a subpackage of aiida/orm/data.

Spec:

entry_points={
"aiida.data": [
"mycode.mydata = aiida_mycode.data.mydat:MyData"
]
}


aiida_mycode/data/mydat.py:

from aiida.orm import Data
class MyData(Data):
...


Usage:

from aiida.plugins import DataFactory
params = DataFactory('mycode.mydata')


aiida.workflows¶

Package AiiDA workflows as follows:

Spec:

entry_points={
"aiida.workflows": [
"mycode.mywf = aiida_mycode.workflows.mywf:MyWorkflow"
]
}


aiida_mycode/workflows/mywf.py:

from aiida.engine.workchain import WorkChain
class MyWorkflow(WorkChain):
...


Usage:

from aiida.plugins import WorkflowFactory
wf = WorkflowFactory('mycode.mywf')


Note

For old-style workflows the entry point mechanism of the plugin system is not supported. Therefore one cannot load these workflows with the WorkflowFactory. The only way to run these, is to store their source code in the aiida/workflows/user directory and use normal python imports to load the classes.

aiida.cmdline¶

verdi uses the click_ framework, which makes it possible to add new subcommands to existing verdi commands, such as verdi data mydata. AiiDA expects each entry point to be either a click.Command or click.CommandGroup.

Spec:

entry_points={
"aiida.cmdline.data": [
"mydata = aiida_mycode.commands.mydata:mydata"
]
}


aiida_mycode/commands/mydata.py:

import click
@click.group()
mydata():
"""commandline help for mydata command"""

@mydata.command('animate')
@click.option('--format')
@click.argument('pk')
create_fancy_animation(format, pk):
"""help"""
...


Usage:

verdi data mydata animate --format=Format PK


aiida.tools.dbexporters¶

If your plugin package adds support for exporting to an external database, use this entry point to have aiida find the module where you define the necessary functions.

aiida.tools.dbimporters¶

If your plugin package adds support for importing from an external database, use this entry point to have aiida find the module where you define the necessary functions.

aiida.schedulers¶

We recommend naming the plugin package after the scheduler (e.g. aiida-myscheduler), so that the entry point name can simply equal the name of the scheduler:

Spec:

entry_points={
"aiida.schedulers": [
"myscheduler = aiida_myscheduler.myscheduler:MyScheduler"
]
}


aiida_myscheduler/myscheduler.py:

from aiida.schedulers import Scheduler
class MyScheduler(Scheduler):
...


Usage: The scheduler is used in the familiar way by entering ‘myscheduler’ as the scheduler option when setting up a computer.

aiida.transports¶

aiida-core ships with two modes of transporting files and folders to remote computers: ssh and local (stub for when the remote computer is actually the same). We recommend naming the plugin package after the mode of transport (e.g. aiida-mytransport), so that the entry point name can simply equal the name of the transport:

Spec:

entry_points={
"aiida.transports": [
"mytransport = aiida_mytransport.mytransport:MyTransport"
]
}


aiida_mytransport/mytransport.py:

from aiida.transports import Transport
class MyTransport(Transport):
...


Usage:

from aiida.plugins import TransportFactory
transport = TransportFactory('mytransport')


When setting up a new computer, specify mytransport as the transport mode.

Plugin test fixtures¶

One concern when running tests for AiiDA plugins is to separate the test environment from your production environment. Typically tests should be run against an empty AiiDA database.

AiiDA ships with tools that take care of this for you. They will:

• start a temporary postgres server

• create a new database

• create a temporary .aiida folder

• create a test profile

• (optional) reset the AiiDA database before every individual test

Note

The overhead for setting up the temporary environment is of the order of a few seconds and occurs only once per test session. You can control the database backend for the temporary profile by setting the AIIDA_TEST_BACKEND environment variable, e.g. export AIIDA_TEST_BACKEND=sqlalchemy.

If you prefer to run tests on an existing profile, say test_profile, simply set the following environment variable before running your tests:

export AIIDA_TEST_PROFILE=test_profile


Note

In order to prevent accidental data loss, AiiDA only allows to run tests on profiles whose name starts with test_.

AiiDA ships with a number of fixtures in aiida.manage.tests.pytest_fixtures for you to use.

In particular: