Version: 0.1

Configuration File

When the modules are implemented, a pipeline can be created in one of two ways: from code or using a configuration file (called config). This page documents pipeline creation using the second way.

What it is#

Config is a YAML file that enables the definition of a pipeline. It accepts some predefined properties: module dependencies and parameters but also pipeline shared parameters and group options.

How to use#

Having a configuration file in YAML, pipeline creation is as simple as:

pipeline = ConfigReader.read(yaml_config: str, module_factory: Type[ModuleFactory])

The read method requires ModuleFactory in order to map previously registered module types to Python classes. It returns BasePipeline.Runtime instance (already built BasePipeline) ready to run or process.

Config example#

Below is a schema of a configuration file based on a simple example. It presents all possible options and parameters that can be configured within the file although most of them aren't required to create a pipeline. More concrete examples are described in the last section and all properties are listed in the next section.

config.yml

modules:                   # list of modules  - name: simple_mod       # module name    type: simple-module    # registered Python type name    group: group_1         # group name    depends_on:            # list of module names      - other_mod       parameters:            # map of module parameters      simple: true
shared_parameters:         # map of shared parameters  threshold: 0.75
groups:                    # additional groups options  - name: group_1          # group name    options:               # map of group options      replicas: 3

Config options#

Every config has to have modules property. Other properties - shared_parameters and groups - are optional.

`modules`#

This property is the only one that's mandatory. In general, it's used to determine dependencies between modules but also allows to set modules parameters and groups (in the case of a parallel pipeline).

Option	Required	Note
`name`	✓	It's the name of the module. There isn't any naming convention but the name specified in this property must be consistent with the module's name in a `depends_on` property of another module.
`type`	✓	It's the string under which the class has been registered in the `ModuleFactory`.
`group`	✗ / ✓	It's the name of a group, which the module belongs to. This property is required only in a parallel pipeline. If at least one module has a defined `group` property, the created pipeline is treated as a parallel pipeline.
`depends_on`	✗	It's a list of module names that the module depends on. Dependencies between all modules defined in a config determine their final order.
`parameters`	✗	It's a dictionary of parameter names and values that are given to the module as its arguments.

`shared_parameters`#

It's a dictionary of some additional parameters that are passed to each module. A similar role is played by a context however the main difference is that the shared parameters can store only simple types. Context usually stores objects or references. Shared parameters can be thought of as regular module parameters that can be accessed by and are the same for every module in a pipeline.

Shared parameters can be passed to a ConfigReader in one of two ways: as a property in a config YAML file or as an argument in the read method. Unlike context, which can be passed only as an argument (as it can store complex types).

pipeline = ConfigReader.read(config_file_path, ModuleFactory,                             context=my_context, shared_parameters=my_params)

It's worth noticing that shared parameters declared in a config YAML file always overwrite shared parameters passed as an argument to the ConfigReader.read method. That's why shared parameters should be provided in one of these ways, but not both.

The usage of the shared_parameters property in config is as simple as it can be - it stores key-value pairs of any simple type. The shared_parameters dictionary from a YAML file is read into Python as a dict.

`groups`#

The groups option isn't mandatory however if it is already in use then its properties are required. It sets additional options in the groups mentioned in the preceding modules property.

Option	Required	Note
`name`	✓	It's the name of a group. Must be consistent with module group names declared in the `modules` property.
`options`	✓	It's a dictionary of option names and values that are set in ray. The list of all valid options can be found in ray documentation. One additional option is the `replicas` property - it determines the size of the actor pool (like in the example below).

Examples of configuration files#

Sequential pipeline#

sequential.config.yml

modules:  - name: mod_a    type: dough-kneading-module  - name: mod_b    type: ingredients-preparing-module    parameters:      double_cheese: true      salami_slices: 30  - name: mod_c    type: pizza-forming-module    depends_on:       - mod_a      - mod_b  - name: mod_d    type: pizza-baking-module    depends_on:      - mod_c    parameters:      temperature: 220
shared_parameters:  recipe_difficulty_level: 5

Every module must consist of at least two parameters: name and type. In the example above, dough-kneading-module has only these two required properties. The second one contains some additional parameters: double_cheese and salami_slices. Both modules' outputs are inputs to the third module as the pizza-forming-module depends on mod_a and mod_b. Similarly, mod_d depends on mod_c and also has one additional parameter.
There are also some shared_parameters added which are accessible from every module.

Sequential pipeline with aggregation module#

aggregated.config.yml

modules:  - name: mod_a    type: tea-oxidation-module  - name: mod_b    type: tea-drying-module    depends_on:       - mod_a    parameters:      days: 5  - name: mod_c    type: tea-firing-module    depends_on:      - mod_b  - name: mod_d    type: leaves-collecting-module    depends_on:       - mod_a  - name: mod_e    type: leaves-analyzing-module    depends_on:       - mod_d

In this example mod_a output is an input to the two consecutive modules. Modules mod_a, mod_b and mod_c (yellow ones) are marked as regular modules as they run during the Pipeline.run phase. In turn, mod_d and mod_e (purple modules) run during the Pipeline.process mode. The module mod_d is an aggregation module - it's stateful so multiple runs of the Pipeline.run only aggregate mod_a outputs. Only during Pipeline.process it runs and gives its output as an input to mod_e.

Parallel pipeline with aggregation module#

parallel.config.yml

modules:  - name: mod_a    type: cocoa-harvesting-module    group: group_1  - name: mod_b    type: cocoa-fermentation-module    group: group_1    depends_on:       - mod_a  - name: mod_c    type: cocoa-drying-module    group: group_2    depends_on:       - mod_b    parameters:      days: 7  - name: mod_d    type: cocoa-roasting-module    group: group_2    depends_on:     -  mod_c  - name: mod_e    type: chocolate-bagging-module    group: group_1    depends_on:       - mod_a  - name: mod_f    type: chocolate-transporting-module    group: group_1    depends_on:       - mod_e  - name: mod_g    type: chocolate-analyzing-module    group: group_3    depends_on:       - mod_f
groups:  - name: group_2    options:      num_gpus: 2

The creation of a parallel pipeline requires an additional mandatory property: group. That's the main difference. Just like a sequential pipeline, a parallel one can have shared_parameters, module parameters property, and can consist of both regular and aggregation modules. But in a parallel pipeline, the group parameter is mandatory. For group_2 there is an additional property defined: num_gpus. However, it's not mandatory to define a group in the group section - group_1 and group_3 are initialized with default values.

ParallelPool with aggregation module#

parallel-actor-pool.config.yml

modules:  - name: mod_a    type: coffee-drying-module    group: group_1  - name: mod_b    type: coffee-milling-module    group: group_1    depends_on:       - mod_a    parameters:      grind_size: medium-coarse  - name: mod_c    type: coffee-roasting-module    group: group_1    depends_on:       - mod_b  - name: mod_d    type: coffee-grinding-module    group: group_2    depends_on:       - mod_c  - name: mod_e    type: coffee-brewing-module    group: group_2    depends_on:       - mod_d  - name: mod_f    type: coffee-storing-module    group: group_1    depends_on:       - mod_a  - name: mod_g    type: coffee-packing-module    group: group_3    depends_on:       - mod_f    parameters:      bag_size: medium  - name: mod_h    type: coffee-distributing-module    group: group_3    depends_on:       - mod_g
shared_parameters:  coffee_type: liberica  origin: Philippines
groups:  - name: group_1    options:      max_calls: 2      num_cpus: 1  - name: group_3    options:      replicas: 3

This example uses all kinds of acceptable properties - shared_parameters, groups, and module parameters. However, the main difference is the replicas option in groups. group_3 is replicated three times within the created parallel pool. group_2 could be replicated as well but not group_1 as it contains an aggregation module that cannot be duplicated.