pytyped-metrics 1.0.0

Type-Driven Development for Python: Automatic Extraction of Metrics for Python Types

pytyped-metrics

pytyped-metrics is a Python package that automatically extracts statsd-style metrics for a given Python type. pytyped-metrics is a part of pytyped collection and follows its philosophy of using types to automate mundane and repetitive tasks. Currently, given a type T, pytyped-metrics automatically extracts a class MetricsExporter[T] which takes a value t: T and returns a list of metrics to be published to a statsd-style metrics collector.

Installation

You can install pytyped-metrics from PyPI:

pip install pytyped-metrics

pytyped-metrics is checked on Python 3.6+.

Why pytyped-metrics?

Metrics are valuable pieces of information in any real-world software and, to our knowledge, pytyped-metrics is the only Python package that automatic exporting of metrics based on reasonably-defined types. Additionally, pytyped-metrics is designed to be extensible. That is, you can define custom metrics exporters for specific types or custom functional types.

Many statsd-style metric collectors such as statsd, influxdb, prometheus, and datadog define a metric as a numeric value which can have a collection of tags with each tag having a name and a value. For example, the load of different cores of a CPU can be defined by a metric called system.cpu.load and a tag core_no=x which defines the load on which core is being reported.

Currently, pytyped-metrics supports the following type driven extractions of metric exporters:

• Metric exporting for basic numeric types such as int, float, and Decimal (which define a singular metric).
• Metric exporting for basic non-numeric types such as bool, date, datetime, and str (which define meaningful tags on other metrics)
• Metric exporting for simple type combinators such as List[T] and Dict[A, B].
• Metric exporting for named product types such as NamedTuples or dataclasses.
• Metric exporting for anonymous product types such as Tuple[T1, T2, ...].
• Metric exporting for anonymous union types such as Optional[T], Union[T1, T2, ...], etc.
• Metric exporting for named union types such as class hierarchies (i.e., when a class A has several subclasses A1, ..., An).
• Metric exporting for generic types and type variables.
• Metric exporting for custom functional types such as Set[T], Secret[T], etc where a custom function is defined for generic types such as Set or Secret and that functional is applied to all instantiations of those generic type.
• Metric exporting for recursive types such as binary trees, etc.

Using pytyped-metrics to extract metric exporters

First, define your type. For example, in the following we want to define an account that can either be a personal account or a business account. Each account (personal or business) has a beneficiary owner and a personal account has one currency and possibly multiple banking products (checking, saving, etc) but the business account can have both multiple currencies and multiple banking products per currency.

from decimal import Decimal
from dataclasses import dataclass
from enum import Enum
from typing import Dict, List


@dataclass
class BankingProductType(Enum):
    Checking = "Checking"
    Saving = "Saving"
    Credit = "Credit card"
    LoC = "Line of Credit"


@dataclass
class BankingProduct:
    type: BankingProductType
    balance: Decimal


@dataclass
class Account:
    owner: str


@dataclass
class PersonalAccount(Account):
    currency: str
    products: List[BankingProduct]


@dataclass
class BusinessAccount(Account):
    currencies: Dict[str, List[BankingProduct]]

Second, use an instance of AutoMetricExporter to extract a metric exporter for type Account:

from pytyped.metrics.exporter import AutoMetricExporter, MetricsExporter

_auto_metric_exporter = AutoMetricExporter()
account_metric_exporter: MetricsExporter[Account] = _auto_metric_exporter.extract(Account)

Third, define some instances of the Account class:

personal_account = PersonalAccount(
    owner = "John Doe",
    currency = "USD",
    products = [
        BankingProduct(type=BankingProductType.Checking, balance=Decimal(1000)),
        BankingProduct(type=BankingProductType.Credit, balance=Decimal(200))
    ]
)

business_account = BusinessAccount(
    owner = "Doe Ltd.",
    currencies = {
        "USD": [
            BankingProduct(type=BankingProductType.Checking, balance=Decimal(100000)),
            BankingProduct(type=BankingProductType.LoC, balance=Decimal(20000))
        ],
        "EUR": [
            BankingProduct(type=BankingProductType.Checking, balance=Decimal(50000)),
        ],
    }
) 

Finally, use account_metric_exporter to convert data in your instances to a list of metrics:

>>> account_metric_exporter.export(["account"], personal_account).to_metrics({})
[
    Metric(
        name='account.products.balance',
        value=Decimal('1000'),
        tags={
            'account.Account': 'PersonalAccount',
            'account.owner': 'John Doe',
            'account.currency': 'USD'
        }
    ),
    Metric(
        name='account.products.balance',
        value=Decimal('200'),
        tags={
            'account.Account': 'PersonalAccount',
            'account.owner': 'John Doe',
            'account.currency': 'USD'
        }
    )
]
>>> account_metric_exporter.export(["account"], business_account).to_metrics({})
[
    Metric(
        name='account.balance',
        value=Decimal('100000'),
        tags={
            'account.Account': 'BusinessAccount',
            'account.owner': 'Doe Ltd.',
            'account.currencies': 'USD'
        }
    ),
    Metric(
        name='account.balance',
        value=Decimal('20000'),
        tags={
            'account.Account': 'BusinessAccount',
            'account.owner': 'Doe Ltd.',
            'account.currencies': 'USD'
        }
    ),
    Metric(
        name='account.balance',
        value=Decimal('50000'),
        tags={
            'account.Account': 'BusinessAccount',
            'account.owner': 'Doe Ltd.',
            'account.currencies': 'EUR'
        }
    )
]

Issues

Please report any issues to the GitHub repository for this package.

Contributors

• Shahab Tasharrofi