Initial commit

This is a FastAPI backend microservice template used with `copier` utility.

Features of applied template are:
- Configuration file processing logic
- Metrics and tracing (both optional) configuration available
- Debug endpoints
- Database migration commands, prepared Alembic environment
- Database usage example in ping_db endpoint
- gitea sanity check pipeline

{{project_slug}}/db/__init__.py

@@ -0,0 +1,21 @@
+"""SQL naming convention for Alembic is defined here."""
+
+from sqlalchemy import MetaData
+from sqlalchemy.orm import declarative_base
+
+convention = {
+    "all_column_names": lambda constraint, _: "_".join([str(column.name) for column in constraint.columns.values()]),
+    "ix": "ix_%(table_name)s_%(all_column_names)s",
+    "uq": "%(table_name)s_%(all_column_names)s_key",
+    "ck": "ck_%(table_name)s_%(column_0_name)s",
+    "fk": "%(table_name)s_fk_%(all_column_names)s__%(referred_table_name)s",
+    "pk": "%(table_name)s_pk",
+}
+
+metadata = MetaData(naming_convention=convention)
+DeclarativeBase = declarative_base(metadata=metadata)
+
+__all__ = [
+    "DeclarativeBase",
+    "metadata",
+]

{{project_slug}}/db/alembic.ini

@@ -0,0 +1,114 @@
+# A generic, single database configuration.
+
+[alembic]
+# path to migration scripts
+script_location = migrator/
+
+# template used to generate migration files
+file_template = %%(year)d-%%(month).2d-%%(day).2d_%%(rev)s_%%(slug)s
+
+# sys.path path, will be prepended to sys.path if present.
+# defaults to the current working directory.
+prepend_sys_path = .
+path_separator = os
+
+# timezone to use when rendering the date within the migration file
+# as well as the filename.
+# If specified, requires the python>=3.9 or backports.zoneinfo library.
+# Any required deps can installed by adding `alembic[tz]` to the pip requirements
+# string value is passed to ZoneInfo()
+# leave blank for localtime
+# timezone =
+
+# max length of characters to apply to the
+# "slug" field
+# truncate_slug_length = 40
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+# set to 'true' to allow .pyc and .pyo files without
+# a source .py file to be detected as revisions in the
+# versions/ directory
+# sourceless = false
+
+# version location specification; This defaults
+# to migrator/versions.  When using multiple version
+# directories, initial revisions must be specified with --version-path.
+# The path separator used here should be the separator specified by "version_path_separator" below.
+# version_locations = %(here)s/bar:%(here)s/bat:migrator/versions
+
+# version path separator; As mentioned above, this is the character used to split
+# version_locations. The default within new alembic.ini files is "os", which uses os.pathsep.
+# If this key is omitted entirely, it falls back to the legacy behavior of splitting on spaces and/or commas.
+# Valid values for version_path_separator are:
+#
+# version_path_separator = :
+# version_path_separator = ;
+# version_path_separator = space
+version_path_separator = os  # Use os.pathsep. Default configuration used for new projects.
+
+# set to 'true' to search source files recursively
+# in each "version_locations" directory
+# new in Alembic version 1.10
+# recursive_version_locations = false
+
+# the output encoding used when revision files
+# are written from script.py.mako
+# output_encoding = utf-8
+
+sqlalchemy.url = postgresql+asyncpg://%(POSTGRES_USER)s:%(POSTGRES_PASSWORD)s@%(POSTGRES_HOST)s:%(POSTGRES_PORT)s/%(POSTGRES_DB)s?target_session_attrs=read-write
+
+
+[post_write_hooks]
+# post_write_hooks defines scripts or Python functions that are run
+# on newly generated revision scripts.  See the documentation for further
+# detail and examples
+
+# format using "black" - use the console_scripts runner, against the "black" entrypoint
+hooks = black
+black.type = console_scripts
+black.entrypoint = black
+black.options = -l 120 REVISION_SCRIPT_FILENAME
+
+# lint with attempts to fix using "ruff" - use the exec runner, execute a binary
+# hooks = ruff
+# ruff.type = exec
+# ruff.executable = %(here)s/.venv/bin/ruff
+# ruff.options = --fix REVISION_SCRIPT_FILENAME
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

{{project_slug}}/db/config.py.jinja

@@ -0,0 +1,43 @@
+"""Database configuration class is defined here."""
+
+from dataclasses import dataclass
+from typing import Any
+
+from {{project_slug}}.utils.secrets import SecretStr
+
+
+@dataclass
+class DBConfig:
+    host: str
+    port: int
+    database: str
+    user: str
+    password: SecretStr
+    pool_size: int
+
+    def __post_init__(self):
+        self.password = SecretStr(self.password)
+
+
+@dataclass
+class MultipleDBsConfig:
+    master: DBConfig
+    replicas: list[DBConfig] | None = None
+
+    def __post_init__(self):
+        _dict_to_dataclass(self, "master", DBConfig)
+        if self.replicas is not None:
+            _list_dict_to_dataclasses(self, "replicas", DBConfig)
+
+
+def _list_dict_to_dataclasses(config_entry: Any, field_name: str, need_type: type) -> None:
+    list_dict = getattr(config_entry, field_name)
+    for i in range(len(list_dict)):  # pylint: disable=consider-using-enumerate
+        if isinstance(list_dict[i], dict):
+            list_dict[i] = need_type(**list_dict[i])
+
+
+def _dict_to_dataclass(config_entry: Any, field_name: str, need_type: type) -> None:
+    value = getattr(config_entry, field_name)
+    if isinstance(value, dict):
+        setattr(config_entry, field_name, need_type(**value))

{{project_slug}}/db/connection/__init__.py

@@ -0,0 +1,7 @@
+"""Module responsible for managing database connections."""
+
+from .manager import PostgresConnectionManager
+
+__all__ = [
+    "PostgresConnectionManager",
+]

{{project_slug}}/db/connection/manager.py.jinja

@@ -0,0 +1,195 @@
+"""Connection manager class and get_connection function are defined here."""
+
+from asyncio import Lock
+from contextlib import asynccontextmanager
+from itertools import cycle
+from typing import Any, AsyncIterator
+
+import structlog
+from sqlalchemy import select, text
+from sqlalchemy.ext.asyncio import AsyncConnection, AsyncEngine, create_async_engine
+
+from {{project_slug}}.db.config import DBConfig
+
+
+class PostgresConnectionManager:  # pylint: disable=too-many-instance-attributes
+    """Connection manager for PostgreSQL database"""
+
+    def __init__(  # pylint: disable=too-many-arguments
+        self,
+        master: DBConfig,
+        replicas: list[DBConfig] | None,
+        logger: structlog.stdlib.BoundLogger,
+        *,
+        engine_options: dict[str, Any] | None = None,
+        application_name: str | None = None,
+    ) -> None:
+        """Initialize connection manager entity."""
+        self._master_engine: AsyncEngine | None = None
+        self._replica_engines: list[AsyncEngine] = []
+        self._master = master
+        self._replicas = replicas or []
+        self._lock = Lock()
+        self._logger = logger
+        self._engine_options = engine_options or {}
+        self._application_name = application_name
+        # Iterator for round-robin through replicas
+        self._replica_cycle = None
+
+    async def update(  # pylint: disable=too-many-arguments
+        self,
+        *,
+        master: DBConfig | None = None,
+        replicas: list[DBConfig] | None = None,
+        logger: structlog.stdlib.BoundLogger | None = None,
+        application_name: str | None = None,
+        engine_options: dict[str, Any] | None = None,
+    ) -> None:
+        """Update connection manager parameters and refresh connection."""
+        self._master = master or self._master
+        self._replicas = replicas or self._replicas
+        self._logger = logger or self._logger
+        self._application_name = application_name or self._application_name
+        self._engine_options = engine_options or self._engine_options
+
+        if self.initialized:
+            await self.refresh()
+
+    @property
+    def initialized(self) -> bool:
+        return self._master_engine is not None
+
+    async def refresh(self, no_force_refresh: bool = False) -> None:
+        """Initialize or reinitialize connection engine.
+
+        Params:
+            no_force_refresh (bool): if set to True and ConnectionManager is already initialized,
+            no refresh is performed
+        """
+        async with self._lock:
+            if no_force_refresh and self.initialized:
+                return
+            await self.shutdown(use_lock=False)
+
+            await self._logger.ainfo(
+                "creating postgres master connection pool",
+                max_size=self._master.pool_size,
+                user=self._master.user,
+                host=self._master.host,
+                port=self._master.port,
+                database=self._master.database,
+            )
+            self._master_engine = create_async_engine(
+                f"postgresql+asyncpg://{self._master.user}:{self._master.password.get_secret_value()}"
+                f"@{self._master.host}:{self._master.port}/{self._master.database}",
+                future=True,
+                pool_size=max(1, self._master.pool_size - 5),
+                max_overflow=min(self._master.pool_size - 1, 5),
+                **self._engine_options,
+            )
+            try:
+                async with self._master_engine.connect() as conn:
+                    cur = await conn.execute(select(text("1")))
+                    assert cur.fetchone()[0] == 1
+            except Exception as exc:
+                self._master_engine = None
+                raise RuntimeError("something wrong with database connection, aborting") from exc
+
+            if len(self._replicas) > 0:
+                for replica in self._replicas:
+                    await self._logger.ainfo(
+                        "creating postgres readonly connection pool",
+                        max_size=replica.pool_size,
+                        user=replica.user,
+                        host=replica.host,
+                        port=replica.port,
+                        database=replica.database,
+                    )
+                    replica_engine = create_async_engine(
+                        f"postgresql+asyncpg://{replica.user}:{replica.password.get_secret_value()}@"
+                        f"{replica.host}:{replica.port}/{replica.database}",
+                        future=True,
+                        pool_size=max(1, self._master.pool_size - 5),
+                        max_overflow=min(self._master.pool_size - 1, 5),
+                        **self._engine_options,
+                    )
+                    try:
+                        async with replica_engine.connect() as conn:
+                            cur = await conn.execute(select(1))
+                            assert cur.fetchone()[0] == 1
+                            self._replica_engines.append(replica_engine)
+                    except Exception as exc:  # pylint: disable=broad-except
+                        await replica_engine.dispose()
+                        await self._logger.aexception("error connecting to replica", host=replica.host, error=repr(exc))
+
+            if self._replica_engines:
+                self._replica_cycle = cycle(self._replica_engines)
+            else:
+                self._replica_cycle = None
+                await self._logger.awarning("no available replicas, read queries will go to the master")
+
+    async def shutdown(self, use_lock: bool = True) -> None:
+        """Dispose connection pool and deinitialize. Can be called multiple times."""
+        if use_lock:
+            async with self._lock:
+                await self.shutdown(use_lock=False)
+                return
+
+        if self.initialized:
+            self._logger.info("shutting down postgres connection engine")
+            await self._master_engine.dispose()
+            self._master_engine = None
+            for engine in self._replica_engines:
+                await engine.dispose()
+            self._replica_engines.clear()
+
+    @asynccontextmanager
+    async def get_connection(self) -> AsyncIterator[AsyncConnection]:
+        """Get an async connection to the database with read-write ability."""
+        if not self.initialized:
+            await self.refresh(no_force_refresh=True)
+        async with self._master_engine.connect() as conn:
+            if self._application_name is not None:
+                await conn.execute(text(f'SET application_name TO "{self._application_name}"'))
+                await conn.commit()
+            yield conn
+
+    @asynccontextmanager
+    async def get_ro_connection(self) -> AsyncIterator[AsyncConnection]:
+        """Get an async connection to the database which can be read-only and will attempt to use replica instances
+        of the database."""
+        if not self.initialized:
+            await self.refresh(no_force_refresh=True)
+
+        # If there are no replicas, use master
+        if self._replica_cycle is None:
+            async with self.get_connection() as conn:
+                yield conn
+            return
+
+        # Select the next replica (round-robin), `self._replica_cycle` is guaranteed to have values here
+        engine = next(self._replica_cycle)  # pylint: disable=stop-iteration-return
+        conn = None
+        try:
+            conn = await engine.connect()
+            if self._application_name is not None:
+                await conn.execute(text(f'SET application_name TO "{self._application_name}"'))
+                await conn.commit()
+        except Exception as exc:  # pylint: disable=broad-except
+            if conn is not None:
+                try:
+                    conn.close()
+                except Exception:  # pylint: disable=broad-except
+                    pass
+            await self._logger.awarning(
+                "error connecting to replica, falling back to master", error=repr(exc), error_type=type(exc).__name__
+            )
+            # On exception from replica fallback to master connection
+            async with self.get_connection() as conn:
+                yield conn
+            return
+
+        try:
+            yield conn
+        finally:
+            await conn.close()

{{project_slug}}/db/migrator/env.py.jinja

@@ -0,0 +1,96 @@
+# pylint: disable=wrong-import-position
+"""Environment preparation for Alembic is performed here."""
+
+import asyncio
+import os
+from logging.config import fileConfig
+
+from alembic import context
+from dotenv import load_dotenv
+from sqlalchemy import pool
+from sqlalchemy.engine import Connection
+from sqlalchemy.ext.asyncio import async_engine_from_config
+
+from {{project_slug}}.config import {{ProjectName}}Config
+from {{project_slug}}.db import DeclarativeBase
+from {{project_slug}}.db.entities import *  # pylint: disable=wildcard-import,unused-wildcard-import
+
+envfile_path = os.environ.get("ENVFILE", ".env")
+if os.path.isfile(envfile_path):
+    try:
+        load_dotenv(envfile_path)
+    except Exception as exc:
+        print(f"Got an error while loading envfile '{envfile_path}': {exc!r}")
+config = context.config
+section = config.config_ini_section
+
+app_settings = {{ProjectName}}Config.from_file(os.getenv("CONFIG_PATH"))
+
+config.set_section_option(section, "POSTGRES_DB", app_settings.db.master.database)
+config.set_section_option(section, "POSTGRES_HOST", app_settings.db.master.host)
+config.set_section_option(section, "POSTGRES_USER", app_settings.db.master.user)
+config.set_section_option(section, "POSTGRES_PASSWORD", app_settings.db.master.password.get_secret_value())
+config.set_section_option(section, "POSTGRES_PORT", str(app_settings.db.master.port))
+
+
+fileConfig(config.config_file_name, disable_existing_loggers=False)
+target_metadata = DeclarativeBase.metadata
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection: Connection) -> None:
+    context.configure(connection=connection, target_metadata=target_metadata)
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations() -> None:
+    """In this scenario we need to create an Engine
+    and associate a connection with the context.
+    """
+
+    connectable = async_engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    async with connectable.connect() as connection:
+        await connection.run_sync(do_run_migrations)
+
+    await connectable.dispose()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode."""
+
+    asyncio.run(run_async_migrations())
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

{{project_slug}}/db/migrator/script.py.mako

@@ -0,0 +1,27 @@
+# pylint: disable=no-member,invalid-name,missing-function-docstring,too-many-statements
+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    ${downgrades if downgrades else "pass"}