feat(database): add managed backup and offline restore (#6359)

app/application/backup.py

@@ -0,0 +1,176 @@
+"""数据库备份与离线还原用例。"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from datetime import datetime, timedelta
+from pathlib import Path
+from typing import Callable, Protocol
+
+from app.adapters.system.backup.files import BackupFiles
+from app.runtime.log import logger
+
+
+@dataclass(frozen=True, slots=True)
+class BackupPolicy:
+    """一次备份操作使用的目录与保留策略快照。"""
+
+    root: Path
+    retention_days: int = 0
+    max_count: int = 0
+
+    def __post_init__(self) -> None:
+        if self.retention_days < 0 or self.max_count < 0:
+            raise ValueError("数据库备份保留策略不能使用负数")
+
+
+@dataclass(frozen=True, slots=True)
+class BackupArtifact:
+    """一个已完成校验并发布的数据库备份文件。"""
+
+    name: str
+    db_type: str
+    created_at: datetime
+    path: Path
+    size: int
+
+
+@dataclass(frozen=True, slots=True)
+class BackupVerification:
+    """数据库备份文件的基础内容校验结果。"""
+
+    valid: bool
+    method: str
+    detail: str | None = None
+
+
+class BackupCheck(Protocol):
+    """数据库适配器校验结果的结构合同。"""
+
+    valid: bool
+    method: str
+    detail: str | None
+
+
+class DatabaseBackupBackend(Protocol):
+    """活动数据库创建、校验和离线还原所需的最小技术端口。"""
+
+    db_type: str
+    suffix: str
+
+    def create(self, destination: Path) -> None:
+        """把活动数据库的一致快照写入目标文件。"""
+
+    def verify(self, artifact: Path) -> BackupCheck:
+        """在不修改数据库的前提下校验备份文件。"""
+
+    def restore(self, artifact: Path) -> None:
+        """把已校验制品还原到离线目标数据库。"""
+
+
+class DatabaseBackupService:
+    """管理单文件数据库备份及明确的离线还原操作。"""
+
+    def __init__(
+        self,
+        *,
+        backend: DatabaseBackupBackend,
+        policy_reader: Callable[[], BackupPolicy],
+        clock: Callable[[], datetime] = datetime.now,
+    ) -> None:
+        self._backend = backend
+        self._policy_reader = policy_reader
+        self._clock = clock
+
+    def create(self) -> BackupArtifact:
+        """创建、校验并发布一个在线一致快照。"""
+        policy = self._policy_reader()
+        files = BackupFiles(policy.root)
+        created_at = self._clock()
+        name = files.available_name(
+            db_type=self._backend.db_type,
+            created_at=created_at,
+            suffix=self._backend.suffix,
+        )
+        temporary = files.create_temporary(self._backend.suffix)
+        try:
+            self._backend.create(temporary)
+            verification = self._backend.verify(temporary)
+            if not verification.valid:
+                detail = f"：{verification.detail}" if verification.detail else ""
+                raise RuntimeError(
+                    f"数据库备份校验失败（{verification.method}）{detail}"
+                )
+            path = files.publish(temporary, name)
+        except Exception:
+            files.discard(temporary)
+            raise
+
+        artifact = self._artifact(path, created_at=created_at)
+        self._prune(files, policy, keep=artifact.name)
+        logger.info(
+            f"数据库备份完成：文件={artifact.name}，类型={artifact.db_type}，"
+            f"大小={artifact.size} bytes"
+        )
+        return artifact
+
+    def list(self) -> tuple[BackupArtifact, ...]:
+        """按创建时间倒序列出受管数据库备份文件。"""
+        files = BackupFiles(self._policy_reader().root)
+        return tuple(self._artifact(path) for path in files.list())
+
+    def verify(self, name: str) -> BackupVerification:
+        """按文件名校验一个受管数据库备份。"""
+        path = BackupFiles(self._policy_reader().root).resolve(name)
+        self._require_matching_type(path)
+        result = self._backend.verify(path)
+        return BackupVerification(result.valid, result.method, result.detail)
+
+    def restore(self, name: str) -> BackupArtifact:
+        """校验后将受管制品还原到当前 CLI 解析出的离线数据库目标。"""
+        path = BackupFiles(self._policy_reader().root).resolve(name)
+        self._require_matching_type(path)
+        verification = self._backend.verify(path)
+        if not verification.valid:
+            detail = f"：{verification.detail}" if verification.detail else ""
+            raise RuntimeError(
+                f"数据库备份校验失败（{verification.method}）{detail}"
+            )
+        self._backend.restore(path)
+        logger.info(
+            f"数据库离线还原完成：文件={path.name}，类型={self._backend.db_type}"
+        )
+        return self._artifact(path)
+
+    def _prune(self, files: BackupFiles, policy: BackupPolicy, *, keep: str) -> None:
+        """新备份发布成功后按天数或份数清理同一目录中的旧文件。"""
+        cutoff = (
+            self._clock() - timedelta(days=policy.retention_days)
+            if policy.retention_days > 0
+            else None
+        )
+        for index, path in enumerate(files.list()):
+            if path.name == keep:
+                continue
+            created_at = files.created_at(path.name)
+            expired = cutoff is not None and created_at < cutoff
+            exceeds_count = policy.max_count > 0 and index >= policy.max_count
+            if expired or exceeds_count:
+                files.delete(path.name)
+
+    def _require_matching_type(self, path: Path) -> None:
+        db_type = BackupFiles.database_type(path.name)
+        if db_type != self._backend.db_type:
+            raise ValueError(
+                f"备份类型 {db_type} 与当前数据库类型 {self._backend.db_type} 不一致"
+            )
+
+    @staticmethod
+    def _artifact(path: Path, *, created_at: datetime | None = None) -> BackupArtifact:
+        return BackupArtifact(
+            name=path.name,
+            db_type=BackupFiles.database_type(path.name),
+            created_at=created_at or BackupFiles.created_at(path.name),
+            path=path,
+            size=path.stat().st_size,
+        )