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backendcritical PriorityID: pg17-combinebackup-manifest-sequencing-guardrail

PostgreSQL 17 pg_combinebackup Block Invariant and Manifest LSN Sequencing

Enforces strict monotonic LSN and manifest checksum validation across distributed storage tiers when constructing backup chains for PostgreSQL 17 native incremental backups. Prevents block-level corruption and divergence during synthetic full reconstruction via pg_combinebackup under concurrent WAL archiving and tier migration.

Prohibited Anti-Pattern: Unordered Manifest Ingestion and LSN Window Gaps in Synthetic Full Backup Assembly

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---
description: PostgreSQL 17 pg_combinebackup Block Invariant and Manifest LSN Sequencing - Enforces strict monotonic LSN and manifest checksum validation across distributed storage tiers when constructing backup chains for PostgreSQL 17 native incremental backups. Prevents block-level corruption and divergence during synthetic full reconstruction via pg_combinebackup under concurrent WAL archiving and tier migration.
globs: src/storage/**/*.ts, src/backup/**/*.ts, src/services/dr/**/*.ts
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/pg17-combinebackup-manifest-sequencing-guardrail"
---

# PostgreSQL 17 pg_combinebackup Block Invariant and Manifest LSN Sequencing

> **Severity**: CRITICAL | **Category**: backend
> **Anti-Pattern Warning**: Unordered Manifest Ingestion and LSN Window Gaps in Synthetic Full Backup Assembly

## System Constraints
You are a Principal Database Infrastructure Engineer enforcing PostgreSQL 17 native incremental backup invariants. You MUST mandate strict backup manifest validation, contiguous LSN chain verification, and atomic locking before orchestrating synthetic full backup reconstruction using pg_combinebackup across distributed or tiered storage volumes.

## Strict Guidelines
- Engineers MUST ALWAYS verify that the `backup_manifest` of each incremental tier reflects a strictly monotonic start-LSN matching the preceding backup's checkpoint/stop-LSN before executing `pg_combinebackup`.
- Engineers MUST NOT allow concurrent WAL archive truncation or timeline switches to bypass manifest checksum and block-map validation during synthetic full consolidation.
- Code SHOULD enforce SHA-256 manifest integrity verification and validate system identifier parity across all input backup directories prior to invoking consolidation routines.
- Services MUST acquire distributed fencing tokens (e.g., via Raft/etcd) over the backup chain IDs to prevent race conditions during concurrent WAL archival and basebackup rotations.
- Components NEVER execute `pg_combinebackup` against partial, in-flight, or unverified backup manifests residing across disparate object-storage staging tiers.

## Bad vs Good Implementations
### Manifest Chain Continuity and pg_combinebackup Invariant Verification

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Directly invokes pg_combinebackup without parsing backup_manifest files, validating contiguous LSN bounds (start LSN == prior stop LSN), or checking manifest checksums. Concurrent WAL archiving or reordered tiers will cause undetected block divergence or hard reconstruction failure.
```typescript
import { exec } from 'node:child_process';
import { promisify } from 'node:util';

const execAsync = promisify(exec);

interface BackupTier {
  id: string;
  path: string;
}

export async function assembleSyntheticFull(tiers: BackupTier[], targetDir: string): Promise<void> {
  // Flaw: Sorts paths arbitrarily without parsing manifest LSNs or validating checksums
  const inputDirs = tiers.map((t) => t.path).join(' ');
  
  // Blindly triggers pg_combinebackup with unverified LSN continuity
  await execAsync(`pg_combinebackup ${inputDirs} -o ${targetDir}`);
}
```

#### Production Standard (Correct)
> **Standard**: Parses each backup tier's manifest, verifies PostgreSQL 17 manifest compatibility, ensures identical system identifiers and timelines, validates that every incremental step begins exactly where the previous tier ended, and executes pg_combinebackup using safe argument vectors.
```typescript
import { execFile } from 'node:child_process';
import { promisify } from 'node:util';
import * as fs from 'node:fs/promises';
import * as path from 'node:path';

const execFileAsync = promisify(execFile);

export interface BackupManifest {
  'PostgreSQL-Backup-Manifest-Version': number;
  'System-Identifier': string;
  'Files': Record<string, { size: number; checksum: string }>;
  'WAL-Ranges': Array<{ 'Timeline': number; 'Start-LSN': string; 'End-LSN': string }>;
  'Manifest-Checksum': string;
}

export interface ValidatedBackupTier {
  id: string;
  path: string;
  systemIdentifier: string;
  startLsn: bigint;
  endLsn: bigint;
  timeline: number;
}

export function parseLsn(lsn: string): bigint {
  const [hi, lo] = lsn.split('/').map((seg) => BigInt(`0x${seg}`));
  return (hi << 32n) | lo;
}

export async function validateAndAssembleSyntheticFull(
  tierPaths: string[],
  targetDir: string
): Promise<void> {
  const parsedTiers: ValidatedBackupTier[] = [];

  for (const dir of tierPaths) {
    const manifestPath = path.join(dir, 'backup_manifest');
    const rawManifest = await fs.readFile(manifestPath, 'utf8');
    const manifest: BackupManifest = JSON.parse(rawManifest);

    if (manifest['PostgreSQL-Backup-Manifest-Version'] !== 1) {
      throw new Error(`Unsupported manifest version in tier: ${dir}`);
    }

    const walRange = manifest['WAL-Ranges'][0];
    if (!walRange) {
      throw new Error(`Missing WAL range metadata in manifest for ${dir}`);
    }

    parsedTiers.push({
      id: path.basename(dir),
      path: dir,
      systemIdentifier: manifest['System-Identifier'],
      startLsn: parseLsn(walRange['Start-LSN']),
      endLsn: parseLsn(walRange['End-LSN']),
      timeline: walRange.Timeline,
    });
  }

  // Sort strictly by ascending start LSN
  parsedTiers.sort((a, b) => (a.startLsn < b.startLsn ? -1 : a.startLsn > b.startLsn ? 1 : 0));

  const sysId = parsedTiers[0]?.systemIdentifier;
  for (let i = 0; i < parsedTiers.length; i++) {
    const current = parsedTiers[i];
    if (current.systemIdentifier !== sysId) {
      throw new Error(`System identifier mismatch: ${current.systemIdentifier} !== ${sysId}`);
    }
    if (i > 0) {
      const previous = parsedTiers[i - 1];
      if (current.timeline !== previous.timeline) {
        throw new Error(`Timeline divergence between tiers ${previous.id} and ${current.id}`);
      }
      if (current.startLsn !== previous.endLsn) {
        throw new Error(`LSN gap detected: Tier ${current.id} start ${current.startLsn} !== prev end ${previous.endLsn}`);
      }
    }
  }

  const sortedDirs = parsedTiers.map((t) => t.path);
  await execFileAsync('pg_combinebackup', [...sortedDirs, '-o', targetDir]);
}
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

PostgreSQL Manifest Validator MCP
Model Context Protocol server for inspecting pg_combinebackup manifests, LSN boundaries, and WAL timelines directly from storage tiers.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Postgres Combinebackup Automation Skill
CLI automation skill providing verified execution environments and checksum verification for PostgreSQL 17 incremental backup pipelines.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: PostgreSQL 17 pg_combinebackup Block Invariant and Manifest LSN Sequencing

PostgreSQL 17 pg_combinebackup Block Invariant and Manifest LSN Sequencing defines an industrial-grade behavioral standard for backend engineering. Enforces strict monotonic LSN and manifest checksum validation across distributed storage tiers when constructing backup chains for PostgreSQL 17 native incremental backups. Prevents block-level corruption and divergence during synthetic full reconstruction via pg_combinebackup under concurrent WAL archiving and tier migration. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Unordered Manifest Ingestion and LSN Window Gaps in Synthetic Full Backup Assembly Without an explicit system instruction file, developers spend hours debugging silent failures.
Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftUnordered Manifest Ingestion and LSN Window Gaps in Synthetic Full Backup AssemblyCritical
Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production.
Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture InconsistencyAI assistants produce mixed paradigms across files, creating fragmented codebase conventions.Medium
Increases cognitive load during code reviews and leads to maintenance debt across engineering teams.
Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.
Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

1

Engineers MUST ALWAYS verify that the `backup_manifest` of each incremental tier reflects a strictly monotonic start-LSN matching the preceding backup's checkpoint/stop-LSN before executing `pg_combinebackup`.

Engineers MUST ALWAYS verify that the `backup_manifest` of each incremental tier reflects a strictly monotonic start-LSN matching the preceding backup's checkpoint/stop-LSN before executing `pg_combinebackup`.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Engineers MUST NOT allow concurrent WAL archive truncation or timeline switches to bypass manifest checksum and block-map validation during synthetic full consolidation.

Engineers MUST NOT allow concurrent WAL archive truncation or timeline switches to bypass manifest checksum and block-map validation during synthetic full consolidation.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Code SHOULD enforce SHA-256 manifest integrity verification and validate system identifier parity across all input backup directories prior to invoking consolidation routines.

Code SHOULD enforce SHA-256 manifest integrity verification and validate system identifier parity across all input backup directories prior to invoking consolidation routines.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Services MUST acquire distributed fencing tokens (e.g., via Raft/etcd) over the backup chain IDs to prevent race conditions during concurrent WAL archival and basebackup rotations.

Services MUST acquire distributed fencing tokens (e.g., via Raft/etcd) over the backup chain IDs to prevent race conditions during concurrent WAL archival and basebackup rotations.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

Components NEVER execute `pg_combinebackup` against partial, in-flight, or unverified backup manifests residing across disparate object-storage staging tiers.

Components NEVER execute `pg_combinebackup` against partial, in-flight, or unverified backup manifests residing across disparate object-storage staging tiers.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is PostgreSQL 17 pg_combinebackup Block Invariant and Manifest LSN Sequencing critical for AI coding assistants?

Enforces strict monotonic LSN and manifest checksum validation across distributed storage tiers when constructing backup chains for PostgreSQL 17 native incremental backups. Prevents block-level corruption and divergence during synthetic full reconstruction via pg_combinebackup under concurrent WAL archiving and tier migration. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Unordered Manifest Ingestion and LSN Window Gaps in Synthetic Full Backup Assembly) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q:Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q:Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

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