Implement RetryPolicy Trait and DefaultRetryPolicy

[unclesp1d3r]

Implement RetryPolicy Trait and DefaultRetryPolicy

Overview

Create retry policy abstraction with hardcoded v1.0 defaults for per-query retry behavior. This enables transient error recovery while avoiding retry storms on permission errors.

Scope

What's Included:

• Define RetryPolicy trait in new file file:dbsurveyor-core/src/adapters/retry.rs:
  • should_retry(&self, category: ErrorCategory, attempt: u32) -> bool
  • backoff_duration(&self, attempt: u32) -> Duration
  • Trait must be Send + Sync for async compatibility
• Implement DefaultRetryPolicy with hardcoded constants:
  • MAX_ATTEMPTS = 3
  • BASE_BACKOFF_MS = 500
  • MAX_BACKOFF_MS = 5000
  • Jitter: random ±100-300ms using rand crate
• Retry decision logic:
  • Return true for ErrorCategory::Timeout, ErrorCategory::Connection, ErrorCategory::Other if attempt < MAX_ATTEMPTS
  • Return false for ErrorCategory::Permission, ErrorCategory::NotFound (never retry)
• Exponential backoff calculation: min(BASE_BACKOFF_MS * 2^attempt + random_jitter(), MAX_BACKOFF_MS)
• Unit tests for retry decision logic covering all error categories
• Unit tests for backoff calculation (verify exponential growth and cap)
• Re-export from file:dbsurveyor-core/src/adapters/mod.rs

What's Explicitly Out:

• Configurable retry parameters (deferred to v1.1+)
• Adapter-specific retry policies (use DefaultRetryPolicy for all adapters in v1.0)
• Actual integration into adapter query execution (handled in ticket:de2eeeb8-bfeb-4a11-98aa-84efc70568b2/6)

Retry Logic Flow

sequenceDiagram
    participant Adapter
    participant RetryPolicy
    participant Database

    Adapter->>Database: Execute query (attempt 1)
    Database-->>Adapter: Timeout error
    Adapter->>RetryPolicy: should_retry(Timeout, 1)?
    RetryPolicy-->>Adapter: true
    Adapter->>RetryPolicy: backoff_duration(1)
    RetryPolicy-->>Adapter: 500ms + jitter
    Adapter->>Adapter: Wait 500ms
    Adapter->>Database: Execute query (attempt 2)
    Database-->>Adapter: Permission denied
    Adapter->>RetryPolicy: should_retry(Permission, 2)?
    RetryPolicy-->>Adapter: false (never retry permission)
    Adapter-->>Adapter: Record failure with retry_attempts=2

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Acceptance Criteria

• RetryPolicy trait compiles and is Send + Sync
• DefaultRetryPolicy returns correct retry decisions for all ErrorCategory variants
• Permission errors (ErrorCategory::Permission) are never retried
• Transient errors (Timeout, Connection) are retried up to 3 attempts
• Backoff duration respects max cap (5000ms) and includes jitter
• Unit tests cover edge cases: attempt 0, max attempts reached, all error categories
• Jitter is random and within ±100-300ms range (verified statistically in tests)

References

• Spec: spec:de2eeeb8-bfeb-4a11-98aa-84efc70568b2/820ca524-8c7d-4939-8097-f1158e7d67ea (Tech Plan - RetryPolicy Trait section)
• Core Flows: spec:de2eeeb8-bfeb-4a11-98aa-84efc70568b2/661dbe3d-b679-4287-991e-26f4a0dd98b9 (Flow 6 - retry transient errors)

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🔗 Related PRs

#51 - feat(collector): implement unified database adapters with feature flag architecture for all 6 database engines [merged]

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