nl2sql

Error Handling + Circuit Breaker

NL2SQL represents failures as structured PipelineError objects and propagates them through state. Retries are managed at the subgraph level, and a single circuit breaker provides fast-fail safety for vector retrieval.

Error contract

PipelineError includes:

• node, message, severity, error_code
• is_retryable derived from severity and error code

Common error codes include MISSING_SQL, EXECUTION_FAILED, PIPELINE_TIMEOUT, SECURITY_VIOLATION.

Circuit breaker

create_breaker() configures pybreaker.CircuitBreaker instances with observability hooks. The system defines exactly one:

• VECTOR_BREAKER (fail_max=5, reset_timeout=30)

Retrieval calls in VectorStore are wrapped with VECTOR_BREAKER. It is the only breaker instance the system defines: LLM calls and SQL execution are not breaker-guarded, and their failures surface as PipelineError values in state.

Failure flow

flowchart TD
    Node[Pipeline Node] --> Error[PipelineError]
    Error --> State[GraphState.errors]
    State --> Retry{is_retryable?}
    Retry -->|yes| Refine[RefinerNode / retry loop]
    Retry -->|no| Stop[Terminate branch]

See ../architecture/failure_recovery.md for failure domains, retry scope, and recovery limitations.

Cancellation and timeouts

• run_with_graph() enforces a global timeout (Settings.global_timeout_sec).
• Cancellation is honored through a per-run nl2sql.common.cancellation.CancellationToken, passed to the graph via config["configurable"]["cancellation_token"], so cancelling one run never affects another.

Source references

• Error contracts: packages/nl2sql/src/nl2sql/common/errors.py
• Circuit breaker: packages/nl2sql/src/nl2sql/common/resilience.py
• Retry logic: packages/nl2sql/src/nl2sql/pipeline/subgraphs/sql_agent.py
• Cancellation: packages/nl2sql/src/nl2sql/common/cancellation.py

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