Failover¶
Switch a protected function from a failed primary path to a prepared alternate so continuity is preserved.
The Diagnostic Story¶
Symptom: A system depends on one primary path—a component, channel, provider, person, or site—and when that path fails or degrades, the essential function stops. There is no prepared alternate; or an alternate exists but has never been activated; or no one is sure who owns the function if the primary is unavailable. Continuity requires the primary to always work, which means any failure becomes a full outage.
Pivot: Prepare an alternate path capable of assuming the protected function, instrument the primary so failure or degradation is detectable, transfer flow and authority to the alternate when triggered, and preserve enough state and context for the alternate to operate safely. Manage recovery or failback according to an explicit policy.
Resolution: The protected function continues through the alternate with bounded disruption and preserved integrity. Ownership is unambiguous, in-flight work is handled safely, and the system can return to the primary—or remain on the alternate—through a governed process that does not corrupt state.
Reach for this when you hear…¶
[database reliability] “We have a replica in another region, but we've never actually promoted it—if the primary goes down tonight, nobody knows the exact steps and the replica might be hours behind.”
[power infrastructure] “The backup generator is tested once a year, but the transfer switch hasn't been exercised under real load, so I'm not confident it'll take over cleanly when we need it.”
[organizational succession] “Our director is the only person with signing authority for contracts over fifty thousand, and there's no named deputy—if she's unreachable we're just stuck.”
When This Archetype Applies¶
Complete catalog groundingAt least one sufficient condition set is fully represented by existing primes or domain-specific abstractions.
Diagnostic problem
Essential function depends on a vulnerable primary path whose failure or degradation would interrupt service.
Show the applicability expression
Applicability expression1 distinct condition
groundedpartly groundedopen
1 condition, all required.
1Required in every casenumbered 1–1
These hold no matter which pattern applies.
Essential single point · grounded
A primary component, path, authority, provider, channel, or process is a single point of interruption for essential function.
This proposition-sized condition was conservatively reconstructed from the authored essence_one_line, compression_statement, components fields; the source file was not modified. In this condition set, the requirement is: A primary component, path, authority, provider, channel, or process is a single point of interruption for essential function.
Other requirements and context (1)
Why these sit outside the expression
Solution feasibility — it describes whether the intervention can work, not whether the diagnostic problem exists.
Solution feasibilityAn alternate path can assume the protected function when the primary is unavailable.
This proposition-sized condition was conservatively reconstructed from the authored essence_one_line, compression_statement, components fields; the source file was not modified. In this archetype, the relevant feasibility condition is: An alternate path can assume the protected function when the primary is unavailable. It identifies something that must be possible or available for the intervention to be workable.
Coverage
1 of 1 conditions grounded.
Related Abstractions¶
Abstractions this archetype builds on — directly (a source ingredient) or as a related pattern. Links follow the typed catalog namespace.
Built directly on (8)
- Alternate Path
- Controlled Reentry: Re-establishing a suspended activity or state through staged, monitored steps with the capacity to abort, because returning to normal is a separate engineered process and not a simple reversal of the exit.
- Health Check
- Observability: Infer internal state externally.
- Recovery Policy
- Redundancy: Duplicate critical components.
- State Synchronization
- Switching Rule
Also references 11 related abstractions
- Boundary: Defines system limits.
- Coupling: Interdependence among subsystems.
- Data Integrity: Accuracy and consistency preserved.
- Fault Tolerance: Continue operating under failure.
- Flow: Structured movement of energy, matter, or information.
- Resilience: Absorb shocks and adapt.
- Resource Management: Allocation of finite assets.
- Robustness: Maintain functionality under stress.
- State and State Transition: Captures system condition and evolution.
- Threshold: Safe vs harmful levels.
Variants¶
Narrower or domain-specific specializations that share this archetype's core structure. Recognized variants are established; candidate variants are provisional.
Primary / Secondary Switchover · implementation variant · recognized
Switch from a primary component, route, or actor to a prepared secondary alternative when the primary fails.
When A Manually Selected Access Path Fails Authorization · implementation variant · recognized
When a manually selected access path fails authorization, add that path to an exclusion set and retry selection among the remaining paths rather than repeating the forbidden choice.
Editorial Notes¶
Problem Classification¶
Classification: Fragility, Failure & Continuity Risk → Fault Containment & Bounded Service Loss
Problem kernel: primary-path failure eliminates service without alternate activation
Rationale: Both reviewers locate the same failure: loss of one primary path can eliminate the protected function because no prepared alternate activates to preserve essential service. Common-mode dependency is nearest when nominally plural alternatives share one upstream cause; failover first concerns whether a local failure remains bounded and an independent alternate can assume the function.
Boundary considered: Fragility, Failure & Continuity Risk → Dependency Concentration & Common-Mode Loss
Why this classification prevailed: Fault containment governs alternate activation after a local primary failure; common-mode loss governs multiple supposed alternatives failing together from shared dependence.
Review outcome: Reconciled after independent review; high confidence.