feat: capacity resilience — ordered subnet/AZ + instance-type fallback#53
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…nstance types A single subnet-id + ec2-instance-type is a single point of failure: when that AZ has no capacity for that type, RunInstances fails and the whole workflow with it. Both inputs now accept comma-separated ordered fallback lists (single values behave byte-identically): ec2-instance-type: c7i.4xlarge,c6i.4xlarge,m7i.4xlarge subnet-id: subnet-aaa,subnet-bbb # different AZs - launchWithFallback walks type × subnet in order — every subnet/AZ is tried before downgrading the instance type (placement is cheaper than a hardware change). Capacity errors advance the chain; non-capacity errors (invalid AMI, auth, quota InstanceLimitExceeded) abort immediately so a misconfig doesn't burn the whole matrix; transient API errors retry within the cell. - classifyRunError buckets RunInstances errors into capacity / transient / fatal (spot capacity codes already included for #39). - retry.js withRetry gains an optional shouldRetry predicate (default unchanged), so a cell retries only transient errors. - New outputs instance-type-used / subnet-id-used report what actually launched. - Each failed placement logs a warn line (type, subnet, code); exhaustion fails with a summary of every attempt. Tests: classifyRunError buckets, launchWithFallback ordering (first-try, mid- chain, full-matrix exhaustion, fatal-abort, quota message), parseCsv, and withRetry shouldRetry (142 tests total). README "Capacity fallback" section + inputs/outputs tables and action.yml updated. Note: spot × fallback composition lands with #39 (spot support); the capacity codes and chain are already spot-ready. Closes #40 Signed-off-by: kurok <22548029+kurok@users.noreply.github.com>
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Closes #40 — roadmap (#49) Phase 1. Multiplies the value of spot (#39); independent of it for on-demand users.
Problem
One
subnet-id+ oneec2-instance-type= single point of failure. When that AZ has no capacity for that type (routine for larger/GPU types),RunInstancesfails and the workflow fails with it. Capacity errors are retriable placement problems — the action should own the retry.Solution
Both inputs accept comma-separated ordered fallback lists (single values behave byte-identically):
InsufficientInstanceCapacity,InsufficientHostCapacity,Unsupported, …) → advance to the next cell.InstanceLimitExceeded) → abort immediately so a misconfig doesn't burn the whole matrix; quota gets a targeted message.withRetry's newshouldRetrypredicate.Outputs
New
instance-type-used/subnet-id-usedreport what actually launched.Tests / build
tests/fallback.test.js:classifyRunErrorbuckets +launchWithFallbackordering — first-try success, mid-chain success (exact subnet-first-then-type call order), full-matrix exhaustion summary, fatal-abort, quota message. PlusparseCsvandwithRetryshouldRetry. 142 tests pass (was 128). Lint clean, dist rebuilt (verify-dist green).Wall-clock bound
Capacity errors advance without per-cell retry; only transient errors retry (bounded by
retry.js). A 9-cell chain of fast capacity rejections resolves in seconds, not minutes.Note on spot
Spot × fallback composition (run the chain for spot, then on-demand) lands with #39; the capacity codes and chain structure are already spot-ready. This PR is complete for on-demand.
Compatibility
Single-value
ec2-instance-type/subnet-idinputs collapse to a one-cell chain — byte-identical to today.