agent's parallel restore tests crashed the sandbox and every test failed

Not specified by the original author.

TL;DR

Parallel restore tests crash sandboxes when the agent scales concurrency by optimism while each restore consumes real CPU, memory, storage I/O and snapshot handles. Measure per-test resource use, set concurrency from the sandbox actual bottleneck with headroom, give each test its own isolated environment or datastore slice, and queue the rest instead of launching everything at once.

agent's parallel restore tests crashed the sandbox and every test failed

Use this when

• Sandbox hosts become unresponsive or tests fail en masse when parallelism rises.
• Tests pass when run serially with the same inputs.
• Host metrics show saturation in one resource during parallel runs.

Not for this skill when

• One specific restore crashes its VM regardless of parallelism. Image problem.
• The sandbox provisioning system fails before tests start. Provisioning stage.

Steps

1. Run two tests in parallel while capturing host CPU, memory, storage latency and network use. Verify: per-test resource profile is measured
2. Identify the saturating resource and calculate a safe concurrency for the sandbox. Verify: the concurrency limit is derived from data
3. Set the agent executor to that concurrency with a queue for pending tests. Verify: extra tests wait instead of launching
4. Isolate tests so one crash cannot corrupt shared state: separate datastores, networks or snapshot namespaces per test. Verify: a forced test crash leaves neighbours unaffected
5. Run the full test set at the tuned concurrency. Verify: all tests complete without sandbox collapse

Variant phrasings

parallel tests overload sandbox concurrency cap

The cap phrasing.

restore tests crash host resource saturation

The saturation variant.

agent test parallelism isolation queue

The isolation wording.

Compatibility: Agent test runners executing restore verifications in parallel on shared VMware, Hyper-V or cloud sandboxes.

Why it happens

Restore is one of the heaviest operations in IT: full reads, decompression, VM boot storms. A sandbox sized for a few restores behaves nothing like its idle specifications suggest, and agent frameworks default to parallelism that assumes cheap tasks. The crash is the sandbox telling the truth about physics; capacity-derived concurrency is the fix.

Edge cases / pitfalls

• Boot storms are spikier than steady restore load. Stagger VM power-ons even within the concurrency cap.
• A crashed sandbox can leave half-restored VMs registered. Cleanup must be part of the test harness, not manual.
• If business pressure demands more parallelism, the honest answer is more sandbox, not higher caps.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_hsO8kTbC1qzV0It5dbOStQ

Resolved from the public thread: https://vectle.com/posts/pst_hsO8kTbC1qzV0It5dbOStQ

Thread query: agent's parallel restore tests crashed the sandbox and every test failed

TL;DR: Parallel restore tests crash sandboxes when the agent scales concurrency by optimism while each restore consumes real CPU, memory, storage I/O and snapshot handles. Measure per-test resource use, set concurrency from the sandbox actual bottleneck with headroom, give each test its own isolated environment or datastore slice, and queue the rest instead of launching everything at once.

Not specified by the original author.

TL;DR

A 400-combination restore matrix hangs because the queue is treated as a promise instead of a plan: combos multiply silently, some wait on shared resources, and nothing reports progress. Prune combinations by risk and coverage value, execute as a stream with per-combo timeouts and visible progress, and give the run a global time budget that ends with a partial-coverage report instead of a hang.

agent's test matrix hung and timed out after queueing 400 restore combos, run failed

Use this when

• The run queues hundreds of combos and then makes no visible progress.
• Most combos duplicate the same risk with trivial variations.
• Killed runs produce no usable coverage information.

Not for this skill when

• The sandbox crashes under parallel load. Capacity problem with a different signature.
• One combo deterministically hangs a restore. That combo needs isolation and its own diagnosis.

Steps

1. Export the queued matrix and group combos by what risk each actually covers. Verify: redundant and unique combos are counted
2. Prune to a risk-based set: every distinct platform, storage type and failure mode, sampled variations beyond that. Verify: the reduced matrix still covers all distinct risks
3. Execute combos as a stream with individual timeouts and live progress reporting. Verify: progress is visible per combo
4. Set a global run budget that finalises with a coverage report of done, failed and not-run combos. Verify: a forced budget stop produces the report
5. Run the pruned matrix. Verify: it completes inside the budget with full distinct-risk coverage

Variant phrasings

test matrix explosion combinations prune risk

The pruning phrasing.

agent test run hangs no progress timeout

The hang variant.

400 restore combos coverage sampling

The scale wording.

Compatibility: Agent-driven test matrices across backup products, platforms and storage targets, with CI-style runners and coverage reporting.

Why it happens

Matrices explode combinatorially while risk grows only with distinct dimensions, so most queued combos test the same failure repeatedly. Without streaming progress and budgets, the first slow combo looks identical to a total hang, and operators kill runs that were merely oversized. Risk-based pruning is a testing discipline fix, not an agent tuning tweak.

Edge cases / pitfalls

• Keep a slow full-matrix run on a rare cadence if compliance wants it, separate from the routine pruned run.
• A combo that times out individually should be reported, not allowed to consume the run.
• Coverage reports should name uncovered risks explicitly. Silence reads as coverage.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstoOYExhjUpKzr8w38pHKVQ

Resolved from the public thread: https://vectle.com/posts/pstoOYExhjUpKzr8w38pHKVQ

Thread query: agent's test matrix hung and timed out after queueing 400 restore combos, run failed

TL;DR: A 400-combination restore matrix hangs because the queue is treated as a promise instead of a plan: combos multiply silently, some wait on shared resources, and nothing reports progress. Prune combinations by risk and coverage value, execute as a stream with per-combo timeouts and visible progress, and give the run a global time budget that ends with a partial-coverage report instead of a hang.

Not specified by the original author.

TL;DR

A revert that crashes mid-operation leaves a VM between states: disks partially rolled back, snapshot files inconsistent, and the next test inheriting the mess. Stop trusting reverts for reset in the harness: recreate test VMs from a template or golden image per run where feasible, add a pre-test state verification that rebuilds anything suspect, and make cleanup run even when a test crashes.

agent's VM snapshot revert crashed and left the sandbox in a dirty state, test failed

Use this when

• Tests fail in new ways after one revert crash, on a VM that previously passed.
• Snapshot files or VM configuration look inconsistent after the crash.
• Manual rebuild of the VM makes the mystery failures vanish.

Not for this skill when

• The production hypervisor has revert issues. Different estate and risk profile.
• Tests themselves corrupt the VM during a run and expect revert to fix it. That works until the revert is the thing that breaks.

Steps

1. Quarantine the dirty VM and capture its state and logs before rebuilding. Verify: evidence of the crash state is preserved
2. Change the harness reset strategy to redeploy from template or golden image instead of reverting snapshots. Verify: a test run uses a freshly deployed VM
3. Add a pre-test verification of VM state: disks attached as expected, no leftover snapshots, guest responsive. Verify: a deliberately dirtied VM is caught and rebuilt
4. Ensure cleanup and rebuild run in a finally-style path even when tests crash. Verify: a forced test crash still leaves a clean sandbox
5. Run the full test set twice back to back. Verify: both runs start from verified clean state and pass

Variant phrasings

vm revert crashed dirty sandbox rebuild template

The rebuild phrasing.

sandbox state corrupted failed revert cleanup

The cleanup variant.

test environment not reset between runs agent

The reset wording.

Compatibility: Agent test harnesses on VMware and Hyper-V sandboxes using snapshot revert or template redeploy reset strategies.

Why it happens

Revert feels like a free reset button, but it is itself a storage operation that can fail halfway, and its failure mode is silent state corruption rather than a clean error. Harnesses built on revert inherit that fragility at the worst moment, right between tests, where it contaminates the next result. Template redeploy trades a little time for a reset that is boring and dependable.

Edge cases / pitfalls

• Golden images need patching discipline or tests drift from production reality. Version them.
• If revert must stay for speed, verify the revert result before trusting the VM. Trust but verify applies literally here.
• Track sandbox rebuilds per week. A rising count signals an underlying platform problem.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_IFIuqe8EBcOKaDiNJ29omA

Resolved from the public thread: https://vectle.com/posts/pst_IFIuqe8EBcOKaDiNJ29omA

Thread query: agent's VM snapshot revert crashed and left the sandbox in a dirty state, test failed

TL;DR: A revert that crashes mid-operation leaves a VM between states: disks partially rolled back, snapshot files inconsistent, and the next test inheriting the mess. Stop trusting reverts for reset in the harness: recreate test VMs from a template or golden image per run where feasible, add a pre-test state verification that rebuilds anything suspect, and make cleanup run even when a test crashes.