Skip lifecycle index creation when disk space is insufficient

[delthas]

Summary

• Before attempting to create lifecycle v2 indexes, check available disk space and estimate the index creation cost.
• If fsFreeSize < 2 * _id_ index size, skip index creation and fall back to v1 listing.
• On error checking disk space, also fall back to v1 (consistent with existing error handling in _indexesGetOrCreate).

Context

When a large bucket fills the MongoDB PV, operators need lifecycle to empty it. The conductor tries to create v2 indexes for the bucket, which either fails (ENOSPC) or further pressures the disk. Currently the conductor retries index creation every cycle, failing each time and logging warnings.

This change adds a proactive disk space check using two MongoDB metadata calls (both ~10ms, no locks):

• getDiskUsage() (dbStats) — filesystem free space
• getCollectionStats() (collStats) — per-collection index sizes

The _id_ index size is used as an estimate for the lifecycle index cost. On a test cluster with 1M objects: _id_ = 76MB, each lifecycle index ≈ 60MB — so 2 * _id_ is a conservative estimate for both indexes combined.

Design decisions

• Check happens per-bucket in _indexesGetOrCreate, only for buckets that actually need index creation (indexes don't exist, auto-create enabled, not at concurrent limit). Most buckets already have indexes and return early.
• getDiskUsage and getCollectionStats run in parallel via async.parallel to minimize latency.
• Falls back to v1 on any error — consistent with every other error path in this method.
• Depends on Arsenal PR Fix getDiskUsage and add getCollectionStats Arsenal#2605 for the fixed getDiskUsage and new getCollectionStats methods.

[bert-e]

Hello delthas,

My role is to assist you with the merge of this
pull request. Please type @bert-e help to get information
on this process, or consult the user documentation.

Available options

name	description	privileged	authored
/after_pull_request	Wait for the given pull request id to be merged before continuing with the current one.
/bypass_author_approval	Bypass the pull request author's approval	⭐
/bypass_build_status	Bypass the build and test status	⭐
/bypass_commit_size	Bypass the check on the size of the changeset TBA	⭐
/bypass_incompatible_branch	Bypass the check on the source branch prefix	⭐
/bypass_jira_check	Bypass the Jira issue check	⭐
/bypass_peer_approval	Bypass the pull request peers' approval	⭐
/bypass_leader_approval	Bypass the pull request leaders' approval	⭐
/approve	Instruct Bert-E that the author has approved the pull request.		✍️
/create_pull_requests	Allow the creation of integration pull requests.
/create_integration_branches	Allow the creation of integration branches.
/no_octopus	Prevent Wall-E from doing any octopus merge and use multiple consecutive merge instead
/unanimity	Change review acceptance criteria from one reviewer at least to all reviewers
/wait	Instruct Bert-E not to run until further notice.

Available commands

name	description	privileged
/help	Print Bert-E's manual in the pull request.
/status	Print Bert-E's current status in the pull request TBA
/clear	Remove all comments from Bert-E from the history TBA
/retry	Re-start a fresh build TBA
/build	Re-start a fresh build TBA
/force_reset	Delete integration branches & pull requests, and restart merge process from the beginning.
/reset	Try to remove integration branches unless there are commits on them which do not appear on the source branch.

Status report is not available.

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 74.76%. Comparing base (51f94a6) to head (e3b661b).

Files with missing lines	Patch %	Lines
...tensions/lifecycle/conductor/LifecycleConductor.js	94.44%	1 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
...tensions/lifecycle/conductor/LifecycleConductor.js	84.16% <94.44%> (+0.45%)	⬆️

... and 3 files with indirect coverage changes

Components	Coverage Δ
Bucket Notification	80.37% <ø> (ø)
Core Library	81.12% <ø> (+0.55%)	⬆️
Ingestion	71.14% <ø> (ø)
Lifecycle	79.10% <94.44%> (+0.09%)	⬆️
Oplog Populator	85.83% <ø> (ø)
Replication	59.61% <ø> (ø)
Bucket Scanner	85.76% <ø> (ø)

@@                 Coverage Diff                 @@
##           development/9.3    #2729      +/-   ##
===================================================
+ Coverage            74.51%   74.76%   +0.25%     
===================================================
  Files                  200      200              
  Lines                13610    13623      +13     
===================================================
+ Hits                 10141    10185      +44     
+ Misses                3459     3428      -31     
  Partials                10       10              

Flag	Coverage Δ
api:retry	9.13% <0.00%> (-0.01%)	⬇️
api:routes	8.95% <0.00%> (-0.01%)	⬇️
bucket-scanner	85.76% <ø> (ø)
ft_test:queuepopulator	10.31% <0.00%> (+1.26%)	⬆️
ingestion	12.53% <0.00%> (-0.02%)	⬇️
lib	7.60% <0.00%> (-0.02%)	⬇️
lifecycle	18.82% <0.00%> (-0.02%)	⬇️
notification	1.02% <0.00%> (-0.01%)	⬇️
oplogPopulator	0.14% <0.00%> (-0.01%)	⬇️
replication	18.46% <0.00%> (-0.02%)	⬇️
unit	51.16% <94.44%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[bert-e]

Waiting for approval

The following approvals are needed before I can proceed with the merge:

• the author

• 2 peers

[claude]

• Missing test coverage for the two new code paths (disk usage error fallback and insufficient disk space fallback). The existing data-driven test structure makes adding these cases straightforward.
  
  Review by Claude Code

[claude]

• Metric label getDiskUsageFailed (line 298) is misleading: async.parallel aggregates errors from both getDiskUsage and getCollectionStats, so the metric could fire for either failure. Consider renaming to diskSpaceCheckFailed.

Review by Claude Code

[claude]

LGTM

The disk space check is well-integrated into the existing guard chain in _indexesGetOrCreate. Error handling is consistent with surrounding code (falls back to v1). The async.parallel usage for the two MongoDB metadata calls is appropriate. Tests cover both the error path and the insufficient-space path.

Review by Claude Code

[delthas]

Confirmed in practice that the indexes created are about the same size as the default id index.