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feat(featureflags): add build-kernel-version flag for new builds #2592

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Merged
ValentaTomas merged 5 commits into from
May 8, 2026
+12 −19
Merged

feat(featureflags): add build-kernel-version flag for new builds #2592

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c68ff37
feat(featureflags): add build-kernel-version flag for new builds
ValentaTomas May 8, 2026
c051086
fix(featureflags): fall back to DefaultKernelVersion when LD flag is …
ValentaTomas May 8, 2026
34c8134
refactor(featureflags): bake empty-fallback into StringFlag opt-in
ValentaTomas May 8, 2026
c9309f1
revert(featureflags): drop StringFlag empty-fallback opt-in
ValentaTomas May 8, 2026
127ca29
chore(api): drop dead Config.DefaultKernelVersion field
ValentaTomas May 8, 2026
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9 changes: 5 additions & 4 deletions packages/api/internal/handlers/deprecated_template_request_build.go
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Original file line number Diff line number Diff line change
Expand Up @@ -160,10 +160,11 @@ func (a *APIStore) buildTemplate(
templateID api.TemplateID,
body api.TemplateBuildRequest,
) (*template.RegisterBuildResponse, *api.APIError) {
// TODO(ENG-3852): Stop sending the firecracker version from the API. The orchestrator
// now resolves its own FC version via the FirecrackerVersions feature flag
// (see packages/orchestrator/pkg/template/build/builder.go)
// TODO(ENG-3852): Stop sending the firecracker/kernel versions from the API.
// The orchestrator resolves them itself via the BuildFirecrackerVersion /
// BuildKernelVersion feature flags (see packages/orchestrator/pkg/template/server/create_template.go).
firecrackerVersion := a.featureFlags.StringFlag(ctx, featureflags.BuildFirecrackerVersion)
kernelVersion := featureflags.ResolveBuildKernelVersion(ctx, a.featureFlags)

var alias *string
var tags []string
Expand Down Expand Up @@ -206,7 +207,7 @@ func (a *APIStore) buildTemplate(
CpuCount: body.CpuCount,
MemoryMB: body.MemoryMB,
Version: templates.TemplateV1Version,
KernelVersion: a.config.DefaultKernelVersion,
KernelVersion: kernelVersion,
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FirecrackerVersion: firecrackerVersion,
}

Expand Down
9 changes: 5 additions & 4 deletions packages/api/internal/handlers/template_request_build_v3.go
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Expand Up @@ -115,10 +115,11 @@ func requestTemplateBuild(ctx context.Context, c *gin.Context, a *APIStore, body
}
span.End()

// TODO(ENG-3852): Stop sending the firecracker version from the API. The orchestrator
// now resolves its own FC version via the FirecrackerVersions feature flag
// (see packages/orchestrator/pkg/template/build/builder.go)
// TODO(ENG-3852): Stop sending the firecracker/kernel versions from the API.
// The orchestrator resolves them itself via the BuildFirecrackerVersion /
// BuildKernelVersion feature flags (see packages/orchestrator/pkg/template/server/create_template.go).
firecrackerVersion := a.featureFlags.StringFlag(ctx, featureflags.BuildFirecrackerVersion)
kernelVersion := featureflags.ResolveBuildKernelVersion(ctx, a.featureFlags)
buildReq := template.RegisterBuildData{
ClusterID: clusters.WithClusterFallback(team.ClusterID),
TemplateID: templateID,
Expand All @@ -129,7 +130,7 @@ func requestTemplateBuild(ctx context.Context, c *gin.Context, a *APIStore, body
CpuCount: body.CpuCount,
MemoryMB: body.MemoryMB,
Version: templates.TemplateV2LatestVersion,
KernelVersion: a.config.DefaultKernelVersion,
KernelVersion: kernelVersion,
FirecrackerVersion: firecrackerVersion,
}

Expand Down
2 changes: 1 addition & 1 deletion packages/orchestrator/pkg/template/server/create_template.go
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Expand Up @@ -57,7 +57,7 @@ func (s *ServerStore) TemplateCreate(ctx context.Context, templateRequest *templ
featureflags.TeamContext(cfg.GetTeamID()),
)

kernelVersion := featureflags.DefaultKernelVersion
kernelVersion := featureflags.ResolveBuildKernelVersion(ctx, s.featureFlags)
firecrackerVersion := s.featureFlags.StringFlag(ctx, featureflags.BuildFirecrackerVersion)

fcInfo, err := fcversion.New(firecrackerVersion)
Expand Down
14 changes: 13 additions & 1 deletion packages/shared/pkg/featureflags/flags.go
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Original file line number Diff line number Diff line change
Expand Up @@ -238,7 +238,6 @@ func NewStringFlag(name string, fallback string) StringFlag {
return flag
}

// This is currently not configurable via feature flags.
const (
DefaultKernelVersion = "vmlinux-6.1.158"
)
Expand All @@ -261,12 +260,25 @@ var FirecrackerVersionMap = map[string]string{
// BuildIoEngine Sync is used by default as there seems to be a bad interaction between Async and a lot of io operations.
var (
BuildFirecrackerVersion = NewStringFlag("build-firecracker-version", env.GetEnv("DEFAULT_FIRECRACKER_VERSION", DefaultFirecrackerVersion))
BuildKernelVersion = NewStringFlag("build-kernel-version", env.GetEnv("DEFAULT_KERNEL_VERSION", DefaultKernelVersion))
BuildIoEngine = NewStringFlag("build-io-engine", "Sync")
DefaultPersistentVolumeType = NewStringFlag("default-persistent-volume-type", "")
BuildNodeInfo = NewJSONFlag("preferred-build-node", ldvalue.Null())
FirecrackerVersions = NewJSONFlag("firecracker-versions", ldvalue.FromJSONMarshal(FirecrackerVersionMap))
)

// ResolveBuildKernelVersion returns the kernel version for new template builds.
// Falls back to DefaultKernelVersion when the LD flag is empty so that defining
// the flag in LD without a value does not produce a "" kernel version downstream.
func ResolveBuildKernelVersion(ctx context.Context, ff *Client) string {
v := ff.StringFlag(ctx, BuildKernelVersion)
if v == "" {
return DefaultKernelVersion
}

return v
}

// ResolveFirecrackerVersion resolves the firecracker version using the FirecrackerVersions feature flag.
// The buildVersion format is "v1.12.1_210cbac" — we extract "v1.12" as the lookup key.
func ResolveFirecrackerVersion(ctx context.Context, ff *Client, buildVersion string) string {
Expand Down
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