papercut: carry serialized metrics as []byte through the plugin inter…

…face boundary

This avoids casting in the plugin implementation at the expense of
casting once in the central business logic.

internal/collector/capacity_scrape.go

@@ -167,7 +167,7 @@ func (c *Collector) processCapacityScrapeTask(_ context.Context, task capacitySc
 	if err == nil {
 		capacitor.ScrapedAt = &task.Timing.FinishedAt
 		capacitor.ScrapeDurationSecs = task.Timing.Duration().Seconds()
-		capacitor.SerializedMetrics = serializedMetrics
+		capacitor.SerializedMetrics = string(serializedMetrics)
 		capacitor.NextScrapeAt = task.Timing.FinishedAt.Add(c.AddJitter(capacityScrapeInterval))
 		capacitor.ScrapeErrorMessage = ""
 		//NOTE: in this case, we continue below, with the cluster_resources update

internal/collector/metrics.go

@@ -236,7 +236,7 @@ func (c *CapacityPluginMetricsCollector) collectOneCapacitor(ch chan<- prometheu
 	if plugin == nil {
 		return
 	}
-	err := plugin.CollectMetrics(ch, instance.SerializedMetrics)
+	err := plugin.CollectMetrics(ch, []byte(instance.SerializedMetrics))
 	successAsFloat := 1.0
 	if err != nil {
 		successAsFloat = 0.0
@@ -331,7 +331,7 @@ func (c *QuotaPluginMetricsCollector) collectOneProjectService(ch chan<- prometh
 	if plugin == nil {
 		return
 	}
-	err := plugin.CollectMetrics(ch, instance.Project, instance.SerializedMetrics)
+	err := plugin.CollectMetrics(ch, instance.Project, []byte(instance.SerializedMetrics))
 	successAsFloat := 1.0
 	if err != nil {
 		successAsFloat = 0.0

internal/collector/scrape.go

@@ -204,7 +204,7 @@ func (c *Collector) processResourceScrapeTask(_ context.Context, task projectScr
 	return fmt.Errorf("during resource scrape of project %s/%s: %w", dbDomain.Name, dbProject.Name, task.Err)
 }
 
-func (c *Collector) writeResourceScrapeResult(dbDomain db.Domain, dbProject db.Project, task projectScrapeTask, resourceData map[string]core.ResourceData, serializedMetrics string) error {
+func (c *Collector) writeResourceScrapeResult(dbDomain db.Domain, dbProject db.Project, task projectScrapeTask, resourceData map[string]core.ResourceData, serializedMetrics []byte) error {
 	srv := task.Service
 
 	tx, err := c.DB.Begin()
@@ -318,7 +318,7 @@ func (c *Collector) writeResourceScrapeResult(dbDomain db.Domain, dbProject db.P
 	//attributes that we have not written yet
 	_, err = tx.Exec(writeResourceScrapeSuccessQuery,
 		task.Timing.FinishedAt, task.Timing.FinishedAt.Add(c.AddJitter(scrapeInterval)), task.Timing.Duration().Seconds(),
-		serializedMetrics, srv.ID,
+		string(serializedMetrics), srv.ID,
 	)
 	if err != nil {
 		return fmt.Errorf("while updating metadata on project service: %w", err)

internal/core/constraints_test.go

@@ -174,8 +174,8 @@ func (p quotaConstraintTestPlugin) ServiceInfo(serviceType string) limes.Service
 func (p quotaConstraintTestPlugin) Rates() []limesrates.RateInfo {
 	return nil
 }
-func (p quotaConstraintTestPlugin) Scrape(project KeystoneProject) (result map[string]ResourceData, serializedMetrics string, err error) {
-	return nil, "", nil
+func (p quotaConstraintTestPlugin) Scrape(project KeystoneProject) (result map[string]ResourceData, serializedMetrics []byte, err error) {
+	return nil, nil, nil
 }
 func (p quotaConstraintTestPlugin) IsQuotaAcceptableForProject(project KeystoneProject, fullQuotas map[string]map[string]uint64, allServiceInfos []limes.ServiceInfo) error {
 	return nil
@@ -188,7 +188,7 @@ func (p quotaConstraintTestPlugin) ScrapeRates(project KeystoneProject, prevSeri
 }
 func (p quotaConstraintTestPlugin) DescribeMetrics(ch chan<- *prometheus.Desc) {
 }
-func (p quotaConstraintTestPlugin) CollectMetrics(ch chan<- prometheus.Metric, project KeystoneProject, serializedMetrics string) error {
+func (p quotaConstraintTestPlugin) CollectMetrics(ch chan<- prometheus.Metric, project KeystoneProject, serializedMetrics []byte) error {
 	return nil
 }
 

internal/core/plugin.go

@@ -118,7 +118,7 @@ type QuotaPlugin interface {
 	//
 	//The serializedMetrics return value is persisted in the Limes DB and
 	//supplied to all subsequent RenderMetrics calls.
-	Scrape(project KeystoneProject) (result map[string]ResourceData, serializedMetrics string, error error)
+	Scrape(project KeystoneProject) (result map[string]ResourceData, serializedMetrics []byte, err error)
 	//IsQuotaAcceptableForProject checks if the given quota set is acceptable
 	//for the given project, and returns nil if the quota is acceptable, or a
 	//human-readable error otherwise. This should only be used when the
@@ -167,7 +167,7 @@ type QuotaPlugin interface {
 	//Some plugins also emit metrics directly within Scrape. This newer interface
 	//should be preferred since metrics emitted here won't be lost between
 	//restarts of limes-collect.
-	CollectMetrics(ch chan<- prometheus.Metric, project KeystoneProject, serializedMetrics string) error
+	CollectMetrics(ch chan<- prometheus.Metric, project KeystoneProject, serializedMetrics []byte) error
 }
 
 // CapacityPlugin is the interface that all capacity collector plugins must
@@ -201,7 +201,7 @@ type CapacityPlugin interface {
 	//
 	//The serializedMetrics return value is persisted in the Limes DB and
 	//supplied to all subsequent RenderMetrics calls.
-	Scrape() (result map[string]map[string]PerAZ[CapacityData], serializedMetrics string, err error)
+	Scrape() (result map[string]map[string]PerAZ[CapacityData], serializedMetrics []byte, err error)
 
 	//DescribeMetrics is called when Prometheus is scraping metrics from
 	//limes-collect, to provide an opportunity to the plugin to emit its own
@@ -218,7 +218,7 @@ type CapacityPlugin interface {
 	//Some plugins also emit metrics directly within Scrape. This newer interface
 	//should be preferred since metrics emitted here won't be lost between
 	//restarts of limes-collect.
-	CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics string) error
+	CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics []byte) error
 }
 
 var (

internal/plugins/archer.go

@@ -94,7 +94,7 @@ func (p *archerPlugin) Rates() []limesrates.RateInfo {
 }
 
 // Scrape implements the core.QuotaPlugin interface.
-func (p *archerPlugin) Scrape(project core.KeystoneProject) (result map[string]core.ResourceData, serializedMetrics string, err error) {
+func (p *archerPlugin) Scrape(project core.KeystoneProject) (result map[string]core.ResourceData, serializedMetrics []byte, err error) {
 	url := p.Archer.ServiceURL("quotas", project.UUID)
 	var res gophercloud.Result
 	//nolint:bodyclose // already closed by gophercloud
@@ -107,7 +107,7 @@ func (p *archerPlugin) Scrape(project core.KeystoneProject) (result map[string]c
 		InUseService  uint64 `json:"in_use_service"`
 	}
 	if err = res.ExtractInto(&archerQuota); err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	result = map[string]core.ResourceData{
@@ -124,7 +124,7 @@ func (p *archerPlugin) Scrape(project core.KeystoneProject) (result map[string]c
 			}),
 		},
 	}
-	return result, "", nil
+	return result, nil, nil
 }
 
 // IsQuotaAcceptableForProject implements the core.QuotaPlugin interface.
@@ -158,7 +158,7 @@ func (p *archerPlugin) DescribeMetrics(ch chan<- *prometheus.Desc) {
 }
 
 // CollectMetrics implements the core.QuotaPlugin interface.
-func (p *archerPlugin) CollectMetrics(ch chan<- prometheus.Metric, project core.KeystoneProject, serializedMetrics string) error {
+func (p *archerPlugin) CollectMetrics(ch chan<- prometheus.Metric, project core.KeystoneProject, serializedMetrics []byte) error {
 	//not used by this plugin
 	return nil
 }

internal/plugins/capacity_cinder.go

@@ -83,7 +83,7 @@ func (p *capacityCinderPlugin) makeResourceName(volumeType string) string {
 }
 
 // Scrape implements the core.CapacityPlugin interface.
-func (p *capacityCinderPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], serializedMetrics string, err error) {
+func (p *capacityCinderPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], serializedMetrics []byte, err error) {
 	//list storage pools
 	var poolData struct {
 		StoragePools []struct {
@@ -102,21 +102,21 @@ func (p *capacityCinderPlugin) Scrape() (result map[string]map[string]core.PerAZ
 
 	allPages, err := schedulerstats.List(p.CinderV3, schedulerstats.ListOpts{Detail: true}).AllPages()
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 	err = allPages.(schedulerstats.StoragePoolPage).ExtractInto(&poolData)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	//list service hosts
 	allPages, err = services.List(p.CinderV3, nil).AllPages()
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 	allServices, err := services.ExtractServices(allPages)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	serviceHostsPerAZ := make(map[string][]string)
@@ -191,7 +191,7 @@ func (p *capacityCinderPlugin) Scrape() (result map[string]map[string]core.PerAZ
 		}
 	}
 
-	return map[string]map[string]core.PerAZ[core.CapacityData]{"volumev2": capaData}, "", nil
+	return map[string]map[string]core.PerAZ[core.CapacityData]{"volumev2": capaData}, nil, nil
 }
 
 // DescribeMetrics implements the core.CapacityPlugin interface.
@@ -200,7 +200,7 @@ func (p *capacityCinderPlugin) DescribeMetrics(ch chan<- *prometheus.Desc) {
 }
 
 // CollectMetrics implements the core.CapacityPlugin interface.
-func (p *capacityCinderPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics string) error {
+func (p *capacityCinderPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics []byte) error {
 	//not used by this plugin
 	return nil
 }

internal/plugins/capacity_manila.go

@@ -102,14 +102,14 @@ func (p *capacityManilaPlugin) makeResourceName(kind string, shareType ManilaSha
 }
 
 // Scrape implements the core.CapacityPlugin interface.
-func (p *capacityManilaPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], _ string, err error) {
+func (p *capacityManilaPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], _ []byte, err error) {
 	allPages, err := services.List(p.ManilaV2, nil).AllPages()
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 	allServices, err := services.ExtractServices(allPages)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	azForServiceHost := make(map[string]limes.AvailabilityZone)
@@ -131,14 +131,14 @@ func (p *capacityManilaPlugin) Scrape() (result map[string]map[string]core.PerAZ
 	for _, shareType := range p.ShareTypes {
 		capForType, err := p.scrapeForShareType(shareType, azForServiceHost)
 		if err != nil {
-			return nil, "", err
+			return nil, nil, err
 		}
 		caps[p.makeResourceName("shares", shareType)] = capForType.Shares
 		caps[p.makeResourceName("share_snapshots", shareType)] = capForType.Snapshots
 		caps[p.makeResourceName("share_capacity", shareType)] = capForType.ShareGigabytes
 		caps[p.makeResourceName("snapshot_capacity", shareType)] = capForType.SnapshotGigabytes
 	}
-	return map[string]map[string]core.PerAZ[core.CapacityData]{"sharev2": caps}, "", nil
+	return map[string]map[string]core.PerAZ[core.CapacityData]{"sharev2": caps}, nil, nil
 }
 
 // DescribeMetrics implements the core.CapacityPlugin interface.
@@ -147,7 +147,7 @@ func (p *capacityManilaPlugin) DescribeMetrics(ch chan<- *prometheus.Desc) {
 }
 
 // CollectMetrics implements the core.CapacityPlugin interface.
-func (p *capacityManilaPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics string) error {
+func (p *capacityManilaPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics []byte) error {
 	//not used by this plugin
 	return nil
 }

internal/plugins/capacity_manual.go

@@ -49,9 +49,9 @@ func (p *capacityManualPlugin) PluginTypeID() string {
 var errNoManualData = errors.New(`missing values for capacitor plugin "manual"`)
 
 // Scrape implements the core.CapacityPlugin interface.
-func (p *capacityManualPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], _ string, err error) {
+func (p *capacityManualPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], _ []byte, err error) {
 	if p.Values == nil {
-		return nil, "", errNoManualData
+		return nil, nil, errNoManualData
 	}
 
 	result = make(map[string]map[string]core.PerAZ[core.CapacityData])
@@ -63,7 +63,7 @@ func (p *capacityManualPlugin) Scrape() (result map[string]map[string]core.PerAZ
 		result[serviceType] = serviceResult
 	}
 
-	return result, "", nil
+	return result, nil, nil
 }
 
 // DescribeMetrics implements the core.CapacityPlugin interface.
@@ -72,7 +72,7 @@ func (p *capacityManualPlugin) DescribeMetrics(ch chan<- *prometheus.Desc) {
 }
 
 // CollectMetrics implements the core.CapacityPlugin interface.
-func (p *capacityManualPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics string) error {
+func (p *capacityManualPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics []byte) error {
 	//not used by this plugin
 	return nil
 }

internal/plugins/capacity_nova.go

@@ -99,46 +99,46 @@ func (p *capacityNovaPlugin) PluginTypeID() string {
 }
 
 // Scrape implements the core.CapacityPlugin interface.
-func (p *capacityNovaPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], serializedMetrics string, err error) {
+func (p *capacityNovaPlugin) Scrape() (result map[string]map[string]core.PerAZ[core.CapacityData], serializedMetrics []byte, err error) {
 	//enumerate aggregates which establish the hypervisor <-> AZ mapping
 	page, err := aggregates.List(p.NovaV2).AllPages()
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 	allAggregates, err := aggregates.ExtractAggregates(page)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	//enumerate hypervisors (cannot use type Hypervisor provided by Gophercloud;
 	//in our clusters, it breaks because some hypervisor report unexpected NULL
 	//values on fields that we are not even interested in)
 	page, err = hypervisors.List(p.NovaV2, nil).AllPages()
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 	var hypervisorData struct {
 		Hypervisors []novaHypervisor `json:"hypervisors"`
 	}
 	err = page.(hypervisors.HypervisorPage).ExtractInto(&hypervisorData)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	//enumerate resource providers (we need to match these to the hypervisors later)
 	page, err = resourceproviders.List(p.PlacementV1, nil).AllPages()
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 	allResourceProviders, err := resourceproviders.ExtractResourceProviders(page)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	//for the instances capacity, we need to know the max root disk size on public flavors
 	maxRootDiskSize, err := getMaxRootDiskSize(p.NovaV2, p.ExtraSpecs)
 	if err != nil {
-		return nil, "", err
+		return nil, nil, err
 	}
 
 	//we need to prepare several aggregations in the big loop below
@@ -159,7 +159,7 @@ func (p *capacityNovaPlugin) Scrape() (result map[string]map[string]core.PerAZ[c
 		//query Placement API for hypervisor capacity
 		hvCapacity, traits, err := hypervisor.getCapacity(p.PlacementV1, allResourceProviders)
 		if err != nil {
-			return nil, "", fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"cannot get capacity for hypervisor %s with .service.host %q from Placement API (falling back to Nova Hypervisor API): %s",
 				hypervisor.HypervisorHostname, hypervisor.Service.Host, err.Error())
 		}
@@ -220,7 +220,7 @@ func (p *capacityNovaPlugin) Scrape() (result map[string]map[string]core.PerAZ[c
 			continue
 		}
 		if len(matchingAggregates) > 1 {
-			return nil, "", fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"hypervisor %s with .service.host %q could not be uniquely matched to an aggregate (matching aggregates = %v)",
 				hypervisor.HypervisorHostname, hypervisor.Service.Host, matchingAggregates)
 		}
@@ -234,7 +234,7 @@ func (p *capacityNovaPlugin) Scrape() (result map[string]map[string]core.PerAZ[c
 			continue
 		}
 		if len(matchingAZs) > 1 {
-			return nil, "", fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"hypervisor %s with .service.host %q could not be uniquely matched to an AZ (matching AZs = %v)",
 				hypervisor.HypervisorHostname, hypervisor.Service.Host, matchingAZs)
 		}
@@ -289,8 +289,8 @@ func (p *capacityNovaPlugin) Scrape() (result map[string]map[string]core.PerAZ[c
 		delete(capacities, "instances")
 	}
 
-	serializedMetricsBytes, err := json.Marshal(metrics)
-	return map[string]map[string]core.PerAZ[core.CapacityData]{"compute": capacities}, string(serializedMetricsBytes), err
+	serializedMetrics, err = json.Marshal(metrics)
+	return map[string]map[string]core.PerAZ[core.CapacityData]{"compute": capacities}, serializedMetrics, err
 }
 
 var novaHypervisorWellformedGauge = prometheus.NewGaugeVec(
@@ -307,9 +307,9 @@ func (p *capacityNovaPlugin) DescribeMetrics(ch chan<- *prometheus.Desc) {
 }
 
 // CollectMetrics implements the core.CapacityPlugin interface.
-func (p *capacityNovaPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics string) error {
+func (p *capacityNovaPlugin) CollectMetrics(ch chan<- prometheus.Metric, serializedMetrics []byte) error {
 	var metrics capacityNovaSerializedMetrics
-	err := json.Unmarshal([]byte(serializedMetrics), &metrics)
+	err := json.Unmarshal(serializedMetrics, &metrics)
 	if err != nil {
 		return err
 	}