diff --git a/pkg/config/config.go b/pkg/config/config.go
index 9d6c0471..c79e2752 100644
--- a/pkg/config/config.go
+++ b/pkg/config/config.go
@@ -34,7 +34,10 @@ type DiscoveryRule struct {
 	MetricsQuery string `yaml:"metricsQuery,omitempty"`
 	// MetricType identifies whether the metrics derived from this rule should be classified
 	// as external or custom metrics.
-	MetricType MetricType `yaml:"metricType"`
+	MetricType MetricType `yaml:"metricType,omitempty"`
+	// ExternalMetricNamespaceLabelName identifies what Prometheus label should be examined
+	// to apply a namespace to metrics creates from this rule.
+	ExternalMetricNamespaceLabelName string `yaml:"externalMetricNamespaceLabelName,omitempty"`
 }
 
 // RegexFilter is a filter that matches positively or negatively against a regex.
@@ -79,3 +82,12 @@ type NameMapping struct {
 
 //MetricType identifies whether a given metric should be handled and interpreted as a Custom or External metric.
 type MetricType string
+
+// Operator represents a key/field's relationship to value(s).
+// See labels.Requirement and fields.Requirement for more details.
+type Operator string
+
+const (
+	External MetricType = "External"
+	Custom   MetricType = "Custom"
+)
diff --git a/pkg/custom-provider/basic_metric_lister.go b/pkg/custom-provider/basic_metric_lister.go
index bf640ee4..1bbbd15d 100644
--- a/pkg/custom-provider/basic_metric_lister.go
+++ b/pkg/custom-provider/basic_metric_lister.go
@@ -48,13 +48,15 @@ type MetricLister interface {
 	ListAllMetrics() (metricUpdateResult, error)
 }
 
+//A MetricListerWithNotification is a MetricLister that has the ability to notify listeners
+//when new metric data is available.
 type MetricListerWithNotification interface {
-	//It can list metrics, just like a normal MetricLister.
 	MetricLister
-	//Because it periodically pulls metrics, it needs to be Runnable.
 	Runnable
-	//It provides notifications when it has new data to supply.
+
+	//AddNotificationReceiver registers a callback to be invoked when new metric data is available.
 	AddNotificationReceiver(func(metricUpdateResult))
+	//UpdateNow forces an immediate refresh from the source data. Primarily for test purposes.
 	UpdateNow()
 }
 
@@ -64,6 +66,7 @@ type basicMetricLister struct {
 	lookback   time.Duration
 }
 
+//NewBasicMetricLister creates a MetricLister that is capable of interactly directly with Prometheus to list metrics.
 func NewBasicMetricLister(promClient prom.Client, namers []MetricNamer, lookback time.Duration) MetricLister {
 	lister := basicMetricLister{
 		promClient: promClient,
diff --git a/pkg/custom-provider/external_info_map.go b/pkg/custom-provider/external_info_map.go
index aae1f360..03933baf 100644
--- a/pkg/custom-provider/external_info_map.go
+++ b/pkg/custom-provider/external_info_map.go
@@ -5,24 +5,37 @@ import (
 	"k8s.io/apimachinery/pkg/labels"
 )
 
+//ExportedMetric is a description of an available metric.
 type ExportedMetric struct {
 	MetricName string
 	Labels     labels.Set
 	Namespace  string
 }
 
+//ExternalInfoMap is a data object that accepts and organizes information
+//about available metrics.
 type ExternalInfoMap interface {
+	//Begins tracking a metric, returning it to the caller.
 	TrackMetric(metricName string, generatedBy MetricNamer) ExternalMetricData
+	//Exports a collection of all of the metrics currently being tracked.
 	ExportMetrics() []ExportedMetric
+	//Finds a tracked metric with the given metric name, if it exists.
 	FindMetric(metricName string) (data ExternalMetricData, found bool)
 }
 
+//ExternalMetricData is a data object that accepts and organizes information
+//about the various series/namespaces that a metric is associated with.
 type ExternalMetricData interface {
+	//MetricName returns the name of the metric represented by this object.
 	MetricName() string
+	//WithSeries associates the provided labels with this metric.
 	WithSeries(labels labels.Set)
+	//WithNamespacedSeries associates the provided labels with this metric, but within a particular namespace.
 	WithNamespacedSeries(namespace string, labels labels.Set)
+	//Exports a collection of all the metrics currently being tracked.
 	ExportMetrics() []ExportedMetric
-	GenerateQuery(selector labels.Selector) (prom.Selector, error)
+	//Generates a query to select the series/values for the metric this object represents.
+	GenerateQuery(namespace string, selector labels.Selector) (prom.Selector, error)
 }
 
 type externalInfoMap struct {
@@ -31,18 +44,20 @@ type externalInfoMap struct {
 
 type externalMetricData struct {
 	metricName     string
-	namespacedData map[string]labels.Set
+	namespacedData map[string][]labels.Set
 	generatedBy    MetricNamer
 }
 
+//NewExternalMetricData creates an ExternalMetricData for the provided metric name and namer.
 func NewExternalMetricData(metricName string, generatedBy MetricNamer) ExternalMetricData {
 	return &externalMetricData{
 		metricName:     metricName,
 		generatedBy:    generatedBy,
-		namespacedData: map[string]labels.Set{},
+		namespacedData: map[string][]labels.Set{},
 	}
 }
 
+//NewExternalInfoMap creates an empty ExternalInfoMap for storing external metric information.
 func NewExternalInfoMap() ExternalInfoMap {
 	return &externalInfoMap{
 		metrics: map[string]ExternalMetricData{},
@@ -78,18 +93,20 @@ func (d *externalMetricData) MetricName() string {
 	return d.metricName
 }
 
-func (d *externalMetricData) GenerateQuery(selector labels.Selector) (prom.Selector, error) {
-	return d.generatedBy.QueryForExternalSeries(d.metricName, selector)
+func (d *externalMetricData) GenerateQuery(namespace string, selector labels.Selector) (prom.Selector, error) {
+	return d.generatedBy.QueryForExternalSeries(namespace, d.metricName, selector)
 }
 
 func (d *externalMetricData) ExportMetrics() []ExportedMetric {
 	results := make([]ExportedMetric, 0)
-	for namespace, labels := range d.namespacedData {
-		results = append(results, ExportedMetric{
-			Labels:     labels,
-			MetricName: d.metricName,
-			Namespace:  namespace,
-		})
+	for namespace, labelSets := range d.namespacedData {
+		for _, labelSet := range labelSets {
+			results = append(results, ExportedMetric{
+				Labels:     labelSet,
+				MetricName: d.metricName,
+				Namespace:  namespace,
+			})
+		}
 	}
 
 	return results
@@ -99,10 +116,13 @@ func (d *externalMetricData) WithSeries(labels labels.Set) {
 	d.WithNamespacedSeries("", labels)
 }
 
-func (d *externalMetricData) WithNamespacedSeries(namespace string, labels labels.Set) {
+func (d *externalMetricData) WithNamespacedSeries(namespace string, seriesLabels labels.Set) {
 	data, found := d.namespacedData[namespace]
 	if !found {
-		data = labels
-		d.namespacedData[namespace] = data
+		data = []labels.Set{}
 	}
+
+	data = append(data, seriesLabels)
+	d.namespacedData[namespace] = data
+
 }
diff --git a/pkg/custom-provider/external_provider.go b/pkg/custom-provider/external_provider.go
index cceb6608..b10a98ce 100644
--- a/pkg/custom-provider/external_provider.go
+++ b/pkg/custom-provider/external_provider.go
@@ -15,16 +15,7 @@ import (
 	conv "github.com/directxman12/k8s-prometheus-adapter/pkg/custom-provider/metric-converter"
 )
 
-//TODO: Make sure everything has the proper licensing disclosure at the top.
-//TODO: I'd like to move these files into another directory, but the compiler was giving me
-//some static around unexported types. I'm going to leave things as-is for now, but it
-//might be worthwhile to, once the shared components are discovered, move some things around.
-
-//TODO: Some of these members may not be necessary.
-//Some of them are definitely duplicated between the
-//external and custom providers. They should probably share
-//the same instances of these objects (especially the SeriesRegistry)
-//to cut down on unnecessary chatter/bookkeeping.
+//TODO: AC - Make sure everything has the proper licensing disclosure at the top.
 type externalPrometheusProvider struct {
 	promClient      prom.Client
 	metricConverter conv.MetricConverter
@@ -32,13 +23,7 @@ type externalPrometheusProvider struct {
 	seriesRegistry ExternalSeriesRegistry
 }
 
-//TODO: It probably makes more sense to, once this is functional and complete, roll the
-//prometheusProvider and externalPrometheusProvider up into a single type
-//that implements both interfaces or provide a thin wrapper that composes them.
-//Just glancing at start.go looks like it would be much more straightforward
-//to do one of those two things instead of trying to run the two providers
-//independently.
-
+//NewExternalPrometheusProvider creates an ExternalMetricsProvider capable of responding to Kubernetes requests for external metric data.
 func NewExternalPrometheusProvider(seriesRegistry ExternalSeriesRegistry, promClient prom.Client, converter conv.MetricConverter) provider.ExternalMetricsProvider {
 	return &externalPrometheusProvider{
 		promClient:      promClient,
@@ -48,21 +33,17 @@ func NewExternalPrometheusProvider(seriesRegistry ExternalSeriesRegistry, promCl
 }
 
 func (p *externalPrometheusProvider) GetExternalMetric(namespace string, metricName string, metricSelector labels.Selector) (*external_metrics.ExternalMetricValueList, error) {
-	selector, found := p.seriesRegistry.QueryForMetric(metricName, metricSelector)
+	selector, found := p.seriesRegistry.QueryForMetric(namespace, metricName, metricSelector)
 
 	if !found {
 		return &external_metrics.ExternalMetricValueList{
 			Items: []external_metrics.ExternalMetricValue{},
 		}, nil
 	}
-	// query := p.queryBuilder.BuildPrometheusQuery(namespace, metricName, metricSelector, queryMetadata)
 
-	//TODO: I don't yet know what a context is, but apparently I should use a real one.
 	queryResults, err := p.promClient.Query(context.TODO(), pmodel.Now(), selector)
 
 	if err != nil {
-		//TODO: Is this how folks normally deal w/ errors? Just propagate them upwards?
-		//I should go look at what the customProvider does.
 		return nil, err
 	}
 
diff --git a/pkg/custom-provider/external_series_registry.go b/pkg/custom-provider/external_series_registry.go
index 0d5fb200..ad1752c9 100644
--- a/pkg/custom-provider/external_series_registry.go
+++ b/pkg/custom-provider/external_series_registry.go
@@ -14,31 +14,33 @@ import (
 	"github.com/directxman12/k8s-prometheus-adapter/pkg/config"
 )
 
+//ExternalSeriesRegistry acts as the top-level converter for transforming Kubernetes requests
+//for external metrics into Prometheus queries.
 type ExternalSeriesRegistry interface {
 	// ListAllMetrics lists all metrics known to this registry
 	ListAllMetrics() []provider.ExternalMetricInfo
-	QueryForMetric(metricName string, metricSelector labels.Selector) (query prom.Selector, found bool)
+	QueryForMetric(namespace string, metricName string, metricSelector labels.Selector) (query prom.Selector, found bool)
 }
 
 // overridableSeriesRegistry is a basic SeriesRegistry
 type externalSeriesRegistry struct {
 	mu sync.RWMutex
 
-	externalInfo map[string]seriesInfo
 	// metrics is the list of all known metrics
 	metrics []provider.ExternalMetricInfo
 
 	mapper apimeta.RESTMapper
 
-	metricLister     MetricListerWithNotification
-	tonyExternalInfo ExternalInfoMap
+	metricLister       MetricListerWithNotification
+	externalMetricInfo ExternalInfoMap
 }
 
+//NewExternalSeriesRegistry creates an ExternalSeriesRegistry driven by the data from the provided MetricLister.
 func NewExternalSeriesRegistry(lister MetricListerWithNotification, mapper apimeta.RESTMapper) ExternalSeriesRegistry {
 	var registry = externalSeriesRegistry{
-		mapper:           mapper,
-		metricLister:     lister,
-		tonyExternalInfo: NewExternalInfoMap(),
+		mapper:             mapper,
+		metricLister:       lister,
+		externalMetricInfo: NewExternalInfoMap(),
 	}
 
 	lister.AddNotificationReceiver(registry.onNewDataAvailable)
@@ -50,7 +52,7 @@ func (r *externalSeriesRegistry) filterMetrics(result metricUpdateResult) metric
 	namers := make([]MetricNamer, 0)
 	series := make([][]prom.Series, 0)
 
-	targetType := config.MetricType("External")
+	targetType := config.External
 
 	for i, namer := range result.namers {
 		if namer.MetricType() == targetType {
@@ -98,10 +100,16 @@ func (r *externalSeriesRegistry) onNewDataAvailable(result metricUpdateResult) {
 			// namespaced := identity.namespaced
 			name := identity.name
 			labels := r.convertLabels(series.Labels)
-			//TODO: Figure out the namespace, if applicable
-			metricNs := ""
+
+			//Check for a label indicating namespace.
+			metricNs, found := series.Labels[model.LabelName(namer.ExternalMetricNamespaceLabelName())]
+
+			if !found {
+				metricNs = ""
+			}
+
 			trackedMetric := updatedCache.TrackMetric(name, namer)
-			trackedMetric.WithNamespacedSeries(metricNs, labels)
+			trackedMetric.WithNamespacedSeries(string(metricNs), labels)
 		}
 	}
 
@@ -112,7 +120,7 @@ func (r *externalSeriesRegistry) onNewDataAvailable(result metricUpdateResult) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 
-	r.tonyExternalInfo = updatedCache
+	r.externalMetricInfo = updatedCache
 	r.metrics = convertedMetrics
 }
 
@@ -135,29 +143,20 @@ func (r *externalSeriesRegistry) ListAllMetrics() []provider.ExternalMetricInfo
 	return r.metrics
 }
 
-func (r *externalSeriesRegistry) QueryForMetric(metricName string, metricSelector labels.Selector) (query prom.Selector, found bool) {
+func (r *externalSeriesRegistry) QueryForMetric(namespace string, metricName string, metricSelector labels.Selector) (query prom.Selector, found bool) {
 	r.mu.RLock()
 	defer r.mu.RUnlock()
-	metric, found := r.tonyExternalInfo.FindMetric(metricName)
+	metric, found := r.externalMetricInfo.FindMetric(metricName)
 
 	if !found {
+		glog.V(10).Infof("external metric %q not registered", metricName)
 		return "", false
 	}
 
-	query, err := metric.GenerateQuery(metricSelector)
-	// info, infoFound := r.info[metricInfo]
-	// if !infoFound {
-	// 	//TODO: Weird that it switches between types here.
-	// 	glog.V(10).Infof("metric %v not registered", metricInfo)
-	// 	return "", false
-	// }
+	query, err := metric.GenerateQuery(namespace, metricSelector)
 
-	// query, err := info.namer.QueryForExternalSeries(info.seriesName, metricSelector)
 	if err != nil {
-		//TODO: See what was being .String() and implement that for ExternalMetricInfo.
-		// errorVal := metricInfo.String()
-		errorVal := "something"
-		glog.Errorf("unable to construct query for metric %s: %v", errorVal, err)
+		glog.Errorf("unable to construct query for external metric %s: %v", metricName, err)
 		return "", false
 	}
 
diff --git a/pkg/custom-provider/metric-converter/matrix_converter.go b/pkg/custom-provider/metric-converter/matrix_converter.go
index 453ce7e3..bd5f9c9b 100644
--- a/pkg/custom-provider/metric-converter/matrix_converter.go
+++ b/pkg/custom-provider/metric-converter/matrix_converter.go
@@ -32,6 +32,6 @@ func (c *matrixConverter) Convert(queryResult prom.QueryResult) (*external_metri
 }
 
 func (c *matrixConverter) convert(result *model.Matrix) (*external_metrics.ExternalMetricValueList, error) {
-	//TODO: Implementation.
+	//TODO: AC - Implementation.
 	return nil, errors.New("converting Matrix results is not yet supported")
 }
diff --git a/pkg/custom-provider/metric-converter/sample_converter.go b/pkg/custom-provider/metric-converter/sample_converter.go
index 8cd3bb23..29444eb3 100644
--- a/pkg/custom-provider/metric-converter/sample_converter.go
+++ b/pkg/custom-provider/metric-converter/sample_converter.go
@@ -30,14 +30,10 @@ func (c *sampleConverter) Convert(sample *model.Sample) (*external_metrics.Exter
 		Timestamp: metav1.Time{
 			sample.Timestamp.Time(),
 		},
-		//TODO: I'm not so sure about this type/conversions.
-		//This can't possibly be the right way to convert this.
-		//Also, does K8S only deal win integer metrics?
-		Value:        *resource.NewQuantity(int64(float64(sample.Value)), resource.DecimalSI),
+		Value:        *resource.NewMilliQuantity(int64(sample.Value*1000.0), resource.DecimalSI),
 		MetricLabels: labels,
 	}
 
-	//TODO: Actual errors?
 	return &singleMetric, nil
 }
 
diff --git a/pkg/custom-provider/metric-converter/scalar_converter.go b/pkg/custom-provider/metric-converter/scalar_converter.go
index 2a4e2095..284f55d5 100644
--- a/pkg/custom-provider/metric-converter/scalar_converter.go
+++ b/pkg/custom-provider/metric-converter/scalar_converter.go
@@ -35,18 +35,11 @@ func (c *scalarConverter) Convert(queryResult prom.QueryResult) (*external_metri
 
 func (c *scalarConverter) convert(input *model.Scalar) (*external_metrics.ExternalMetricValueList, error) {
 	result := external_metrics.ExternalMetricValueList{
-		//Using prometheusProvider.metricsFor(...) as an example,
-		//it seems that I don't need to provide values for
-		//TypeMeta and ListMeta.
-		//TODO: Get some confirmation on this.
 		Items: []external_metrics.ExternalMetricValue{
 			{
 				Timestamp: metav1.Time{
 					input.Timestamp.Time(),
 				},
-				//TODO: I'm not so sure about this type/conversions.
-				//Is there a meaningful loss of precision here?
-				//Does K8S only deal win integer metrics?
 				Value: *resource.NewMilliQuantity(int64(input.Value*1000.0), resource.DecimalSI),
 			},
 		},
diff --git a/pkg/custom-provider/metric-converter/vector_converter.go b/pkg/custom-provider/metric-converter/vector_converter.go
index 71b13631..9171d5ca 100644
--- a/pkg/custom-provider/metric-converter/vector_converter.go
+++ b/pkg/custom-provider/metric-converter/vector_converter.go
@@ -2,6 +2,7 @@ package provider
 
 import (
 	"errors"
+	"fmt"
 
 	prom "github.com/directxman12/k8s-prometheus-adapter/pkg/client"
 	"github.com/prometheus/common/model"
@@ -46,8 +47,13 @@ func (c *vectorConverter) convert(result model.Vector) (*external_metrics.Extern
 	}
 
 	for _, val := range result {
-		//TODO: Care about potential errors here.
-		singleMetric, _ := c.SampleConverter.Convert(val)
+
+		singleMetric, err := c.SampleConverter.Convert(val)
+
+		if err != nil {
+			return nil, fmt.Errorf("unable to convert vector: %v", err)
+		}
+
 		items = append(items, *singleMetric)
 	}
 
diff --git a/pkg/custom-provider/metric_name_converter.go b/pkg/custom-provider/metric_name_converter.go
index a35d6b2d..6a3c26f6 100644
--- a/pkg/custom-provider/metric_name_converter.go
+++ b/pkg/custom-provider/metric_name_converter.go
@@ -8,6 +8,7 @@ import (
 	"github.com/directxman12/k8s-prometheus-adapter/pkg/config"
 )
 
+//MetricNameConverter provides functions for naming custom metrics from Promethes series.
 type MetricNameConverter interface {
 	GetMetricNameForSeries(series prom.Series) (string, error)
 }
@@ -17,6 +18,8 @@ type metricNameConverter struct {
 	nameAs      string
 }
 
+//NewMetricNameConverter creates a MetricNameConverter capable of translating Prometheus series names
+//into custom metric names.
 func NewMetricNameConverter(mapping config.NameMapping) (MetricNameConverter, error) {
 	var nameMatches *regexp.Regexp
 	var err error
diff --git a/pkg/custom-provider/metric_namer.go b/pkg/custom-provider/metric_namer.go
index f1ee45d7..248a9988 100644
--- a/pkg/custom-provider/metric_namer.go
+++ b/pkg/custom-provider/metric_namer.go
@@ -34,9 +34,10 @@ type MetricNamer interface {
 	// QueryForSeries returns the query for a given series (not API metric name), with
 	// the given namespace name (if relevant), resource, and resource names.
 	QueryForSeries(series string, resource schema.GroupResource, namespace string, names ...string) (prom.Selector, error)
-	QueryForExternalSeries(series string, metricSelector labels.Selector) (prom.Selector, error)
+	QueryForExternalSeries(namespace string, series string, metricSelector labels.Selector) (prom.Selector, error)
 	IdentifySeries(series prom.Series) (seriesIdentity, error)
 	MetricType() config.MetricType
+	ExternalMetricNamespaceLabelName() string
 }
 
 type seriesIdentity struct {
@@ -58,7 +59,8 @@ type metricNamer struct {
 	metricNameConverter MetricNameConverter
 	mapper              apimeta.RESTMapper
 
-	metricType config.MetricType
+	metricType                   config.MetricType
+	externalMetricNamespaceLabel string
 }
 
 // queryTemplateArgs are the arguments for the metrics query template.
@@ -74,6 +76,10 @@ func (n *metricNamer) MetricType() config.MetricType {
 	return n.metricType
 }
 
+func (n *metricNamer) ExternalMetricNamespaceLabelName() string {
+	return n.externalMetricNamespaceLabel
+}
+
 func (n *metricNamer) IdentifySeries(series prom.Series) (seriesIdentity, error) {
 	// TODO: warn if it doesn't match any resources
 	resources, namespaced := n.resourceConverter.ResourcesForSeries(series)
@@ -219,15 +225,26 @@ func NamersFromConfig(cfg *config.MetricsDiscoveryConfig, mapper apimeta.RESTMap
 			return nil, fmt.Errorf("unable to create a MetricNameConverter associated with series query %q: %v", rule.SeriesQuery, err)
 		}
 
+		namespaceLabel := ""
+		if rule.MetricType == config.External {
+			namespaceLabel = rule.ExternalMetricNamespaceLabelName
+		}
+
+		metricType := rule.MetricType
+		if metricType == config.MetricType("") {
+			metricType = config.Custom
+		}
+
 		namer := &metricNamer{
 			seriesQuery: prom.Selector(rule.SeriesQuery),
 			mapper:      mapper,
 
-			resourceConverter:   resourceConverter,
-			queryBuilder:        queryBuilder,
-			seriesFilterer:      seriesFilterer,
-			metricNameConverter: metricNameConverter,
-			metricType:          rule.MetricType,
+			resourceConverter:            resourceConverter,
+			queryBuilder:                 queryBuilder,
+			seriesFilterer:               seriesFilterer,
+			metricNameConverter:          metricNameConverter,
+			metricType:                   metricType,
+			externalMetricNamespaceLabel: namespaceLabel,
 		}
 
 		namers[i] = namer
@@ -236,8 +253,28 @@ func NamersFromConfig(cfg *config.MetricsDiscoveryConfig, mapper apimeta.RESTMap
 	return namers, nil
 }
 
-func (n *metricNamer) QueryForExternalSeries(series string, metricSelector labels.Selector) (prom.Selector, error) {
-	queryParts := n.createQueryPartsFromSelector(metricSelector)
+func (n *metricNamer) buildNamespaceQueryPartForExternalSeries(namespace string) (queryPart, error) {
+	return queryPart{
+		labelName: n.externalMetricNamespaceLabel,
+		values:    []string{namespace},
+	}, nil
+}
+
+func (n *metricNamer) QueryForExternalSeries(namespace string, series string, metricSelector labels.Selector) (prom.Selector, error) {
+	queryParts := []queryPart{}
+
+	if namespace != "" {
+		//Build up the namespace part of the query.
+		namespaceQueryPart, err := n.buildNamespaceQueryPartForExternalSeries(namespace)
+		if err != nil {
+			return "", err
+		}
+
+		queryParts = append(queryParts, namespaceQueryPart)
+	}
+
+	//Build up the query parts from the selector.
+	queryParts = append(queryParts, n.createQueryPartsFromSelector(metricSelector)...)
 
 	selector, err := n.queryBuilder.BuildSelector(series, "", []string{}, queryParts)
 	if err != nil {
diff --git a/pkg/custom-provider/periodic_metric_lister.go b/pkg/custom-provider/periodic_metric_lister.go
index 81fceee7..2100865b 100644
--- a/pkg/custom-provider/periodic_metric_lister.go
+++ b/pkg/custom-provider/periodic_metric_lister.go
@@ -87,69 +87,3 @@ func (l *periodicMetricLister) notifyListeners() {
 func (l *periodicMetricLister) UpdateNow() {
 	l.updateMetrics()
 }
-
-// func (l *periodicMetricLister) updateMetrics() (metricUpdateResult, error) {
-
-// 	result := metricUpdateResult{
-// 		series: make([][]prom.Series, 0),
-// 		namers: make([]MetricNamer, 0),
-// 	}
-
-// 	startTime := pmodel.Now().Add(-1 * l.updateInterval)
-
-// 	// these can take a while on large clusters, so launch in parallel
-// 	// and don't duplicate
-// 	selectors := make(map[prom.Selector]struct{})
-// 	selectorSeriesChan := make(chan selectorSeries, len(l.namers))
-// 	errs := make(chan error, len(l.namers))
-// 	for _, namer := range l.namers {
-// 		sel := namer.Selector()
-// 		if _, ok := selectors[sel]; ok {
-// 			errs <- nil
-// 			selectorSeriesChan <- selectorSeries{}
-// 			continue
-// 		}
-// 		selectors[sel] = struct{}{}
-// 		go func() {
-// 			series, err := l.promClient.Series(context.TODO(), pmodel.Interval{startTime, 0}, sel)
-// 			if err != nil {
-// 				errs <- fmt.Errorf("unable to fetch metrics for query %q: %v", sel, err)
-// 				return
-// 			}
-// 			errs <- nil
-// 			selectorSeriesChan <- selectorSeries{
-// 				selector: sel,
-// 				series:   series,
-// 			}
-// 		}()
-// 	}
-
-// 	// don't do duplicate queries when it's just the matchers that change
-// 	seriesCacheByQuery := make(map[prom.Selector][]prom.Series)
-
-// 	// iterate through, blocking until we've got all results
-// 	for range l.namers {
-// 		if err := <-errs; err != nil {
-// 			return result, fmt.Errorf("unable to update list of all metrics: %v", err)
-// 		}
-// 		if ss := <-selectorSeriesChan; ss.series != nil {
-// 			seriesCacheByQuery[ss.selector] = ss.series
-// 		}
-// 	}
-// 	close(errs)
-
-// 	newSeries := make([][]prom.Series, len(l.namers))
-// 	for i, namer := range l.namers {
-// 		series, cached := seriesCacheByQuery[namer.Selector()]
-// 		if !cached {
-// 			return result, fmt.Errorf("unable to update list of all metrics: no metrics retrieved for query %q", namer.Selector())
-// 		}
-// 		newSeries[i] = namer.FilterSeries(series)
-// 	}
-
-// 	glog.V(10).Infof("Set available metric list from Prometheus to: %v", newSeries)
-
-// 	result.series = newSeries
-// 	result.namers = l.namers
-// 	return result, nil
-// }
diff --git a/pkg/custom-provider/provider.go b/pkg/custom-provider/provider.go
index 011456a9..15ec3cec 100644
--- a/pkg/custom-provider/provider.go
+++ b/pkg/custom-provider/provider.go
@@ -46,12 +46,11 @@ type prometheusProvider struct {
 	SeriesRegistry
 }
 
+//NewPrometheusProvider creates an CustomMetricsProvider capable of responding to Kubernetes requests for custom metric data.
 func NewPrometheusProvider(mapper apimeta.RESTMapper, kubeClient dynamic.Interface, promClient prom.Client, namers []MetricNamer, updateInterval time.Duration) (provider.CustomMetricsProvider, Runnable) {
+	//TODO: AC - Consider injecting these objects and calling .Run() before calling this function.
 	basicLister := NewBasicMetricLister(promClient, namers, updateInterval)
-	//TODO: Be sure to run this runnable.
-	// periodicLister, periodicRunnable := NewPeriodicMetricLister(basicLister, updateInterval)
 	periodicLister, _ := NewPeriodicMetricLister(basicLister, updateInterval)
-
 	seriesRegistry := NewBasicSeriesRegistry(periodicLister, mapper)
 
 	return &prometheusProvider{
diff --git a/pkg/custom-provider/query_builder.go b/pkg/custom-provider/query_builder.go
index 64db037b..ebaa8037 100644
--- a/pkg/custom-provider/query_builder.go
+++ b/pkg/custom-provider/query_builder.go
@@ -9,6 +9,7 @@ import (
 	prom "github.com/directxman12/k8s-prometheus-adapter/pkg/client"
 )
 
+//QueryBuilder provides functions for generating Prometheus queries.
 type QueryBuilder interface {
 	BuildSelector(seriesName string, groupBy string, groupBySlice []string, queryParts []queryPart) (prom.Selector, error)
 }
@@ -17,6 +18,7 @@ type queryBuilder struct {
 	metricsQueryTemplate *template.Template
 }
 
+//NewQueryBuilder creates a QueryBuilder.
 func NewQueryBuilder(metricsQuery string) (QueryBuilder, error) {
 	metricsQueryTemplate, err := template.New("metrics-query").Delims("<<", ">>").Parse(metricsQuery)
 	if err != nil {
diff --git a/pkg/custom-provider/query_builder_test.go b/pkg/custom-provider/query_builder_test.go
index 300a7cf7..308794c7 100644
--- a/pkg/custom-provider/query_builder_test.go
+++ b/pkg/custom-provider/query_builder_test.go
@@ -79,4 +79,4 @@ func TestQueryWithGroupBy(t *testing.T) {
 	require.Equal(t, selector, expectation)
 }
 
-//TODO: Ensure that the LabelValuesByName and GroupBySlice placeholders function correctly.
+//TODO: AC - Ensure that the LabelValuesByName and GroupBySlice placeholders function correctly.
diff --git a/pkg/custom-provider/resource_converter.go b/pkg/custom-provider/resource_converter.go
index 006ec12f..6008ac02 100644
--- a/pkg/custom-provider/resource_converter.go
+++ b/pkg/custom-provider/resource_converter.go
@@ -17,6 +17,9 @@ import (
 	pmodel "github.com/prometheus/common/model"
 )
 
+//ResourceConverter is a type for extracting associated Kubernetes GroupResource objects from
+//Prometheus series and generating appropriate labels to target specific Kubernetes GroupResource
+//objects.
 type ResourceConverter interface {
 	// ResourcesForSeries returns the group-resources associated with the given series,
 	// as well as whether or not the given series has the "namespace" resource).
@@ -34,6 +37,7 @@ type resourceConverter struct {
 	labelTemplate     *template.Template
 }
 
+//NewResourceConverter creates a ResourceConverter that will use the provided parameters to map data between Prometheus and Kubernetes.
 func NewResourceConverter(resourceTemplate string, overrides map[string]config.GroupResource, mapper apimeta.RESTMapper) (ResourceConverter, error) {
 	converter := &resourceConverter{
 		labelToResource: make(map[pmodel.LabelName]schema.GroupResource),
diff --git a/pkg/custom-provider/series_filterer.go b/pkg/custom-provider/series_filterer.go
index 5a05444f..303b572d 100644
--- a/pkg/custom-provider/series_filterer.go
+++ b/pkg/custom-provider/series_filterer.go
@@ -7,6 +7,8 @@ import (
 	"github.com/directxman12/k8s-prometheus-adapter/pkg/config"
 )
 
+//SeriesFilterer provides functions for filtering collections of Prometheus series
+//to only those that meet certain requirements.
 type SeriesFilterer interface {
 	FilterSeries(series []prom.Series) []prom.Series
 	AddRequirement(filter config.RegexFilter) error
@@ -16,6 +18,8 @@ type seriesFilterer struct {
 	seriesMatchers []*reMatcher
 }
 
+//NewSeriesFilterer creates a SeriesFilterer that will remove any series that do not
+//meet the requirements of the provided RegexFilter(s).
 func NewSeriesFilterer(filters []config.RegexFilter) (SeriesFilterer, error) {
 	seriesMatchers := make([]*reMatcher, len(filters))
 	for i, filterRaw := range filters {
diff --git a/pkg/custom-provider/series_registry.go b/pkg/custom-provider/series_registry.go
index 092f7fe4..77b58726 100644
--- a/pkg/custom-provider/series_registry.go
+++ b/pkg/custom-provider/series_registry.go
@@ -21,7 +21,6 @@ import (
 
 	"github.com/kubernetes-incubator/custom-metrics-apiserver/pkg/provider"
 	apimeta "k8s.io/apimachinery/pkg/api/meta"
-	"k8s.io/apimachinery/pkg/labels"
 
 	prom "github.com/directxman12/k8s-prometheus-adapter/pkg/client"
 	"github.com/directxman12/k8s-prometheus-adapter/pkg/config"
@@ -49,8 +48,6 @@ type SeriesRegistry interface {
 	// SeriesForMetric looks up the minimum required series information to make a query for the given metric
 	// against the given resource (namespace may be empty for non-namespaced resources)
 	QueryForMetric(info provider.CustomMetricInfo, namespace string, resourceNames ...string) (query prom.Selector, found bool)
-	// TODO: Don't house the external metric stuff side-by-side with the custom metric stuff.
-	QueryForExternalMetric(info provider.ExternalMetricInfo, metricSelector labels.Selector) (query prom.Selector, found bool)
 	// MatchValuesToNames matches result values to resource names for the given metric and value set
 	MatchValuesToNames(metricInfo provider.CustomMetricInfo, values pmodel.Vector) (matchedValues map[string]pmodel.SampleValue, found bool)
 }
@@ -78,6 +75,7 @@ type basicSeriesRegistry struct {
 	metricLister MetricListerWithNotification
 }
 
+//NewBasicSeriesRegistry creates a SeriesRegistry driven by the data from the provided MetricLister.
 func NewBasicSeriesRegistry(lister MetricListerWithNotification, mapper apimeta.RESTMapper) SeriesRegistry {
 	var registry = basicSeriesRegistry{
 		mapper:       mapper,
@@ -93,7 +91,7 @@ func (r *basicSeriesRegistry) filterMetrics(result metricUpdateResult) metricUpd
 	namers := make([]MetricNamer, 0)
 	series := make([][]prom.Series, 0)
 
-	targetType := config.MetricType("Custom")
+	targetType := config.Custom
 
 	for i, namer := range result.namers {
 		if namer.MetricType() == targetType {
@@ -205,30 +203,6 @@ func (r *basicSeriesRegistry) QueryForMetric(metricInfo provider.CustomMetricInf
 	return query, true
 }
 
-func (r *basicSeriesRegistry) QueryForExternalMetric(metricInfo provider.ExternalMetricInfo, metricSelector labels.Selector) (query prom.Selector, found bool) {
-	r.mu.RLock()
-	defer r.mu.RUnlock()
-	//TODO: Implementation
-	return "", false
-	// info, infoFound := r.info[metricInfo]
-	// if !infoFound {
-	// 	//TODO: Weird that it switches between types here.
-	// 	glog.V(10).Infof("metric %v not registered", metricInfo)
-	// 	return "", false
-	// }
-
-	// query, err := info.namer.QueryForExternalSeries(info.seriesName, metricSelector)
-	// if err != nil {
-	// 	//TODO: See what was being .String() and implement that for ExternalMetricInfo.
-	// 	// errorVal := metricInfo.String()
-	// 	errorVal := "something"
-	// 	glog.Errorf("unable to construct query for metric %s: %v", errorVal, err)
-	// 	return "", false
-	// }
-
-	// return query, true
-}
-
 func (r *basicSeriesRegistry) MatchValuesToNames(metricInfo provider.CustomMetricInfo, values pmodel.Vector) (matchedValues map[string]pmodel.SampleValue, found bool) {
 	r.mu.RLock()
 	defer r.mu.RUnlock()