improve Prometheus API mini docs

opsani · Feb 2, 2022 · 8a76d0f · 8a76d0f
1 parent af194da
commit 8a76d0f
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Showing 2 changed files with 19 additions and 10 deletions.
diff --git a/sources/prometheus/containers.go b/sources/prometheus/containers.go
@@ -12,7 +12,6 @@ import (
  "reflect"
  "strings"
  "text/template"
- "time"
 
  v1 "github.com/prometheus/client_golang/api/prometheus/v1"
  "github.com/prometheus/common/model"
@@ -25,7 +24,7 @@ import (
 // get request or limit values for all resources of all containers of the specificed application
 func getContainersResources(ctx context.Context, promApi v1.API, app *appmodel.App, timeRange v1.Range, queryTemplate *template.Template, querySelectors *QuerySelectors, resourceFieldName string) (v1.Warnings, error) {
  // set up query context with timeout
- ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) // TODO: fix constant
+ ctx, cancel := context.WithTimeout(context.Background(), queryTimeout)
  defer cancel()
 
  // prepare query string by injecting selector data into the provided query template
@@ -102,7 +101,7 @@ func getContainersResources(ctx context.Context, promApi v1.API, app *appmodel.A
 
 func getContainersUseValueMap(ctx context.Context, promApi v1.API, app *appmodel.App, timeRange v1.Range, queryTemplate *template.Template, querySelectors *QuerySelectors) (map[string]float64, v1.Warnings, error) {
  // set up query context with timeout
- ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) // TODO: fix constant
+ ctx, cancel := context.WithTimeout(context.Background(), queryTimeout)
  defer cancel()
 
  var allWarnings v1.Warnings
@@ -227,7 +226,7 @@ func handleWarnErr(allWarnings v1.Warnings, newWarnings v1.Warnings, newError er
 
 func collectContainersInfo(ctx context.Context, promApi v1.API, app *appmodel.App, timeRange v1.Range) (v1.Warnings, error) {
  // set up query context with timeout
- ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) // TODO: fix constant
+ ctx, cancel := context.WithTimeout(context.Background(), queryTimeout)
  defer cancel()
 
  var allWarnings v1.Warnings

diff --git a/sources/prometheus/prometheus.go b/sources/prometheus/prometheus.go
@@ -28,7 +28,17 @@ import (
 )
 
 // Example API usage: https://github.com/prometheus/client_golang/blob/master/api/prometheus/v1/example_test.go
-// See also: https://stackoverflow.com/questions/63471775/extract-prometheus-metrics-in-go
+// Note:
+// Query() returns model.Vector
+// QueryRange() returns model.Matrix
+// In turn, these have pointers to SampleStream
+// In turn, the stream contains (a) Metric (name and LabelSet) and (b) Values of type []SamplePair
+// In turn, SamplePair contains (a) TimeStamp and (b) SampleValue (typically a float)
+// Use the following command to get relevant references:
+// go doc v1.API.{Query|QueryValues|LabelValues}
+// go doc model.{Matrix|Vector|SampleStream|SamplePair|Metric|Value|LabelSet|LabelValue}
+
+const queryTimeout = 10*time.Second // TODO: consider making configurable
 
 type QuerySelectors struct {
  appmodel.AppMetadata
@@ -48,7 +58,7 @@ func createAPI(uri *url.URL) (v1.API, error) {
 
 func collectNamespaces(ctx context.Context, promApi v1.API, timeRange v1.Range) (model.LabelValues, v1.Warnings, error) {
  // set up query context with timeout
- ctx, cancel := context.WithTimeout(ctx, 10*time.Second) // TODO: fix constant
+ ctx, cancel := context.WithTimeout(ctx, queryTimeout)
  defer cancel()
 
  // Collect namespaces
@@ -73,11 +83,11 @@ func collectNamespaces(ctx context.Context, promApi v1.API, timeRange v1.Range)
 
 func getAggregateMetric(ctx context.Context, promApi v1.API, app *appmodel.App, timeRange v1.Range, metric string, aggrFunc string) (*float64, v1.Warnings, error) {
  // set up query context with timeout
- ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) // TODO: fix constant
+ ctx, cancel := context.WithTimeout(context.Background(), queryTimeout)
  defer cancel()
 
  // prepare query string
- podRE := fmt.Sprintf("%v-.*", app.Metadata.Workload) // pod naming template is <deployment_name>-<pod_spec_hash>-<pod_unique_id> - TODO: tighten RE to avoid unlikelyconflicts
+ podRE := fmt.Sprintf("%v-.*", app.Metadata.Workload) // pod naming template is <deployment_name>-<pod_spec_hash>-<pod_unique_id> - TODO: tighten RE to avoid unlikely conflicts
  query := fmt.Sprintf("%v(%v{namespace=%q,pod=~%q})", aggrFunc, metric, app.Metadata.Namespace, podRE)
 
  // Collect values
@@ -128,7 +138,7 @@ func getAggregateMetric(ctx context.Context, promApi v1.API, app *appmodel.App,
 
 func getRangedMetric(ctx context.Context, promApi v1.API, app *appmodel.App, timeRange v1.Range, queryTemplate *template.Template, querySelectors *QuerySelectors) (*float64, v1.Warnings, error) {
  // set up query context with timeout
- ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second) // TODO: fix constant
+ ctx, cancel := context.WithTimeout(context.Background(), queryTimeout)
  defer cancel()
 
  // prepare query string by injecting selector data into the provided query template
@@ -264,7 +274,7 @@ func mapNamespace(ctx context.Context, promApi v1.API, namespace model.LabelValu
  apps = []*appmodel.App{}
 
  // set up query context with timeout
- reqCtx, cancel := context.WithTimeout(ctx, 10*time.Second) // TODO: fix constant
+ reqCtx, cancel := context.WithTimeout(ctx, queryTimeout)
  defer cancel()
 
  // Collect values