fix(prometheus): instant vector query support (#69)

.github/workflows/merge-master.yaml

@@ -21,7 +21,7 @@ jobs:
       release_notes: ${{ steps.semantic.outputs.new_release_notes }}
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
       with:
         token: ${{ secrets.ACCESS_TOKEN }}
 
@@ -51,15 +51,15 @@ jobs:
     needs: prepare
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Go
-      uses: actions/setup-go@v2
+      uses: actions/setup-go@v3
       with:
         go-version: '1.17'
 
     - name: Cache Go modules
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: ~/go/pkg/mod
         key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}

.github/workflows/pull-request.yaml

@@ -15,15 +15,15 @@ jobs:
     runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
 
     - name: Setup Go
-      uses: actions/setup-go@v2
+      uses: actions/setup-go@v3
       with:
         go-version: '1.17'
 
     - name: Cache Go modules
-      uses: actions/cache@v2
+      uses: actions/cache@v3
       with:
         path: ~/go/pkg/mod
         key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}

pkg/common/clients/prometheus_client.go

@@ -60,3 +60,19 @@ func (c PrometheusClient) QueryRange(ctx context.Context, query string, startAt,
 	}
 	return result, nil
 }
+
+// Query returns an instant vector, given the following parameters:
+//    - query: Prometheus query
+//    - moment: moment in time
+// It returns the result vector and the execution error encountered.
+func (c PrometheusClient) Query(ctx context.Context, query string, moment time.Time) (model.Value, error) {
+	result, warnings, err := c.api.Query(ctx, query, moment)
+	if err != nil {
+		c.logger.Errorf("Error querying Prometheus: %v", err)
+		return nil, err
+	}
+	if len(warnings) > 0 {
+		c.logger.Warnf("Prometheus query warnings result: %v", warnings)
+	}
+	return result, nil
+}