[receiver/snmpreceiver] fix scalar RA # check (#26363)

**Description:** 
Fixed a bug introduced by
[#25174](#25174)

There was check that was supposed to ensure that all resource attributes
added to a metric were scalar, but it was really checking if the number
of resource attributes on a metric was the same as the total number of
possible scalar resource attributes defined in the config. This check
has been updated to explicitly verify that all of the resource
attributes on the metric are scalar.

Bug examples:
- A column metric indexed by a column attribute has two scalar resource
attributes with different names but the same oid value. They are the
only two scalar RAs defined in the config. Since the oids are added to a
map whose length is checked, they are seen as one value and the
comparison fails so many resources are created instead of one.
- A column metric indexed by a column attribute has only one scalar
resource attribute when two possible attributes are defined in the
config. The check fails and many resources are created instead of one.

**Testing:** 
- Test that a metric with one scalar resource attribute when two are
available still creates only one resource
- First bug does not feel necessary to unit test, it has been tested
locally and is fixed.

**Documentation:**
- N/A

Author: kuiperda

.chloggen/fix-snmp-scalar-ra-check.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: snmpreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix how to determine how many RAs on a metric are scalar
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [26363]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: We now create the proper number of resources for configurations where a resource uses fewer than the available number of scalar resource attribtues.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/snmpreceiver/scraper.go

@@ -221,9 +221,16 @@ func (s *snmpScraper) indexedDataToMetric(
 	// with the row index of the SNMP data
 	resourceAttributeNames := configHelper.getResourceAttributeNames(data.columnOID)
 
+	// Check how many of the resource attributes on this metric are scalar
+	var numScalarResourceAttributes int
+	for name := range resourceAttributes {
+		if s.cfg.ResourceAttributes[name].ScalarOID != "" {
+			numScalarResourceAttributes++
+		}
+	}
 	var resourceKey string
-	// If we only have scalar resource attributes, we don't need multiple resources
-	if len(resourceAttributes) == len(columnOIDScalarResourceAttributeValues) {
+	// If the only resource attributes on this metric are scalar, we don't need multiple resources
+	if len(resourceAttributes) == numScalarResourceAttributes {
 		resourceKey = getResourceKey(resourceAttributeNames, "")
 	} else {
 		resourceKey = getResourceKey(resourceAttributeNames, indexString)

receiver/snmpreceiver/scraper_test.go

@@ -2982,6 +2982,103 @@ func TestScrape(t *testing.T) {
 				require.NoError(t, err)
 			},
 		},
+		{
+			desc: "Metric does not use all available scalar RAs and still behaves properly (near copy of (24)) (29)",
+			testFunc: func(t *testing.T) {
+				mockClient := new(MockClient)
+				scalarRA1 := SNMPData{
+					oid:       ".5.0",
+					value:     "scalar",
+					valueType: stringVal,
+				}
+				scalarRA2 := SNMPData{
+					oid:       ".6.0",
+					value:     "also scalar",
+					valueType: stringVal,
+				}
+				coidAttr11 := SNMPData{
+					columnOID: ".1",
+					oid:       ".1.1",
+					value:     "string1",
+					valueType: stringVal,
+				}
+				coidAttr12 := SNMPData{
+					columnOID: ".1",
+					oid:       ".1.2",
+					value:     "string2",
+					valueType: stringVal,
+				}
+				coid21 := SNMPData{
+					columnOID: ".2",
+					oid:       ".2.1",
+					value:     int64(3),
+					valueType: integerVal,
+				}
+				coid22 := SNMPData{
+					columnOID: ".2",
+					oid:       ".2.2",
+					value:     int64(4),
+					valueType: integerVal,
+				}
+				mockClient.On("Connect").Return(nil)
+				mockClient.On("Close").Return(nil)
+				mockClient.On("GetScalarData", []string{".5.0", ".6.0"}, mock.Anything).Return([]SNMPData{scalarRA1, scalarRA2}).Once()
+				mockClient.On("GetIndexedData", []string{".1"}, mock.Anything).Return([]SNMPData{coidAttr11, coidAttr12}).Once()
+				mockClient.On("GetIndexedData", []string{".2"}, mock.Anything).Return([]SNMPData{coid21, coid22}).Once()
+				scraper := &snmpScraper{
+					cfg: &Config{
+						ResourceAttributes: map[string]*ResourceAttributeConfig{
+							"rattr1": {
+								ScalarOID: ".5.0",
+							},
+							"rattr2": {
+								ScalarOID: ".6.0",
+							},
+						},
+						Attributes: map[string]*AttributeConfig{
+							"attr1": {
+								OID: ".1",
+							},
+						},
+						Metrics: map[string]*MetricConfig{
+							"metric1": {
+								Description: "test description",
+								Unit:        "By",
+								Gauge: &GaugeMetric{
+									ValueType: "int",
+								},
+								ColumnOIDs: []ColumnOID{
+									{
+										OID:                ".2",
+										ResourceAttributes: []string{"rattr1"},
+										Attributes: []Attribute{
+											{
+												Name: "attr1",
+											},
+										},
+									},
+								},
+							},
+						},
+					},
+					settings: receivertest.NewNopCreateSettings(),
+					client:   mockClient,
+					logger:   zap.NewNop(),
+				}
+
+				expectedMetricGen := func(t *testing.T) pmetric.Metrics {
+					goldenPath := filepath.Join("testdata", "expected_metrics", "29_metric_does_not_use_all_available_scalar_RAs_golden.yaml")
+					expectedMetrics, err := golden.ReadMetrics(goldenPath)
+					require.NoError(t, err)
+					return expectedMetrics
+				}
+				expectedMetrics := expectedMetricGen(t)
+				metrics, err := scraper.scrape(context.Background())
+				require.NoError(t, err)
+				err = pmetrictest.CompareMetrics(expectedMetrics, metrics, pmetrictest.IgnoreTimestamp())
+				require.NoError(t, err)
+			},
+		},
 	}
 
 	for _, tc := range testCases {

receiver/snmpreceiver/testdata/expected_metrics/29_metric_does_not_use_all_available_scalar_RAs_golden.yaml

@@ -0,0 +1,28 @@
+resourceMetrics:
+  - resource:
+      attributes:
+        - key: rattr1
+          value:
+            stringValue: scalar
+    scopeMetrics:
+      - metrics:
+          - description: test description
+            gauge:
+              dataPoints:
+                - asInt: "3"
+                  attributes:
+                    - key: attr1
+                      value:
+                        stringValue: string1
+                  timeUnixNano: "1651783494931319000"
+                - asInt: "4"
+                  attributes:
+                    - key: attr1
+                      value:
+                        stringValue: string2
+                  timeUnixNano: "1651783494931319000"
+            name: metric1
+            unit: By
+        scope:
+          name: otelcol/snmpreceiver
+          version: latest