AzureMonitor: Support decimal (as float64) type in analytics/logs (grafana#28480)

loss of precision but will make the response work instead of erroring
follows work already done in the ADX plugin
fixes grafana#28278

Author: kylebrandt

pkg/tsdb/azuremonitor/azure-log-analytics-table-frame.go

@@ -69,6 +69,7 @@ var converterMap = map[string]data.FieldConverter{
 	"long":     longConverter,
 	"real":     realConverter,
 	"bool":     boolConverter,
+	"decimal":  decimalConverter,
 }
 
 var stringConverter = data.FieldConverter{
@@ -194,3 +195,41 @@ var longConverter = data.FieldConverter{
 		return &out, err
 	},
 }
+
+// decimalConverter converts the Kusto 128-bit type number to
+// a float64. We do not have 128 bit numbers in our dataframe
+// model yet (and even if we did, not sure how javascript would handle them).
+// In the future, we may want to revisit storing this will proper precision,
+// but for now it solves the case of people getting an error response.
+// If we were to keep it a string, it would not work correctly with calls
+// to functions like sdk's data.LongToWide.
+var decimalConverter = data.FieldConverter{
+	OutputFieldType: data.FieldTypeNullableFloat64,
+	Converter: func(v interface{}) (interface{}, error) {
+		var af *float64
+		if v == nil {
+			return af, nil
+		}
+
+		jS, sOk := v.(string)
+		if sOk {
+			out, err := strconv.ParseFloat(jS, 64)
+			if err != nil {
+				return nil, err
+			}
+			return &out, err
+		}
+
+		// As far as I can tell this always comes in a string, but this is in the
+		// ADX code, so leaving this in case values do sometimes become a number somehow.
+		jN, nOk := v.(json.Number)
+		if !nOk {
+			return nil, fmt.Errorf("unexpected type, expected json.Number or string but got type %T with a value of %v", v, v)
+		}
+		out, err := jN.Float64() // Float64 calls strconv.ParseFloat64
+		if err != nil {
+			return nil, err
+		}
+		return &out, nil
+	},
+}

pkg/tsdb/azuremonitor/azure-log-analytics-table-frame_test.go

@@ -112,10 +112,11 @@ func TestLogTableToFrame(t *testing.T) {
 					data.NewField("XLong", nil, []*int64{pointer.Int64(9223372036854775807)}),
 					data.NewField("XReal", nil, []*float64{pointer.Float64(1.797693134862315708145274237317043567981e+308)}),
 					data.NewField("XTimeSpan", nil, []*string{pointer.String("00:00:00.0000001")}),
+					data.NewField("XDecimal", nil, []*float64{pointer.Float64(79228162514264337593543950335)}),
 				)
 				frame.Meta = &data.FrameMeta{
 					Custom: &LogAnalyticsMeta{ColumnTypes: []string{"bool", "string", "datetime",
-						"dynamic", "guid", "int", "long", "real", "timespan"}},
+						"dynamic", "guid", "int", "long", "real", "timespan", "decimal"}},
 				}
 				return frame
 			},

pkg/tsdb/azuremonitor/testdata/loganalytics/7-log-analytics-all-types-table.json

@@ -38,6 +38,10 @@
           {
             "name": "XTimeSpan",
             "type": "timespan"
+          },
+          {
+            "name":"XDecimal",
+            "type":"decimal"
           }
         ],
         "rows": [
@@ -50,10 +54,11 @@
             2147483647,
             9223372036854775807,
             1.7976931348623157e+308,
-            "00:00:00.0000001"
+            "00:00:00.0000001",
+            "79228162514264337593543950335"
           ]
         ]
       }
     ]
   }
-  
+