[processor/probabilisticsampler] Allow non-bytes attributes (open-tel…

…emetry#26564)

When doing a probabilistic sampling for logs, the probabilistic sampler
currently requires the source attribute to be of bytes value. This PR
changes that to allow any value type to be used.

Fixes open-telemetry#18222

Signed-off-by: Juraci Paixão Kröhling <[email protected]>

---------

Signed-off-by: Juraci Paixão Kröhling <[email protected]>

.chloggen/18222-probabilisticsampler-allow-non-bytes.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: 'enhancement'
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: processor/probabilisticsampler
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Allow non-bytes values to be used as the source for the sampling decision
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [18222]
+
+# (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:
+
+# 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]

processor/probabilisticsamplerprocessor/logsprocessor.go

@@ -64,7 +64,7 @@ func (lsp *logSamplerProcessor) processLogs(ctx context.Context, ld plog.Logs) (
 				if lidBytes == nil && lsp.samplingSource != "" {
 					if value, ok := l.Attributes().Get(lsp.samplingSource); ok {
 						tagPolicyValue = lsp.samplingSource
-						lidBytes = value.Bytes().AsRaw()
+						lidBytes = getBytesFromValue(value)
 					}
 				}
 				priority := lsp.scaledSamplingRate
@@ -102,3 +102,10 @@ func (lsp *logSamplerProcessor) processLogs(ctx context.Context, ld plog.Logs) (
 	}
 	return ld, nil
 }
+
+func getBytesFromValue(value pcommon.Value) []byte {
+	if value.Type() == pcommon.ValueTypeBytes {
+		return value.Bytes().AsRaw()
+	}
+	return []byte(value.AsString())
+}

processor/probabilisticsamplerprocessor/logsprocessor_test.go

@@ -116,6 +116,15 @@ func TestLogsSampling(t *testing.T) {
 			},
 			received: 23,
 		},
+		{
+			name: "sampling_source sampling as string",
+			cfg: &Config{
+				SamplingPercentage: 50,
+				AttributeSource:    recordAttributeSource,
+				FromAttribute:      "bar",
+			},
+			received: 29, // probabilistic... doesn't yield the same results as foo
+		},
 		{
 			name: "sampling_priority",
 			cfg: &Config{
@@ -149,10 +158,11 @@ func TestLogsSampling(t *testing.T) {
 				ib := byte(i)
 				traceID := [16]byte{0, 0, 0, 0, 0, 0, 0, 0, ib, ib, ib, ib, ib, ib, ib, ib}
 				record.SetTraceID(traceID)
-				// set half of records with a foo attribute
+				// set half of records with a foo (bytes) and a bar (string) attribute
 				if i%2 == 0 {
 					b := record.Attributes().PutEmptyBytes("foo")
 					b.FromRaw(traceID[:])
+					record.Attributes().PutStr("bar", record.TraceID().String())
 				}
 				// set a fourth of records with a priority attribute
 				if i%4 == 0 {