feat: add default sampling rate to mlobs logger (#567)

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# Description
<!-- Briefly describe the motivation for the change. Please include
illustrations where appropriate. -->
As of now, the mlobs logger logs every single message sent to the
logger. As there is no good way at the moment to use different logger
configuration for different model, tentatively, we will be adding a
default sampling rate that will apply to all models that enable mlobs
logger.

# Modifications
<!-- Summarize the key code changes. -->
Add a 2% sampling rate to mlobs sink.

# Tests
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scenarios should be tested? Consider the backward compatibility of the
changes, whether corner cases are covered, etc. Please describe the
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- [x] Deploying new and existing standard models
- [ ] Deploying PyFunc models
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# Checklist
- [ ] Added PR label
- [ ] Added unit test, integration, and/or e2e tests
- [ ] Tested locally
- [ ] Updated documentation
- [ ] Update Swagger spec if the PR introduce API changes
- [ ] Regenerated Golang and Python client if the PR introduces API
changes

# Release Notes
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```release-note

```

api/pkg/inference-logger/logger/mlobs_sink.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math/rand"
 
 	"google.golang.org/protobuf/types/known/timestamppb"
 
@@ -19,6 +20,10 @@ var (
 	ErrMalformedLogEntry = errors.New("malformed log entry")
 )
 
+const (
+	SamplingRate = 0.01
+)
+
 type MLObsSink struct {
 	logger   *zap.SugaredLogger
 	producer KafkaProducer
@@ -163,6 +168,9 @@ func (m *MLObsSink) buildNewKafkaMessage(predictionLog *upiv1.PredictionLog) (*k
 
 func (m *MLObsSink) Sink(rawLogEntries []*LogEntry) error {
 	for _, rawLogEntry := range rawLogEntries {
+		if rand.Float64() >= SamplingRate {
+			continue
+		}
 		predictionLog, err := m.newPredictionLog(rawLogEntry)
 		if err != nil {
 			m.logger.Errorf("unable to convert log entry: %v", err)