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feat(collector/receiver): support extra fields in structured JSON function logs #2251

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34b1730
feat: json logging extra fields support
tomsobpl Feb 27, 2026
56f6141
feat: removed hardcoded prefix and extended tests
tomsobpl Mar 17, 2026
a211735
Merge remote-tracking branch 'origin/main' into feat/extra-fields-sup…
tomsobpl Mar 17, 2026
d9c75a0
chore: unifying the codebase
tomsobpl Mar 17, 2026
1ad4f56
Merge remote-tracking branch 'origin/main' into feat/extra-fields-sup…
tomsobpl Apr 14, 2026
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13 changes: 13 additions & 0 deletions collector/receiver/telemetryapireceiver/receiver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -490,6 +490,19 @@ func (r *telemetryAPIReceiver) createLogs(slice []event) (plog.Logs, error) {
}
} else if line, ok := record["message"].(string); ok {
logRecord.Body().SetStr(line)

for key, value := range record {
switch key {
case "level", "message", "requestId", "timestamp":
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@wpessers wpessers Apr 22, 2026

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You really should include "type" here as well. Look at:

opentelemetry-lambda/collector/receiver/telemetryapireceiver/receiver.go

Line 430 in e0f470f

logRecord.Attributes().PutStr("type", el.Type)

Every log record gets an attribute with key "type" and a value like "function" or "platform.start", = the event type from the Telemetry API.

Now what if we have a log line originating from a user's lambda function code:

{
  "message": "buy order",
  "type": "checkout",
  "orderId": "123"
}

So now in your newly added code below (in the default branch) you will simply overwrite the type attribute. And its value will now be "checkout" instead of "function"...

Another, maybe better, option would be to prefix the additional fields that are in a user's logs so we can keep both.

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@tomsobpl tomsobpl Apr 22, 2026

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That was an oversight, good catch.

In the first place I was thinking about adding prefixes to the fields but after some thought I abandoned this option. Developers should be familiar with limitations and reserved fields and should handle that themselves on business logic level.

But maybe it's worth to update documentation and point out all the reserved internal fields with info that they will be prioritized over users metadata. WDYT?

continue
default:
attr, _ := logRecord.Attributes().GetOrPutEmpty(key)
if err := attr.FromRaw(value); err != nil {
r.logger.Warn(fmt.Sprintf("error creating attribute: %s", key), zap.Error(err))
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@wpessers wpessers Apr 22, 2026

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fmt.Sprintf is okay but I'd prefer leveraging zap as much as possible here. Also not sure why we'd prefer logging this as a warning vs an error level but happy to hear your thoughts on that. I'd suggest something like:

Suggested change
r.logger.Warn(fmt.Sprintf("error creating attribute: %s", key), zap.Error(err))
r.logger.Warn("Failed to convert field to attribute", zap.String("key", key), zap.Error(err))

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@tomsobpl tomsobpl Apr 22, 2026

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I personally do not feel that after emiting an error level process should continue and that's why I chose warning here.

Probably it is more preferred to prioritize handling request correctly instead stopping it due to malformed log metadata. Warning developer that something was not correctly logged should be enough IMHO.

Anyway agree on the zap usage.

continue
}
Comment on lines +500 to +503
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@wpessers wpessers Apr 22, 2026

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If an error is returned out of the FromRaw call you log but shouldn't you also remove the attribute from the map?

}
}
}
} else {
if requestId := r.getCurrentRequestId(); requestId != "" {
Expand Down
111 changes: 111 additions & 0 deletions collector/receiver/telemetryapireceiver/receiver_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -359,6 +359,7 @@ func TestCreateLogs(t *testing.T) {
containsRequestId bool
requestId string
severityNumber plog.SeverityNumber
attributes map[string]interface{}
}

testCases := []struct {
Expand Down Expand Up @@ -479,6 +480,109 @@ func TestCreateLogs(t *testing.T) {
},
expectError: false,
},
{
desc: "function json with extra fields",
slice: []event{
{
Time: "2026-02-26T20:15:32.000Z",
Type: "function",
Record: map[string]any{
"timestamp": "2026-02-26T20:15:32.000Z",
"level": "INFO",
"requestId": "79b4f56e-95b1-4643-9700-2807f4e6",
"message": "Hello world, I am a function with extra data!",
"extraString": "stringValue",
"extraNumber": 2217,
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@wpessers wpessers Apr 22, 2026

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This can never happen in production. a Record is always populated via json.Unmarshal into, which always decodes JSON numbers as float64. Consider using float64(2217) as input so the test mirrors reality.

See: https://pkg.go.dev/encoding/json#Unmarshal

"extraFloat": 3.14,
"extraBoolean": true,
"extraNull": nil,
"extraArrayOfStrings": []any{"stringValue", "stringValue"},
"extraArrayOfNumbers": []any{2217, 2217},
"extraArrayOfMixedTypes": []any{"stringValue", 2217, true, nil},
"extraArrayWithNesting": []any{"stringValue", []any{2217, []any{true, nil}}},
"extraObject": map[string]any{
"stringValue": "stringValue",
"numberValue": 2217,
"booleanValue": true,
"nullValue": nil,
},
"extraObjectWithNesting": map[string]any{
"stringValue": "stringValue",
"numberValue": 2217,
"booleanValue": true,
"nullValue": nil,
"arrayValue": []any{"stringValue", 2217},
"objectValue": map[string]any{
"stringValue": "stringValue",
"numberValue": 2217,
},
},
},
},
},
expectedLogs: []logInfo{
{
logType: "function",
timestamp: "2026-02-26T20:15:32.000Z",
body: "Hello world, I am a function with extra data!",
containsRequestId: true,
requestId: "79b4f56e-95b1-4643-9700-2807f4e6",
severityText: "Info",
severityNumber: plog.SeverityNumberInfo,
attributes: map[string]any{
"extraString": "stringValue",
"extraNumber": int64(2217),
"extraFloat": float64(3.14),
"extraBoolean": true,
"extraNull": nil,
"extraArrayOfStrings": []any{
"stringValue",
"stringValue",
},
"extraArrayOfNumbers": []any{
int64(2217),
int64(2217),
},
"extraArrayOfMixedTypes": []any{
"stringValue",
int64(2217),
true,
nil,
},
"extraArrayWithNesting": []any{
"stringValue",
[]any{
int64(2217),
[]any{
true, nil,
},
},
},
"extraObject": map[string]any{
"stringValue": "stringValue",
"numberValue": int64(2217),
"booleanValue": true,
"nullValue": nil,
},
"extraObjectWithNesting": map[string]any{
"stringValue": "stringValue",
"numberValue": int64(2217),
"booleanValue": true,
"nullValue": nil,
"arrayValue": []any{
"stringValue",
int64(2217),
},
"objectValue": map[string]any{
"stringValue": "stringValue",
"numberValue": int64(2217),
},
},
},
},
},
expectError: false,
},
{
desc: "extension text",
slice: []event{
Expand Down Expand Up @@ -820,6 +924,13 @@ func TestCreateLogs(t *testing.T) {
require.Equal(t, expected.severityText, logRecord.SeverityText())
require.Equal(t, expected.severityNumber, logRecord.SeverityNumber())
require.Equal(t, expected.body, logRecord.Body().Str())

// Check extra attributes
for key, value := range expected.attributes {
attr, ok := logRecord.Attributes().Get(key)
require.True(t, ok, "expected attribute %s not found", key)
require.Equal(t, value, attr.AsRaw(), "expected attribute %s to have value %v, got %v", key, value, attr.AsRaw())
}
}
})
}
Expand Down