feat(logs): custom attributes API #1435

JoshuaMoelans · 2025-10-30T15:08:43Z

With the logs_with_attributes option set to true, we can still parse the message string as a format string, but we take the first varg passed into sentry_log_X as an attributes object.
If the passed-in value is not a sentry_value_t object, we will just ignore it (as long as it is still a sentry_value_t type, otherwise we hit UNREACHABLE("invalid value type"); when trying to parse it)

sentry_options_set_logs_with_attributes(options, true);
...
sentry_value_t attributes = sentry_value_new_object();
sentry_value_t attr = sentry_value_new_attribute(sentry_value_new_string("my_attribute"), NULL);
sentry_value_t attr_2 = sentry_value_new_attribute(sentry_value_new_int64(INT64_MAX), "fermions");
sentry_value_t attr_3 = sentry_value_new_attribute(sentry_value_new_int64(INT64_MIN), "bosons");
sentry_value_set_by_key(attributes, "my.custom.attribute", attr);
sentry_value_set_by_key(attributes, "number.first", attr_2);
sentry_value_set_by_key(attributes, "number.second", attr_3);

sentry_log_debug("logging with %d custom attributes", attributes, 3);

sentry_log_debug("logging with %s custom attributes", sentry_value_new_object(), "no");

Which shows up in the UI as such:

This is also useful for downstream SDKs which might not need string interpolation, but still want to pass down message.parameter.X attributes:

sentry_value_t param_attributes = sentry_value_new_object();
sentry_value_t param_attr = sentry_value_new_attribute(sentry_value_new_string("parameter"), NULL);
sentry_value_set_by_key(param_attributes,"message.parameter.0", param_attr);
sentry_log_fatal("logging with a custom parameter attributes", param_attributes);

‼️ custom attributes take precedence over the default attributes, except for sentry.message.parameter.X values; if you pass in a string with format specifiers, these are used for the message parameter values.

sentry_value_t param_attributes = sentry_value_new_object();
sentry_value_t param_attr = sentry_value_new_attribute(sentry_value_new_string("parameter"), NULL);
sentry_value_t param_attr_2 = sentry_value_new_attribute(sentry_value_new_string("custom-sdk-name"), NULL);
sentry_value_set_by_key(param_attributes, "sentry.message.parameter.0", param_attr);
sentry_value_set_by_key(param_attributes, "sentry.sdk.name", param_attr_2);
sentry_log_fatal("logging with a custom parameter %s attributes", param_attributes, "and format-string");

--> the custom-sdk-name shows up, but the sentry.message.parameter.0 value is "and format-string", not "parameter".

github-actions · 2025-10-30T15:09:12Z

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 660cc77

src/sentry_logs.c

limbonaut · 2025-11-03T13:39:24Z

I gave it a spin in the Godot SDK, and it works fine!

JoshuaMoelans · 2025-11-03T14:18:21Z

examples/example.c

+        sentry_value_set_by_key(
+            param_attributes, "message.parameter.0", param_attr);
+        sentry_value_set_by_key(
+            param_attributes, "sentry.sdk.name", param_attr_2);
+        // TODO discuss; param_attributes[message.parameter.0] gets overwritten
+        //  by 'and format string'. Is this expected?
+        sentry_log_fatal("logging with a custom parameter %s attributes",
+            param_attributes, "and format-string");


IMO we can overwrite all default attributes except for string format values that are passed in; otherwise there would be a mismatch between the string template + sentry.message.parameter.X and the log body value

I think using both the attributes to pass message.parameter.0 and the sentry-native interpolation API is already a misuse. I don't think we need to be protective about it. Let it be an undefined behavior.

JoshuaMoelans · 2025-11-03T14:22:54Z

src/sentry_logs.c

+            if (sentry_value_get_type(custom_attributes)
+                == SENTRY_VALUE_TYPE_OBJECT) {
+                // TODO do we want to inspect that the object is attribute-like?
+                sentry_value_decref(attributes);
+                attributes = sentry__value_clone(custom_attributes);
+            } else {


I'm not sure how far we need to go to protect from user error. An invalid attribute (no "type" and "value" keys) seems to just get ignored in processing (the log still makes it to the UI)

JoshuaMoelans · 2025-11-04T10:20:57Z

@sentry review

sentry · 2025-11-04T10:23:15Z

src/sentry_logs.c

    sentry_value_t log = sentry_value_new_object();
    sentry_value_t attributes = sentry_value_new_object();

-    va_list args_copy_1, args_copy_2, args_copy_3;
-    va_copy(args_copy_1, args);
-    va_copy(args_copy_2, args);
-    va_copy(args_copy_3, args);
-    int len = vsnprintf(NULL, 0, message, args_copy_1) + 1;
-    va_end(args_copy_1);
-    size_t size = (size_t)len;
-    char *fmt_message = sentry_malloc(size);
-    if (!fmt_message) {
+    SENTRY_WITH_OPTIONS (options) {
+        // Extract custom attributes if the option is enabled
+        if (sentry_options_get_logs_with_attributes(options)) {
+            va_list args_copy;
+            va_copy(args_copy, args);


The removal of the fallback sentry.sdk.name attribute (previously added unconditionally) is now handled by the add_attribute() no-op behavior when custom attributes override it. However, verify that in the non-custom-attributes path, sentry.sdk.name is still being added consistently by add_scope_and_options_data(). The logic depends on add_attribute() being called with sentry.sdk.name from somewhere else in the flow.
_{Severity: MEDIUM}

🤖 Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not valid. Location: src/sentry_logs.c#L647-L680 Potential issue: The removal of the fallback `sentry.sdk.name` attribute (previously added unconditionally) is now handled by the `add_attribute()` no-op behavior when custom attributes override it. However, verify that in the non-custom-attributes path, `sentry.sdk.name` is still being added consistently by `add_scope_and_options_data()`. The logic depends on `add_attribute()` being called with `sentry.sdk.name` from somewhere else in the flow.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

sentry · 2025-11-04T10:23:18Z

src/sentry_logs.c

@@ -708,14 +744,6 @@
    // to the log


The entire message formatting and parameter parsing logic is now wrapped inside SENTRY_WITH_OPTIONS. While this ensures thread-safe access to options, it's a behavioral change from the original implementation. Verify that the lock scope doesn't negatively impact performance for high-frequency logging scenarios, and consider documenting why this lock scope is necessary.
_{Severity: MEDIUM}

🤖 Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not valid. Location: src/sentry_logs.c#L679-L744 Potential issue: The entire message formatting and parameter parsing logic is now wrapped inside `SENTRY_WITH_OPTIONS`. While this ensures thread-safe access to options, it's a behavioral change from the original implementation. Verify that the lock scope doesn't negatively impact performance for high-frequency logging scenarios, and consider documenting why this lock scope is necessary.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

There is no exclusive lock over the options, since we only increment the refcount (and the options themselves are read-only). So there is no real performance impact here.

limbonaut

LGTM 🙃

JoshuaMoelans commented Oct 31, 2025

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src/sentry_logs.c Show resolved Hide resolved

JoshuaMoelans mentioned this pull request Oct 31, 2025

Structured Logs: follow-up #1398

Open

JoshuaMoelans added 12 commits November 3, 2025 12:52

initial attributes value implementation

573a683

add logs custom attributes + option

95494e7

CHANGELOG.md

fe2416a

format

44089a3

format + cleanup

ad53186

fix memleaks

1415f3e

update example.c log callback to use attribute creator

15bb9bb

add custom-attributes X format string POC

46cd9f1

infer attribute type from sentry_value_t value

878a488

fix attribute memleak

33a4471

logs take ownership of custom attributes

c753b66

fix unused variable

1ea83a8

JoshuaMoelans force-pushed the joshua/feat/logs_custom_attributes branch from e1f307a to 1ea83a8 Compare November 3, 2025 11:54

limbonaut mentioned this pull request Nov 3, 2025

feat: String interpolation in structured logging getsentry/sentry-godot#435

Draft

don't let default attributes overwrite custom ones

5408b75

JoshuaMoelans commented Nov 3, 2025

View reviewed changes

JoshuaMoelans added 4 commits November 3, 2025 15:25

cleanup

ad7b2fd

decref duplicate attributes

e54fbe3

cleanup TODOs

e6f2655

fix for 32-bit windows test

660cc77

JoshuaMoelans marked this pull request as ready for review November 4, 2025 10:20

sentry bot reviewed Nov 4, 2025

View reviewed changes

JoshuaMoelans requested a review from limbonaut November 4, 2025 11:18

JoshuaMoelans requested a review from mujacica November 4, 2025 11:18

limbonaut approved these changes Nov 4, 2025

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