[FR] Allow custom attributes on built-in traces via global attribute API

[jrodiz]

[FR] Allow custom attributes on built-in traces (#6664)

Summary

Resolves #6664

Firebase Performance already had putAttribute/getAttribute/removeAttribute/getAttributes on FirebasePerformance backed by a ConcurrentHashMap, but these were @hide and not wired into built-in trace serialization. This change makes them public and ensures global attributes are included on all traces and network requests — built-in and custom alike.

Changes

• FirebasePerformance.java — Made 4 global attribute methods (putAttribute, removeAttribute, getAttribute, getAttributes) and 3 constants (MAX_TRACE_CUSTOM_ATTRIBUTES, MAX_ATTRIBUTE_KEY_LENGTH, MAX_ATTRIBUTE_VALUE_LENGTH) public
• api.txt — Added the 4 methods to the public FirebasePerformance API surface
• TraceMetricBuilder.java — Merges global attributes into all Trace-based metrics (screen traces, custom traces); trace-level attributes override global on key conflict
• AppStartTrace.java — Applies global attributes to the _app_start trace metric
• AppStateMonitor.java — Applies global attributes to foreground (_fs) and background (_bs) session traces
• NetworkRequestMetricBuilder.java — Merges global attributes into all network request metrics (auto-instrumented OkHttp and manual HttpMetric); per-request attributes override global on key conflict

Usage

// In Application.onCreate() — set once, applies to all built-in and custom traces
FirebasePerformance.getInstance().putAttribute("build_type", "debug");
FirebasePerformance.getInstance().putAttribute("user_tier", "premium");

These attributes will appear on _app_start, _app_in_foreground, _app_in_background, screen traces (_st_*), network requests, and all custom traces automatically.

Design Notes

• Attribute precedence: trace/request-level attributes override global attributes with the same key
• Attribute limit: global attributes are validated at 5 max by existing checkAttribute() logic
• Thread safety: mCustomAttributes is a ConcurrentHashMap; getAttributes() returns a defensive copy
• Timing for _app_start: global attributes must be set before the first activity resumes (e.g., in Application.onCreate())
• Backward compatible: all methods already existed; only visibility was changed

Test Coverage

• _app_start — AppStartTraceTest
• _app_in_foreground (_fs) — AppStateMonitorTest
• _app_in_background (_bs) — AppStateMonitorTest
• Screen traces (_st_*) — AppStateMonitorTest
• Network requests — NetworkRequestMetricBuilderTest
• All events via ApplicationInfo — TransportManagerTest

[gemini-code-assist]

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for GitHub and other Google products, sign up here.

[jrodiz]

/gemini review

[gemini-code-assist]

Code Review

This pull request makes global attribute methods and constants public in FirebasePerformance and ensures these attributes are merged into all traces (built-in and custom) and network requests. Feedback suggests enforcing the MAX_TRACE_CUSTOM_ATTRIBUTES limit during the merge process to prevent events from being dropped by the backend and optimizing map allocations by utilizing the defensive copy returned by getAttributes().

[gemini-code-assist]

The merging logic can result in a network request having more than MAX_TRACE_CUSTOM_ATTRIBUTES (5) attributes if both global and local attributes are set. Since the backend typically enforces a limit of 5 custom attributes per event, this could lead to events being dropped or truncated. Consider enforcing the limit during the merge, giving priority to local attributes.

[gemini-code-assist]

The merging logic can result in a trace having more than MAX_TRACE_CUSTOM_ATTRIBUTES (5) attributes if both global and local attributes are set. Since the backend typically enforces a limit of 5 custom attributes per event, this could lead to events being dropped or truncated. Consider enforcing the limit during the merge, giving priority to local attributes.

[gemini-code-assist]

The current implementation creates a new HashMap and then copies the global attributes into it. Since FirebasePerformance.getAttributes() already returns a defensive copy (a new HashMap), you can use it directly to avoid an extra map allocation and redundant copies.

Suggested change

	Map<String, String> merged = new HashMap<>();
	try {
	merged.putAll(FirebasePerformance.getInstance().getAttributes());
	} catch (IllegalStateException e) {
	// FirebaseApp not initialized yet, skip global attributes
	}
	merged.putAll(attributes);
	builder.clearCustomAttributes().putAllCustomAttributes(merged);
	Map<String, String> merged;
	try {
	merged = FirebasePerformance.getInstance().getAttributes();
	} catch (IllegalStateException e) {
	// FirebaseApp not initialized yet, skip global attributes
	merged = new HashMap<>();
	}
	merged.putAll(attributes);
	builder.clearCustomAttributes().putAllCustomAttributes(merged);

[gemini-code-assist]

The current implementation creates a new HashMap and then copies the global attributes into it. Since FirebasePerformance.getAttributes() already returns a defensive copy (a new HashMap), you can use it directly to avoid an extra map allocation and redundant copies.

Suggested change

	Map<String, String> mergedAttributes = new HashMap<>();
	try {
	mergedAttributes.putAll(FirebasePerformance.getInstance().getAttributes());
	} catch (IllegalStateException e) {
	// FirebaseApp not initialized yet, skip global attributes
	}
	mergedAttributes.putAll(trace.getAttributes());
	traceMetric.putAllCustomAttributes(mergedAttributes);
	Map<String, String> mergedAttributes;
	try {
	mergedAttributes = FirebasePerformance.getInstance().getAttributes();
	} catch (IllegalStateException e) {
	// FirebaseApp not initialized yet, skip global attributes
	mergedAttributes = new HashMap<>();
	}
	mergedAttributes.putAll(trace.getAttributes());
	traceMetric.putAllCustomAttributes(mergedAttributes);