APMSP-3552 Redact sensitive data in DI log-probe messages

[p-datadog]

What does this PR do?

Redacts DI log probe messages the same way that the values are redacted in snapshots.

Motivation:

Currently it is possible to bypass value redaction by explicitly referencing values in the message template.

The behavior of most tracers is to redact in messages also. This PR makes Ruby aligned with the majority of tracers.

Change log entry

Yes. Dynamic Instrumentation now redacts sensitive identifiers and types in log probe messages, matching the redaction already applied to captured snapshots.

How to test the change?

Unit tests added.

[dd-octo-sts]

Typing analysis

Note: Ignored files are excluded from the next sections.

steep:ignore comments

This PR introduces 8 steep:ignore comments, and clears 8 steep:ignore comments.

steep:ignore comments (+8-8)

❌ Introduced:

lib/datadog/di/el/compiler.rb:60
lib/datadog/di/el/compiler.rb:72
lib/datadog/di/el/compiler.rb:82
lib/datadog/di/el/compiler.rb:85
lib/datadog/di/el/expression.rb:39
lib/datadog/di/serializer.rb:264
lib/datadog/di/serializer.rb:404
lib/datadog/di/serializer.rb:529

✅ Cleared:

lib/datadog/di/el/compiler.rb:37
lib/datadog/di/el/compiler.rb:49
lib/datadog/di/el/compiler.rb:59
lib/datadog/di/el/compiler.rb:62
lib/datadog/di/el/expression.rb:34
lib/datadog/di/serializer.rb:257
lib/datadog/di/serializer.rb:389
lib/datadog/di/serializer.rb:504

Untyped methods

This PR introduces 5 partially typed methods, and clears 5 partially typed methods. It increases the percentage of typed methods from 69.48% to 69.49% (+0.01%).

Partially typed methods (+5-5)

❌ Introduced:

sig/datadog/di/serializer.rbs:25
└── def combine_args: (Array[untyped] args, Hash[Symbol, untyped] kwargs, Object target_self) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:26
└── def serialize_args: (Array[untyped] args, Hash[Symbol, untyped] kwargs, untyped instance_vars, ?depth: Integer, ?attribute_count: Integer?, ?length: Integer?, ?collection_size: Integer?) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:27
└── def serialize_vars: (Hash[Symbol, untyped] vars, ?depth: Integer, ?attribute_count: Integer?, ?length: Integer?, ?collection_size: Integer?) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:28
└── def serialize_value: (any value, ?name: (Symbol | String)?, ?depth: Integer, ?attribute_count: Integer?, ?length: Integer?, ?collection_size: Integer?, ?type: Class?) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:31
└── def self.register: (?condition: Proc?) {
        (Serializer serializer, any value, name: ::Symbol?, depth: ::Integer, ?attribute_count: ::Integer?) -> untyped } -> void

✅ Cleared:

sig/datadog/di/serializer.rbs:24
└── def combine_args: (Array[untyped] args, Hash[Symbol, untyped] kwargs, Object target_self) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:25
└── def serialize_args: (Array[untyped] args, Hash[Symbol, untyped] kwargs, untyped instance_vars, ?depth: Integer, ?attribute_count: Integer?, ?length: Integer?, ?collection_size: Integer?) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:26
└── def serialize_vars: (Hash[Symbol, untyped] vars, ?depth: Integer, ?attribute_count: Integer?, ?length: Integer?, ?collection_size: Integer?) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:27
└── def serialize_value: (any value, ?name: (Symbol | String)?, ?depth: Integer, ?attribute_count: Integer?, ?length: Integer?, ?collection_size: Integer?, ?type: Class?) -> Hash[Symbol, untyped]
sig/datadog/di/serializer.rbs:30
└── def self.register: (?condition: Proc?) {
        (Serializer serializer, any value, name: ::Symbol?, depth: ::Integer, ?attribute_count: ::Integer?) -> untyped } -> void

Untyped other declarations

This PR introduces 1 partially typed other declaration, and clears 1 partially typed other declaration. It increases the percentage of typed other declarations from 84.91% to 84.93% (+0.02%).

Partially typed other declarations (+1-1)

❌ Introduced:

sig/datadog/di/serializer.rbs:9
└── @@flat_registry: ::Array[{condition: ::Proc?, proc: ^(Serializer serializer, any value, name: ::Symbol?, depth: ::Integer, ?attribute_count: ::Integer?) -> untyped}]

✅ Cleared:

sig/datadog/di/serializer.rbs:8
└── @@flat_registry: ::Array[{condition: ::Proc?, proc: ^(Serializer serializer, any value, name: ::Symbol?, depth: ::Integer, ?attribute_count: ::Integer?) -> untyped}]

If you believe a method or an attribute is rightfully untyped or partially typed, you can add # untyped:accept on the line before the definition to remove it from the stats.

[p-datadog]

@codex review

[Copilot]

Pull request overview

Updates Dynamic Instrumentation’s log-probe message serialization to apply the same redaction decisions already used for snapshot capture, preventing message templates from leaking sensitive values by explicitly referencing them.

Changes:

• Add a dedicated [redacted] placeholder for log-probe message serialization.
• Redact message output when a value’s type matches redaction configuration.
• Redact message output for Hash values / object instance variables when the identifier matches redaction configuration.
• Add unit test cases covering redaction behavior in #serialize_value_for_message.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
lib/datadog/di/serializer.rb	Adds message-path redaction logic for redacted types and identifiers in serialize_value_for_message.
spec/datadog/di/serializer_spec.rb	Adds unit coverage for redaction behavior in message serialization.
sig/datadog/di/serializer.rbs	Exposes the new REDACTED_VALUE_FOR_MESSAGE constant in the RBS signature.

---

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 2a9189c268

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[datadog-datadog-prod-us1-2]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 16.67%
• Overall Coverage: 90.00% (-0.04%)

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: c0328cc | Docs | Datadog PR Page | Give us feedback!}

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-08-05 23:50:45

Comparing candidate commit c0328cc in PR branch di-message-serializer-redaction with baseline commit 5bd4a58 in branch master.

📊 Benchmarking dashboard

Found 0 performance improvements and 0 performance regressions! Performance is the same for 48 metrics, 1 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

Unstable benchmarks

These benchmarks have a confidence interval too wide to call a change; treat them as noise rather than signal.

scenario:tracing - trace.to_digest - Continue

• unstable throughput [-1481.883op/s; +1523.972op/s] or [-5.039%; +5.182%]