[martincostello]

Changes

Refactor redaction of environment variables to avoid allocations by using spans.

I had a GitHub Copilot cloud agent do a performance optimisation sweep, and it found this. Not on the hot-path and opt-in, but big enough to consider taking.

Benchmarks

BenchmarkDotNet v0.16.0-preview.2, Linux Ubuntu 24.04.3 LTS, Intel Xeon Platinum 8370C CPU 2.80GHz, .NET 11.0.0 (11.0.0-rc.3.26522.148), DefaultJob:

Method	AttributeCount	Mean	Error	StdDev	Ratio	Gen0	Gen1	Allocated	Alloc Ratio
SplitBased	3	477.1 ns	18.36 ns	52.69 ns	1.00	0.0396	-	1,000 B	1.00
SpanBased	3	189.2 ns	5.87 ns	17.04 ns	0.40	0.0076	-	192 B	0.19
SplitBased	12	2,234.7 ns	75.96 ns	216.72 ns	1.00	0.1984	-	5,048 B	1.00
SpanBased	12	1,129.3 ns	32.71 ns	94.37 ns	0.51	0.0629	-	1,616 B	0.32
SplitBased	40	7,839.8 ns	297.71 ns	863.70 ns	1.00	0.6866	0.0153	17,368 B	1.00
SpanBased	40	3,018.1 ns	60.33 ns	128.57 ns	0.39	0.2136	-	5,424 B	0.31

Benchmarks code

using System.Collections.Frozen;
using BenchmarkDotNet.Attributes;
using OpenTelemetry.Internal;

namespace Benchmarks.Diagnostics;

[MemoryDiagnoser]
public class ResourceAttributeRedactionBenchmarks
{
    private static readonly FrozenSet<string> SafeKeys = new[]
    {
        "deployment.environment",
        "deployment.environment.name",
        "service.instance.id",
        "service.name",
        "service.namespace",
        "service.version",
    }.ToFrozenSet(StringComparer.OrdinalIgnoreCase);

    private static readonly string[] SafePrefixes =
    [
        "cloud.",
        "container.",
        "host.",
        "k8s.",
        "os.",
        "process.runtime.",
        "telemetry.distro.",
        "telemetry.sdk.",
    ];

    private string value = string.Empty;

    [Params(3, 12, 40)]
    public int AttributeCount { get; set; }

    [GlobalSetup]
    public void Setup()
    {
        var attributes = new string[this.AttributeCount];

        for (var i = 0; i < attributes.Length; i++)
        {
            attributes[i] = i switch
            {
                0 => "service.name=checkout",
                1 => "deployment.environment=production",
                2 => "k8s.namespace.name=payments",
                _ => $"tenant.attribute{i}=sensitive-value-{i}",
            };
        }

        this.value = string.Join(',', attributes);
    }

    [Benchmark(Baseline = true)]
    public string SplitBased()
    {
        var pairs = this.value.Split(',');
        var builder = StringBuilderCache.Acquire(this.value.Length);

        for (var i = 0; i < pairs.Length; i++)
        {
            if (i > 0)
            {
                builder.Append(',');
            }

            var pair = pairs[i];
            if (pair.Length == 0)
            {
                continue;
            }

            var parts = pair.Split(['='], 2);
            if (parts.Length != 2)
            {
                builder.Append(SensitiveDataHelper.RedactedValue);
                continue;
            }

            builder.Append(parts[0]).Append('=');
            builder.Append(IsSafeResourceAttributeKey(parts[0].Trim()) ? parts[1] : SensitiveDataHelper.RedactedValue);
        }

        return StringBuilderCache.GetStringAndRelease(builder);
    }

    [Benchmark]
    public string SpanBased()
    {
        var builder = StringBuilderCache.Acquire(this.value.Length);
        var remaining = this.value.AsSpan();
        var first = true;

        while (true)
        {
            var separator = remaining.IndexOf(',');
            var pair = separator < 0 ? remaining : remaining[..separator];

            if (!first)
            {
                builder.Append(',');
            }

            if (!pair.IsEmpty)
            {
                var equals = pair.IndexOf('=');
                if (equals < 0)
                {
                    builder.Append(SensitiveDataHelper.RedactedValue);
                }
                else
                {
                    var key = pair[..equals];
                    builder.Append(key).Append('=');
                    builder.Append(IsSafeResourceAttributeKey(key.Trim()) ? pair[(equals + 1)..] : SensitiveDataHelper.RedactedValue);
                }
            }

            if (separator < 0)
            {
                break;
            }

            remaining = remaining[(separator + 1)..];
            first = false;
        }

        return StringBuilderCache.GetStringAndRelease(builder);
    }

    private static bool IsSafeResourceAttributeKey(string key)
    {
        if (SafeKeys.Contains(key))
        {
            return true;
        }

        foreach (var prefix in SafePrefixes)
        {
            if (key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
            {
                return true;
            }
        }

        return false;
    }

    private static bool IsSafeResourceAttributeKey(ReadOnlySpan<char> key)
    {
        var alternateLookup = SafeKeys.GetAlternateLookup<ReadOnlySpan<char>>();
        if (alternateLookup.Contains(key))
        {
            return true;
        }

        foreach (var prefix in SafePrefixes)
        {
            if (key.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
            {
                return true;
            }
        }

        return false;
    }
}

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, successful build/tests, etc.)
• Tests added/updated
• CHANGELOG.md file(s) updated for non-trivial changes
• Changes in public API reviewed (if applicable)
• AI usage disclosure:
  • No AI used
  • AI-assisted
  • Bulk AI-generated
• I have the experience and knowledge necessary to understand, review, and validate all content in this PR¹

Footnotes

1. Yes, I can answer maintainer questions about the content of this PR without using AI. ↩

[opentelemetry-pr-dashboard]

Pull request dashboard status

Merged · refreshed 2026-11-10 01:06 UTC

Status above doesn't look right?

• Anything look wrong? Report it with what you expected; it helps us improve the dashboard.

[Copilot]

🟢 Approval recommended

No active review issues block the resource-attribute redaction allocation optimization.

No open issues 🎉

What changed in this PR

Reduces allocations when redacting resource attributes in the SDK's opt-in self-diagnostics output, while preserving the existing redaction policy.

Changes:

• Replaces comma and equals-sign string splitting with span-based parsing.
• Appends keys directly from the original string.
• Uses span-based safe-key lookup on modern .NET, retaining a string fallback for older targets.

File	Description
src/​OpenTelemetry/​Internal/​Diagnostics/​SelfDiagnosticsEnvironmentVariablePolicy.cs	Refactors resource-attribute parsing and safe-key lookup to reduce temporary allocations.

_{Review effort: Balanced}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.11%. Comparing base (1e88560) to head (25bc7c3).
⚠️ Report is 2 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8102      +/-   ##
==========================================
+ Coverage   93.09%   93.11%   +0.01%     
==========================================
  Files         397      397              
  Lines       23335    23343       +8     
  Branches     4359     4361       +2     
==========================================
+ Hits        21724    21735      +11     
+ Misses       1103     1100       -3     
  Partials      508      508              

Flag	Coverage Δ
unittests-Project-Experimental	93.20% <100.00%> (-0.01%)	⬇️
unittests-Project-Stable	93.17% <100.00%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ostics/SelfDiagnosticsEnvironmentVariablePolicy.cs	98.64% <100.00%> (+0.05%)	⬆️

... and 1 file with indirect coverage changes

[xiang17]

Nit: this block adds the comma without checking whether the pair could be empty or malformed and would end up with a comma without its content.

Input                             Output
service.name=checkout,broken       service.name=checkout,[REDACTED]
service.name=checkout,             service.name=checkout,
service.name=checkout,,            service.name=checkout,,

Although this is the same behavior as before the change and not in scope of this PR.

[martincostello]

#8104