Azure/azure-sdk-for-net Azure.Monitor.OpenTelemetry.Exporter

1.6.0-beta.2 (2026-01-12)

Default Sampler Changed (#54942): The default sampling behavior has been changed from
ApplicationInsightsSampler with 100% sampling (all traces sampled) to
RateLimitedSampler with 5.0 traces per second. This change significantly
reduces telemetry volume for high-traffic applications and provides better
cost optimization out of the box.
Impact: Applications with more than 5 requests per second will see fewer
traces exported by default.
Migration: To maintain the previous behavior (100% sampling), explicitly
configure the sampler:
```
// Option 1: Set SamplingRatio and clear TracesPerSecond
builder.Services.AddOpenTelemetry()
    .UseAzureMonitorExporter(options =>
    {
        options.SamplingRatio = 1.0f;
        options.TracesPerSecond = null;
    });
// Option 2: Use environment variables
// OTEL_TRACES_SAMPLER=microsoft.fixed_percentage
// OTEL_TRACES_SAMPLER_ARG=1.0
```

Fixed performance counter metrics not using configured resource attributes
(cloud_RoleName and cloud_RoleInstance), which previously showed
"unknown_service:appName" instead of the configured values.
(#54944)