Azure Monitor Exporter: consume microsoft.availability.testTimestamp to override envelope time

[Copilot]

Implements support for the new microsoft.availability.testTimestamp attribute introduced in microsoft/ApplicationInsights-dotnet#3153. When this ISO 8601 attribute is present on an availability log record, the exporter now uses it as the TelemetryItem envelope time instead of the wall-clock logRecord.Timestamp, preserving the user-specified test start time end-to-end.

Changes

• LogsHelper.cs

  • Added AvailabilityTestTimestampAttributeName constant and TestTimestamp property to AvailabilityInfo struct
  • Added explicit case for the attribute in ExtractAvailabilityInfo — prevents it leaking into AvailabilityData.Properties via the default: branch
  • OtelToAzureMonitorLogs: availability branch parses TestTimestamp using CultureInfo.InvariantCulture for deterministic culture-independent parsing and normalizes the result to UTC via .ToUniversalTime(); falls back to logRecord.Timestamp if absent or unparseable

• TelemetryItem.cs

  • Added constructor overload TelemetryItem(string name, DateTimeOffset envelopeTime, LogRecord logRecord, ...) accepting an explicit envelope time
  • Existing LogRecord constructor delegates to the new overload (no duplication)

• AvailabilityTests.cs

  • VerifyAvailabilityTelemetryWithTestTimestamp: asserts TelemetryItem.Time equals the parsed (UTC-normalized, culture-invariant) timestamp and attribute is absent from AvailabilityData.Properties
  • VerifyAvailabilityTelemetryWithoutTestTimestamp: asserts existing behavior (envelope time from logRecord.Timestamp) is unchanged when attribute is absent

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Original prompt

Background

microsoft/ApplicationInsights-dotnet#3153 adds a new attribute microsoft.availability.testTimestamp (ISO 8601 string) to the log record properties when AvailabilityTelemetry.Timestamp != default. This allows the downstream exporter to use the user-specified test start time as the envelope timestamp instead of the wall-clock time of the log record.

The Azure Monitor Exporter must be updated to consume this new attribute.

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Files to change

1. sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs

a) Add new constant alongside the other availability attribute constants (~line 41):

private const string AvailabilityTestTimestampAttributeName = "microsoft.availability.testTimestamp";

b) Add a field to AvailabilityInfo struct (at the bottom of the file, ~line 436):

public string? TestTimestamp { get; set; }

c) In ExtractAvailabilityInfo, add a local variable string? availabilityTestTimestamp = null; alongside the others, and handle it in the switch:

case AvailabilityTestTimestampAttributeName:
    availabilityTestTimestamp = item.Value?.ToString();
    break;

Also populate it when constructing the return value:

TestTimestamp = availabilityTestTimestamp,

This ensures the attribute is explicitly consumed and not leaked into AvailabilityData.Properties via the default: branch.

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2. sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Customizations/Models/TelemetryItem.cs

The TelemetryItem constructor used for log records (line ~139) always derives the envelope Time from logRecord.Timestamp. Since Time is a get-only property set in the base constructor, overriding it requires a different approach.

Add a new constructor overload that accepts an explicit DateTimeOffset for the time to be used when testTimestamp is available:

public TelemetryItem(string name, DateTimeOffset envelopeTime, LogRecord logRecord, AzureMonitorResource? resource, string instrumentationKey, LogContextInfo logContext) :
    this(name, envelopeTime)
{
    // ... same body as the existing LogRecord constructor ...
}

Or alternatively, modify the existing OtelToAzureMonitorLogs method in LogsHelper.cs to override Time after construction — but since Time is readonly, the constructor overload approach is needed.

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3. sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs — OtelToAzureMonitorLogs

In the else if (availabilityInfo is not null) branch (~line 111), use the testTimestamp to set the envelope time:

else if (availabilityInfo is not null)
{
    DateTimeOffset envelopeTime = availabilityInfo.Value.TestTimestamp != null
        && DateTimeOffset.TryParse(
            availabilityInfo.Value.TestTimestamp,
            null,
            System.Globalization.DateTimeStyles.RoundtripKind,
            out var parsedTs)
        ? parsedTs
        : TelemetryItem.FormatUtcTimestamp(logRecord.Timestamp);

    telemetryItem = new TelemetryItem("Availability", envelopeTime, logRecord, resource, instrumentationKey, logContext)
    {
        Data = new MonitorBase
        {
            BaseType = "AvailabilityData",
            BaseData = new AvailabilityData(Version, availabilityInfo.Value, properties, logRecord),
        }
    };
    telemetrySchemaTypeCounter._availabilityCount++;
}

Note: TelemetryItem.FormatUtcTimestamp is currently internal static — make sure it remains accessible from LogsHelper.cs (it's already in the same assembly so this is fine).

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4. Tests — sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/E2ETelemetryItemValidation/AvailabilityTests.cs

Add a new test VerifyAvailabilityTelemetryWithTestTimestamp that:

1. Logs an availability record that includes microsoft.availability.testTimestamp with a specific past timestamp (e.g., "2025-04-19T12:10:59.9930000+00:00").
2. Asserts that the resulting TelemetryItem.Time equals that parsed timestamp.
3. Asserts that microsoft.availability.testTimestamp does not appear in AvailabilityData.Properties.

Also add a test VerifyAvailabilityTelemetryWithoutTestTimestamp that verifies the existing behavior is unchanged when the attribute is absent (envelope time comes from logRecord.Timestamp).

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Key constraint

The microsoft.availability.testTimestamp attribute must be consumed (not passed through to AvailabilityData.Properties). The default: branch in ExtractAvailabilityInfo adds any unrecognized attribute to properties. Adding an explicit case for the new attribute name prevents this leakage.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: @microsoft/ApplicationInsights-dotnet/pull/3153 - A new attribute is added to ava...

This pull request was created from Copilot chat.

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[Copilot]

Pull request overview

Updates the Azure Monitor OpenTelemetry Exporter to honor a new microsoft.availability.testTimestamp log attribute by using it as the Availability telemetry envelope timestamp, preserving the original test start time end-to-end.

Changes:

• Consume microsoft.availability.testTimestamp during availability attribute extraction and prevent it from leaking into AvailabilityData.Properties.
• Add a TelemetryItem constructor overload to allow explicitly setting the envelope Time for log-based telemetry.
• Add E2E validation tests covering both presence and absence of testTimestamp.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs	Parses and applies testTimestamp for Availability envelope time; consumes the attribute during extraction.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Customizations/Models/TelemetryItem.cs	Adds constructor overload to set envelope time explicitly for log-based telemetry items.
sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/tests/Azure.Monitor.OpenTelemetry.Exporter.Tests/E2ETelemetryItemValidation/AvailabilityTests.cs	Adds coverage verifying envelope time override and no property leakage.

[rajkumar-rangaraj]

@copilot apply changes based on the comments in this thread

[Copilot]

@copilot apply changes based on the comments in this thread

Applied both review suggestions in commit 45d3e2c:

• LogsHelper.cs: changed null → CultureInfo.InvariantCulture for DateTimeOffset.TryParse, and added .ToUniversalTime() to normalize the result to UTC.
• AvailabilityTests.cs: changed null → CultureInfo.InvariantCulture for DateTimeOffset.Parse (and aligned expectedTime with the same UTC normalization).

[rajkumar-rangaraj]

/check-enforcer override