feat(otlp): add OTLP/JSON channel (@microsoft/applicationinsights-otlpchannel-js)

.aiAutoMinify.json

@@ -118,6 +118,15 @@
         },
         "@microsoft/applicationinsights-osplugin-js": {
             "constEnums": []
+        },
+        "@microsoft/applicationinsights-otlpchannel-js": {
+            "constEnums": [
+                "eOtlpSignal",
+                "eOtlpSpanKind",
+                "eOtlpStatusCode",
+                "eOtlpSeverityNumber",
+                "ePropertyType"
+            ]
         }
     }
 }

RELEASES.md

@@ -4,6 +4,17 @@
 
 <!-- ## Unreleased Changes -->
 
+## Unreleased Changes
+
+### New: OTLP/JSON Channel (`@microsoft/applicationinsights-otlpchannel-js` 0.1.0)
+
+- Added a new preview channel that converts telemetry to [OTLP/JSON](https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md) in memory and exports it to an OpenTelemetry Protocol (OTLP) HTTP endpoint (`/v1/traces` and `/v1/logs`). It requires no `@opentelemetry/*` dependency and can be used on its own or alongside the existing sender, which forwards every item along the chain (the tee channel is only needed when the channels must be in separate queues).
+- Conversion and serialization happen on the `processTelemetry` path as each item is received, and records are buffered pre-grouped by resource and signal with incremental byte accounting, so sending a batch performs no conversion work. This keeps the page unload path as fast as possible.
+- `RequestData` / `RemoteDependencyData` / `PageviewData` are exported as spans and `MessageData` / `ExceptionData` / `EventData` / `PageviewPerformanceData` as log records. Native Common Schema spans (`OTelSpan`) are exported as spans directly, preserving their kind, parent, trace state and status. Context tags are promoted onto the OTLP `Resource`; everything else becomes record attributes, with Application Insights specific values namespaced under `microsoft.`.
+- Values that the Common Schema marks as PII or customer content are dropped by default (configurable via `piiMode`), since OTLP has no equivalent marker.
+- Includes Sender-equivalent session-storage buffering for unsent and unacknowledged records, plus browser online/offline recovery. The generic `OfflineChannel` adapter is intentionally disabled because its single-endpoint payload contract cannot safely replay OTLP's separate trace and log signals.
+- Added `examples/otlp`, a multi page test site that runs two independent SDK instances per page against a local mock OTLP collector. It can be driven manually or run headlessly (`npm test`), and validates the OTLP envelope, resource attributes, span/log field validity, nanosecond timestamp precision, attribute well-formedness, and that the two instances stay fully isolated from each other.
+
 ## 3.4.3 (July 2nd, 2026)
 
 This is a maintenance release for the 3.4.x version line adding a new SDK statistics feature, a PostChannel reliability fix, and dependency security hardening. The `@microsoft/1ds-post-js` channel is numbered 4.4.3 and requires v3.4.3.

channels/otlp-channel-js/.npmignore

@@ -0,0 +1,21 @@
+# NPM Ignore
+
+# ignore everything
+*
+
+# ... but these files
+!package.json
+!tsconfig.json
+!dist-es*/**
+!dist/**
+!browser/**
+!types/**
+!/CODE_OF_CONDUCT.md
+!/CONTRIBUTING.md
+!/README.md
+!/SECURITY.md
+!/SUPPORT.md
+!/NOTICE
+!/PRIVACY
+!/LICENSE
+!/LICENSE.TXT

channels/otlp-channel-js/LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) Microsoft Corporation
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

channels/otlp-channel-js/NOTICE

@@ -0,0 +1,17 @@
+NOTICES AND INFORMATION
+Do Not Translate or Localize
+
+This software incorporates material from third parties. Microsoft makes certain
+open source code available at https://3rdpartysource.microsoft.com, or you may
+send a check or money order for US $5.00, including the product name, the open
+source component name, and version number, to:
+
+Source Code Compliance Team
+Microsoft Corporation
+One Microsoft Way
+Redmond, WA 98052
+USA
+
+Notwithstanding any other terms, you may reverse engineer this software to the
+extent required to debug changes to any libraries licensed under the GNU Lesser
+General Public License.

channels/otlp-channel-js/PRIVACY

@@ -0,0 +1,3 @@
+# Data Collection
+
+The software may collect information about you and your use of the software and send it to Microsoft. Microsoft may use this information to provide services and improve our products and services. You may turn off the telemetry as described in the repository. There are also some features in the software that may enable you and Microsoft to collect data from users of your applications. If you use these features, you must comply with applicable law, including providing appropriate notices to users of your applications together with a copy of Microsoft’s privacy statement. Our privacy statement is located at https://go.microsoft.com/fwlink/?LinkID=824704. You can learn more about data collection and use in the help documentation and our privacy statement. Your use of the software operates as your consent to these practices.

channels/otlp-channel-js/README.md

@@ -0,0 +1,247 @@
+# Microsoft Application Insights JavaScript SDK - OTLP/JSON Channel
+
+An Application Insights channel that converts telemetry into [OTLP/JSON](https://github.com/open-telemetry/opentelemetry-proto/blob/main/docs/specification.md)
+and exports it to an OpenTelemetry Protocol (OTLP) HTTP endpoint.
+
+The channel sits at the end of the plugin chain and receives every telemetry item the SDK produces
+(`trackEvent`, `trackTrace`, `trackException`, `trackPageView`, `trackDependencyData`, and any spans
+created through `startSpan`), converts it in memory, and POSTs it to `/v1/traces` and `/v1/logs`.
+
+No `@opentelemetry/*` package is required.
+
+## Getting Started
+
+### Install
+
+```bash
+npm install --save @microsoft/applicationinsights-otlpchannel-js
+```
+
+### Basic usage
+
+A channel must be supplied through the `channels` configuration, not `extensions`.
+
+```js
+import { ApplicationInsights } from "@microsoft/applicationinsights-web";
+import { OtlpChannel } from "@microsoft/applicationinsights-otlpchannel-js";
+
+const otlpChannel = new OtlpChannel();
+
+const appInsights = new ApplicationInsights({
+    config: {
+        instrumentationKey: "YOUR_INSTRUMENTATION_KEY",
+        channels: [[ otlpChannel ]],
+        extensionConfig: {
+            [otlpChannel.identifier]: {
+                endpointUrl: "https://your-collector.example.com"
+            }
+        }
+    }
+});
+
+appInsights.loadAppInsights();
+```
+
+### Exporting to both Application Insights and an OTLP collector
+
+Use the tee channel to send the same telemetry to more than one channel queue.
+
+```js
+import { ApplicationInsights } from "@microsoft/applicationinsights-web";
+import { TeeChannel } from "@microsoft/applicationinsights-teechannel-js";
+import { OtlpChannel } from "@microsoft/applicationinsights-otlpchannel-js";
+
+const teeChannel = new TeeChannel();
+const otlpChannel = new OtlpChannel();
+
+const appInsights = new ApplicationInsights({
+    config: {
+        instrumentationKey: "YOUR_INSTRUMENTATION_KEY",
+        channels: [[ teeChannel ], [ otlpChannel ]],
+        extensionConfig: {
+            [otlpChannel.identifier]: {
+                endpointUrl: "https://your-collector.example.com"
+            }
+        }
+    }
+});
+```
+
+## How it works
+
+The channel converts each telemetry item into its **final OTLP representation as the item is
+received**, not when a batch is sent. Converted records are serialized immediately and appended to
+buffers that are already grouped by resource and signal, with the payload size tracked
+incrementally. The original telemetry items are retained alongside the serialized fragments until
+the batch completes so notification listeners and SDK stats receive item-accurate callbacks.
+
+Sending a batch is therefore only a string join and an HTTP POST -- no mapping, no attribute
+building and no serialization. This matters most during page unload, where the browser gives the
+page very little time to finish its work.
+
+Set `preSerialize: false` to keep the converted objects and serialize the whole payload at send
+time instead. The item to OTLP conversion still happens at ingress in that mode.
+
+## Signal mapping
+
+| Application Insights `baseType` | OTLP |
+| --- | --- |
+| `RequestData` | Span, `kind = SERVER` |
+| `RemoteDependencyData` | Span, `kind = CLIENT` (or `INTERNAL` for an `InProc` dependency) |
+| `PageviewData` | Span, `kind = INTERNAL` (configurable, see `pageViewAs`) |
+| `MessageData` | LogRecord |
+| `ExceptionData` | LogRecord with the `exception.*` attributes |
+| `EventData` | LogRecord with `eventName` |
+| `PageviewPerformanceData` | LogRecord |
+| `MetricData` | Ignored unless `metricsAsLogs` is enabled (the OTLP metrics signal is not supported yet) |
+
+Context tags such as `ai.cloud.role`, `ai.cloud.roleInstance` and `ai.application.ver` are promoted
+onto the OTLP `Resource` as `service.name`, `service.instance.id` and `service.version`, so they are
+not repeated on every record. Everything else -- custom properties, measurements, Part C, the Part A
+extensions and the remaining tags -- becomes record attributes. Values that have no OpenTelemetry
+semantic convention equivalent are emitted under the `microsoft.` namespace.
+
+## Configuration
+
+All values below are supplied under the `OtlpChannel` key of `extensionConfig` and may be changed at
+runtime.
+
+| Name | Default | Description |
+| --- | --- | --- |
+| `endpointUrl` | | The base OTLP/HTTP endpoint. `/v1/traces` and `/v1/logs` are appended. |
+| `tracesEndpointUrl` | | The complete url used to export spans, overrides `endpointUrl`. |
+| `logsEndpointUrl` | | The complete url used to export log records, overrides `endpointUrl`. |
+| `headers` | | Additional headers added to every request, typically for authentication. |
+| `resourceAttributes` | | Additional resource attributes, these override the derived values. |
+| `scopeName` | `@microsoft/applicationinsights-web` | The reported instrumentation scope name. |
+| `scopeVersion` | package version | The reported instrumentation scope version. |
+| `preSerialize` | `true` | Serialize each record as it is received rather than when it is sent. |
+| `pageViewAs` | `"span"` | Whether a page view is exported as a `span` or a `log`. |
+| `metricsAsLogs` | `true` | Export `MetricData` as log records instead of ignoring it. |
+| `samplingPercentage` | `100` | Percentage of telemetry to retain; MetricData is never sampled out. |
+| `piiMode` | `"drop"` | How Common Schema PII / customer content values are handled: `drop`, `keep` or `hash`. |
+| `maxBatchSizeInBytes` | `65536` | Send once this many bytes have been buffered. |
+| `maxRecordsPerBatch` | `512` | Send once this many records have been buffered. |
+| `maxBatchInterval` | `15000` | The maximum time (ms) to buffer records before sending. |
+| `eventsLimitInMem` | `10000` | The maximum records held in memory, then the oldest are dropped. |
+| `enableSessionStorageBuffer` | `true` | Persist unsent and unacknowledged records across page reloads. |
+| `namePrefix` | | Prefix used for this channel's session-storage keys. |
+| `bufferOverride` | `false` | Custom storage implementation used instead of session storage. |
+| `transports` | | The ordered transports to use when sending asynchronously. |
+| `unloadTransports` | | The ordered transports to use during page unload. |
+| `httpXHROverride` | | A user supplied transport used in preference to the built in transports. |
+| `fetchCredentials` | | The `credentials` value used for `fetch` based requests. |
+| `disableXhrSync` | `false` | Disable synchronous `XMLHttpRequest` during unload. |
+| `disableFetchKeepAlive` | `false` | Disable `fetch` with `keepalive` during unload. |
+| `disableSendBeaconSplit` | `true` | Disable single-record unload splitting for keepalive-sized payloads. |
+| `xhrTimeout` | | The timeout (ms) applied to `XMLHttpRequest` based requests. |
+| `maxRetryAttempts` | `6` | The maximum retries before a failed batch is discarded. |
+| `isRetryDisabled` | `false` | Disable retrying failed export requests. |
+| `retryCodes` | | Override the HTTP status codes that trigger a retry. |
+| `enablePayloadCompression` | `false` | Gzip asynchronous payloads when `CompressionStream` is available. |
+| `maxUnloadRetryAttempts` | `2` | The maximum retries while the page is unloading (maximum `10`). |
+| `disableTelemetry` | `false` | Stop exporting, items still flow down the plugin chain. |
+| `consumeEvents` | `false` | Stop passing items to the next plugin once converted. |
+| `includeIKeyInResource` | `false` | Include the instrumentation key as a resource attribute. |
+
+## Channel ordering
+
+The channel calls `processNext`, sorts last by priority, and is discoverable by identifier, so it can
+be placed behind other channels in the same channel queue:
+
+| Channel | Priority |
+| --- | --- |
+| `TeeChannel` | 999 |
+| `OfflineChannel` | 1000 |
+| `Sender` (Application Insights) | 1001 |
+| `PostChannel` (1DS) | 1011 |
+| **`OtlpChannel`** | **1021** |
+
+Set `consumeEvents: true` if this channel is genuinely last and nothing after it should see the item.
+
+The channel includes its own Sender-equivalent session-storage buffer and online/offline listener.
+It intentionally does not advertise the generic `OfflineChannel` adapter: that adapter supports one
+endpoint per stored payload, while OTLP requires separate trace and log envelopes and endpoints.
+
+## Privacy
+
+The Common Schema marks individual fields as PII or customer content, and OTLP has no equivalent
+marker. By default (`piiMode: "drop"`) any value carrying such a marker is **omitted** from the
+exported payload. Set `piiMode` to `"hash"` to export a stable non reversible hash instead, or to
+`"keep"` to export the value along with a `microsoft.pii.<key>` marker attribute so that a
+downstream collector can scrub it.
+
+The channel does not use `navigator.sendBeacon` because it cannot reliably preserve OTLP's
+`application/json` content type or authentication headers. A collector must allow the CORS preflight
+that OTLP/JSON with custom headers requires.
+
+## Retries and partial success
+
+Requests that fail with `401`, `403`, `408`, `429`, `500`, `502`, `503`, `504`, or that do not
+complete at all, are retried with an exponential backoff (honouring any `Retry-After` header) up to
+`maxRetryAttempts`. Use `retryCodes` to replace the HTTP status list or `isRetryDisabled` to disable
+retries.
+
+A `200` response whose body reports `partialSuccess` means the collector permanently rejected some
+records; those are **not** retried. The rejection is logged and reported through the
+`eventsDiscarded` notification.
+
+The channel emits the same send lifecycle notifications used by the classic Sender:
+`eventsSendRequest`, `eventsSent`, `eventsRetry`, and `eventsDiscarded`. `isCompletelyIdle()` reports
+whether the channel has buffered, in-flight, or pending retry work.
+
+## Persistent storage and offline recovery
+
+Session-storage persistence is enabled by default. Serialized OTLP records remain in an unsent
+buffer until dispatch, then move to an unacknowledged sent buffer until the collector responds.
+Both buffers are recovered after a page reload, including requests interrupted while in flight.
+
+When the browser is known to be offline, records remain persisted and are sent after the online
+event. An offline unload does not consume the retry budget or discard recoverable records.
+
+Fetch keepalive reports success when the browser queues an unload request, not when the collector
+acknowledges it. The channel therefore retains unload records for at-least-once replay after reload;
+duplicate delivery is preferred over silent telemetry loss.
+
+Use `namePrefix` to isolate storage keys between SDK instances, or `bufferOverride` to provide the
+same custom storage contract supported by the classic Sender.
+
+## Limitations
+
+- The OTLP metrics signal (`/v1/metrics`) is not implemented.
+- Span events and links are not populated.
+- Telemetry created from a span has already been flattened into the Application Insights shape by
+  the time the channel sees it, so the conversion back to OTLP is not perfectly lossless. Custom
+  attributes are preserved verbatim through `baseData.properties`.
+
+## Build
+
+```bash
+npm install
+npm run build --silent
+```
+
+## Test
+
+```bash
+npm run test
+```
+
+## Data Collection
+
+As this SDK is designed to enable applications to perform data collection which is sent to the
+Microsoft collection endpoints the following is required to identify our privacy statement.
+
+The software may collect information about you and your use of the software and send it to Microsoft.
+Microsoft may use this information to provide services and improve our products and services. You may
+turn off the telemetry as described in the repository. There are also some features in the software
+that may enable you and Microsoft to collect data from users of your applications. If you use these
+features, you must comply with applicable law, including providing appropriate notices to users of
+your applications together with a copy of Microsoft's privacy statement. Our privacy statement is
+located at https://go.microsoft.com/fwlink/?LinkID=824704. You can learn more about data collection
+and use in the help documentation and our privacy statement. Your use of the software operates as
+your consent to these practices.
+
+## License
+
+[MIT](LICENSE)