Expand OpenTelemetry documentation: add Lambda layer inspection instructions and detailed layer contents.

Author: monodot

_articles/opentelemetry.md

@@ -20,25 +20,117 @@ lede: Vendor-neutral telemetry for infra and applications.
 
 ## Lambdas/serverless
 
-opentelemetry-lambda:
+We can inspect what's inside each Lambda layer like this:
 
-- See https://github.com/open-telemetry/opentelemetry-lambda/releases
+```shell
+URL=$(aws lambda get-layer-version --layer-name $LAYER_ARN \
+  --version-number $LAYER_VERSION \
+  --query 'Content.Location' \
+  --region us-east-1 --output text) \
+  && curl -s "$URL" -o /tmp/layer.zip && unzip -l /tmp/layer.zip
+```
+
+### OpenTelemetry Lambda Layer (upstream)
+
+- https://github.com/open-telemetry/opentelemetry-lambda/releases
 - ARNs like:
   - `arn:aws:lambda:<region>:184161586896:layer:opentelemetry-javaagent-0_17_0:1`
   - `arn:aws:lambda:<region>:184161586896:layer:opentelemetry-nodejs-0_19_0:1`
   - `arn:aws:lambda:<region>:184161586896:layer:opentelemetry-collector-<amd64|arm64>-0_12_0:1` (a stripped-down version of OTel Collector inside an AWS Extension Layer)
 
-ADOT (AWS Distribution of OpenTelemetry):
+#### What's inside
+
+```shell
+export LAYER_ARN=arn:aws:lambda:us-east-1:184161586896:layer:opentelemetry-javaagent-0_17_0
+export LAYER_VERSION=1
+```
+
+Gives:
+
+```terminaloutput
+  Length      Date    Time    Name
+---------  ---------- -----   ----
+     1164  11-27-2025 17:55   otel-handler
+ 23942900  11-27-2025 14:16   opentelemetry-javaagent.jar
+---------                     -------
+ 23944064                     2 files
+```
 
+### AWS Distro for OpenTelemetry (ADOT)
+
+- https://github.com/aws-observability/aws-otel-lambda
 - ADOT is a **downstream repo of opentelemetry-lambda**
+- Bundles a trimmed-down version of ADOT Collector
 - AWS-managed OpenTelemetry Lambda layers that are preconfigured for use with AWS services and bundle the reduced ADOT Collector
 - ARNs like:
   - `arn:aws:lambda:ca-central-1:901920570463:layer:aws-otel-nodejs-amd64-ver-1-18-0:1` - "legacy" layer which includes an embedded collector.
-  - `arn:aws:lambda:eu-central-1:615299751070:layer:AWSOpenTelemetryDistroPython:21` - new-style layer which works with CloudWatch **only**. 
+  - `arn:aws:lambda:us-east-1:615299751070:layer:AWSOpenTelemetryDistroJava:9` - new-style layer which works with CloudWatch **only**. 
+
+#### What's inside - Layer with Collector embedded
+
+```shell
+export LAYER_ARN=arn:aws:lambda:us-east-1:901920570463:layer:aws-otel-java-agent-amd64-ver-1-32-0
+export LAYER_VERSION=6
+```
+
+Gives:
+
+```terminaloutput
+  Length      Date    Time    Name
+---------  ---------- -----   ----
+        0  05-29-2025 21:21   collector-config/
+      364  05-29-2025 21:21   collector-config/config.yaml
+        0  05-29-2025 21:21   extensions/
+ 42049720  05-29-2025 21:21   extensions/collector
+ 23958345  05-29-2025 21:21   opentelemetry-javaagent.jar
+      520  05-29-2025 21:21   otel-handler
+     1164  05-29-2025 21:17   otel-handler-upstream
+---------                     -------
+ 66010113                     7 files
+```
 
-[grafana/collector-lambda-extension](https://github.com/grafana/collector-lambda-extension/):
+#### What's inside - New-style layer, exports in OTLP to X-Ray by default
+
+```shell
+export LAYER_ARN=arn:aws:lambda:us-east-1:615299751070:layer:AWSOpenTelemetryDistroJava
+export LAYER_VERSION=9
+```
+
+Gives:
+
+```terminaloutput
+  Length      Date    Time    Name
+---------  ---------- -----   ----
+ 46104116  01-30-2026 20:15   aws-opentelemetry-javaagent.jar
+     3074  01-30-2026 20:15   otel-instrument
+---------                     -------
+ 46107190                     2 files
+```
+
+### [grafana/collector-lambda-extension](https://github.com/grafana/collector-lambda-extension/)
 
 - Custom distribution of the [opentelemetry-lambda collector](https://github.com/open-telemetry/opentelemetry-lambda/tree/main/collector) layer, built for Grafana Cloud
 - Designed to be used in conjunction with an opentelemetry-lambda instrumentation layer, like `arn:aws:lambda:<region>:184161586896:layer:opentelemetry-nodejs-0_19_0:1`
 - ARNs like:
-  - `arn:aws:lambda:eu-west-2:050451360540:layer:opentelemetry-collector-grafana-arm64-v0_138_0:2`
+  - `arn:aws:lambda:us-east-1:050451360540:layer:opentelemetry-collector-grafana-arm64-v0_138_0:2`
+
+#### What's inside
+
+```shell
+export LAYER_ARN=arn:aws:lambda:us-east-1:050451360540:layer:opentelemetry-collector-grafana-arm64-v0_138_0
+export LAYER_VERSION=2
+```
+
+Gives:
+
+```terminaloutput
+  Length      Date    Time    Name
+---------  ---------- -----   ----
+        0  10-29-2025 07:54   collector-config/
+     1167  10-29-2025 07:54   collector-config/config.yaml
+        0  10-29-2025 07:54   extensions/
+ 48758968  10-29-2025 07:54   extensions/collector
+---------                     -------
+ 48760135                     4 files
+```
+