example: otel-wrapper-shim.sh + symlinks to trace nodejs builds (#339)

* example: otel-wrapper-shim.sh + symlinks to trace nodejs builds

* copy changes

demos/30-trace-build-process/bash

@@ -0,0 +1 @@
+otel-wrapper-shim.sh

demos/30-trace-build-process/otel-wrapper-shim.sh

@@ -0,0 +1,43 @@
+#!/bin/bash
+
+# Build Process Tracing Example
+#
+# It's possible to instrument complex build processes in nodejs (npm/yarn/pnpm) and
+# C (make/cmake/ninja) by injecting instrumented versions of some key commands into $PATH.
+#
+# This example is a folder with a shim script in it, and a bunch of fake tools that are just
+# symlinks to the shim. It needs to be a folder so that it can be cleanly injected into $PATH.
+#
+# To see this working, start `otel-desktop-viewer` as discribed in the main README.md, and then:
+# (
+#   cd .. && \
+#   ([ -d mermaid ] || git clone https://github.com/mermaid-js/mermaid) && \
+#   cd mermaid/ && \
+#   ../otel-cli/demos/30-trace-build-process/pnpm install
+# )
+#
+# For more complex build processes, I have found jaeger to be quite good, because it also includes
+# a black "critical path line". See https://www.jaegertracing.io/docs/1.54/getting-started/ for
+# their all-in-one docker conainer setup instructions. Otherwise, everything else is the same as
+# when using otel-desktop-viewer.
+
+set -euo pipefail
+
+export OTEL_EXPORTER_OTLP_ENDPOINT="${OTEL_EXPORTER_OTLP_ENDPOINT:-localhost:4317}"
+
+TOOL_NAME="$(basename $0)"
+LOCATION_IN_PATH="$(dirname $0)"
+HERE="$(dirname $(readlink -f $0))"
+# This is just a guess, based on what's left after we've removed ourselves and any symlinks we know about from the results.
+# If we're symlinked into $PATH in more than once place then we could still end up in loops.
+# If this becomes a problem, we could instead iterate over each location and call readlink,
+# and drop anything that resolves to $HERE.
+ORIGINAL_TOOL_PATH="$(which -a "$TOOL_NAME" | grep -Ev "($HERE|$LOCATION_IN_PATH)" | head -n1)"
+
+# Put this dir first in $PATH so that nested calls out to bash and pnpm are instrumented
+# (tools like npm have a habit of messing with $PATH to put themselves first in subshells).
+# This will probably get quite long if there is a lot of recursion.
+# If this causes problems, we could prune ouselves out before inserting ourself at the head.
+export PATH="$HERE:$PATH"
+
+otel-cli exec --service "$TOOL_NAME" --name "$*" -- $ORIGINAL_TOOL_PATH "$@"

demos/30-trace-build-process/pnpm

@@ -0,0 +1 @@
+otel-wrapper-shim.sh

demos/30-trace-build-process/sh

@@ -0,0 +1 @@
+otel-wrapper-shim.sh

demos/30-trace-build-process/tsx

@@ -0,0 +1 @@
+otel-wrapper-shim.sh