doc: add abnormal termination step 1

Confirming if the process was exited for proactive invocation of `process.exit`.

PR-URL: #344
Reviewed-By: Michael Dawson <[email protected]>
Reviewed-By: Matheus Marchini <[email protected]>
Reviewed-By: Gerhard Stöbich <@Flarna>

Author: legendecas

documentation/abnormal_termination/step1/using_exit_stack_traces.md

@@ -1 +1,45 @@
-//TODO
+# Using Exit Stack Traces for Debugging
+
+`--trace-exit` CLI option will print a stack trace on every proactive
+`process.exit` invocation. It is convenient to confirm if the abnormal exit of
+the process was initiated from an invocation of `process.exit` or something
+other crashes.
+
+> Caveat:
+> `--trace-exit` CLI option is available since Node.js v13.5.0.
+
+## How To
+
+There are conditions that we used an third party library that we have trivial
+knowledge of the implementation details. It is hard to determine where the exit
+is trigger in which library in these conditions. On the first step we have to
+determine if it is a proactive `process.exit` invocation and where it is to
+prevent follow up not trivial work of detailed digging the exit reasons.
+
+The simple step is to add an option `--trace-exit` on starting the Node.js
+process. Since then, we can see a stacktrace on each call of `process.exit`.
+
+```bash
+ > node --trace-exit src/abnormal-exit.js
+(node:26480) WARNING: Exited the environment with code 0
+    at exit (internal/process/per_thread.js:168:13)
+    at /node_modules/some-obscure-library:199:32 # this is the actual location.
+    at Module._compile (internal/modules/cjs/loader.js:1139:30)
+    at Module._extensions..js (internal/modules/cjs/loader.js:1159:10)
+    at Module.load (internal/modules/cjs/loader.js:988:32)
+    at Module._load (internal/modules/cjs/loader.js:896:14)
+    at executeUserEntryPoint (internal/modules/run_main.js:71:12)
+```
+
+With the knowledge of where the calls of `process.exit` is, we can check around
+the invocation to understand the reasons and prevent it from abnormal exits.
+
+If the process doesn't output a stack trace on exit, we can come to a
+conclusion that the process exited for other reasons, and we
+can deploy strategy according to the [abnormal termination guides on common symptoms].
+
+## Useful Links
+
+- https://nodejs.org/docs/latest/api/cli.html#cli_trace_exit
+
+[abnormal termination guides on common symptoms]: ../README.md#Common_Symptoms