Part-2a.-Extending-my-first-service.md

@@ -30,10 +30,33 @@ You'll note a lot of new files have appeared, of note are:
 * _stop.sh_\
   The bash shell-script `stop.sh` will stop the service if it is running, it is used by `start.sh`, and in general we should have to worry about it.
 * _view.sh_\
-  Running the service in the background is nice, but if we ever want to inspect what the service  is doing `view.sh` will display the log of the service
+  Running the service in the background is nice, but if we ever want to inspect what the service is doing `view.sh` will display the log of the service
 * _.vimrc_\
   Finally, we've added some configuration to vim, to make things a little more enjoyable here as well.\
   First up, line-numbers and syntax highlighting, which should improve on legibility\
   Second, we've bound **F5** to the `start.sh` script, so now updating packages and restarting the service is as simple as pressing **F5**.
 
-## Before we start adding stuff, lets introduce some timestamps, everyone loves timestamps!
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+## Before we start adding stuff, lets introduce some timestamps, everyone loves timestamps!
+
+FastAPI has a concept called _middleware_ - from te documentation:
+
+_A "middleware" is a function that works with every **request** before it is processed by any specific path operation._\
+_And also with every **response** before returning it._
+
+Lets take advantage of that, to add timing data our request/response cycle, run `vim main.py`
+
+Enter insert-mode ( press `i` ), and insert the following code at line 12 ( below `app = FastAPI()` )
+
+```
+from time import time
+from fastapi import Request
+
+@app.middleware("http")
+async def add_process_time_header(request: Request, call_next):
+    start_time = time()
+    response = await call_next(request)
+    process_time = time() - start_time
+
+    response.headers["X-Process-Time"] = str(process_time)
+    return response
+```
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