From 4cf49ba50b2b99ab82e9b46e7666118291c5b05e Mon Sep 17 00:00:00 2001
From: "steinkirch.eth, phd" <steinkirch@protonmail.com>
Date: Sat, 15 Jul 2023 12:36:39 -0700
Subject: [PATCH] add fundamentals of backend engineering and protocols

---
 README.md                                   | 40 +++++++++++----------
 code/protocol_demos/sync-async/async.js     |  7 ++++
 code/protocol_demos/sync-async/file.txt     |  1 +
 code/protocol_demos/sync-async/package.json | 12 +++++++
 code/protocol_demos/sync-async/sync.js      | 10 ++++++
 communication/README.md                     | 34 +++++++++++++++++-
 6 files changed, 84 insertions(+), 20 deletions(-)
 create mode 100644 code/protocol_demos/sync-async/async.js
 create mode 100644 code/protocol_demos/sync-async/file.txt
 create mode 100644 code/protocol_demos/sync-async/package.json
 create mode 100644 code/protocol_demos/sync-async/sync.js

diff --git a/README.md b/README.md
index 46e3e56..32f92f9 100755
--- a/README.md
+++ b/README.md
@@ -13,21 +13,35 @@
 
 <br>
 
-* **[communication](communication/)**
+* **[communication patterns](communication/)**
   * Request Response model
   * Synchronous vs. Asynchronous workloads
   * Push
   * Polling and Long Polling
-  * Server Sent Events
-  * Publish Subscribe (Pub/Sub)
+  * Server-Sent Events
+  * Publish-Subscribe (Pub/Sub)
   * Multiplexing vs. Demultiplexing
   * Stateful vs. Stateless
   * Sidecar Pattern
 
 <br>
 
+* **[execution patterns](execution/)**
+  * backend execution patterns
+  * the process, the thread, the cpu time
+  * reading and sending socket data
+  * the listener, the acceptor, the reader
+  * single listener, acceptor, and reader thread execution pattern
+  * single listener, acceptor, and multiple readers thread execution pattern
+  * single listener, acceptor, readers with message load-balancing execution pattern
+  * multiple accepter threads on a single socket execution pattern
+  * multiple listeners, acceptors, and reader with socket-sharding execution pattern
+  * backend idempotency
+  * nagle's algorithm
+
+  <br>
+
 * **[protocols](protocols/)**
-  * protocol properties
   * protocol properties
   * OSI model
   * internet protocol
@@ -41,8 +55,10 @@
   * gRPC
   * WebRTC
 
+
   <br>
 
+
 * **[HTTP](https/)**
   * https communication 
   * https over TCP with TLS 1.2
@@ -54,21 +70,6 @@
 
   <br>
 
-* **[execution](execution/)**
-  * backend execution patterns
-  * the process, the thread, the cpu time
-  * reading and sending socket data
-  * the listener, the acceptor, the reader
-  * single listener, acceptor, and reader thread execution pattern
-  * single listener, acceptor, and multiple readers thread execution pattern
-  * single listener, acceptor, reader with message load balancing execution pattern
-  * multiple accepter threads on a single socket execution pattern
-  * multiple listeners, acceptors, and reader with socket sharding execution pattern
-  * backend idempotency
-  * nagle's algorithm
-
-  <br>
-
 * **[proxy and load balance](proxy_and_lb)**
   * proxy vs. reverse proxy
   * Layer 4 vs. Layer 7 load balancers
@@ -91,6 +92,7 @@
 * **[gcp](code/gcp)**
 * **[chef](code/chef)**
 * **[kafka](code/kafka)**
+* **[protocol demos](code/protocol_demos/)**
 
 <br>
 
diff --git a/code/protocol_demos/sync-async/async.js b/code/protocol_demos/sync-async/async.js
new file mode 100644
index 0000000..6bfea90
--- /dev/null
+++ b/code/protocol_demos/sync-async/async.js
@@ -0,0 +1,7 @@
+const fs = require("fs");
+
+console.log("first");
+
+fs.readFile("file.txt", (err,data)=> console.log(data.toString()));
+
+console.log("second");
diff --git a/code/protocol_demos/sync-async/file.txt b/code/protocol_demos/sync-async/file.txt
new file mode 100644
index 0000000..c211a99
--- /dev/null
+++ b/code/protocol_demos/sync-async/file.txt
@@ -0,0 +1 @@
+gm anon
\ No newline at end of file
diff --git a/code/protocol_demos/sync-async/package.json b/code/protocol_demos/sync-async/package.json
new file mode 100644
index 0000000..b6c1bff
--- /dev/null
+++ b/code/protocol_demos/sync-async/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "demo_sync-async",
+  "version": "1.0.0",
+  "description": "",
+  "main": "async.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": ""
+}
diff --git a/code/protocol_demos/sync-async/sync.js b/code/protocol_demos/sync-async/sync.js
new file mode 100644
index 0000000..1a3246b
--- /dev/null
+++ b/code/protocol_demos/sync-async/sync.js
@@ -0,0 +1,10 @@
+const fs = require("fs");
+
+console.log("first");
+
+const res = fs.readFileSync("file.txt");
+
+console.log(res);
+
+console.log("second");
+
diff --git a/communication/README.md b/communication/README.md
index aa04100..b5c96d2 100644
--- a/communication/README.md
+++ b/communication/README.md
@@ -119,12 +119,39 @@ curl -v --trace marinasouza.xyz
 #### Async workload is everywhere
     - async programming (promises, futures)
     - async backend processing
+    - async commits in postgres
+    - async IO in Linux (epoll, io_uring)
+    - async replication
+    - async OS fsync (filesystem cache)
 
 <br>
 
 ----
 
-### Push
+### Push 
+
+<br>
+
+#### pros and coins
+
+    - real time
+    - the client must be online (connected to the server)
+    - the client must be able to handle the load
+    - polling is preferred for light clients
+
+<br>
+
+#### basic idea
+
+    1. client connects to a server
+    2. server sends data to the client
+    3. client doesn't have to request anything
+    4. protocol must be bidirectional
+
+<br>
+#### used in
+
+    - RabbitMQ (clients consume the queues, and the messages are pushed to the clients)
 
 
 <br>
@@ -133,6 +160,11 @@ curl -v --trace marinasouza.xyz
 
 ### Polling
 
+<br>
+
+#### basic idea
+    - when a request takes long time to process (e.g., upload a video)
+    - the backend want to sends notification
 
 <br>