From d8b6c59606d53278da6034b21361aa932d8487f6 Mon Sep 17 00:00:00 2001
From: SrIzan10 <66965250+SrIzan10@users.noreply.github.com>
Date: Sun, 12 Nov 2023 16:59:43 +0100
Subject: [PATCH] feat: new mongodb blog post

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+---
+id: 2
+title: My tales of MongoDB migration
+description: Here I ramble about the last service migration I did, MongoDB, and all the difficulties that came with it.
+date: 12/11/2023
+---
+
+# The last service migration: MongoDB
+
+## Introduction
+
+So, the last few months I've been migrating services from my good old Raspberry Pi into my new HP server and the last service I migrated was MongoDB.
+
+I've been using MongoDB for a while now and I've been using it for a few things, like my discord bots, [webhooks-ui](https://github.com/SrIzan10/webhooks-ui) and probably other projects I don't remember right now.
+
+So, let's get started!
+
+## Testing the plan
+
+My database instance is on Docker with a replica set of 1 node (itself) so [Prisma](https://www.prisma.io/) works.
+
+My idea is to add the HP server as a secondary replica and then promote it to be the primary one, but I don't know if that will work, so we need to test some stuff.
+
+I first created 2 docker containers on my [main `Ryzen` machine](https://gist.github.com/SrIzan10/50bc2ba689a4cc43bcbac2799cc733c9)'s WSL Ubuntu instance.
+
+I created a `docker-compose.yml` file with the following content:
+
+```yml
+version: "3.8"
+services:
+  mongo1:
+    image: mongo:4.4.17-rc0-focal
+    container_name: mongo1
+    restart: always
+    ports:
+      - 27017:27017
+    volumes:
+      - ./mongo1:/data/db
+    command: mongod --replSet mongoset
+    networks:
+      - mongo
+  mongo2:
+    image: mongo:4.4.17-rc0-focal
+    container_name: mongo2
+    restart: always
+    ports:
+      - 27018:27017
+    volumes:
+      - ./mongo2:/data/db
+    command: mongod --replSet mongoset
+    networks:
+      - mongo
+networks:
+  mongo:
+```
+
+and ran it with `docker compose up -d`.
+
+I went to connect with MongoDB Compass and it didn't work for some reason. I asked GPT and nothing. It looks like it accepted the connection but it won't connect, so I installed `mongosh` and tried to connect with that.
+
+```bash
+$ mongosh mongodb://localhost:27017
+```
+...and it worked! That didn't make any sense, but okay, we can work with it.
+
+I then connected to the `mongo1` instance and ran the following commands:
+
+```bash
+> rs.initiate()
+```
+and it worked, but only that same database connected. Before adding the second database to the replica, I went ahead and pinged it from the first container (just to check if the network configuration worked):
+
+```bash
+docker exec mongo1 sh -c "rm /bin/ping;apt update;apt install inetutils-ping -y;ping mongo2"
+```
+
+I removed /bin/ping because I tried to transfer the binary from WSL to the container but it still needed some libraries and I didn't want to bother, so I just installed the package.
+
+It worked, so I went ahead and added the second database to the replica set:
+
+```bash
+> rs.add("mongo2")
+```
+
+After waiting for it, the second database connected and everything was working fine. Let's create a collection and some documents on the primary replica (mongo1):
+
+```bash
+> use test
+> db.createCollection("test")
+> db.test.insertOne({ name: "test" })
+```
+
+and then, let's check if it's on the second replica (mongo2):
+
+```bash
+$ mongosh mongodb://localhost:27017
+```
+
+```bash
+> use test
+> db.getMongo().setReadPref("secondaryPreferred")
+> db.test.find()
+```
+and, yeah, that worked.
+
+I don't really know if ORMs will read when connecting to the second replica, but for now it's fine as the main plan is on track.  
+So, to promote I connected to the primary replica (mongo1) and ran the following command:
+
+```bash
+> rs.stepDown()
+```
+And that worked! Woo! The second replica is now the primary one. We can now start *drum rolls please*:
+
+## The migration
+
+This is it. We're doing it.
+
+I went ahead and created a new docker-compose file on my server with the following content:
+
+```yml
+version: "3.8"
+services:
+    mongo:
+        image: mongo:4.4.17-rc0-focal
+        container_name: mongodb
+        restart: unless-stopped
+        ports:
+            - 27017:27017
+        volumes:
+            - ./mongo:/data/db
+        command: mongod --replSet rs0
+```
+After deploying the stack, I connected using mongosh to the primary db and ran the following command:
+```bash
+> rs.add("ip")
+```
+and after waiting for a while it looked like it worked. I then connected to the new database and ran the following command to check if the replica cloned fine:
+```bash
+> db.getMongo().setReadPref("secondaryPreferred")
+```
+and let's just let the results speak for themselves:
+```bash
+rs0 [direct: secondary] test> show dbs
+# author's note: some dbs are redacted for privacy reasons 
+admin         80.00 KiB
+api           80.00 KiB
+ava           40.00 KiB
+bask         168.00 KiB
+config       144.00 KiB
+local        348.00 KiB
+vinci        428.00 KiB
+rs0 [direct: secondary] test> use vinci
+switched to db vinci
+rs0 [direct: secondary] vinci> show tables
+afk
+birthdays
+chatgpt
+giveaways-enters
+giveaways-message
+padyama
+suggestions
+twitter
+warns
+youtube
+rs0 [direct: secondary] vinci> db.afk.find()
+[
+  {
+    _id: ObjectId("sadfsad fsadfsdf"),
+    id: 'redacted',
+    reason: 'redacted',
+    __v: 0
+  },
+  {
+    _id: ObjectId("asdfsadfadf"),
+    id: 'redacted',
+    reason: 'readacted',
+    __v: 0
+  }
+]
+rs0 [direct: secondary] vinci>
+```
+Nice. let's now try to write something to the database from Vinci:  
+![](https://img.srizan.dev/Discord_a2iXkWYxwn.png)  
+That just worked and we can see it on the secondary replica:
+```bash
+rs0 [direct: secondary] vinci> db.afk.find({ id: '703974042700611634' })
+[
+  {
+    _id: ObjectId("6550eccc6154a8c9030fe76a"),
+    id: '703974042700611634',
+    reason: 'test',
+    __v: 0
+  }
+]
+```
+
+Let's now edit all .envs and change the database url to the new secondary one. For this I checked all dbs that I have and then go from top to bottom editing the secrets.
+
+After that was done I needed to deploy all changes. I went ahead and created too many tabs on my terminal and ran the all deployment commands on each tab. At the same time.  
+I really hope that doesn't make my server run out of ram, because I'm really short on that.
+
+After executing all the commands I `rs.stepDown()`'ed the primary Raspberry Pi replica and, as expected, the HP Server took over.
+
+The last command of the day:
+```bash
+> rs.remove("ip")
+```
+
+...SIKE! I needed to check the logs of the containers to see if everything was working fine. The `api` and `vinci` to be exact.  
+This is because `api` runs Prisma and `vinci` runs the now defunct in my stack, [mongoose](https://mongoosejs.com/).
+
+Luckily enough, both were fine, so I was free. Yay!
+
+## Conclusion
+
+Welp, that was a lot of work. I'm glad it's over. I got my HP server on July and it's now November and I just finished migrating.  
+Could I have done it in less time? Yes.  
+Was I lazy? Also yes.
+
+So that answers all your questions.
+
+I hope you enjoyed this my first blog post, and thankfully it was a big one.  
+This took 3 hours in total, but at the end of the day, it was worth it.
+
+I'll see you in the next one!
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