Skip to content

salahuddinjony/docker-test-app

BranchesTags

Repository files navigation

docker-testapp

Small Express + MongoDB demo. You can run the API on the host (node server.js), run only the database with Docker Compose while you code, or run the pre-built image from Docker Hub together with Compose.

Table of contents

Core ideas (read this first)

Term What it is Why it matters
Image Read-only template (layers + metadata) Built from a Dockerfile or pulled from a registry; immutable until you rebuild or pull a new tag.
Container Running instance of an image Has its own filesystem overlay, network namespace, and PIDs. Deleting a container does not delete the image.
Dockerfile Recipe: base image + COPY, RUN, CMD, … Reproducible builds; same file should produce the same logical app version (modulo latest base drift).
Registry (e.g. Docker Hub) Stores images by name user/repo:tag User A pushes; User B pulls—no need to share the whole git repo for running a released image.
Compose YAML file describing several services, networks, volumes One command starts Mongo + app + tools with correct hostnames and env between containers.

Typical flow

  1. Build (optional if you pull): docker build reads the Dockerfile and creates a local image.
  2. Run: docker run (or Compose) creates a container from that image and starts the process (CMD).
  3. Persist data: attach a volume or bind mount so database files survive container removal.
  4. Publish: tag as dockerhub-user/repo:tag and docker push so others can docker pull.

Project layout

Path Role
server.js Express app, Mongo connection, routes (/getUsers, /addUser, static files).
public/ Static HTML (e.g. forms, dashboard).
Dockerfile Builds the Node app image (COPY project into /testapp, node testapp/server.js).
docker-compose.yml app (Hub image), mongodb, mongo-express; networks and Mongo bind mount.
package.json Dependencies (express, mongodb).

API (high level)

  • GET /getUsers — JSON list from users collection.
  • GET|POST /addUser — redirect or insert user from form body.

Using this project with Docker

When to use what

Goal Why What to run
Full stack in one command Compose wires app → Mongo with hostname mongodb and MONGO_URL docker compose up -d
Only database + optional UI You run node server.js locally and want real Mongo on localhost:27018 docker compose up -d mongodb (and optionally mongo-express)
Only the published app image No local build; trust Docker Hub docker pull … then docker run with correct Mongo reachability (see below)

Stack overview (Compose)

Service Image Ports (host → container) Notes
app salahuddinjony/testapp:latest 5052 → 5050 PORT=5050 inside container; browse http://localhost:5052.
mongodb mongo:7 27018 → 27017 Host 27018 avoids clashing with a Mongo already on host 27017.
mongo-express mongo-express:latest 8082 → 8081 Browser UI for Mongo; Basic Auth from compose env.

Start everything (detached)

docker compose up -d

Watch logs (example: app only)

docker compose logs -f app

Stop containers (default: keeps bind-mounted Mongo files on your disk)

docker compose down

Also remove anonymous volumes Compose created (read carefully—may delete data not on bind mounts)

docker compose down -v

This project’s Mongo data for mongodb uses a bind mount to /Users/salah/Desktop/mongoData, so that folder is not removed by down -v unless you also used a named volume for the same data (this compose file does not).

Rebuild the app service (only if your docker-compose.yml has a build: section; the current file uses image: only—rebuild happens on Hub or you build locally and retag)

docker build -t salahuddinjony/testapp:latest .
docker compose up -d
# or push to Hub after tagging with your namespace

Run the app container without the full Compose stack

Scenario: Mongo is already up (e.g. docker compose up -d mongodb), and you only want the Node container.

Why MONGO_URL matters: Inside Docker, localhost is not your Mac. This repo’s server.js detects /.dockerenv and defaults to host.docker.internal:27018 so the app reaches Mongo published on the host at 27018. You can override with -e MONGO_URL=....

docker compose up -d mongodb
docker pull salahuddinjony/testapp:latest
docker run --rm -p 5052:5050 \
  -e PORT=5050 \
  -e MONGO_URL='mongodb://admin:qwerty@host.docker.internal:27018/?authSource=admin' \
  salahuddinjony/testapp:latest

When the app service runs inside Compose, compose sets MONGO_URL to mongodb://admin:qwerty@mongodb:27017/?authSource=admin because all services share a network and the Mongo hostname is the service name mongodb.

Build the image locally (before push)

Why: You changed code and want to test an image on your machine or tag it for Hub.

npm install
docker build -t testapp:1.0 .
docker run --rm -p 5052:5050 testapp:1.0

This Dockerfile uses COPY . /testapp, so dependencies must exist under node_modules on the host at build time unless you change the Dockerfile to run npm ci inside the image.

Networking: why localhost breaks inside containers

flowchart LR
  subgraph host [Your Mac - host]
    Browser[Browser localhost:5052]
    Port27018[Host port 27018]
  end
  subgraph bridge [Docker network]
    App[app container]
    MongoC[mongodb container]
  end
  Browser --> Port27018
  App -->|"MONGO_URL host.docker.internal:27018"| Port27018
  App -->|"Compose: mongodb:27017"| MongoC
Loading
Where the app runs Use this Mongo address Reason
Host (node server.js) localhost:27018 (with this compose port map) Process shares the host network namespace for loopback.
Container + Mongo also in Compose mongodb:27017 Docker DNS resolves mongodb to the DB container; port is inside the network.
Container + Mongo only published on host host.docker.internal:27018 (Desktop) or host gateway on Linux Container’s localhost is itself, not the host.

Linux note: If host.docker.internal is missing, run with:

--add-host=host.docker.internal:host-gateway

Environment variables

Variable Default in code Compose app service Meaning
PORT 5052 if unset 5050 HTTP port inside the container; map with -p HOST:CONTAINER.
MONGO_URL See defaultMongoUrl() in server.js Set to mongodb://…@mongodb:27017/… Full Mongo connection string; overrides all defaults when set.

authSource=admin matches the root user created by MONGO_INITDB_ROOT_* in the official Mongo image on first init.

User A (publisher) and User B (consumer) on Docker Hub

Roles

Role Typical tasks Needs Docker Hub account?
User A Build, tag with namespace, push Yes (owner or collaborator on repo)
User B Pull (public) or pull (private after login), run Only if image is private

User A — detailed push workflow

  1. Create a repository on hub.docker.com (e.g. testapp) under your user—optional for automated first push but avoids confusion.
  2. docker login — use your username and a Personal Access Token (recommended) or password. Tokens are safer for CI and can be revoked.
  3. docker build -t YOUR_USER/testapp:1.0 . — YOUR_USER must match your Docker Hub namespace (usually your username).
  4. docker tag (optional) — same image ID, extra names (e.g. latest).
  5. docker push YOUR_USER/testapp:1.0 — uploads layers; User B can pin to :1.0 for repeatable deploys.
  6. docker push YOUR_USER/testapp:latest — convenience tag; :latest is a moving target—document versions for production.
docker login
docker build -t YOUR_DOCKERHUB_USERNAME/testapp:1.0 .
docker tag YOUR_DOCKERHUB_USERNAME/testapp:1.0 YOUR_DOCKERHUB_USERNAME/testapp:latest
docker push YOUR_DOCKERHUB_USERNAME/testapp:1.0
docker push YOUR_DOCKERHUB_USERNAME/testapp:latest

This repo’s compose references salahuddinjony/testapp:latest; substitute your own namespace when you fork.

User B — detailed pull and run workflow

  1. docker pull YOUR_USER/testapp:latest (or :1.0) — updates local cache if a new digest exists.
  2. Start dependencies — for this project, Mongo must be reachable with correct credentials.
  3. docker run — publish PORT, pass MONGO_URL if defaults are wrong for your layout.
docker pull YOUR_DOCKERHUB_USERNAME/testapp:latest
docker run --rm -p 5052:5050 YOUR_DOCKERHUB_USERNAME/testapp:latest

Pinning by digest (maximum reproducibility): after pull, docker images --digests shows IMAGE ID and digest; in production YAML you can reference @sha256:… (advanced; see Docker docs).

Volumes in this repo

Kind Where used Behavior
Bind mount mongodb: host /Users/salah/Desktop/mongoData → container /data/db Data lives in a folder you control; back it up like normal files. Path is machine-specific—edit docker-compose.yml on other computers.
Named volume Not used in current compose for Mongo Would look like mongodb_data:/data/db plus a top-level volumes: mongodb_data: block. Good for “Docker manages the path.”

Anonymous volumes — created if you use -v /container/path with no host side; harder to find on disk; docker volume prune can delete unused ones.

Docker command reference

Long flags use two dashes: --name, --no-cache, --volume. Short flags: -d, -p, -e.

Images

Command When Why
docker images Inspect local cache See tags, sizes, image IDs
docker rmi IMAGE Remove unused tags Free space; may fail if a container still references it
docker image prune Cleanup Removes dangling images (untagged intermediates)
docker image prune -a Aggressive cleanup Unused images not referenced by any container—double-check first
docker build -t name:tag PATH Build from Dockerfile PATH is build context (often .)
docker build --no-cache -t name:tag . Cache suspected Forces re-run of every RUN layer
docker build -f Dockerfile.other . Non-default filename Explicit dockerfile path

Containers

Command When Why
docker ps Running only Default view
docker ps -a Include exited Find crashed or stopped containers
docker run IMAGE New container Pulls if missing; attaches stdout
docker run -d IMAGE Daemon / server Runs in background
docker run --rm IMAGE One-off jobs Auto-remove container on exit—good for tests
docker run --name myapp IMAGE Stable name docker logs myapp, docker stop myapp
docker run -p HOST:CONTAINER IMAGE Publish ports Maps host TCP to container
docker run -e KEY=VALUE IMAGE Config Same image, different environments
docker run --env-file .env IMAGE Many variables Keeps secrets out of shell history
docker start CONTAINER Restart existing Reuses created filesystem + config
docker stop CONTAINER Graceful stop SIGTERM then SIGKILL after timeout
docker restart CONTAINER Quick bounce Stop + start
docker inspect CONTAINER Deep debug JSON: mounts, env, network settings
docker rm CONTAINER Delete stopped Use docker rm -f to kill and remove

Logs and debugging

Command When Why
docker logs CONTAINER After crash One-shot stdout/stderr
docker logs -f --tail 100 CONTAINER Live tail Like tail -f
docker exec -it CONTAINER sh Shell inside Explore files; bash if installed

Docker Hub

Command When Why
docker pull USER/REPO:tag Fresh machine / CI Download image
docker push USER/REPO:tag After login + build Publish
docker login Auth Required for push and private pulls
docker logout Shared PC Clear creds
docker search TERM Discovery Limited; website search is richer

Volumes

Command When Why
docker volume ls Inventory Named + anonymous (some)
docker volume create NAME Pre-create Ensures specific volume exists
docker volume rm NAME Unused volume Fails if still attached
docker volume prune Cleanup Deletes unused—data loss risk
docker run -v name:/path IMAGE Named mount Persist data
docker run -v /host/path:/path IMAGE Bind mount Direct host directory
docker run --mount type=bind,src=/host,dst=/path,readonly IMAGE Read-only bind Safer for config dirs

Networks

Command When Why
docker network ls See bridges Compose creates project_default
docker network create mynet Custom topology Attach with docker run --network mynet
docker network rm mynet Unused
docker network prune Cleanup Removes unused networks

Compose

Command When Why
docker compose up -d Start stack Detached
docker compose up -d --build Rebuild + start When Dockerfile / build section changed
docker compose down Stop + remove containers Networks too; volumes depend on flags
docker compose ps Status Service health / ports
docker compose logs -f SERVICE Per-service logs
docker compose config Validate YAML Catches schema errors before run

Host maintenance

Command When Why
docker system df Disk usage Images, containers, volumes
docker system prune General cleanup Interactive; can remove stopped containers and unused networks

Troubleshooting

Symptom Likely cause What to try
Authentication failed (Mongo) Connecting to wrong Mongo (e.g. host mongod on 27017) with admin/qwerty Ensure URL points at this compose Mongo; check lsof -iTCP:27017 on host.
ECONNREFUSED 127.0.0.1:27018 in container localhost inside container is not the host Use host.docker.internal:27018 or compose mongodb:27017.
EADDRINUSE on app port Host port already taken Change left side of -p or stop other process.
volumes must be a mapping / Additional property … not allowed Invalid top-level volumes: in compose Top-level keys must be volume names, not host paths; bind mounts go under services.
App exits immediately Mongo not ready or wrong MONGO_URL docker compose logs app; start mongodb first; wait a few seconds.
validating docker-compose.yml errors Indentation / tabs / wrong types Run docker compose config.

Security and production

  • Example Mongo user/password and mongo-express Basic Auth in docker-compose.yml are for local development only.
  • Do not bake real secrets into ENV in Dockerfiles if images are shared—prefer runtime docker run -e or secrets (Swarm/Kubernetes) in real deployments.
  • Use specific image tags (mongo:7.0.15 or digest) instead of drifting latest where reproducibility matters.
  • Restrict bind mount paths to non-sensitive directories; correct filesystem permissions on host data dirs.

Quick checklist for this repository

  1. Mongo data path: /Users/salah/Desktop/mongoData in compose—adjust per machine.
  2. Credentials: Development-only; rotate for any shared environment.
  3. App + DB: Align MONGO_URL with where the app runs (host vs Compose vs standalone container).
  4. Build: Run npm install before docker build with the current Dockerfile layout.

About

docker pull salahuddinjony/testapp:latest

Topics

docker dockerfile docker-compose docker-container docker-registry port bindings yml-files dockernetwork

Resources

Readme
Activity

Stars

0 stars

Watchers

0 watching

Forks

0 forks
Report repository

Releases 1

v1.0.0 Latest
May 12, 2026

Packages

 
 
 

Contributors

Languages