How to wait for MSSQL in Docker Compose?

After searching and trying many different scenarios, I was able to add waiting using the following composer file. This is for asp.net core solution. The key is that you have to overwrite entrypoint if it is specified in dockerfile. Also, you need to make sure to save "wait-for-it.sh" LF as line ending instead of CRLF, otherwise you'll get the error of file not found.

The dockerfile should have the following (download it from here: https://raw.githubusercontent.com/vishnubob/wait-for-it/master/wait-for-it.sh, make sure to save the file):

COPY ./wait-for-it.sh /wait-for-it.sh
RUN chmod +x wait-for-it.sh

docker-compose.yml

version: '3.7'

services:

  vc-db:
    image: mcr.microsoft.com/mssql/server:latest
    ports:
      - "${DOCKER_SQL_PORT:-1433}:1433"
    expose:  
      - 1433  
    environment: 
      - ACCEPT_EULA=Y
      - MSSQL_PID=Express
      - SA_PASSWORD=v!rto_Labs!
    networks:
      - virto

  vc-platform-web:
    image: virtocommerce/platform:${DOCKER_TAG:-latest}
    ports:
      - "${DOCKER_PLATFORM_PORT:-8090}:80"
    environment:
      - ASPNETCORE_URLS=http://+
    depends_on:
      - vc-db
    entrypoint: ["/wait-for-it.sh", "vc-db:1433", "-t", "120", "--", "dotnet", "VirtoCommerce.Platform.Web.dll"]
    networks:
      - virto

Create two separate dockerfiles (e.g):

1. Mssql.Dockerfile
2. App.Dockerfile

Set up the sequence within docker-compose.yml

Mssql.Dockerfile

FROM mcr.microsoft.com/mssql/server AS base

ENV ACCEPT_EULA=Y
ENV SA_PASSWORD=Password123

COPY . .
COPY ["Db/Scripts/*", "Db/Scripts/"]
VOLUME ./Db:/var/opt/mssql/data

HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=10 \
    CMD /opt/mssql-tools/bin/sqlcmd -S . -U sa -P Password123 -i Db/Scripts/SetupDb.sql || exit 1

App.Dockerfile:

    FROM mcr.microsoft.com/dotnet/core/aspnet:3.1-buster-slim AS base
    WORKDIR /app
    EXPOSE 80
    EXPOSE 443

    FROM mcr.microsoft.com/dotnet/core/sdk:3.1-buster AS build
    WORKDIR /src
    COPY ["AspNetCoreWebApplication/AspNetCoreWebApplication.csproj", "AspNetCoreWebApplication/"]
    COPY ["WebApp.Data.EF/WebApp.Data.EF.csproj", "WebApp.Data.EF/"]
    COPY ["WebApp.Service/WebApp.Service.csproj", "WebApp.Service/"]

    RUN dotnet restore "AspNetCoreWebApplication/AspNetCoreWebApplication.csproj"
    COPY . .
    WORKDIR "/src/AspNetCoreWebApplication"
    RUN dotnet build "AspNetCoreWebApplication.csproj" -c Release -o /app/build
    FROM build AS publish
    RUN dotnet publish "AspNetCoreWebApplication.csproj" -c Release -o /app/publish

    FROM base AS final
    WORKDIR /app
    COPY --from=publish /app/publish .
    ENTRYPOINT ["dotnet", "AspNetCoreWebApplication.dll"]

Docker-compose.yml:

version: '3.7'

services:
    api:
        image: aspnetcore/mentoring_api
        container_name: mentoring_api
        build:
            context: .
            dockerfile: App.Dockerfile
        ports:
            - 8081:80
        expose: 
            - 8081
        environment:
            ASPNETCORE_ENVIRONMENT: Development
        depends_on:
            - sqlserver
    sqlserver:
        image: aspnetcore/mentoring_db
        container_name: mentoring_db
        build:
            context: .
            dockerfile: Mssql.Dockerfile
        ports:
            - "1433:1433"
        expose: 
            - 1433
        environment:
            - ACCEPT_EULA=Y
            - SA_PASSWORD=Password123
        volumes:
            - ./Db:/var/opt/mssql/data

Note: The connection string will look like: "Server=sqlserver;Database=Northwind;Trusted_Connection=False;User Id=sa;Password=Password123;MultipleActiveResultSets=true"

You can write a simple script, which will be launched in container with your app. For example, you can just set a delay, using sleep N ( where N it is a time which is needed for starting your DB), or you can use a until cycle in which you to can try to connect to your DB, and when it will be possible, then you can start your app.

I know this is not a perfect solution, but it helped me when I had a similar problem

Here is a complete example

version: "3.8"

services:
  ms-db-server:
    image: mcr.microsoft.com/mssql/server
    environment: 
      - SA_PASSWORD=P@ssw0rd
      - ACCEPT_EULA=Y
    volumes:
      - ./data/db/mssql/scripts:/scripts/
    ports:
      - "1433:1433"
    #entrypoint: /bin/bash
    command:
      - /bin/bash
      - -c
      - |
        /opt/mssql/bin/sqlservr &
        pid=$$!

        echo "Waiting for MS SQL to be available ⏳"
        /opt/mssql-tools/bin/sqlcmd -l 30 -S localhost -h-1 -V1 -U sa -P $$SA_PASSWORD -Q "SET NOCOUNT ON SELECT \"YAY WE ARE UP\" , @@servername"
        is_up=$$?
        while [ $$is_up -ne 0 ] ; do
          echo -e $$(date)
          /opt/mssql-tools/bin/sqlcmd -l 30 -S localhost -h-1 -V1 -U sa -P $$SA_PASSWORD -Q "SET NOCOUNT ON SELECT \"YAY WE ARE UP\" , @@servername"
          is_up=$$?
          sleep 5
        done

        for foo in /scripts/*.sql
          do /opt/mssql-tools/bin/sqlcmd -U sa -P $$SA_PASSWORD -l 30 -e -i $$foo
        done
        echo "All scripts have been executed. Waiting for MS SQL(pid $$pid) to terminate."

        wait $$pid

  tempo:
    image: grafana/tempo:latest
    command: ["-config.file=/etc/tempo.yaml"]
    volumes:
      - ./etc/tempo-local.yaml:/etc/tempo.yaml
      - ./data/tempo-data:/tmp/tempo
    ports:
      - "14268"      # jaeger ingest, Jaeger - Thrift HTTP
      - "14250"      # Jaeger - GRPC
      - "55680"      # OpenTelemetry
      - "3100"       # tempo
      - "6831/udp"   # Jaeger - Thrift Compact
      - "6832/udp"   # Jaeger - Thrift Binary   

  tempo-query:
    image: grafana/tempo-query:latest
    command: ["--grpc-storage-plugin.configuration-file=/etc/tempo-query.yaml"]
    volumes:
      - ./etc/tempo-query.yaml:/etc/tempo-query.yaml
    ports:
      - "16686:16686"  # jaeger-ui
    depends_on:
      - tempo

  loki:
    image: grafana/loki:2.1.0
    command: -config.file=/etc/loki/loki-local.yaml
    ports:
      - "3101:3100"                                   # loki needs to be exposed so it receives logs
    environment:
      - JAEGER_AGENT_HOST=tempo
      - JAEGER_ENDPOINT=http://tempo:14268/api/traces # send traces to Tempo
      - JAEGER_SAMPLER_TYPE=const
      - JAEGER_SAMPLER_PARAM=1
    volumes:
      - ./etc/loki-local.yaml:/etc/loki/loki-local.yaml
      - ./data/loki-data:/tmp/loki

  nodejs-otel-tempo-api:
    build: .
    command: './wait-for.sh ms-db-server:1433 -- node ./dist/server.js'
    ports:
      - "5555:5555"
    environment:
      - OTEL_EXPORTER_JAEGER_ENDPOINT=http://tempo:14268/api/traces
      - OTEL_SERVICE_NAME=nodejs-opentelemetry-tempo
      - LOG_FILE_NAME=/app/logs/nodejs-opentelemetry-tempo.log
      - DB_USER=sa
      - DB_PASS=P@ssw0rd
      - DB_SERVER=ms-db-server
      - DB_NAME=OtelTempo
    volumes:
      - ./data/logs:/app/logs
      - ./etc/wait-for.sh:/app/bin/wait-for.sh   #https://github.com/eficode/wait-for
    depends_on:
      - ms-db-server
      - tempo-query

  promtail:
    image: grafana/promtail:master-ee9c629
    command: -config.file=/etc/promtail/promtail-local.yaml
    volumes:
      - ./etc/promtail-local.yaml:/etc/promtail/promtail-local.yaml
      - ./data/logs:/app/logs
    depends_on:
      - nodejs-otel-tempo-api
      - loki

  prometheus:
    image: prom/prometheus:latest
    volumes:
      - ./etc/prometheus.yaml:/etc/prometheus.yaml
    entrypoint:
      - /bin/prometheus
      - --config.file=/etc/prometheus.yaml
    ports:
      - "9090:9090"
    depends_on:
      - nodejs-otel-tempo-api

  grafana:
    image: grafana/grafana:7.4.0-ubuntu
    volumes:
      - ./data/grafana-data/datasources:/etc/grafana/provisioning/datasources
      - ./data/grafana-data/dashboards-provisioning:/etc/grafana/provisioning/dashboards
      - ./data/grafana-data/dashboards:/var/lib/grafana/dashboards
    environment:
      - GF_AUTH_ANONYMOUS_ENABLED=true
      - GF_AUTH_ANONYMOUS_ORG_ROLE=Admin
      - GF_AUTH_DISABLE_LOGIN_FORM=true
    ports:
      - "3000:3000"
    depends_on:
      - prometheus
      - tempo-query
      - loki