Docker容器中数据库容器和docker中的java容器之间的连接被拒绝

Question

I am using docker compose to start a mysql da and a springboot app.

This is my docker-compose.yml

version: '3'
services:
  sql:
    image: mysql
    environment:
      MYSQL_DATABASE: people
      MYSQL_USER: root
      MYSQL_PASSWORD: my-secret-pw
      MYSQL_ROOT_PASSWORD: my-secret-pw
    ports:
      - "3307:3306"
  appointment-service:
    depends_on:
      - sql # This service depends on mysql. Start that first.
    environment: # Pass environment variables to the service
      - DATABASE_HOST=sql
      - DATABASE_USER=root
      - DATABASE_PASSWORD=my-secret-pw
      - DATABASE_NAME=people
      - DATABASE_PORT=3306
    links:
      - "sql:localhost"
    build: .
    ports:
      - "8081:8081"

This is my application.properties

server.port=8081

spring.datasource.url=jdbc:mysql://localhost:3306/people?useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=my-secret-pw

url.organizations = https://hr.apografi.gov.gr/api/public/organizations
url.db = jdbc:mysql://localhost:3306/people?serverTimezone=UTC
url.username = root
url.password = my-secret-pw

and here I create the jdbi:

private Jdbi jdbi = Jdbi.create("jdbc:mysql://localhost:3306/people?useSSL=false&allowPublicKeyRetrieval=true", "root", "my-secret-pw");

no matter what i tried i could not make the containers talk to each-other inside the docker. If I start the sql alone, I can see the connection in my host machine (in datagrip). If I run the java program from container, it sees the database in my host machine. Even if I run my docker-compose file, both the containers are created and I can access them from my host machine. I know that inside the DockerVM the database exists with the name sql/ I have tried both with sql name and the localhost name (from the links property). But no matter what I tried I was not able to access it from my java program inside the Docker.

Here is the stackTrace

docker-compose up --build
Building appointment-service
Step 1/4 : FROM openjdk:8-jdk-alpine
 ---> a3562aa0b991
Step 2/4 : ARG JAR_FILE=target/*.jar
 ---> Using cache
 ---> 603b2c59103f
Step 3/4 : COPY ${JAR_FILE} app.jar
 ---> Using cache
 ---> 4783d891166c
Step 4/4 : ENTRYPOINT ["java","-jar","/app.jar"]
 ---> Using cache
 ---> 24deebb3147a
Successfully built 24deebb3147a
Successfully tagged appointments-service_appointment-service:latest
Starting appointments-service_sql_1 ... done
Starting appointments-service_appointment-service_1 ... done
Attaching to appointments-service_sql_1, appointments-service_appointment-service_1
sql_1                  | 2020-09-11 16:47:27+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.21-1debian10 started.
sql_1                  | 2020-09-11 16:47:27+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
sql_1                  | 2020-09-11 16:47:27+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.21-1debian10 started.
sql_1                  | 2020-09-11T16:47:28.258555Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.21) starting as process 1
sql_1                  | 2020-09-11T16:47:28.275621Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
sql_1                  | 2020-09-11T16:47:28.641173Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
sql_1                  | 2020-09-11T16:47:28.823110Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '::' port: 33060, socket: /var/run/mysqld/mysqlx.sock
sql_1                  | 2020-09-11T16:47:28.988711Z 0 [Warning] [MY-010068] [Server] CA certificate ca.pem is self signed.
sql_1                  | 2020-09-11T16:47:28.989000Z 0 [System] [MY-013602] [Server] Channel mysql_main configured to support TLS. Encrypted connections are now supported for this channel.
sql_1                  | 2020-09-11T16:47:28.999907Z 0 [Warning] [MY-011810] [Server] Insecure configuration for --pid-file: Location '/var/run/mysqld' in the path is accessible to all OS users. Consider choosing a different directory.
sql_1                  | 2020-09-11T16:47:29.056993Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.21'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Server - GPL.
appointment-service_1  |
appointment-service_1  |   .   ____          _            __ _ _
appointment-service_1  |  /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
appointment-service_1  | ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
appointment-service_1  |  \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
appointment-service_1  |   '  |____| .__|_| |_|_| |_\__, | / / / /
appointment-service_1  |  =========|_|==============|___/=/_/_/_/
appointment-service_1  |  :: Spring Boot ::        (v2.3.2.RELEASE)
appointment-service_1  |
appointment-service_1  | 2020-09-11 16:47:30.628  INFO 1 --- [           main] c.a.service.ServiceApplication           : Starting ServiceApplication v0.0.1-SNAPSHOT on 5bbe74d3ddb0 with PID 1 (/app.jar started by root in /)
appointment-service_1  | 2020-09-11 16:47:30.635  INFO 1 --- [           main] c.a.service.ServiceApplication           : No active profile set, falling back to default profiles: default
appointment-service_1  | 2020-09-11 16:47:32.822  INFO 1 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFERRED mode.
appointment-service_1  | 2020-09-11 16:47:32.876  INFO 1 --- [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 33ms. Found 0 JPA repository interfaces.
appointment-service_1  | 2020-09-11 16:47:34.254  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8081 (http)
appointment-service_1  | 2020-09-11 16:47:34.300  INFO 1 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
appointment-service_1  | 2020-09-11 16:47:34.302  INFO 1 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.37]
appointment-service_1  | 2020-09-11 16:47:34.472  INFO 1 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
appointment-service_1  | 2020-09-11 16:47:34.473  INFO 1 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 3697 ms
appointment-service_1  | 2020-09-11 16:47:35.055  INFO 1 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
appointment-service_1  | 2020-09-11 16:47:35.100  INFO 1 --- [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
appointment-service_1  | 2020-09-11 16:47:36.338 ERROR 1 --- [           main] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Exception during pool initialization.
appointment-service_1  |
appointment-service_1  | com.mysql.cj.jdbc.exceptions.CommunicationsException: Communications link failure
appointment-service_1  |
appointment-service_1  | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
appointment-service_1  |    at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:836) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:456) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:246) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:197) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:138) ~[HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:358) ~[HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:206) ~[HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:477) [HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at com.zaxxer.hikari.pool.HikariPool.checkFailFast(HikariPool.java:560) [HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at com.zaxxer.hikari.pool.HikariPool.<init>(HikariPool.java:115) [HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:112) [HikariCP-3.4.5.jar!/:na]
appointment-service_1  |    at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:158) [spring-jdbc-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:116) [spring-jdbc-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:79) [spring-jdbc-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:324) [spring-jdbc-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.boot.jdbc.EmbeddedDatabaseConnection.isEmbedded(EmbeddedDatabaseConnection.java:120) [spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateDefaultDdlAutoProvider.getDefaultDdlAuto(HibernateDefaultDdlAutoProvider.java:42) [spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaConfiguration.lambda$getVendorProperties$1(HibernateJpaConfiguration.java:130) [spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings.getDdlAuto(HibernateSettings.java:41) ~[spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties.determineDdlAuto(HibernateProperties.java:136) ~[spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties.getAdditionalProperties(HibernateProperties.java:102) ~[spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties.determineHibernateProperties(HibernateProperties.java:94) ~[spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaConfiguration.getVendorProperties(HibernateJpaConfiguration.java:132) [spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.autoconfigure.orm.jpa.JpaBaseConfiguration.entityManagerFactory(JpaBaseConfiguration.java:133) ~[spring-boot-autoconfigure-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_212]
appointment-service_1  |    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_212]
appointment-service_1  |    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_212]
appointment-service_1  |    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_212]
appointment-service_1  |    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:650) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:635) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1336) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1176) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:556) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1109) ~[spring-context-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551) ~[spring-context-5.2.8.RELEASE.jar!/:5.2.8.RELEASE]
appointment-service_1  |    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.3.2.RELEASE.jar!/:2.3.2.RELEASE]
appointment-service_1  |    at com.appointments.service.ServiceApplication.main(ServiceApplication.java:10) ~[classes!/:0.0.1-SNAPSHOT]
appointment-service_1  |    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_212]
appointment-service_1  |    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_212]
appointment-service_1  |    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_212]
appointment-service_1  |    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_212]
appointment-service_1  |    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49) ~[app.jar:0.0.1-SNAPSHOT]
appointment-service_1  |    at org.springframework.boot.loader.Launcher.launch(Launcher.java:109) ~[app.jar:0.0.1-SNAPSHOT]
appointment-service_1  |    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58) ~[app.jar:0.0.1-SNAPSHOT]
appointment-service_1  |    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88) ~[app.jar:0.0.1-SNAPSHOT]
appointment-service_1  | Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
appointment-service_1  |
appointment-service_1  | The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
appointment-service_1  |    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_212]
appointment-service_1  |    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_212]
appointment-service_1  |    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_212]
appointment-service_1  |    at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_212]
appointment-service_1  |    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:61) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:105) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.exceptions.ExceptionFactory.createException(ExceptionFactory.java:151) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.exceptions.ExceptionFactory.createCommunicationsException(ExceptionFactory.java:167) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:91) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.NativeSession.connect(NativeSession.java:144) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:956) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:826) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    ... 57 common frames omitted
appointment-service_1  | Caused by: java.net.ConnectException: Connection refused (Connection refused)
appointment-service_1  |    at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_212]
appointment-service_1  |    at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_212]
appointment-service_1  |    at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_212]
appointment-service_1  |    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_212]
appointment-service_1  |    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_212]
appointment-service_1  |    at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_212]
appointment-service_1  |    at com.mysql.cj.protocol.StandardSocketFactory.connect(StandardSocketFactory.java:155) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    at com.mysql.cj.protocol.a.NativeSocketConnection.connect(NativeSocketConnection.java:65) ~[mysql-connector-java-8.0.21.jar!/:8.0.21]
appointment-service_1  |    ... 60 common frames omitted
appointment-service_1 

|

Answer 1

• links: is deprecated and useless in this case - just delete that line.
• localhost used inside the java container will point to the container itself. You must use the service name that you gave for your sql container( sql in your case). The service name will be resolved to the IP of the SQL container.
• depends_on: will make the java containers wait for the SQL containers to start , but this does not guarantee that the SQL is up and running, ready to accept connections. The are several ways to solve this problem(wait-for-it, restart: on-failure , this post etc.)
• you don't need to specify the MYSQL_USER: root nor the MYSQL_PASSWORD: my-secret-pw if your intent is to use just the root user.(this has nothing to do with your current problem)

version: '3'
services:
  sql:
    image: mysql
    environment:
      MYSQL_DATABASE: people
      MYSQL_ROOT_PASSWORD: my-secret-pw
    ports:
      - "3307:3306"
  appointment-service:
    depends_on:
      - sql # This service depends on mysql. Start that first.
    restart: on-failure
    environment: # Pass environment variables to the service
      - DATABASE_HOST=sql
      - DATABASE_USER=root
      - DATABASE_PASSWORD=my-secret-pw
      - DATABASE_NAME=people
      - DATABASE_PORT=3306
    build: .
    ports:
      - "8081:8081"

server.port=8081

spring.datasource.url=jdbc:mysql://sql:3306/people?useSSL=false&allowPublicKeyRetrieval=true
spring.datasource.username=root
spring.datasource.password=my-secret-pw

url.organizations = https://hr.apografi.gov.gr/api/public/organizations
url.db = jdbc:mysql://sql:3306/people?serverTimezone=UTC
url.username = root
url.password = my-secret-pw

private Jdbi jdbi = Jdbi.create("jdbc:mysql://sql:3306/people?useSSL=false&allowPublicKeyRetrieval=true", "root", "my-secret-pw");

Answer 2

localhost always points to the loopback interface (either 127.0.0.1 or ::1 ). You cannot, and should not attempt to, override this.

When using docker-compose, you can user service names as hostnames, so the proper JDBC URL for your database would be:

jdbc:mysql://sql:3306/people?useSSL=false&allowPublicKeyRetrieval=true