psql: could not translate host name “somePostgres”

问题:

I am building a java spring mvc application in docker and dockefile build involves interacting with postgres container. Whenever i run docker-compose up the step in dockerfile which interacts with the postrges sometimes fails with an exception

psql: could not translate host name "somePostgres" to address: Name or service not known FAILED

FAILURE: Build failed with an exception.

DockerCompose file:

abcdweb:
  links:
  - abcdpostgres
  build: .
  ports:
  - "8080:8080"
  volumes:
  - .:/abcd-myproj
  container_name: someWeb
abcdpostgres:
  image: postgres
  environment:
  - POSTGRES_PASSWORD=postgres
  - POSTGRES_USER=postgres
  container_name: somePostgres

The somePostgres seems to start very quickly and There is no late loading of postgres container problem. Currently i am running this in virtual box created by docker-machine. Unable to get error as it's not persistent.

PS: Added Dockerfile

FROM java:7
RUN apt-get update && apt-get install -y postgresql-client-9.4
ADD . ./abcd-myproj
WORKDIR /abcd-myproj
RUN ./gradlew build -x test 
RUN sh db/importdata.sh
CMD ./gradlew jettyRun

回答1:

Basically what this error means is that psql was unable to resolve the host name, try using the ip address instead.

https://github.com/postgres/postgres/blob/313f56ce2d1b9dfd3483e4f39611baa27852835a/src/interfaces/libpq/fe-connect.c#L2275-L2285

case CHT_HOST_NAME:
    ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
                             &conn->addrlist);
    if (ret || !conn->addrlist)
    {
        appendPQExpBuffer(&conn->errorMessage,
                          libpq_gettext("could not translate host name \"%s\" to address: %s\n"),
                          ch->host, gai_strerror(ret));
        goto keep_going;
    }
break;

https://github.com/postgres/postgres/blob/8255c7a5eeba8f1a38b7a431c04909bde4f5e67d/src/common/ip.c#L57-L75

int
pg_getaddrinfo_all(const char *hostname, const char *servname,
                   const struct addrinfo *hintp, struct addrinfo **result)
{
    int         rc;

    /* not all versions of getaddrinfo() zero *result on failure */
    *result = NULL;

#ifdef HAVE_UNIX_SOCKETS
    if (hintp->ai_family == AF_UNIX)
        return getaddrinfo_unix(servname, hintp, result);
#endif

    /* NULL has special meaning to getaddrinfo(). */
    rc = getaddrinfo((!hostname || hostname[0] == '\0') ? NULL : hostname,
                     servname, hintp, result);

    return rc;
}

回答2:

I think links are not encouraged lately.

But, if you want to have services to communicate over network and explicitly here is the config: You need to configure network an both services to attach to that network. It is something like:

networks:
  network:
    external: true
abcdweb:
  links:
  - abcdpostgres
  build: .
  ports:
  - "8080:8080"
  volumes:
  - .:/abcd-myproj
  container_name: someWeb
  networks:
    network: null
abcdpostgres:
  image: postgres
  environment:
  - POSTGRES_PASSWORD=postgres
  - POSTGRES_USER=postgres
  container_name: somePostgres
  networks:
    network: null

In this way the service will communicate via the network with service names as adress.