pg_dump：错误：无法将主机名“localhost”转换为地址：未知服务器错误

Question

I have a code that should do a backup of existing PostgreSQL, but when I run the code am getting an error

pg_dump: error: could not translate hostname "localhost" to address: Unknown server error

I kept the folder path of bin and lib in an environment variable, but it is still showing the same error, Can anyone help me in this, please

below is the code:

import subprocess
import os

os.chdir('C:/Program Files/PostgreSQL/14/bin')

DB_NAME = 'postgress'  # your db name

DB_USER = 'postgres' # you db user
DB_HOST = "localhost"
DB_PASSWORD = 'ABC'# your db password
dump_success = 0
print('Backing up %s database ' % (DB_NAME))

command_for_dumping = f'pg_dump --host={DB_HOST} ' \
            f'--dbname={DB_NAME} ' \
            f'--username={DB_USER} ' \
            f'--no-password ' \
            f'--file=tmp/backup.dmp '
try:
     proc = subprocess.Popen(command_for_dumping, shell=True, env={
                   'PGPASSWORD': DB_PASSWORD
                   })
     proc.wait()

except Exception as e:
        dump_success = 0
        print('Exception happened during dump %s' %(e))


if dump_success:
    print('db dump successfull')
print(' restoring to a new database database')


backup_file = 'tmp/backup.dmp'
"""give absolute path of your dump file. This script will create the backup.dmp in the same directory from which u are running the script """

if not dump_success:
    print('dump unsucessfull. retsore not possible')
else:
    try:
        process = subprocess.Popen(
                        ['pg_restore',
                         '--no-owner',
                         '--dbname=postgresql://{}:{}@{}:{}/{}'.format('postgres',#db user
                                                                       'ABC', #db password
                                                                       'localhost',  #db host
                                                                       '5432', 'ReplicaDB'), #db port ,#db name
                         '-v',
                         backup_file],
                        stdout=subprocess.PIPE
                    )
        output = process.communicate()[0]
    except Exception as e:
           print('Exception during restore %e' %(e) )

So in Output it shows an error:

pg_dump: error: could not translate host name "localhost" to address: Unknown server error

I am new to this language, So am not sure of mistake i did. can anyone please guide me.

Answer 1

It's probably a bit late for OP but hopefully this may help others.

This seems to only happen on Windows. Try adding SYSTEMROOT to env:

env={
    'PGPASSWORD': DB_PASSWORD,
    'SYSTEMROOT': os.environ['SYSTEMROOT']
}

This fixed it for me calling pg_dump from python in a similar way. I first tried using IP address directly as host, then had a different error:

Socket: The requested service provider could not be loaded or initialized

Searching for this error led me to this post: https://travis-ci.community/t/socket-the-requested-service-provider-could-not-be-loaded-or-initialized/1127

Which suggested SYSTEMROOT environment variable is needed for DLLs to correctly load regarding opening socket.