Django with GeoDjango on AWS EC2, Postgres Postgis on RDS

Question

I'm trying to build an application with server code on AWS EC2 and the Spatial DB Postgis on RDS. I can access the Postgres from EC2 using command line:

psql --host=mydbpostgres.qazwsxedcrfv.us-west-1.rds.amazonaws.com --port=5432 --username=ec2 --password --dbname=mydb
mydb=>

I use GeoDjango on the EC2, and this is the setting for my DB:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'mydb',
    'USER': 'ec2',
    'PASSWORD': 'password',
    'HOST': 'mydbpostgres.qazwsxedcrfv.us-west-1.rds.amazonaws.com',
    'PORT': '5432',
    }
}

But when I run migration, it gives my error like this:

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/lib/python2.6/site-packages/django/core/management/__init__.py", line 399, in execute_from_command_line
    utility.execute()
  File "/usr/lib/python2.6/site-packages/django/core/management/__init__.py", line 392, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.6/site-packages/django/core/management/base.py", line 242, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/python2.6/site-packages/django/core/management/base.py", line 280, in execute
    translation.activate('en-us')
  File "/usr/lib/python2.6/site-packages/django/utils/translation/__init__.py", line 130, in activate
    return _trans.activate(language)
  File "/usr/lib/python2.6/site-packages/django/utils/translation/trans_real.py", line 188, in activate
    _active.value = translation(language)
  File "/usr/lib/python2.6/site-packages/django/utils/translation/trans_real.py", line 177, in translation
    default_translation = _fetch(settings.LANGUAGE_CODE)
  File "/usr/lib/python2.6/site-packages/django/utils/translation/trans_real.py", line 159, in _fetch
    app = import_module(appname)
  File "/usr/lib/python2.6/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
  File "/usr/lib/python2.6/site-packages/django/contrib/admin/__init__.py", line 6, in <module>
    from django.contrib.admin.sites import AdminSite, site
  File "/usr/lib/python2.6/site-packages/django/contrib/admin/sites.py", line 4, in <module>
    from django.contrib.admin.forms import AdminAuthenticationForm
  File "/usr/lib/python2.6/site-packages/django/contrib/admin/forms.py", line 6, in <module>
    from django.contrib.auth.forms import AuthenticationForm
  File "/usr/lib/python2.6/site-packages/django/contrib/auth/forms.py", line 17, in <module>
    from django.contrib.auth.models import User
  File "/usr/lib/python2.6/site-packages/django/contrib/auth/models.py", line 48, in <module>
    class Permission(models.Model):
  File "/usr/lib/python2.6/site-packages/django/db/models/base.py", line 96, in __new__
    new_class.add_to_class('_meta', Options(meta, **kwargs))
  File "/usr/lib/python2.6/site-packages/django/db/models/base.py", line 264, in add_to_class
    value.contribute_to_class(cls, name)
  File "/usr/lib/python2.6/site-packages/django/db/models/options.py", line 124, in contribute_to_class
    self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
  File "/usr/lib/python2.6/site-packages/django/db/__init__.py", line 34, in __getattr__
    return getattr(connections[DEFAULT_DB_ALIAS], item)
  File "/usr/lib/python2.6/site-packages/django/db/utils.py", line 198, in __getitem__
    backend = load_backend(db['ENGINE'])
  File "/usr/lib/python2.6/site-packages/django/db/utils.py", line 113, in load_backend
    return import_module('%s.base' % backend_name)
  File "/usr/lib/python2.6/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
  File "/usr/lib/python2.6/site-packages/django/contrib/gis/db/backends/postgis/base.py", line 5, in <module>
    from django.contrib.gis.db.backends.postgis.operations import PostGISOperations
  File "/usr/lib/python2.6/site-packages/django/contrib/gis/db/backends/postgis/operations.py", line 8, in <module>
    from django.contrib.gis.geometry.backend import Geometry
  File "/usr/lib/python2.6/site-packages/django/contrib/gis/geometry/backend/__init__.py", line 8, in <module>
    module = import_module('django.contrib.gis.geometry.backend.%s' % geom_backend)
  File "/usr/lib/python2.6/site-packages/django/utils/importlib.py", line 40, in import_module
    __import__(name)
  File "/usr/lib/python2.6/site-packages/django/contrib/gis/geometry/backend/geos.py", line 1, in <module>
    from django.contrib.gis.geos import (
  File "/usr/lib/python2.6/site-packages/django/contrib/gis/geos/__init__.py", line 7, in <module>
    from .libgeos import geos_version, geos_version_info, GEOS_PREPARE
  File "/usr/lib/python2.6/site-packages/django/contrib/gis/geos/libgeos.py", line 58, in <module>
    lgeos = CDLL(lib_path)
      File "/usr/lib64/python2.6/ctypes/__init__.py", line 353, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: libgeos_c.so.1: cannot open shared object file: No such file or directory

It looks like I'm missing some libraries of postgis on my EC2. My question is, do I need to install a postgis instance on my ec2 so that my server can find all that necessary libs? Or how can I make my server to look for the libs on the RDS?

Thanks very much!

Answer 1

It looks like you're just missing the "geos" library. If you're running Amazon Linux, installing that is as simple as yum install geos. That library provides the file: /usr/lib/libgeos_c.so.1