Only protocol 3 supported

ghz 昨天 ⋅ 4 views

I try to configure Django with PostgreSQL on Windows 10. When I run server usually I get an error

only protocol 3 supported

but sometimes the server starts properly.

I installed 32-bit Postgres 9.6 and psycopg2 2.7.1.

In settings.py I have

DATABASES = {
 'default': {
  'ENGINE': 'django.db.backends.postgresql_psycopg2',
  'NAME': 'postgres',
  'USER': 'django',
  'PASSWORD': 'django',
  'HOST': 'localhost',
  'PORT': '5432',
 }
}

Do you know any solutions for the problem?

Answer

The error message "only protocol 3 supported" typically points to a mismatch between the PostgreSQL server and the version of psycopg2 or the configuration of PostgreSQL. Here are a few steps you can take to resolve the issue:

1. Ensure PostgreSQL is Configured Correctly

First, check that your PostgreSQL server is running correctly and that it supports the correct protocol version. In PostgreSQL, protocol versions are typically associated with specific versions of the client libraries and PostgreSQL itself.

  • Ensure PostgreSQL is running: Run the following command to ensure PostgreSQL is up and running:

    pg_ctl status

    If PostgreSQL is not running, start it using:

    pg_ctl start

  • Check PostgreSQL Version: Make sure the version you're using supports protocol 3. You can check the version by running:

    psql --version

    The error you see might be caused if you're using an old PostgreSQL version with a newer version of psycopg2. Ensure your PostgreSQL installation supports protocol version 3, which is typically supported by all versions of PostgreSQL 9.x and above.

2. Upgrade psycopg2 Version

You mentioned using psycopg2 2.7.1, which might not be fully compatible with your PostgreSQL version or might have bugs. The latest version of psycopg2 is likely to resolve many issues related to protocol and compatibility. Try upgrading it:

pip install --upgrade psycopg2

Alternatively, you can use psycopg2-binary, which is easier to install and includes the necessary binary dependencies:

pip install psycopg2-binary

After upgrading psycopg2, restart your Django server.

3. Check PostgreSQL Configuration (pg_hba.conf)

Check your PostgreSQL configuration to make sure it's set up to allow connections from your Django application. The file pg_hba.conf controls the client authentication, and you may need to modify it to ensure proper connections are allowed.

  1. Find the pg_hba.conf file, typically located in the PostgreSQL data directory. The path to this file can vary, but it's often in the directory where PostgreSQL is installed (e.g., C:\Program Files\PostgreSQL\9.6\data).

  2. Open pg_hba.conf and look for a line like this:

    host    all             all             127.0.0.1/32            md5

  3. If it's not already there, add or ensure the line allowing localhost connections with password authentication exists.

  4. After making changes, restart PostgreSQL:

    pg_ctl restart

4. Verify Connection Settings in Django

In your settings.py, the connection settings seem fine, but just to confirm:

  1. Ensure that the PostgreSQL username and password are correct (i.e., USER='django' and PASSWORD='django' in your DATABASES setting).

  2. Ensure that PostgreSQL is listening on localhost and is accepting connections from your Django application on port 5432 (default).

  3. Try specifying the full path to the PostgreSQL socket in the HOST if needed, but normally localhost should work.

5. Ensure You're Using the Correct Python Environment

If you have multiple Python environments (e.g., system Python, virtualenv, Anaconda), make sure you have installed psycopg2 in the correct environment that your Django project is using. You can check your current environment by running:

which python  # On Windows, use `where python`

Then ensure psycopg2 is installed for that environment:

pip show psycopg2

If it's missing, you can install it using:

pip install psycopg2-binary

6. Restart Django Server and PostgreSQL

After making the changes:

  1. Restart your PostgreSQL server.
  2. Restart your Django server to ensure that all changes take effect.

7. Check PostgreSQL Logs

If the issue persists, check PostgreSQL's logs for more detailed error messages that may explain why the connection is not being established properly. Logs are usually stored in the pg_log directory inside the PostgreSQL installation folder.

Summary

  • Upgrade psycopg2 to the latest version using pip install --upgrade psycopg2 or psycopg2-binary.
  • Check your PostgreSQL version and ensure it's up and running.
  • Ensure that PostgreSQL is configured to allow connections from localhost in pg_hba.conf.
  • Restart both PostgreSQL and Django servers after making any changes.

By following these steps, you should be able to fix the "only protocol 3 supported" issue and get your Django application running smoothly with PostgreSQL on Windows 10.

#py