Develop Reference

Docker SDK - Can't connect to DB from HOST

I want to create a temporary MySQL database for unit testing in Python. I decided to go with docker as the tests will be run on different machines.
As a first thing I run the container:
client = docker.from_env()
container = client.containers.run("ubuntu/mysql", detach=True, ports={3306:3307},environment={
'MYSQL_USER':'mysqluser',
'MYSQL_PASSWORD':'password',
'MYSQL_DATABASE':'mydb',
})
print('Container Started : {}'.format(container.status))
And then I try to connect using SQLAlchemy:
engine = sa.create_engine(f'mysql+pymysql://mysqluser:password#localhost:3307/mydb')
engine.connect()
which returns:
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2013, 'Lost connection to MySQL server during query')
EDIT
After putting sleep(10) after container.run, the response is different:
sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2003, "Can't connect to MySQL server on 'localhost' ([Errno 111] Connection refused)")
Do you know what I'm doing wrong?
What I want to do is to connect to MySQL database on port 3307 (as one server already runs on the host). Then I want to create and populate a table.
EDIT2
Switching ports to {3307:3306} returns error:
docker.errors.APIError: 500 Server Error for http+docker://localhost/v1.41/containers/67a04b384bf3d39407881d4dfc73961932a3ce72fe8dc82c3cd6aedd57da2821/start: Internal Server Error ("driver failed programming external connectivity on endpoint hopeful_leakey (97840eb42d2c09b5e9754b634481d8e048c57ba2de8ffc10b34261de2f76600b): Error starting userland proxy: listen tcp4 0.0.0.0:3306: bind: address already in use")

Connecting Python to Redshift through SSH and SQLAlchemy

My current connection configuration is as follow, this is for redshift db
con=('postgresql://username:password#hostname:port/databasename')
server = SSHTunnelForwarder(
('ssh host', 22),
ssh_username="-",
ssh_password="-",
remote_bind_address=('db host', port)
)
server.start()
local_port = str(server.local_bind_port)
engine = sa.create_engine(con)
######## Reaches here then times out when reading the table
df_read = pd.read_sql_table('tablename',engine)
However, the Redshift database also has an SSH, which might be affecting the connection? It creates the engine but when reading the SQL in pd.read_sql_query I reach this error.
(psycopg2.OperationalError) could not connect to server: Connection timed out (0x0000274C/10060)
Is the server running on host "xxx" (xxx) and accepting
TCP/IP connections on port xxx?
(Background on this error at: http://sqlalche.me/e/e3q8)

You cannot SSH into a Redshift cluster but you can use SSL to secure the connection.
Amazon Redshift security overview
Configuring security options for connections

psycopg2 connecting to postgresql database - error

I have problem to connect to my postgreSQL database.
I have databasename, password, hostname, port and I use this:
conn_string = "host='localhost' dbname='my_database' user='postgres' password='secret'"
But I got error like this:
Is the server running on host "...." and accepting TCP/IP connections on port 5432
I don't know if I used correctly host, I insert the value of hostname.
What is the difference between hostname and host? Anyone could help me?

psycopg2.connect(dbname=dbname, user=user, password=password, host=postgres_address, port=postgres_port)
This is working example to connect, you must define early dbname, user, password, postgres_address. If you have connection error, you can use ping for testing connection and telnet for testing openning port. Or you can use Beaver for test connection to postgres server.

Most likely your database has a firewall, be sure to whitelist the IP you are trying to connect from.

Difference of host and hostname
The difference of host and hostname really depends on the context. In your context of psycopg2 and PostgreSQL connection, the host normally means the IP address of the PostgreSQL server or the resolvable name of the PostgreSQL server such as DNS name if it has. If you are running linux server, the output of command hostname is unlikely to work in your case.
psycopg2 connection
Your connection string looks OK. But I will suggest you to use below connection format:
import psycopg2
try:
connection = psycopg2.connect(user = "sysadmin",
password = "pynative##29",
host = "127.0.0.1",
port = "5432",
database = "postgres_db")
except (Exception, psycopg2.Error) as error :
print ("Error while connecting to PostgreSQL", error)
You should use the IP address as the host value.
Troubleshooting
In the case of connection error, you should use other tools to test the connection of PostgreSQL server such as psql, pgAdmin4 or DBeaver.
You can also use telnet or netcat tools to test the network connection of PostgreSQL server, such as
telnet PostgreSQL_ip_address 5432
nc -v PostgreSQL_ip_address 5432

Connect to remote Postgres server via SQLAlchemy

I am trying to send some commands to a remote Postgres server using SQLAlchemy but each time I receive an error.
Please note that I can connect to the remote Postgres using SSH username and password to login to the server. For that I have used my local terminal, PuTTY and WinSCP so the problem appears to be in the Python code I have written
# create postgres engine to connect to the database
engine = create_engine('postgres://server_username:server_password#server_name:port/database')
with engine.connect() as conn:
ex = conn.execute("SELECT version();")
conn.close() # not needed but keep just in case
print(ex)
Running the code above yields the following error:
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) SSL SYSCALL error: Connection reset by peer (0x00002746/10054)
expected authentication request from server, but received S
I have also tried adding the SSL verification parameter as follows
create_engine('postgres://server_username:server_password#server_name:port/database?sslmode=verify-full')
which returned the error
sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) root certificate file "C:\Users\aris.pavlides\AppData\Roaming/postgresql/root.crt" does not exist
Either provide the file or change sslmode to disable server certificate verification.
at which point I had nothing to lose so I disabled certificate verification altogether
create_engine('postgres://server_username:server_password#server_name:port/database?sslmode=disable')
which returned the initial error message.
Do you have any ideas on how I can modify the code to make it work?

PYODBC can't connect to SQL Express instance

I'm running an instance of SQL Server Express 2017 on my computer. I am attempting to connect to it with the following connection string:
"Driver=ODBC Driver 13 for SQL Server;Server=COMPUTERNAME\\SQLEXPRESS,1433;Database=databasename;Uid=testuser;Pwd=testpassword;Encrypt=yes;TrustServerCertificate=no;Connection Timeout=30;"
I have successfully connected to the server manually using those connections and SQL Server Authentication using SQL Server Management Studio.
Firewall shouldn't be an issue as it's a locally hosted server, but I've opened port 1433 for inbound and outbound connections anyway.
This connection string format has worked in the past with a database hosted on Azure (which I can no longer afford to do).
The error message:
pyodbc.OperationalError: ('08001', '[08001] [Microsoft][ODBC Driver 13 for SQL Server]TCP Provider: No connection could be made because the target machine actively refused it.\r\n (10061) (SQLDriverConnect); [08001] [Microsoft][ODBC Driver 13 for SQL Server]Login timeout expired (0); [08001] [Microsoft][ODBC Driver 13 for SQL Server]Invalid connection string attribute (0); [08001] [Microsoft][ODBC Driver 13 for SQL Server]A network-related or instance-specific error has occurred while establishing a connection to SQL Server. Server is not found or not accessible. Check if instance name is correct and if SQL Server is configured to allow remote connections. For more information see SQL Server Books Online. (10061)')
Any more suggestions?

I'm going to answer this question in case someone else finds it, even though it's old.
What worked pretty well for me was:
Finding out the port used by the SQL Express instance (which in my case turned out to be good 'ol 1433)
Using Network Library=DBMSSOCN to avoid issues regarding named instances (couldn't make it work that way)
How?
Doing it this way:
pyodbc.connect('driver={SQL Server Native Client 11.0};server='+DBIPAddress+';port='+DBPort+';Network Library=DBMSSOCN;database='+DBName+';uid='+DBUser+';pwd='+DBPass)
Where
DBIPAddress is the IP address of the SQL Server server
DBPort is the port
DBName is the name of the database you're trying to connect to
DBUser is the username you're using
DBPass is the password
I guess you could use {SQL Server} driver also, but I haven't tried. What we're doing is forcing a connection using the IP and port regardless of the existence of a named instance.