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testgres

PostgreSQL testing utility. Python 3.8+ is supported.

Installation

To install testgres, run:

pip install testgres

We encourage you to use virtualenv for your testing environment.

Usage

Environment

Note: by default testgres runs initdb, pg_ctl, psql provided by PATH.

There are several ways to specify a custom postgres installation:

export PG_CONFIG environment variable pointing to the pg_config executable;
export PG_BIN environment variable pointing to the directory with executable files.

Example:

export PG_BIN=$HOME/pg_10/bin
python my_tests.py

Examples

Here is an example of what you can do with testgres:

# create a node with random name, port, etc
with testgres.get_new_node() as node:

    # run inidb
    node.init()

    # start PostgreSQL
    node.start()

    # execute a query in a default DB
    print(node.execute('select 1'))

# ... node stops and its files are about to be removed

There are four API methods for running queries:

Command	Description
`node.psql(query, ...)`	Runs query via `psql` command and returns tuple `(error code, stdout, stderr)`.
`node.safe_psql(query, ...)`	Same as `psql()` except that it returns only `stdout`. If an error occurs during the execution, an exception will be thrown.
`node.execute(query, ...)`	Connects to PostgreSQL using `psycopg2` or `pg8000` (depends on which one is installed in your system) and returns two-dimensional array with data.
`node.connect(dbname, ...)`	Returns connection wrapper (`NodeConnection`) capable of running several queries within a single transaction.

The last one is the most powerful: you can use begin(isolation_level), commit() and rollback():

with node.connect() as con:
    con.begin('serializable')
    print(con.execute('select %s', 1))
    con.rollback()

Logging

By default, cleanup() removes all temporary files (DB files, logs etc) that were created by testgres' API methods. If you'd like to keep logs, execute configure_testgres(node_cleanup_full=False) before running any tests.

Note: context managers (aka with) call stop() and cleanup() automatically.

testgres supports python logging, which means that you can aggregate logs from several nodes into one file:

import logging

# write everything to /tmp/testgres.log
logging.basicConfig(filename='/tmp/testgres.log')

# enable logging, and create two different nodes
testgres.configure_testgres(use_python_logging=True)
node1 = testgres.get_new_node().init().start()
node2 = testgres.get_new_node().init().start()

# execute a few queries
node1.execute('select 1')
node2.execute('select 2')

# disable logging
testgres.configure_testgres(use_python_logging=False)

Look at tests/test_simple.py file for a complete example of the logging configuration.

Backup & replication

It's quite easy to create a backup and start a new replica:

with testgres.get_new_node('master') as master:
    master.init().start()

    # create a backup
    with master.backup() as backup:

        # create and start a new replica
        replica = backup.spawn_replica('replica').start()

        # catch up with master node
        replica.catchup()

        # execute a dummy query
        print(replica.execute('postgres', 'select 1'))

Benchmarks

testgres is also capable of running benchmarks using pgbench:

with testgres.get_new_node('master') as master:
    # start a new node
    master.init().start()

    # initialize default DB and run bench for 10 seconds
    res = master.pgbench_init(scale=2).pgbench_run(time=10)
    print(res)

Custom configuration

It's often useful to extend default configuration provided by testgres.

testgres has default_conf() function that helps control some basic options. The append_conf() function can be used to add custom lines to configuration lines:

ext_conf = "shared_preload_libraries = 'postgres_fdw'"

# initialize a new node
with testgres.get_new_node().init() as master:

    # ... do something ...
	
    # reset main config file
    master.default_conf(fsync=True,
                        allow_streaming=True)

    # add a new config line
    master.append_conf('postgresql.conf', ext_conf)

Note that default_conf() is called by init() function; both of them overwrite the configuration file, which means that they should be called before append_conf().

Remote mode

Testgres supports the creation of PostgreSQL nodes on a remote host. This is useful when you want to run distributed tests involving multiple nodes spread across different machines.

To use this feature, you need to use the RemoteOperations class. This feature is only supported with Linux. Here is an example of how you might set this up:

from testgres import ConnectionParams, RemoteOperations, TestgresConfig, get_remote_node

# Set up connection params
conn_params = ConnectionParams(
    host='your_host',  # replace with your host
    username='user_name',  # replace with your username
    ssh_key='path_to_ssh_key'  # replace with your SSH key path
)
os_ops = RemoteOperations(conn_params)

# Add remote testgres config before test
TestgresConfig.set_os_ops(os_ops=os_ops)

# Proceed with your test
def test_basic_query(self):
    with get_remote_node(conn_params=conn_params) as node:
        node.init().start()
        res = node.execute('SELECT 1')
        self.assertEqual(res, [(1,)])

Authors

Ildar Musin
Dmitry Ivanov
Ildus Kurbangaliev
Yury Zhuravlev