testgres

PostgreSQL testing utility. Both Python 2.7 and 3.3+ are 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 runnig 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 occures 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().

Authors

Ildar Musin
Dmitry Ivanov
Ildus Kurbangaliev
Yury Zhuravlev

postgrespro/testgres

postgrespro

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