--- /dev/null
+.. change::
+ :tags: bug, postgresql
+ :tickets: 4392
+
+ Fixed issue in psycopg2 dialect where the "multiple hosts" feature
+ implemented for :ticket:`4392`, where multiple ``host:port`` pairs could be
+ passed in the query string as
+ ``?host=host1:port1&host=host2:port2&host=host3:port3`` was not implemented
+ correctly, as it did not propagate the "port" parameter appropriately.
+ Connections that didn't use a different "port" likely worked without issue,
+ and connections that had "port" for some of the entries may have
+ incorrectly passed on that hostname. The format is now corrected to pass
+ hosts/ports appropriately.
+
+ As part of this change, maintained support for another multihost style that
+ worked unintentionally, which is comma-separated
+ ``?host=h1,h2,h3&port=p1,p2,p3``. This format is more consistent with
+ libpq's query-string format, whereas the previous format is inspired by a
+ different aspect of libpq's URI format but is not quite the same thing.
+
+ If the two styles are mixed together, an error is raised as this is
+ ambiguous.
\ No newline at end of file
psycopg2 supports multiple connection points in the connection string.
When the ``host`` parameter is used multiple times in the query section of
the URL, SQLAlchemy will create a single string of the host and port
-information provided to make the connections::
+information provided to make the connections. Tokens may consist of
+``host::port`` or just ``host``; in the latter case, the default port
+is selected by libpq. In the example below, three host connections
+are specified, for ``HostA::PortA``, ``HostB`` connecting to the default port,
+and ``HostC::PortC``::
create_engine(
- "postgresql+psycopg2://user:password@/dbname?host=HostA:port1&host=HostB&host=HostC"
+ "postgresql+psycopg2://user:password@/dbname?host=HostA:PortA&host=HostB&host=HostC:PortC"
)
-A connection to each host is then attempted until either a connection is successful
-or all connections are unsuccessful in which case an error is raised.
+As an alternative, libpq query string format also may be used; this specifies
+``host`` and ``port`` as single query string arguments with comma-separated
+lists - the default port can be chosen by indicating an empty value
+in the comma separated list::
+
+ create_engine(
+ "postgresql+psycopg2://user:password@/dbname?host=HostA,HostB,HostC&port=PortA,,PortC"
+ )
+
+With either URL style, connections to each host is attempted based on a
+configurable strategy, which may be configured using the libpq
+``target_session_attrs`` parameter. Per libpq this defaults to ``any``
+which indicates a connection to each host is then attempted until a connection is successful.
+Other strategies include ``primary``, ``prefer-standby``, etc. The complete
+list is documented by PostgreSQL at
+`libpq connection strings <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING>`_.
+
+For example, to indicate two hosts using the ``primary`` strategy::
+
+ create_engine(
+ "postgresql+psycopg2://user:password@/dbname?host=HostA:PortA&host=HostB&host=HostC:PortC&target_session_attrs=primary"
+ )
+
+.. versionchanged:: 1.4.40 Port specification in psycopg2 multiple host format
+ is repaired, previously ports were not correctly interpreted in this context.
+ libpq comma-separated format is also now supported.
.. versionadded:: 1.3.20 Support for multiple hosts in PostgreSQL connection
string.
.. seealso::
- `PQConnString \
- <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING>`_
+ `libpq connection strings <https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING>`_ - please refer
+ to this section in the libpq documentation for complete background on multiple host support.
+
Empty DSN Connections / Environment Variable Connections
---------------------------------------------------------
if "host" in url.query:
is_multihost = isinstance(url.query["host"], (list, tuple))
- if opts:
+ if opts or url.query:
+ if not opts:
+ opts = {}
if "port" in opts:
opts["port"] = int(opts["port"])
opts.update(url.query)
if is_multihost:
- opts["host"] = ",".join(url.query["host"])
- # send individual dbname, user, password, host, port
- # parameters to psycopg2.connect()
- return ([], opts)
- elif url.query:
- # any other connection arguments, pass directly
- opts.update(url.query)
- if is_multihost:
- opts["host"] = ",".join(url.query["host"])
+ hosts, ports = zip(
+ *[
+ token.split(":") if ":" in token else (token, "")
+ for token in url.query["host"]
+ ]
+ )
+ opts["host"] = ",".join(hosts)
+ if "port" in opts:
+ raise exc.ArgumentError(
+ "Can't mix 'multihost' formats together; use "
+ '"host=h1,h2,h3&port=p1,p2,p3" or '
+ '"host=h1:p1&host=h2:p2&host=h3:p3" separately'
+ )
+ opts["port"] = ",".join(ports)
return ([], opts)
else:
# no connection arguments whatsoever; psycopg2.connect()
from sqlalchemy import bindparam
from sqlalchemy import cast
from sqlalchemy import Column
+from sqlalchemy import create_engine
from sqlalchemy import DateTime
from sqlalchemy import DDL
from sqlalchemy import event
from sqlalchemy.sql.selectable import LABEL_STYLE_TABLENAME_PLUS_COL
from sqlalchemy.testing import config
from sqlalchemy.testing import engines
+from sqlalchemy.testing import expect_raises_message
from sqlalchemy.testing import fixtures
from sqlalchemy.testing import is_
from sqlalchemy.testing import is_false
eq_(cargs, [])
eq_(cparams, {"host": "somehost", "any_random_thing": "yes"})
- def test_psycopg2_nonempty_connection_string_w_query_two(self):
+ @testing.combinations(
+ (
+ "postgresql+psycopg2://USER:PASS@/DB?host=hostA",
+ {
+ "database": "DB",
+ "user": "USER",
+ "password": "PASS",
+ "host": "hostA",
+ },
+ ),
+ (
+ "postgresql+psycopg2://USER:PASS@/DB"
+ "?host=hostA&host=hostB&host=hostC",
+ {
+ "database": "DB",
+ "user": "USER",
+ "password": "PASS",
+ "host": "hostA,hostB,hostC",
+ "port": ",,",
+ },
+ ),
+ (
+ "postgresql+psycopg2://USER:PASS@/DB"
+ "?host=hostA&host=hostB:portB&host=hostC:portC",
+ {
+ "database": "DB",
+ "user": "USER",
+ "password": "PASS",
+ "host": "hostA,hostB,hostC",
+ "port": ",portB,portC",
+ },
+ ),
+ (
+ "postgresql+psycopg2://USER:PASS@/DB?"
+ "host=hostA:portA&host=hostB:portB&host=hostC:portC",
+ {
+ "database": "DB",
+ "user": "USER",
+ "password": "PASS",
+ "host": "hostA,hostB,hostC",
+ "port": "portA,portB,portC",
+ },
+ ),
+ (
+ "postgresql+psycopg2:///"
+ "?host=hostA:portA&host=hostB:portB&host=hostC:portC",
+ {"host": "hostA,hostB,hostC", "port": "portA,portB,portC"},
+ ),
+ (
+ "postgresql+psycopg2:///"
+ "?host=hostA:portA&host=hostB:portB&host=hostC:portC",
+ {"host": "hostA,hostB,hostC", "port": "portA,portB,portC"},
+ ),
+ (
+ "postgresql+psycopg2:///"
+ "?host=hostA,hostB,hostC&port=portA,portB,portC",
+ {"host": "hostA,hostB,hostC", "port": "portA,portB,portC"},
+ ),
+ argnames="url_string,expected",
+ )
+ def test_psycopg_multi_hosts(self, url_string, expected):
dialect = psycopg2_dialect.dialect()
- url_string = "postgresql://USER:PASS@/DB?host=hostA"
u = url.make_url(url_string)
cargs, cparams = dialect.create_connect_args(u)
eq_(cargs, [])
- eq_(cparams["host"], "hostA")
+ eq_(cparams, expected)
- def test_psycopg2_nonempty_connection_string_w_query_three(self):
+ @testing.combinations(
+ "postgresql+psycopg2:///?host=H&host=H&port=5432,5432",
+ "postgresql+psycopg2://user:pass@/dbname?host=H&host=H&port=5432,5432",
+ argnames="url_string",
+ )
+ def test_psycopg_no_mix_hosts(self, url_string):
dialect = psycopg2_dialect.dialect()
- url_string = (
- "postgresql://USER:PASS@/DB"
- "?host=hostA:portA&host=hostB&host=hostC"
- )
- u = url.make_url(url_string)
- cargs, cparams = dialect.create_connect_args(u)
- eq_(cargs, [])
- eq_(cparams["host"], "hostA:portA,hostB,hostC")
+ with expect_raises_message(
+ exc.ArgumentError, "Can't mix 'multihost' formats together"
+ ):
+ u = url.make_url(url_string)
+ dialect.create_connect_args(u)
def test_psycopg2_disconnect(self):
class Error(Exception):
eq_(dialect.is_disconnect("not an error", None, None), False)
+class BackendDialectTest(fixtures.TestBase):
+ __backend__ = True
+
+ @testing.only_on(["+psycopg", "+psycopg2"])
+ @testing.combinations(
+ "host=H:P&host=H:P&host=H:P",
+ "host=H:P&host=H&host=H",
+ "host=H:P&host=H&host=H:P",
+ "host=H&host=H:P&host=H",
+ "host=H,H,H&port=P,P,P",
+ )
+ def test_connect_psycopg_multiple_hosts(self, pattern):
+ """test the fix for #4392"""
+
+ tdb_url = testing.db.url
+
+ host = tdb_url.host
+ if host == "127.0.0.1":
+ host = "localhost"
+ port = str(tdb_url.port) if tdb_url.port else "5432"
+
+ query_str = pattern.replace("H", host).replace("P", port)
+ url_string = "%s://%s:" "%s@/%s?%s" % (
+ tdb_url.drivername,
+ tdb_url.username,
+ tdb_url.password,
+ tdb_url.database,
+ query_str,
+ )
+
+ e = create_engine(url_string)
+ with e.connect() as conn:
+ eq_(conn.exec_driver_sql("select 1").scalar(), 1)
+
+
class PGCodeTest(fixtures.TestBase):
__only_on__ = "postgresql"
projects / thirdparty / sqlalchemy / sqlalchemy.git / commitdiff
