From f9ef7fd30b3f0613bc9dd912621856b3262d23bc Mon Sep 17 00:00:00 2001 From: RamonWill Date: Wed, 2 Sep 2020 18:43:53 -0400 Subject: Support for multiple hosts in PostgreSQL connection string Provide support for multiple hosts in the PostgreSQL connection string. A user requested for SQLAlchemy to support multiple hosts within a PostgreSQL URL string. The proposed fix allows this. In the event that the url contains multiple hosts the proposed code will convert the query["hosts"] tuple into a single string. This allows the hosts to then get converted into a valid dsn variable in the psycopg2 connect function. This pull request is: - [ ] A documentation / typographical error fix - Good to go, no issue or tests are needed - [X ] A short code fix - please include the issue number, and create an issue if none exists, which must include a complete example of the issue. one line code fixes without an issue and demonstration will not be accepted. - Please include: `Fixes: #` in the commit message - please include tests. one line code fixes without tests will not be accepted. - [ ] A new feature implementation - please include the issue number, and create an issue if none exists, which must include a complete example of how the feature would look. - Please include: `Fixes: #` in the commit message - please include tests. **Have a nice day!** Fixes: #4392 Closes: #5554 Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5554 Pull-request-sha: 3f7a0ab8df9f1411a9f1ac0e152583bc7bf0c365 Change-Id: I3f3768d51b8331de786ffdc025b7ecfc662eafe5 --- lib/sqlalchemy/dialects/postgresql/psycopg2.py | 31 ++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) (limited to 'lib/sqlalchemy/dialects/postgresql/psycopg2.py') diff --git a/lib/sqlalchemy/dialects/postgresql/psycopg2.py b/lib/sqlalchemy/dialects/postgresql/psycopg2.py index 91576c4d2..3c9ef72c4 100644 --- a/lib/sqlalchemy/dialects/postgresql/psycopg2.py +++ b/lib/sqlalchemy/dialects/postgresql/psycopg2.py @@ -71,6 +71,28 @@ using ``host`` as an additional keyword argument:: `PQconnectdbParams \ `_ +Multiple Hosts in Connection String +------------------------ +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:: + + create_engine( + "postgresql+psycopg2://user:password@/dbname?host=HostA:port1&host=HostB&host=HostC" + ) + +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. + +.. versionadded:: 1.3.20 Support for multiple hosts in PostgreSQL connection + string. + +.. seealso:: + + `PQConnString \ + `_ + Empty DSN Connections / Environment Variable Connections --------------------------------------------------------- @@ -929,16 +951,25 @@ class PGDialect_psycopg2(PGDialect): def create_connect_args(self, url): opts = url.translate_connect_args(username="user") + + is_multihost = False + if "host" in url.query: + is_multihost = isinstance(url.query["host"], (list, tuple)) + if 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"]) return ([], opts) else: # no connection arguments whatsoever; psycopg2.connect() -- cgit v1.2.1