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https://github.com/psycopg/psycopg2.git
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Reshuffling and indexing of replication docs
This commit is contained in:
Daniele Varrazzo
parent
2a4d6027a4
commit
9a4f8f915f
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@ -423,7 +423,7 @@ this will be probably implemented in a future release.
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Support for coroutine libraries
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-------------------------------
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.. versionadded:: 2.2.0
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.. versionadded:: 2.2
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Psycopg can be used together with coroutine_\-based libraries and participate
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in cooperative multithreading.
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@ -509,3 +509,88 @@ resources about the topic.
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conn.commit()
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cur.close()
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conn.close()
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.. index::
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single: Replication
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Replication protocol support
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----------------------------
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.. versionadded:: 2.7
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Modern PostgreSQL servers (version 9.0 and above) support replication. The
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replication protocol is built on top of the client-server protocol and can be
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operated using ``libpq``, as such it can be also operated by ``psycopg2``.
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The replication protocol can be operated on both synchronous and
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:ref:`asynchronous <async-support>` connections.
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Server version 9.4 adds a new feature called *Logical Replication*.
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.. seealso::
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- PostgreSQL `Streaming Replication Protocol`__
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.. __: http://www.postgresql.org/docs/current/static/protocol-replication.html
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Logical replication Quick-Start
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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You must be using PostgreSQL server version 9.4 or above to run this quick
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start.
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Make sure that replication connections are permitted for user ``postgres`` in
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``pg_hba.conf`` and reload the server configuration. You also need to set
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``wal_level=logical`` and ``max_wal_senders``, ``max_replication_slots`` to
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value greater than zero in ``postgresql.conf`` (these changes require a server
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restart). Create a database ``psycopg2test``.
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Then run the following code to quickly try the replication support out. This
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is not production code -- it has no error handling, it sends feedback too
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often, etc. -- and it's only intended as a simple demo of logical
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replication::
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from __future__ import print_function
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import sys
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import psycopg2
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import psycopg2.extras
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conn = psycopg2.connect('dbname=psycopg2test user=postgres',
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connection_factory=psycopg2.extras.LogicalReplicationConnection)
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cur = conn.cursor()
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try:
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# test_decoding produces textual output
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cur.start_replication(slot_name='pytest', decode=True)
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except psycopg2.ProgrammingError:
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cur.create_replication_slot('pytest', output_plugin='test_decoding')
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cur.start_replication(slot_name='pytest', decode=True)
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class DemoConsumer(object):
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def __call__(self, msg):
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print(msg.payload)
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msg.cursor.send_feedback(flush_lsn=msg.data_start)
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democonsumer = DemoConsumer()
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print("Starting streaming, press Control-C to end...", file=sys.stderr)
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try:
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cur.consume_stream(democonsumer)
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except KeyboardInterrupt:
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cur.close()
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conn.close()
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print("The slot 'pytest' still exists. Drop it with "
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"SELECT pg_drop_replication_slot('pytest'); if no longer needed.",
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file=sys.stderr)
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print("WARNING: Transaction logs will accumulate in pg_xlog "
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"until the slot is dropped.", file=sys.stderr)
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You can now make changes to the ``psycopg2test`` database using a normal
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psycopg2 session, ``psql``, etc. and see the logical decoding stream printed
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by this demo client.
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This will continue running until terminated with ``Control-C``.
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For the details see :ref:`replication-objects`.
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@ -141,81 +141,15 @@ Logging cursor
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.. autoclass:: MinTimeLoggingCursor
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Replication protocol support
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Modern PostgreSQL servers (version 9.0 and above) support replication. The
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replication protocol is built on top of the client-server protocol and can be
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operated using ``libpq``, as such it can be also operated by ``psycopg2``.
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The replication protocol can be operated on both synchronous and
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:ref:`asynchronous <async-support>` connections.
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Server version 9.4 adds a new feature called *Logical Replication*.
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.. seealso::
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- PostgreSQL `Streaming Replication Protocol`__
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.. __: http://www.postgresql.org/docs/current/static/protocol-replication.html
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Logical replication Quick-Start
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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You must be using PostgreSQL server version 9.4 or above to run this quick
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start.
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Make sure that replication connections are permitted for user ``postgres`` in
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``pg_hba.conf`` and reload the server configuration. You also need to set
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``wal_level=logical`` and ``max_wal_senders``, ``max_replication_slots`` to
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value greater than zero in ``postgresql.conf`` (these changes require a server
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restart). Create a database ``psycopg2test``.
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Then run the following code to quickly try the replication support out. This
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is not production code -- it has no error handling, it sends feedback too
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often, etc. -- and it's only intended as a simple demo of logical
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replication::
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from __future__ import print_function
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import sys
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import psycopg2
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import psycopg2.extras
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conn = psycopg2.connect('dbname=psycopg2test user=postgres',
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connection_factory=psycopg2.extras.LogicalReplicationConnection)
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cur = conn.cursor()
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try:
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cur.start_replication(slot_name='pytest', decode=True) # test_decoding produces textual output
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except psycopg2.ProgrammingError:
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cur.create_replication_slot('pytest', output_plugin='test_decoding')
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cur.start_replication(slot_name='pytest', decode=True)
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class DemoConsumer(object):
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def __call__(self, msg):
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print(msg.payload)
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msg.cursor.send_feedback(flush_lsn=msg.data_start)
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democonsumer = DemoConsumer()
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print("Starting streaming, press Control-C to end...", file=sys.stderr)
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try:
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cur.consume_stream(democonsumer)
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except KeyboardInterrupt:
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cur.close()
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conn.close()
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print("The slot 'pytest' still exists. Drop it with SELECT pg_drop_replication_slot('pytest'); if no longer needed.", file=sys.stderr)
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print("WARNING: Transaction logs will accumulate in pg_xlog until the slot is dropped.", file=sys.stderr)
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You can now make changes to the ``psycopg2test`` database using a normal
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psycopg2 session, ``psql``, etc. and see the logical decoding stream printed
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by this demo client.
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This will continue running until terminated with ``Control-C``.
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.. _replication-objects:
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Replication connection and cursor classes
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.. index::
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pair: Connection; replication
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.. autoclass:: ReplicationConnectionBase
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@ -253,6 +187,9 @@ The following replication types are defined:
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`ReplicationCursor` for actual communication with the server.
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.. index::
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pair: Message; replication
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The individual messages in the replication stream are represented by
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`ReplicationMessage` objects (both logical and physical type):
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@ -290,6 +227,9 @@ The individual messages in the replication stream are represented by
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A reference to the corresponding `ReplicationCursor` object.
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.. index::
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pair: Cursor; replication
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.. autoclass:: ReplicationCursor
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.. method:: create_replication_slot(slot_name, slot_type=None, output_plugin=None)
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