feat: default enable multiplex session for all operations unless explicitly set to false #1394

rahul2393 · 2025-07-16T06:05:09Z

Read-Only, Read-Write and Partition Ops transactions now use a single multiplexed session, instead of a session from the session pool. Multiplexed sessions can handle any number of queries and read-only, read-write and partition ops transactions transactions at the same time.

The use of multiplexed sessions can be disabled for read-only, read-write and partition-ops transactions by setting the environment variables.

GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS=false
GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS_FOR_RW=false.
GOOGLE_CLOUD_SPANNER_MULTIPLEXED_SESSIONS_PARTITIONED_OPS=false.

See https://cloud.google.com/spanner/docs/sessions#multiplexed_sessions for more background information about multiplexed sessions.

…et to false

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

…pis/python-spanner into multiplex-default-enable

rahul2393 · 2025-07-17T11:01:18Z

.github/workflows/integration-tests-against-emulator-with-regular-session.yaml

@@ -21,7 +21,7 @@ jobs:
      - name: Setup Python
        uses: actions/setup-python@v5
        with:
-          python-version: 3.8
+          python-version: 3.12


this is because in followup PR we will be removing 3.8 runtime support
#1395

rahul2393 · 2025-07-17T11:38:56Z

tests/system/test_dbapi.py

+
+        if is_multiplexed_enabled(transaction_type=TransactionType.READ_WRITE):
+            pytest.skip(
+                "Mutiplexed session can't be deleted and this test relies on session deletion."


Reference: https://github.com/googleapis/googleapis/blob/master/google/spanner/v1/spanner.proto#L412

tests/mockserver_tests/mock_server_test_base.py

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

sakthivelmanii · 2025-07-24T04:16:53Z

google/cloud/spanner_v1/snapshot.py

@@ -1031,7 +1030,7 @@ def _update_for_transaction_pb(self, transaction_pb: Transaction) -> None:
            self._transaction_id = transaction_pb.id

        if transaction_pb.precommit_token:
-            self._update_for_precommit_token_pb(transaction_pb.precommit_token)
+            self._update_for_precommit_token_pb_unsafe(transaction_pb.precommit_token)


any reason why we need two methods?

_update_for_precommit_token_pb, _update_for_precommit_token_pb_unsafe

there was a deadlock happening, transaction was locked already when calling _update_for_transaction_pb, and in _update_for_precommit_token_pb we were again trying to lock it.

This was the issue from previous release which got uncovered once I tried making mux default enabled.

Read this comment The caller is responsible for locking until the transaction ID is updated.

https://github.com/googleapis/python-spanner/blob/main/google/cloud/spanner_v1/snapshot.py#L1026-L1029

And then when we were calling _update_for_precommit_token_pb we were taking the lock again
https://github.com/googleapis/python-spanner/blob/main/google/cloud/spanner_v1/snapshot.py#L1046

So we needed 2 methods which takes lock when updating precommit token from unlocked code, and one which is called from places which assume lock is already taken

feat: enable multiplex session for all operations unless explicitly s…

ced5d4b

…et to false

rahul2393 requested review from a team as code owners July 16, 2025 06:05

blunderbuss-gcf bot assigned surbhigarg92 Jul 16, 2025

rahul2393 requested a review from sakthivelmanii July 16, 2025 06:05

product-auto-label bot added size: s Pull request size is small. api: spanner Issues related to the googleapis/python-spanner API. size: m Pull request size is medium. and removed size: s Pull request size is small. labels Jul 16, 2025

rahul2393 changed the title ~~feat: enable multiplex session for all operations unless explicitly set to false~~ feat: default enable multiplex session for all operations unless explicitly set to false Jul 16, 2025

fix tests

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rename job name

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fux emulator systest

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update python version for emulator tests

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fix test

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fix test

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fix systests

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skip dbapi test which depends on session delete

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revert timestamp changes

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rahul2393 force-pushed the multiplex-default-enable branch from 0798969 to 8741633 Compare July 17, 2025 07:43

revert timestamp changes

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Merge branch 'multiplex-default-enable' of https://github.com/googlea…

8976025

…pis/python-spanner into multiplex-default-enable

product-auto-label bot added size: xl Pull request size is extra large. and removed size: l Pull request size is large. labels Jul 17, 2025

rahul2393 force-pushed the multiplex-default-enable branch from 3c5c5ad to 6450b4d Compare July 17, 2025 09:38

more fixes

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rahul2393 force-pushed the multiplex-default-enable branch from eefc798 to 63bac62 Compare July 17, 2025 09:43

rahul2393 commented Jul 17, 2025

View reviewed changes

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fix regular session systests

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rahul2393 dismissed stale reviews from surbhigarg92 and sakthivelmanii via 739a78e July 24, 2025 02:21

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expect precommit token only when session is multiplexed.

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sakthivelmanii reviewed Jul 24, 2025

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pin emulator version to make multiplex session with emulator pass

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rahul2393 merged commit 651ca9c into main Jul 24, 2025
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rahul2393 deleted the multiplex-default-enable branch July 24, 2025 05:27

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chore(main): release 3.56.0 #1386

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feat: default enable multiplex session for all operations unless explicitly set to false #1394

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feat: default enable multiplex session for all operations unless explicitly set to false #1394

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