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fix(spanner): attach routing hints to read-write transaction requests #14786

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fix(spanner): attach routing hints to read-write transaction requests #14786

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274edca
fix(spanner): attach routing hints to read-write transaction requests
samyakpjgoogle Oct 27, 2026
927605f
test(spanner): assert split-level routing hint and clarify preferLeader
samyakpjgoogle Oct 27, 2026
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24 changes: 24 additions & 0 deletions ...r/google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/KeyAwareChannel.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1164,6 +1164,18 @@ private RoutingDecision routeFromRequest(ReadRequest.Builder reqBuilder) {
boolean routePreferLeader = transactionId.isEmpty() && preferLeader;
endpoint = finder.findServer(reqBuilder, routePreferLeader, excludedEndpoints);
preferLeader = routePreferLeader;
} else if (finder != null) {
// The request belongs to a read-write transaction and stays pinned to the transaction's
// affinity endpoint. Still populate the routing hint (operation UID, key and target range)
// so that:
// - the server returns key recipes for this statement shape, which the client otherwise
// never learns for statements that only run inside read-write transactions; and
// - the server can serve the request on the fastpath, or forward it through the fastpath
// when the key is not local to the transaction owner.
// The endpoint selected by the finder is ignored to preserve transaction affinity.
// preferLeader is intentionally left unchanged (true for read-write transactions): the
// hint must describe the leader tablet, as read-write requests are served by the leader.
finder.findServer(reqBuilder, preferLeader, excludedEndpoints);
}
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samyakpjgoogle marked this conversation as resolved.
return new RoutingDecision(
finder, endpoint, databaseId, operationUid(reqBuilder.getRoutingHint()), preferLeader);
Expand All @@ -1186,6 +1198,18 @@ private RoutingDecision routeFromRequest(ExecuteSqlRequest.Builder reqBuilder) {
boolean routePreferLeader = transactionId.isEmpty() && preferLeader;
endpoint = finder.findServer(reqBuilder, routePreferLeader, excludedEndpoints);
preferLeader = routePreferLeader;
} else if (finder != null) {
// The request belongs to a read-write transaction and stays pinned to the transaction's
// affinity endpoint. Still populate the routing hint (operation UID, key and target range)
// so that:
// - the server returns key recipes for this statement shape, which the client otherwise
// never learns for statements that only run inside read-write transactions; and
// - the server can serve the request on the fastpath, or forward it through the fastpath
// when the key is not local to the transaction owner.
// The endpoint selected by the finder is ignored to preserve transaction affinity.
// preferLeader is intentionally left unchanged (true for read-write transactions): the
// hint must describe the leader tablet, as read-write requests are served by the leader.
finder.findServer(reqBuilder, preferLeader, excludedEndpoints);
}
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return new RoutingDecision(
finder, endpoint, databaseId, operationUid(reqBuilder.getRoutingHint()), preferLeader);
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72 changes: 72 additions & 0 deletions ...ogle-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/KeyAwareChannelTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1314,6 +1314,78 @@ public void unaryReadWithTransactionIdRoutesToAffinityEndpoint() throws Exceptio
assertThat(harness.defaultManagedChannel.callCount()).isEqualTo(1);
}

@Test
public void readWriteTransactionReadAttachesRoutingHintWhilePinnedToAffinityEndpoint()
throws Exception {
TestHarness harness = createHarness();
ByteString transactionId = ByteString.copyFromUtf8("rw-read-routing-hint");
seedReadWriteTransactionAffinity(harness, transactionId);

// Key "n" is owned by server-b, but the transaction is pinned to server-a.
ClientCall<ReadRequest, PartialResultSet> call =
harness.channel.newCall(SpannerGrpc.getStreamingReadMethod(), CallOptions.DEFAULT);
call.start(new CapturingListener<PartialResultSet>(), new Metadata());
call.sendMessage(
ReadRequest.newBuilder()
.setSession(SESSION)
.setTable("T")
.setTransaction(TransactionSelector.newBuilder().setId(transactionId))
.setRoutingHint(RoutingHint.newBuilder().setKey(bytes("n")))
.build());

assertThat(harness.endpointCache.callCountForAddress("server-a:1234")).isEqualTo(2);
assertThat(harness.endpointCache.callCountForAddress("server-b:1234")).isEqualTo(0);
@SuppressWarnings("unchecked")
RecordingClientCall<ReadRequest, PartialResultSet> delegate =
(RecordingClientCall<ReadRequest, PartialResultSet>)
harness.endpointCache.latestCallForAddress("server-a:1234");
RoutingHint routingHint = delegate.lastMessage.getRoutingHint();
assertThat(routingHint.getOperationUid()).isNotEqualTo(0L);
assertThat(routingHint.getDatabaseId()).isEqualTo(7L);
// The hint describes the split covering key "n" ([m, z), group 2) and its leader tablet.
assertThat(routingHint.getKey()).isEqualTo(bytes("m"));
assertThat(routingHint.getLimitKey()).isEqualTo(bytes("z"));
assertThat(routingHint.getGroupUid()).isEqualTo(2L);
assertThat(routingHint.getSplitId()).isEqualTo(2L);
assertThat(routingHint.getTabletUid()).isEqualTo(2L);
}

@Test
public void readWriteTransactionQueryAttachesRoutingHintWhilePinnedToAffinityEndpoint()
throws Exception {
TestHarness harness = createHarness();
ByteString transactionId = ByteString.copyFromUtf8("rw-query-routing-hint");
seedReadWriteTransactionAffinity(harness, transactionId);

// Key "n" is owned by server-b, but the transaction is pinned to server-a.
ClientCall<ExecuteSqlRequest, PartialResultSet> call =
harness.channel.newCall(SpannerGrpc.getExecuteStreamingSqlMethod(), CallOptions.DEFAULT);
call.start(new CapturingListener<PartialResultSet>(), new Metadata());
call.sendMessage(
ExecuteSqlRequest.newBuilder()
.setSession(SESSION)
.setSql("SELECT * FROM T WHERE K = @k")
.setTransaction(TransactionSelector.newBuilder().setId(transactionId))
.setRoutingHint(RoutingHint.newBuilder().setKey(bytes("n")))
.build());

assertThat(harness.endpointCache.callCountForAddress("server-a:1234")).isEqualTo(2);
assertThat(harness.endpointCache.callCountForAddress("server-b:1234")).isEqualTo(0);
@SuppressWarnings("unchecked")
RecordingClientCall<ExecuteSqlRequest, PartialResultSet> delegate =
(RecordingClientCall<ExecuteSqlRequest, PartialResultSet>)
harness.endpointCache.latestCallForAddress("server-a:1234");
RoutingHint routingHint = delegate.lastMessage.getRoutingHint();
assertThat(routingHint.getOperationUid()).isNotEqualTo(0L);
assertThat(routingHint.getDatabaseId()).isEqualTo(7L);
// The hint describes the split covering key "n" ([m, z), group 2) and its leader tablet.
assertThat(routingHint.getKey()).isEqualTo(bytes("m"));
assertThat(routingHint.getLimitKey()).isEqualTo(bytes("z"));
assertThat(routingHint.getGroupUid()).isEqualTo(2L);
assertThat(routingHint.getSplitId()).isEqualTo(2L);
assertThat(routingHint.getTabletUid()).isEqualTo(2L);
}

@Test
public void genericUnimplementedReroutesOnceAndLearnsDefaultOnlyMethod() throws Exception {
TestHarness harness = createHarness();
Expand Down
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