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Update dual channel replication conf to mention the local buffer is imited by COB (#2824) 

After introducing the dual channel replication in #60, we decided in #915
not to add a new configuration item to limit the replica's local replication
buffer, just use "client-output-buffer-limit replica hard" to limit it.

We need to document this behavior and mention that once the limit is reached,
all future data will accumulate in the primary side.

Signed-off-by: Binbin <binloveplay1314@qq.com>
This commit is contained in:
Binbin 2025-11-23 23:27:50 +08:00 committed by GitHub
parent 8189fe5c42
commit 8ea7f1330c
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GPG Key ID: B5690EEEBB952194
3 changed files with 11 additions and 2 deletions
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5
src/replication.c
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@ -3211,7 +3211,10 @@ void bufferReplData(connection *conn) {
if (readlen && remaining_bytes == 0) { if (readlen && remaining_bytes == 0) {
if (server.client_obuf_limits[CLIENT_TYPE_REPLICA].hard_limit_bytes && if (server.client_obuf_limits[CLIENT_TYPE_REPLICA].hard_limit_bytes &&
server.pending_repl_data.len > server.client_obuf_limits[CLIENT_TYPE_REPLICA].hard_limit_bytes) { server.pending_repl_data.len > server.client_obuf_limits[CLIENT_TYPE_REPLICA].hard_limit_bytes) {
dualChannelServerLog(LL_NOTICE, "Replication buffer limit reached, stopping buffering."); dualChannelServerLog(LL_NOTICE,
"Replication buffer limit reached (%llu bytes), stopping buffering. "
"Further accumulation will occur on primary side.",
server.client_obuf_limits[CLIENT_TYPE_REPLICA].hard_limit_bytes);
/* Stop accumulating primary commands. */ /* Stop accumulating primary commands. */
connSetReadHandler(conn, NULL); connSetReadHandler(conn, NULL);
break; break;

2
tests/integration/dual-channel-replication.tcl
View File

@ -431,7 +431,7 @@ start_server {tags {"dual-channel-replication external:skip"}} {
populate 10000 primary 10; # set ~ 100kb populate 10000 primary 10; # set ~ 100kb
# Wait for replica's buffer limit reached # Wait for replica's buffer limit reached
wait_for_condition 50 1000 { wait_for_condition 50 1000 {
[log_file_matches $replica1_log "*Replication buffer limit reached, stopping buffering*"] [log_file_matches $replica1_log "*Replication buffer limit reached (*), stopping buffering*"]
} else { } else {
fail "Replica buffer should fill" fail "Replica buffer should fill"
} }

6
valkey.conf
View File

@ -818,6 +818,12 @@ repl-diskless-load disabled
# generally beneficial as it prevents potential performance degradation on the primary # generally beneficial as it prevents potential performance degradation on the primary
# server, which is typically handling more critical operations. # server, which is typically handling more critical operations.
# #
# During the dual channel full sync, the maximum size of the local replication buffer
# on the replica is limited by the hard limit of the replica client output buffer on
# the replica side. When the replica reaches the limit, it will stop accumulating the
# further data. At this point, any additional data accumulation will occur on primary
# side, which is depending on the replica client output buffer on the primary side.
#
# When toggling this configuration on or off during an ongoing synchronization process, # When toggling this configuration on or off during an ongoing synchronization process,
# it does not change the already running sync method. The new configuration will take # it does not change the already running sync method. The new configuration will take
# effect only for subsequent synchronization processes. # effect only for subsequent synchronization processes.