adds note on msg_store_credit_disc_bound

1 files changed, 7 insertions, 1 deletions

diff --git a/ebin/rabbit_app.in b/ebin/rabbit_app.in
index 2e1304e0f0..97e72c0b65 100644
--- a/ebin/rabbit_app.in
+++ b/ebin/rabbit_app.in
@@ -84,7 +84,13 @@
          {ssl_apps, [asn1, crypto, public_key, ssl]},
          %% see rabbitmq-server#114
          {mirroring_flow_control, true},
-         %% see rabbitmq-server#227 and related tickets
+         %% see rabbitmq-server#227 and related tickets.
+         %% msg_store_credit_disc_bound only takes effect when
+         %% messages are persisted to the message store. If messages
+         %% are embedded on the queue index, then modifying this
+         %% setting has no effect because credit_flow is not used when
+         %% writing to the queue index. See the setting
+         %% queue_index_embed_msgs_below above.
          {msg_store_credit_disc_bound, {2000, 500}},
          {msg_store_io_batch_size, 2048}
         ]}]}.