basic question in understanding publishing and subscribing

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I have a node that publishes the distance and the angle to be traversed by the rover.It is subscribed by another node which publishes the cmd_velocity on the basis of the topic(distance and angle) subscribed.Now i will have have a array of distances and angles to be sent to the other node.How do i make sure that every message is published.I have tried to keep the buffer size but still it is loosing messages in between.Basically the message has to wait for the previous message to be executed and then publish the next message. Could you please suggest a way to come across this?Please excuse me if this is a silly question .Thanking you