Orderly offlining in a distributed, multi-stage switch fabric architecture

A routing system comprising:

• a switch fabric including a set of distributed switching components that provide a plurality of paths between a set of ingresses and a set of egresses of the switch fabric;
• and
• a plurality of central processing units (CPUs), wherein each of the plurality of CPUs is associated with a respective plurality of the set of switching components,
• wherein the CPUs concurrently compute adjusted spray weights for each of the switching components positioned along multiple paths in an order from the switching component to be offlined to a plurality of the switching components coupled to the ingresses of the switch fabric, wherein the adjusted spray weights are respectively computed in order at each of the switching components along the respective path of the multiple paths, and wherein the adjusted spray weights control proportions of packets to be forwarded to outputs of the switching components,
• wherein the CPUs apply the adjusted spray weights with the switching components along the multiple paths in a respective opposite order from the ingresses of the switch fabric to the switching component to be offlined, and
• wherein the distributed switching components switch packets through the switch fabric in accordance with the applied adjusted spray weights.

A non-transitory computer-readable storage medium of a routing system, the non-transitory computer-readable storage medium comprising instructions for causing a programmable processor to:

• send a series of offlining prepare messages to a plurality of distributed forwarding components of the routing system, wherein the series of offlining prepare messages are sent in response to a determination that a switching component of the routing system is to be offlined, wherein the plurality of distributed forwarding components lie along different paths within a switch fabric of the routing system to different switch fabric ingresses, wherein each of the paths extends through the switch fabric from one of the switch fabric ingresses to the switching component to be offlined,
• wherein each of the offlining prepare messages indicates that the distributed forwarding component receiving the offlining prepare message should, based on the switching component to be offlined, compute adjusted spray weights for the distributed forwarding component and store the adjusted spray weights without applying the adjusted spray weights, wherein the spray weights control proportions of packets to be forwarded to outputs of the switching component;
• and
• send a series of commit messages from the routing component to the distributed forwarding components along each of the paths, wherein the commit messages indicate that the distributed forwarding components should apply the adjusted spray weights and begin forwarding traffic in accordance with the adjusted spray weights.