• Hoang Huu Le's avatar
    tipc: update a binding service via broadcast · cad2929d
    Hoang Huu Le authored
    Currently, updating binding table (add service binding to
    name table/withdraw a service binding) is being sent over replicast.
    However, if we are scaling up clusters to > 100 nodes/containers this
    method is less affection because of looping through nodes in a cluster one
    by one.
    
    It is worth to use broadcast to update a binding service. This way, the
    binding table can be updated on all peer nodes in one shot.
    
    Broadcast is used when all peer nodes, as indicated by a new capability
    flag TIPC_NAMED_BCAST, support reception of this message type.
    
    Four problems need to be considered when introducing this feature.
    1) When establishing a link to a new peer node we still update this by a
    unicast 'bulk' update. This may lead to race conditions, where a later
    broadcast publication/withdrawal bypass the 'bulk', resulting in
    disordered publications, or even that a withdrawal may arrive before the
    corresponding publication. We solve this by adding an 'is_last_bulk' bit
    in the last bulk messages so that it can be distinguished from all other
    messages. Only when this message has arrived do we open up for reception
    of broadcast publications/withdrawals.
    
    2) When a first legacy node is added to the cluster all distribution
    will switch over to use the legacy 'replicast' method, while the
    opposite happens when the last legacy node leaves the cluster. This
    entails another risk of message disordering that has to be handled. We
    solve this by adding a sequence number to the broadcast/replicast
    messages, so that disordering can be discovered and corrected. Note
    however that we don't need to consider potential message loss or
    duplication at this protocol level.
    
    3) Bulk messages don't contain any sequence numbers, and will always
    arrive in order. Hence we must exempt those from the sequence number
    control and deliver them unconditionally. We solve this by adding a new
    'is_bulk' bit in those messages so that they can be recognized.
    
    4) Legacy messages, which don't contain any new bits or sequence
    numbers, but neither can arrive out of order, also need to be exempt
    from the initial synchronization and sequence number check, and
    delivered unconditionally. Therefore, we add another 'is_not_legacy' bit
    to all new messages so that those can be distinguished from legacy
    messages and the latter delivered directly.
    
    v1->v2:
     - fix warning issue reported by kbuild test robot <lkp@intel.com>
     - add santiy check to drop the publication message with a sequence
    number that is lower than the agreed synch point
    Signed-off-by: default avatarkernel test robot <lkp@intel.com>
    Signed-off-by: default avatarHoang Huu Le <hoang.h.le@dektech.com.au>
    Acked-by: default avatarJon Maloy <jmaloy@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    cad2929d
node.c 76.1 KB