• Sage Weil's avatar
    ceph: MDS client · 2f2dc053
    Sage Weil authored
    The MDS (metadata server) client is responsible for submitting
    requests to the MDS cluster and parsing the response.  We decide which
    MDS to submit each request to based on cached information about the
    current partition of the directory hierarchy across the cluster.  A
    stateful session is opened with each MDS before we submit requests to
    it, and a mutex is used to control the ordering of messages within
    each session.
    
    An MDS request may generate two responses.  The first indicates the
    operation was a success and returns any result.  A second reply is
    sent when the operation commits to disk.  Note that locking on the MDS
    ensures that the results of updates are visible only to the updating
    client before the operation commits.  Requests are linked to the
    containing directory so that an fsync will wait for them to commit.
    
    If an MDS fails and/or recovers, we resubmit requests as needed.  We
    also reconnect existing capabilities to a recovering MDS to
    reestablish that shared session state.  Old dentry leases are
    invalidated.
    Signed-off-by: default avatarSage Weil <sage@newdream.net>
    2f2dc053
mds_client.h 9.61 KB