===================================== Configuring Monitor/OSD Interaction ===================================== .. index:: heartbeat After you have completed your initial Ceph configuration, you may deploy and run Ceph. When you execute a command such as ``ceph health`` or ``ceph -s``, the :term:`Ceph Monitor` reports on the current state of the :term:`Ceph Storage Cluster`. The Ceph Monitor knows about the Ceph Storage Cluster by requiring reports from each :term:`Ceph OSD Daemon`, and by receiving reports from Ceph OSD Daemons about the status of their neighboring Ceph OSD Daemons. If the Ceph Monitor doesn't receive reports, or if it receives reports of changes in the Ceph Storage Cluster, the Ceph Monitor updates the status of the :term:`Ceph Cluster Map`. Ceph provides reasonable default settings for Ceph Monitor/Ceph OSD Daemon interaction. However, you may override the defaults. The following sections describe how Ceph Monitors and Ceph OSD Daemons interact for the purposes of monitoring the Ceph Storage Cluster. .. index:: heartbeat interval OSDs Check Heartbeats ===================== Each Ceph OSD Daemon checks the heartbeat of other Ceph OSD Daemons at random intervals less than every 6 seconds. If a neighboring Ceph OSD Daemon doesn't show a heartbeat within a 20 second grace period, the Ceph OSD Daemon may consider the neighboring Ceph OSD Daemon ``down`` and report it back to a Ceph Monitor, which will update the Ceph Cluster Map. You may change this grace period by adding an ``osd heartbeat grace`` setting under the ``[mon]`` and ``[osd]`` or ``[global]`` section of your Ceph configuration file, or by setting the value at runtime. .. ditaa:: +---------+ +---------+ | OSD 1 | | OSD 2 | +---------+ +---------+ | | |----+ Heartbeat | | | Interval | |<---+ Exceeded | | | | Check | | Heartbeat | |------------------->| | | |<-------------------| | Heart Beating | | | |----+ Heartbeat | | | Interval | |<---+ Exceeded | | | | Check | | Heartbeat | |------------------->| | | |----+ Grace | | | Period | |<---+ Exceeded | | | |----+ Mark | | | OSD 2 | |<---+ Down | .. index:: OSD down report OSDs Report Down OSDs ===================== By default, two Ceph OSD Daemons from different hosts must report to the Ceph Monitors that another Ceph OSD Daemon is ``down`` before the Ceph Monitors acknowledge that the reported Ceph OSD Daemon is ``down``. But there is chance that all the OSDs reporting the failure are hosted in a rack with a bad switch which has trouble connecting to another OSD. To avoid this sort of false alarm, we consider the peers reporting a failure a proxy for a potential "subcluster" over the overall cluster that is similarly laggy. This is clearly not true in all cases, but will sometimes help us localize the grace correction to a subset of the system that is unhappy. ``mon osd reporter subtree level`` is used to group the peers into the "subcluster" by their common ancestor type in CRUSH map. By default, only two reports from different subtree are required to report another Ceph OSD Daemon ``down``. You can change the number of reporters from unique subtrees and the common ancestor type required to report a Ceph OSD Daemon ``down`` to a Ceph Monitor by adding an ``mon osd min down reporters`` and ``mon osd reporter subtree level`` settings under the ``[mon]`` section of your Ceph configuration file, or by setting the value at runtime. .. ditaa:: +---------+ +---------+ +---------+ | OSD 1 | | OSD 2 | | Monitor | +---------+ +---------+ +---------+ | | | | OSD 3 Is Down | | |---------------+--------------->| | | | | | | | | OSD 3 Is Down | | |--------------->| | | | | | | | | |---------+ Mark | | | | OSD 3 | | |<--------+ Down .. index:: peering failure OSDs Report Peering Failure =========================== If a Ceph OSD Daemon cannot peer with any of the Ceph OSD Daemons defined in its Ceph configuration file (or the cluster map), it will ping a Ceph Monitor for the most recent copy of the cluster map every 30 seconds. You can change the Ceph Monitor heartbeat interval by adding an ``osd mon heartbeat interval`` setting under the ``[osd]`` section of your Ceph configuration file, or by setting the value at runtime. .. ditaa:: +---------+ +---------+ +-------+ +---------+ | OSD 1 | | OSD 2 | | OSD 3 | | Monitor | +---------+ +---------+ +-------+ +---------+ | | | | | Request To | | | | Peer | | | |-------------->| | | |<--------------| | | | Peering | | | | | | Request To | | | Peer | | |----------------------------->| | | | |----+ OSD Monitor | | | Heartbeat | |<---+ Interval Exceeded | | | | Failed to Peer with OSD 3 | |-------------------------------------------->| |<--------------------------------------------| | Receive New Cluster Map | .. index:: OSD status OSDs Report Their Status ======================== If an Ceph OSD Daemon doesn't report to a Ceph Monitor, the Ceph Monitor will consider the Ceph OSD Daemon ``down`` after the ``mon osd report timeout`` elapses. A Ceph OSD Daemon sends a report to a Ceph Monitor when a reportable event such as a failure, a change in placement group stats, a change in ``up_thru`` or when it boots within 5 seconds. You can change the Ceph OSD Daemon minimum report interval by adding an ``osd mon report interval`` setting under the ``[osd]`` section of your Ceph configuration file, or by setting the value at runtime. A Ceph OSD Daemon sends a report to a Ceph Monitor every 120 seconds irrespective of whether any notable changes occur. You can change the Ceph Monitor report interval by adding an ``osd mon report interval max`` setting under the ``[osd]`` section of your Ceph configuration file, or by setting the value at runtime. .. ditaa:: +---------+ +---------+ | OSD 1 | | Monitor | +---------+ +---------+ | | |----+ Report Min | | | Interval | |<---+ Exceeded | | | |----+ Reportable | | | Event | |<---+ Occurs | | | | Report To | | Monitor | |------------------->| | | |----+ Report Max | | | Interval | |<---+ Exceeded | | | | Report To | | Monitor | |------------------->| | | |----+ Monitor | | | Fails | |<---+ | +----+ Monitor OSD | | Report Timeout |<---+ Exceeded | +----+ Mark | | OSD 1 |<---+ Down Configuration Settings ====================== When modifying heartbeat settings, you should include them in the ``[global]`` section of your configuration file. .. index:: monitor heartbeat Monitor Settings ---------------- .. confval:: mon_osd_min_up_ratio .. confval:: mon_osd_min_in_ratio .. confval:: mon_osd_laggy_halflife .. confval:: mon_osd_laggy_weight .. confval:: mon_osd_laggy_max_interval .. confval:: mon_osd_adjust_heartbeat_grace .. confval:: mon_osd_adjust_down_out_interval .. confval:: mon_osd_auto_mark_in .. confval:: mon_osd_auto_mark_auto_out_in .. confval:: mon_osd_auto_mark_new_in .. confval:: mon_osd_down_out_interval .. confval:: mon_osd_down_out_subtree_limit .. confval:: mon_osd_report_timeout .. confval:: mon_osd_min_down_reporters .. confval:: mon_osd_reporter_subtree_level .. index:: OSD heartbeat OSD Settings ------------ .. confval:: osd_heartbeat_interval .. confval:: osd_heartbeat_grace .. confval:: osd_mon_heartbeat_interval .. confval:: osd_mon_heartbeat_stat_stale .. confval:: osd_mon_report_interval