osaf/services/saf/immsv/README | 2 + osaf/services/saf/immsv/README.SC_ABSENCE | 78 +++++++++++++++++++++++++++++++ 2 files changed, 80 insertions(+), 0 deletions(-)
Add readme for SC absence feature. diff --git a/osaf/services/saf/immsv/README b/osaf/services/saf/immsv/README --- a/osaf/services/saf/immsv/README +++ b/osaf/services/saf/immsv/README @@ -2779,6 +2779,8 @@ provided during absent SC depends on the of the IMM service, the service provided during SC absence is in essence only the reading of config data. +See: osaf/services/saf/immsv/README.SC_ABSENCE for details. + Add attribute definition flag SA_IMM_ATTR_STRONG_DEFAULT (5.0) =============================================================== diff --git a/osaf/services/saf/immsv/README.SC_ABSENCE b/osaf/services/saf/immsv/README.SC_ABSENCE new file mode 100644 --- /dev/null +++ b/osaf/services/saf/immsv/README.SC_ABSENCE @@ -0,0 +1,78 @@ +SC ABSENCE: Allow IMMNDs to survive SC absence (5.0) +==================================================== +Prior to this enhancement, absence of both SCs will cause IMMNDs to restart, +also the cluster will be reboot by AMF. With this feature, IMMNDs on payloads +continue to provide limited service until an SC is back. + + +CONFIGURATION +============= +To enable this feature, IMMSV_SC_ABSENCE_ALLOWED environment variable must be +set for IMMD (immd.conf) + + export IMMSV_SC_ABSENCE_ALLOWED=900 + +The value indicates the number of seconds cluster will tolerate SC absence, +value of zero indicates the feature is disabled. +See immd.conf for more details. + + +IMMND +===== +With SC absence feature enabled, IMMNDs on payloads now can be coordinator. +That can happen even when the SCs are not absent. + +For example, the cluster only has one SC and IMMND on SC restarts, one of the +IMMNDs on payloads will be elected as new coordinator. Without SC absence +enabled, the cluster will not tolerate that situation and a cluster reboot will +occur. + +If PBE is configured together with this feature, make sure that the shared file +system (where sqlite database is located) is accessible from all nodes of the +cluster. + +Upon receiving the IMMD down event, payload based IMMNDs unregister with MDS +and then: +- remove all local clients, +- discard all implementers, +- finalize all admin owners, +- abort all non-critical CCBs. + +That means the IMMNDs only keep class definitions and object information in +their memories during SC absence. + +After cleaning up those things, MDS will be registered again to allow clients to +read the objects but only config data can be read because there's currently no +OI attached for runtime data. + +Other operations with IMM service will get SA_AIS_ERR_TRY_AGAIN during SC +absence. +If you retry the APIs on SA_AIS_ERR_TRY_AGAIN, you should retry at least the +amount of time that you set for IMMSV_SC_ABSENCE_ALLOWED. + +If you get SA_AIS_ERR_BAD_HANDLE, you must re-initialize the handles. + + +IMMD +==== +After coming back from SC absence, the active IMMD will wait for the veteran +IMMNDs to introduce for 3 seconds. If there's no introduction from veteran IMMND +within 3 seconds, IMMD will start to load from repository. This is to avoid the +race condition where IMMD receives and processes introduce message from the +local IMMND or a newly joined IMMND before the veteran IMMNDs. + +The veteran IMMNDs also include highest fevs, latest id of implementer/admo/ccb +in the introduce message to help IMMD restore these counters back to the state +right before SC absence. + +IMMD then elects one of the veteran IMMNDs as new coordinator and the data is +sync'ed to the SC based IMMNDs. After that, IMM service becomes fully functional +again. + + +SC ABSENCE and 2PBE +=================== +Support for absent IMMD is incompatible with 2PBE. If both are configured then +2PBE will win and the absence of IMMD feature will be ignored. An error message +is printed in this case to the syslog at startup. + ------------------------------------------------------------------------------ _______________________________________________ Opensaf-devel mailing list Opensaf-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/opensaf-devel
