SSG is a group membership microservice based on the Mercury RPC system. It provides mechanisms for bootstrapping sets of Mercury processes into logical groups and for managing the membership of these process groups over time. At a high-level, each group collectively maintains a group view, which is just a mapping from group member identifiers to Mercury address information. The inital group membership view is specified completely when the group is bootstrapped (created). Currently, SSG offers the following group bootstrapping methods:
- MPI communicator-based bootstrap
- config file-based bootstrap
- generic bootstrap method using an array of Mercury address strings
Process groups are referenced using unique group identifiers which encode Mercury address information that can be used to connect with a representative member of the group. These identifiers may be transmitted to other processes so they can join the group or attach to the group (attachment provides non-group members a way to access a group's view).
Optionally, SSG can be configured to use the SWIM failure detection and group membership protocol internally to detect and respond to group member failures. SWIM uses a randomized probing mechanism to detect faulty group members and uses an efficient gossip protocol to dissmeninate group membership changes to other group members. SSG propagates group membership view updates back to the SSG user using a callback interface.
NOTE: SSG does not currently support group members dynamically leaving or joining a group, though this should be supported in the near future. This means that, for now, SSG groups are immutable after creation. When using SWIM, this means members can be marked as faulty, but they cannot be fully evicted from the group view yet.
NOTE: SSG does not currently allow for user-specified group member identifiers, and instead assigns identifiers as dense ranks into the list of address strings specified at group creation time. That is, the group member with the first address string in the list is rank 0, and so on.
- mercury (git clone --recurse-submodules https://github.com/mercury-hpc/mercury.git)
- argobots (git clone https://github.com/pmodels/argobots.git)
- margo (git clone https://xgitlab.cels.anl.gov/sds/margo.git)
- libev (e.g libev-dev package on Ubuntu or Debian)
(if configuring for the first time) ./prepare.sh
./configure [standard options] PKG_CONFIG_PATH=/path/to/pkgconfig/files
make
make install
MPI support is by default optionally included. If you wish to compile with MPI support, set CC=mpicc (or equivalent) in configure. If you wish to disable MPI entirely, use --disable-mpi (you can also force MPI inclusion through --enable-mpi).