Fix sync_spawn_command hang triggered by bug in vnode proxy overload handling #884
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If we call riak_core_vnode_master:sync_spawn_command, it ends up sending a gen_event all-state event to the proxy for forwarding. However, in handle_overload, the old code only had case clauses for '$gen_event' and not '$gen_all_state_event'. This means the event would be passed to handle_overload_info instead of handle_overload_request, which would likely skip the vnode callback code that sends a response. In Riak this meant that certain operations would hang during overload, since the caller to sync_spawn_command would never be sent a response. (This situation was made worse by the fact that the call is being done with an infinity timeout, but that's an issue we'll have to address some other time.)
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If we call
riak_core_vnode_master:sync_spawn_command, it ends up sendinga gen_event all-state event to the proxy for forwarding. However, in
handle_overload, the old code only had case clauses for'$gen_event'andnot
'$gen_all_state_event'. This means the event would be passed tohandle_overload_infoinstead ofhandle_overload_request, which wouldlikely skip the vnode callback code that sends a response.
In Riak this meant that certain operations would hang during overload,
since the caller of
sync_spawn_commandwould never get a response.(This situation was made worse by the fact that the call is being done
with an
infinitytimeout, but that's an issue we'll have to address someother time.)