rebalance failed because memcached drops the connection ( UI says "change_filter_failed" )

Run regression test rebalancetests.RebalanceInOutWithParallelLoad.test_load,replica=2,do-stop=True
During this test, rebalance failed with error:

[ns_server:debug] [2012-06-13 8:22:26] [ns_1@10.1.3.82:<0.31153.111>:ns_replicas_builder:spawn_replica_builder:246] Replica building ebucketmigrator for vbucket 502 into 'ns_1@10.1.3.85' is <16961.29616.25>
[ns_server:debug] [2012-06-13 8:22:26] [ns_1@10.1.3.82:<0.31153.111>:ns_replicas_builder:spawn_replica_builder:246] Replica building ebucketmigrator for vbucket 502 into 'ns_1@10.1.3.87' is <16962.25655.16>
[ns_server:debug] [2012-06-13 8:22:26] [ns_1@10.1.3.82:<0.29704.111>:ns_vbm_sup:apply_changes:81] Applying changes:
[

{add_replica,'ns_1@10.1.3.87','ns_1@10.1.3.84',69}

,

{add_replica,'ns_1@10.1.3.84','ns_1@10.1.3.82',69}

]

[ns_server:debug] [2012-06-13 8:22:26] [ns_1@10.1.3.82:<0.31118.111>:ebucketmigrator_srv:init:228] killing tap named: replication_building_241_'ns_1@10.1.3.82'
[rebalance:debug] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.29704.111>:ns_vbucket_mover:terminate:169] Savings: 0 (from 165)

[ns_server:info] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.31113.111>:ns_single_vbucket_mover:mover_inner:88] Got exit message (parent is <0.29704.111>). Exiting...
{'EXIT',<0.29704.111>,
{{change_filter_failed,
{'EXIT',
{normal,
{gen_server,call,
[<16690.2164.10>,start_vbucket_filter_change,30000]}}}},
[

{ns_vbm_sup,change_vbucket_filter,4},
{ns_vbm_sup,'-set_replicas/3-fun-2-',5},
{lists,foldl,3},
{ns_vbm_sup,set_replicas,3},
{ns_vbm_sup,'-set_replicas_on_nodes/3-fun-1-',3},
{lists,foreach,2},
{ns_vbm_sup,apply_changes,2},
{ns_vbucket_mover,sync_replicas,0}]}}
[ns_server:info] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.31075.111>:ns_single_vbucket_mover:mover_inner:88] Got exit message (parent is <0.29704.111>). Exiting...
{'EXIT',<0.29704.111>,
{{change_filter_failed,
{'EXIT',
{normal,
{gen_server,call,
[<16690.2164.10>,start_vbucket_filter_change,30000]}}}},
[{ns_vbm_sup,change_vbucket_filter,4}

,

{ns_vbm_sup,'-set_replicas/3-fun-2-',5},
{lists,foldl,3},
{ns_vbm_sup,set_replicas,3},
{ns_vbm_sup,'-set_replicas_on_nodes/3-fun-1-',3},
{lists,foreach,2},
{ns_vbm_sup,apply_changes,2},
{ns_vbucket_mover,sync_replicas,0}]}}
[ns_server:info] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.31152.111>:ns_single_vbucket_mover:mover_inner:88] Got exit message (parent is <0.29704.111>). Exiting...
{'EXIT',<0.29704.111>,
{{change_filter_failed,
{'EXIT',
{normal,
{gen_server,call,
[<16690.2164.10>,start_vbucket_filter_change,30000]}}}},
[{ns_vbm_sup,change_vbucket_filter,4},
{ns_vbm_sup,'-set_replicas/3-fun-2-',5}

,

{lists,foldl,3},
{ns_vbm_sup,set_replicas,3},
{ns_vbm_sup,'-set_replicas_on_nodes/3-fun-1-',3},
{lists,foreach,2},
{ns_vbm_sup,apply_changes,2},
{ns_vbucket_mover,sync_replicas,0}]}}
[ns_server:info] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.31114.111>:ns_replicas_builder:build_replicas_main:113] Got exit not from child ebucketgrator. Assuming it's our parent: {'EXIT', <0.31113.111>, shutdown}
[ns_server:info] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.31114.111>:ns_replicas_builder:kill_a_bunch_of_tap_names:219] Killed the following tap names on 'ns_1@10.1.3.84': [<<"replication_building_241_'ns_1@10.1.3.82'">>,
<<"replication_building_241_'ns_1@10.1.3.87'">>]
[error_logger:error] [2012-06-13 8:22:27] [ns_1@10.1.3.82:error_logger:ale_error_logger_handler:log_report:72]
=========================CRASH REPORT=========================
crasher:
initial call: ns_single_vbucket_mover:mover/6
pid: <0.31113.111>
registered_name: []
exception exit: {exited,
{'EXIT',<0.29704.111>,
{{change_filter_failed,
{'EXIT',
{normal,
{gen_server,call,
[<16690.2164.10>,start_vbucket_filter_change,
30000]}}}},
[{ns_vbm_sup,change_vbucket_filter,4},
{ns_vbm_sup,'-set_replicas/3-fun-2-',5},
{lists,foldl,3}

,

{ns_vbm_sup,set_replicas,3},
{ns_vbm_sup,'-set_replicas_on_nodes/3-fun-1-',3},
{lists,foreach,2},
{ns_vbm_sup,apply_changes,2},
{ns_vbucket_mover,sync_replicas,0}]}}}
in function ns_single_vbucket_mover:mover_inner/6
in call from ns_replicas_builder:try_with_maybe_ignorant_after/2
in call from ns_single_vbucket_mover:mover/6
ancestors: [<0.29704.111>,<0.29682.111>]
messages: [{'EXIT',<0.29704.111>,
{{change_filter_failed,
{'EXIT',
{normal,
{gen_server,call,
[<16690.2164.10>,
start_vbucket_filter_change,30000]}}}},
[{ns_vbm_sup,change_vbucket_filter,4},
{ns_vbm_sup,'-set_replicas/3-fun-2-',5},
{lists,foldl,3},
{ns_vbm_sup,set_replicas,3}

,

{ns_vbm_sup,'-set_replicas_on_nodes/3-fun-1-',3}

,

{lists,foreach,2}

,

{ns_vbm_sup,apply_changes,2}

,

{ns_vbucket_mover,sync_replicas,0}

]}}]
links: [<0.29704.111>]
dictionary: [

{cleanup_list,[<0.31114.111>]}

]
trap_exit: true
status: running
heap_size: 2584
stack_size: 24
reductions: 2909
neighbours:

[rebalance:info] [2012-06-13 8:22:27] [ns_1@10.1.3.82:<0.31151.111>:ebucketmigrator_srv:init:252] Starting tap stream:
[{vbuckets,[86,342,343,344,345,346,347,348,349,350,351,352,353,354,355,356,
357,358,359,360,361,362,363,364,365,366,367,368,369,370,371,372,

Log file store here:
https://s3.amazonaws.com/packages.couchbase/diag-logs/log-rebalance-change_filter_failed.tgz