Couchbase Server

rebalancing can get stuck due to a bug detecting the backfill completion during vbucket takeover

Details

Description

Install couchbase server 1.8.0 release with hotfix mb-4738 on 4 nodes (12 GB RAM each) cluster in ec2.
Load 38 million items to cluster.
Resident ratio: 41%
Data size on disk: 78GB
Remove a node.
Rebalance OK.
Add another node in (not the removed node).
Rebalance hang at around 80+%
  1. Text File
    107.22.11.161_tap.txt
    08/Mar/12 5:30 PM
    4 kB
    Thuan Nguyen
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    107.22.70.136_tap.txt
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    Thuan Nguyen
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    107.22.84.123_stat.txt
    02/Mar/12 4:55 PM
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    Thuan Nguyen
  4. Text File
    107.22.84.123_tap.txt
    08/Mar/12 5:30 PM
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    Thuan Nguyen
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    107.22.84.123_tap.txt
    02/Mar/12 4:55 PM
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    Thuan Nguyen
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    23.20.45.23_stat.txt
    02/Mar/12 4:55 PM
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    Thuan Nguyen
  8. Text File
    23.20.45.23_tap.txt
    08/Mar/12 5:30 PM
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    Thuan Nguyen
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    23.20.45.23_tap.txt
    02/Mar/12 4:55 PM
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    Thuan Nguyen
  11. Text File
    23.20.50.242_stat.txt
    02/Mar/12 4:55 PM
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    Thuan Nguyen
  12. Text File
    23.20.50.242_tap.txt
    08/Mar/12 5:30 PM
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    Thuan Nguyen
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    23.20.50.242_tap.txt
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    Thuan Nguyen
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    50.17.157.98_stat.txt
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    Thuan Nguyen
  16. Text File
    50.17.157.98_tap.txt
    02/Mar/12 4:55 PM
    15 kB
    Thuan Nguyen

Activity

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Thuan Nguyen added a comment -
Do rebalance out 2 nodes and rebalance hang

eq_tapq:rebalance_169:ack_log_size: 0
 eq_tapq:rebalance_169:ack_playback_size: 0
 eq_tapq:rebalance_169:ack_seqno: 41291
 eq_tapq:rebalance_169:ack_window_full: false
 eq_tapq:rebalance_169:backfill_completed: false
 eq_tapq:rebalance_169:bg_backlog_size: 0
 eq_tapq:rebalance_169:bg_jobs_completed: 37724
 eq_tapq:rebalance_169:bg_jobs_issued: 37724
 eq_tapq:rebalance_169:bg_queued: 37724
 eq_tapq:rebalance_169:bg_result_size: 0
 eq_tapq:rebalance_169:bg_results: 0
 eq_tapq:rebalance_169:bg_wait_for_results: false
 eq_tapq:rebalance_169:complete: false
 eq_tapq:rebalance_169:connected: true
 eq_tapq:rebalance_169:created: 1019807
 eq_tapq:rebalance_169:empty: false
 eq_tapq:rebalance_169:flags: 93 (ack,backfill,vblist,takeover,checkpoints)
 eq_tapq:rebalance_169:has_item: false
 eq_tapq:rebalance_169:has_queued_item: true
 eq_tapq:rebalance_169:idle: false
 eq_tapq:rebalance_169:num_tap_nack: 0
 eq_tapq:rebalance_169:num_tap_tmpfail_survivors: 0
 eq_tapq:rebalance_169:paused: 1
 eq_tapq:rebalance_169:pending_backfill: false
 eq_tapq:rebalance_169:pending_disconnect: false
 eq_tapq:rebalance_169:pending_disk_backfill: false
 eq_tapq:rebalance_169:qlen: 0
 eq_tapq:rebalance_169:qlen_high_pri: 0
 eq_tapq:rebalance_169:qlen_low_pri: 1
 eq_tapq:rebalance_169:queue_backfillremaining: 0
 eq_tapq:rebalance_169:queue_backoff: 0
 eq_tapq:rebalance_169:queue_drain: 41329
 eq_tapq:rebalance_169:queue_fill: 0
 eq_tapq:rebalance_169:queue_itemondisk: 0
 eq_tapq:rebalance_169:queue_memory: 0
 eq_tapq:rebalance_169:rec_fetched: 3609
 eq_tapq:rebalance_169:recv_ack_seqno: 41290
 eq_tapq:rebalance_169:reserved: 1
 eq_tapq:rebalance_169:seqno_ack_requested: 41290
 eq_tapq:rebalance_169:supports_ack: true
 eq_tapq:rebalance_169:suspended: false
 eq_tapq:rebalance_169:total_backlog_size: 1
 eq_tapq:rebalance_169:total_noops: 7935
 eq_tapq:rebalance_169:type: producer
 eq_tapq:rebalance_169:vb_filter: { 169 }
 eq_tapq:rebalance_169:vb_filters: 1
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Thuan Nguyen added a comment - Do rebalance out 2 nodes and rebalance hang eq_tapq:rebalance_169:ack_log_size: 0  eq_tapq:rebalance_169:ack_playback_size: 0  eq_tapq:rebalance_169:ack_seqno: 41291  eq_tapq:rebalance_169:ack_window_full: false  eq_tapq:rebalance_169:backfill_completed: false  eq_tapq:rebalance_169:bg_backlog_size: 0  eq_tapq:rebalance_169:bg_jobs_completed: 37724  eq_tapq:rebalance_169:bg_jobs_issued: 37724  eq_tapq:rebalance_169:bg_queued: 37724  eq_tapq:rebalance_169:bg_result_size: 0  eq_tapq:rebalance_169:bg_results: 0  eq_tapq:rebalance_169:bg_wait_for_results: false  eq_tapq:rebalance_169:complete: false  eq_tapq:rebalance_169:connected: true  eq_tapq:rebalance_169:created: 1019807  eq_tapq:rebalance_169:empty: false  eq_tapq:rebalance_169:flags: 93 (ack,backfill,vblist,takeover,checkpoints)  eq_tapq:rebalance_169:has_item: false  eq_tapq:rebalance_169:has_queued_item: true  eq_tapq:rebalance_169:idle: false  eq_tapq:rebalance_169:num_tap_nack: 0  eq_tapq:rebalance_169:num_tap_tmpfail_survivors: 0  eq_tapq:rebalance_169:paused: 1  eq_tapq:rebalance_169:pending_backfill: false  eq_tapq:rebalance_169:pending_disconnect: false  eq_tapq:rebalance_169:pending_disk_backfill: false  eq_tapq:rebalance_169:qlen: 0  eq_tapq:rebalance_169:qlen_high_pri: 0  eq_tapq:rebalance_169:qlen_low_pri: 1  eq_tapq:rebalance_169:queue_backfillremaining: 0  eq_tapq:rebalance_169:queue_backoff: 0  eq_tapq:rebalance_169:queue_drain: 41329  eq_tapq:rebalance_169:queue_fill: 0  eq_tapq:rebalance_169:queue_itemondisk: 0  eq_tapq:rebalance_169:queue_memory: 0  eq_tapq:rebalance_169:rec_fetched: 3609  eq_tapq:rebalance_169:recv_ack_seqno: 41290  eq_tapq:rebalance_169:reserved: 1  eq_tapq:rebalance_169:seqno_ack_requested: 41290  eq_tapq:rebalance_169:supports_ack: true  eq_tapq:rebalance_169:suspended: false  eq_tapq:rebalance_169:total_backlog_size: 1  eq_tapq:rebalance_169:total_noops: 7935  eq_tapq:rebalance_169:type: producer  eq_tapq:rebalance_169:vb_filter: { 169 }  eq_tapq:rebalance_169:vb_filters: 1
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Chiyoung Seo added a comment -
Fixed in 1.8.1 branch
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Chiyoung Seo added a comment - Fixed in 1.8.1 branch
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Farshid Ghods added a comment -
This reason was that there is a bug in detecting the backfill completion for a vbucket takeover during rebalance.

For example, the following are the TAP stats for vbucket 685 takeover:

 eq_tapq:rebalance_685:ack_window_full: false
 eq_tapq:rebalance_685:backfill_completed: false
 ...
 eq_tapq:rebalance_685:pending_backfill: false
 eq_tapq:rebalance_685:pending_disconnect: false
 eq_tapq:rebalance_685:pending_disk_backfill: false
 eq_tapq:rebalance_685:queue_backfillremaining: 0

You can see that there are no items remaining for backfill, but "backfill_completed" flag is still false, which caused the takeover operation to be stuck.
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Farshid Ghods added a comment - This reason was that there is a bug in detecting the backfill completion for a vbucket takeover during rebalance. For example, the following are the TAP stats for vbucket 685 takeover:  eq_tapq:rebalance_685:ack_window_full: false  eq_tapq:rebalance_685:backfill_completed: false  ...  eq_tapq:rebalance_685:pending_backfill: false  eq_tapq:rebalance_685:pending_disconnect: false  eq_tapq:rebalance_685:pending_disk_backfill: false  eq_tapq:rebalance_685:queue_backfillremaining: 0 You can see that there are no items remaining for backfill, but "backfill_completed" flag is still false, which caused the takeover operation to be stuck.

People

  • Assignee:
    Chiyoung Seo
    Reporter:
    Thuan Nguyen
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Dates

  • Created:
    Updated:
    Resolved: