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Type:
Bug
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Resolution: Cannot Reproduce
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Priority:
Major - P3
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None
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Affects Version/s: 3.0.0
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Component/s: Replication, WiredTiger
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None
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Fully Compatible
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ALL
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We noticed that one of our 4 shards had a secondary with high replication lag.
Replica shard log has periodic very slow serverStatus with large values for "after oplog":
2015-03-18T18:30:44.539+0000 I COMMAND [conn82] serverStatus was very slow:
{ after basic: 0, after asserts: 0, after connections: 0, after cursors: 0, after extra_info: 0, after globalLock: 0, after locks: 0, after network: 0, after opcounters: 0, after opcountersRepl: 0, after oplog: 72189, after repl: 72189, after storageEngine: 72189, after wiredTiger: 72189, at end: 72189 }Restarted the replica shard hoping that this was a fluke, but the shard quickly went back to a low insertion rate.
Running db.getSiblingDB("local").oplog.rs.stats() produces:
{
"ns" : "local.oplog.rs",
"count" : 174896077,
"size" : 125833992359,
"avgObjSize" : 719,
"storageSize" : 62140203008,
"capped" : true,
"max" : -1,
"maxSize" : NumberLong("125829120000"),
"wiredTiger" : {
"metadata" : {
"formatVersion" : 1,
"oplogKeyExtractionVersion" : 1
},
"creationString" : "allocation_size=4KB,app_metadata=(formatVersion=1,oplogKeyExtractionVersion=1),block_allocation=best,block_compressor=snappy,cache_resident=0,checkpoint=(WiredTigerCheckpoint.23998=(addr=\"01e30ad2de81e436162abee3ddf13ebde46538e310e3ddf17bb3e43c3b848d808080e50e77d81fc0e50bad737fc0\",order=23998,time=1426703669,size=50154676224,write_gen=20018662)),checkpoint_lsn=(7514,101134976),checksum=uncompressed,collator=,columns=,dictionary=0,format=btree,huffman_key=,huffman_value=,id=9,internal_item_max=0,internal_key_max=0,internal_key_truncate=,internal_page_max=4KB,key_format=q,key_gap=10,leaf_item_max=0,leaf_key_max=0,leaf_page_max=32KB,leaf_value_max=1MB,memory_page_max=10m,os_cache_dirty_max=0,os_cache_max=0,prefix_compression=0,prefix_compression_min=4,split_deepen_min_child=0,split_deepen_per_child=0,split_pct=90,value_format=u,version=(major=1,minor=1)",
"type" : "file",
"uri" : "statistics:table:local/collection-2--4790446482890547801",
"LSM" : {
"bloom filters in the LSM tree" : 0,
"bloom filter false positives" : 0,
"bloom filter hits" : 0,
"bloom filter misses" : 0,
"bloom filter pages evicted from cache" : 0,
"bloom filter pages read into cache" : 0,
"total size of bloom filters" : 0,
"sleep for LSM checkpoint throttle" : 0,
"chunks in the LSM tree" : 0,
"highest merge generation in the LSM tree" : 0,
"queries that could have benefited from a Bloom filter that did not exist" : 0,
"sleep for LSM merge throttle" : 0
},
"block-manager" : {
"file allocation unit size" : 4096,
"blocks allocated" : 176633,
"checkpoint size" : 50154676224,
"allocations requiring file extension" : 0,
"blocks freed" : 206417,
"file magic number" : 120897,
"file major version number" : 1,
"minor version number" : 0,
"file bytes available for reuse" : 12083351552,
"file size in bytes" : 62140203008
},
"btree" : {
"column-store variable-size deleted values" : 0,
"column-store fixed-size leaf pages" : 0,
"column-store internal pages" : 0,
"column-store variable-size leaf pages" : 0,
"pages rewritten by compaction" : 0,
"number of key/value pairs" : 0,
"fixed-record size" : 0,
"maximum tree depth" : 32,
"maximum internal page key size" : 368,
"maximum internal page size" : 4096,
"maximum leaf page key size" : 3276,
"maximum leaf page size" : 32768,
"maximum leaf page value size" : 1048576,
"overflow pages" : 0,
"row-store internal pages" : 0,
"row-store leaf pages" : 0
},
"cache" : {
"bytes read into cache" : 5684148385,
"bytes written from cache" : 5626150236,
"checkpoint blocked page eviction" : 11413,
"unmodified pages evicted" : 175446,
"page split during eviction deepened the tree" : 1,
"modified pages evicted" : 3911,
"data source pages selected for eviction unable to be evicted" : 2675,
"hazard pointer blocked page eviction" : 589,
"internal pages evicted" : 1882,
"pages split during eviction" : 585,
"in-memory page splits" : 553,
"overflow values cached in memory" : 0,
"pages read into cache" : 178344,
"overflow pages read into cache" : 0,
"pages written from cache" : 176607
},
"compression" : {
"raw compression call failed, no additional data available" : 0,
"raw compression call failed, additional data available" : 0,
"raw compression call succeeded" : 0,
"compressed pages read" : 176000,
"compressed pages written" : 173316,
"page written failed to compress" : 3,
"page written was too small to compress" : 3288
},
"cursor" : {
"create calls" : 128,
"insert calls" : 10935859,
"bulk-loaded cursor-insert calls" : 0,
"cursor-insert key and value bytes inserted" : 5679356593,
"next calls" : 7327404,
"prev calls" : 35,
"remove calls" : 561,
"cursor-remove key bytes removed" : 5049,
"reset calls" : 10937358,
"search calls" : 0,
"search near calls" : 1122,
"update calls" : 0,
"cursor-update value bytes updated" : 0
},
"reconciliation" : {
"dictionary matches" : 0,
"internal page multi-block writes" : 25,
"leaf page multi-block writes" : 605,
"maximum blocks required for a page" : 236,
"internal-page overflow keys" : 0,
"leaf-page overflow keys" : 0,
"overflow values written" : 0,
"pages deleted" : 2780,
"page checksum matches" : 5294,
"page reconciliation calls" : 6475,
"page reconciliation calls for eviction" : 1885,
"leaf page key bytes discarded using prefix compression" : 0,
"internal page key bytes discarded using suffix compression" : 175625
},
"session" : {
"object compaction" : 0,
"open cursor count" : 128
},
"transaction" : {
"update conflicts" : 0
}
},
"nindexes" : 0,
"totalIndexSize" : 0,
"indexSizes" : {
},
"ok" : 1
}