Recentemente, um cliente encontrou uma corrupção de arquivo de dados causada por uma queda de energia sem um backup de um banco de dados mongodb de instância única. Devido às necessidades de negócios do cliente
E a insensibilidade dos dados, é necessário restaurar o negócio o mais rápido possível, usando o comando de reparo de reparo automático do Mongdb para reparar. Felizmente, para ajudar os usuários a fazer
O serviço foi restaurado em breve, e o triste é que os dados no arquivo de dados relevante são perdidos sob a condição de que o cliente possa aceitá-los. Aqui, para fazer um resumo deste processo e explicar ao mesmo tempo
Por que os dados são perdidos após o reparo.
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Consulta de dados mongodb normal
> show dbs;
admin 0.000GB
config 0.000GB
dns_testdb 0.009GB
local 0.000GB
> use dns_testdb
switched to db dns_testdb
> db.test_collection.find();
{ "_id" : ObjectId("5fedd03d9d2569ee04ab62e1"), "name" : "elephant", "user_id" : 0, "boolean" : false, "added_at" : ISODate("2020-12-31T13:21:01.226Z"), "number" : 5129 }
{ "_id" : ObjectId("5fedd03d9d2569ee04ab62e2"), "name" : "dog", "user_id" : 1, "boolean" : false, "added_at" : ISODate("2020-12-31T13:21:01.237Z"), "number" : 9699 }
{ "_id" : ObjectId("5fedd03d9d2569ee04ab62e3"), "name" : "lion", "user_id" : 2, "boolean" : false, "added_at" : ISODate("2020-12-31T13:21:01.238Z"), "number" : 1783 }
Type "it" for more
> 2. O arquivo de dados da simulação está danificado
[mongo@centos7 dns_testdb]$ du -sh *
28M collection-8--6736947369024546614.wt
9.5M index-9--6736947369024546614.wt
[mongo@centos7 dns_testdb]$
[mongo@centos7 dns_testdb]$
[mongo@centos7 dns_testdb]$ pwd
/opt/mongo/data/single/dns_testdb
[mongo@centos7 dns_testdb]$ dd if=/dev/null of=/opt/mongo/data/single/dns_testdb/collection-8--6736947369024546614.wt bs=1024k count=5
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000132203 s, 0.0 kB/s
[mongo@centos7 dns_testdb]$3. Reinicie o mongodb
> use admin
switched to db admin
> db.shutdownServer();
[mongo@centos7 data]$ mongod --dbpath /opt/mongo/data/single --port 50001 --oplogSize 512 --fork --bind_ip 0.0.0.0 --logpath /opt/mongo/logs/single.log --logappend --journal --directoryperdb --profile=1
about to fork child process, waiting until server is ready for connections.
forked process: 102882
child process started successfully, parent exiting4. Embora o processo mongodb possa ser iniciado, a coleta de dados após o arquivo de dados ser danificado fará com que o mongod trave
[mongo@centos7 data]$ mongo --port 50001
MongoDB shell version v4.2.3
connecting to: mongodb://127.0.0.1:50001/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("09b6c6aa-059d-4a41-9e0d-e6553966399b") }
MongoDB server version: 4.2.3
Server has startup warnings:
> show dbs;
admin 0.000GB
config 0.000GB
dns_testdb 0.037GB
local 0.000GB
> use dns_testdb;
switched to db dns_testdb
> db.test_collection.find();
2020-12-31T08:43:45.115-0500 I NETWORK [js] DBClientConnection failed to receive message from 127.0.0.1:50001 - HostUnreachable: Connection closed by peer
Error: error doing query: failed: network error while attempting to run command 'find' on host '127.0.0.1:50001'
2020-12-31T08:43:45.118-0500 I NETWORK [js] trying reconnect to 127.0.0.1:50001 failed
2020-12-31T08:43:45.118-0500 I NETWORK [js] reconnect 127.0.0.1:50001 failed failed
> 5. Observe o log do mongodb, sugerindo que o arquivo de dados está danificado e é recomendado usar o reparo para reparar
2020-12-31T08:43:45.103-0500 E STORAGE [conn1] WiredTiger error (-31802) [1609422225:103947][102882:0x7f96713b5700], file:dns_testdb/collection-8--6736947369024546614.wt, WT_SESSION.open_cursor: __desc_read, 351: dns_testdb/collection-8--6736947369024546614.wt does not appear to be a WiredTiger file: WT_ERROR: non-specific WiredTiger error Raw: [1609422225:103947][102882:0x7f96713b5700], file:dns_testdb/collection-8--6736947369024546614.wt, WT_SESSION.open_cursor: __desc_read, 351: dns_testdb/collection-8--6736947369024546614.wt does not appear to be a WiredTiger file: WT_ERROR: non-specific WiredTiger error
2020-12-31T08:43:45.104-0500 E STORAGE [conn1] Failed to open a WiredTiger cursor. Reason: UnknownError: -31802: WT_ERROR: non-specific WiredTiger error, uri: table:dns_testdb/collection-8--6736947369024546614, config:
2020-12-31T08:43:45.104-0500 E STORAGE [conn1] This may be due to data corruption. Please read the documentation for starting MongoDB with --repair here: http://dochub.mongodb.org/core/repair
2020-12-31T08:43:45.104-0500 F - [conn1] Fatal Assertion 50882 at src/mongo/db/storage/wiredtiger/wiredtiger_session_cache.cpp 101
2020-12-31T08:43:45.104-0500 F - [conn1]
***aborting after fassert() failure6. Siga o log do mongod para reparar o banco de dados
[mongo@centos7 data]$ mongod --dbpath /opt/mongo/data/single --port 50001 --oplogSize 512 --fork --bind_ip 0.0.0.0 --logpath /opt/mongo/logs/single.log --logappend --journal --directoryperdb --profile=1 --repair
about to fork child process, waiting until server is ready for connections.
forked process: 102942
child process started successfully, parent exiting
[mongo@centos7 data]$ 7. Durante o processo de reparo, o log do mongod avisa que a coleção de dados danificados e o índice são reconstruídos
2020-12-31T08:44:45.646-0500 I STORAGE [initandlisten] repairDatabase dns_testdb
2020-12-31T08:44:45.646-0500 I STORAGE [initandlisten] Repairing collection dns_testdb.test_collection
2020-12-31T08:44:45.647-0500 E STORAGE [initandlisten] WiredTiger error (-31802) [1609422285:647413][102942:0x7fca99ec8c40], file:dns_testdb/collection-8--6736947369024546614.wt, WT_SESSION.verify: __desc_read, 351: dns_testdb/collection-8--6736947369024546614.wt does not appear to be a WiredTiger file: WT_ERROR: non-specific WiredTiger error Raw: [1609422285:647413][102942:0x7fca99ec8c40], file:dns_testdb/collection-8--6736947369024546614.wt, WT_SESSION.verify: __desc_read, 351: dns_testdb/collection-8--6736947369024546614.wt does not appear to be a WiredTiger file: WT_ERROR: non-specific WiredTiger error
2020-12-31T08:44:45.647-0500 I STORAGE [initandlisten] Verify failed on uri table:dns_testdb/collection-8--6736947369024546614. Running a salvage operation.
2020-12-31T08:44:45.647-0500 E STORAGE [initandlisten] WiredTiger error (-31802) [1609422285:647930][102942:0x7fca99ec8c40], file:dns_testdb/collection-8--6736947369024546614.wt, WT_SESSION.salvage: __desc_read, 351: dns_testdb/collection-8--6736947369024546614.wt does not appear to be a WiredTiger file: WT_ERROR: non-specific WiredTiger error Raw: [1609422285:647930][102942:0x7fca99ec8c40], file:dns_testdb/collection-8--6736947369024546614.wt, WT_SESSION.salvage: __desc_read, 351: dns_testdb/collection-8--6736947369024546614.wt does not appear to be a WiredTiger file: WT_ERROR: non-specific WiredTiger error
2020-12-31T08:44:45.648-0500 W STORAGE [initandlisten] Salvage failed for uri table:dns_testdb/collection-8--6736947369024546614: Salvage failed: -31802: WT_ERROR: non-specific WiredTiger error. The file will be moved out of the way and a new ident will be created.
2020-12-31T08:44:45.648-0500 W STORAGE [initandlisten] Moving data file /opt/mongo/data/single/dns_testdb/collection-8--6736947369024546614.wt to backup as /opt/mongo/data/single/dns_testdb/collection-8--6736947369024546614.wt.corrupt
2020-12-31T08:44:45.648-0500 W STORAGE [initandlisten] Rebuilding ident dns_testdb/collection-8--6736947369024546614
2020-12-31T08:44:45.708-0500 I STORAGE [initandlisten] Successfully re-created table:dns_testdb/collection-8--6736947369024546614.
2020-12-31T08:44:45.718-0500 I INDEX [initandlisten] index build: starting on dns_testdb.test_collection properties: { v: 2, key: { _id: 1 }, name: "_id_", ns: "dns_testdb.test_collection" } using method: Foreground
2020-12-31T08:44:45.718-0500 I INDEX [initandlisten] build may temporarily use up to 200 megabytes of RAM
2020-12-31T08:44:45.718-0500 I STORAGE [initandlisten] Index build initialized: 2ddee833-ea97-4964-98c0-7137e71a99c9: dns_testdb.test_collection: indexes: 1
2020-12-31T08:44:45.722-0500 I STORAGE [initandlisten] Index builds manager starting: 2ddee833-ea97-4964-98c0-7137e71a99c9: dns_testdb.test_collection
2020-12-31T08:44:45.724-0500 I INDEX [initandlisten] index build: inserted 0 keys from external sorter into index in 0 seconds
2020-12-31T08:44:45.727-0500 I INDEX [initandlisten] index build: done building index _id_ on ns dns_testdb.test_collection
2020-12-31T08:44:45.727-0500 I STORAGE [initandlisten] Index builds manager completed successfully: 2ddee833-ea97-4964-98c0-7137e71a99c9: dns_testdb.test_collection. Index specs requested: 1. Indexes in catalog before build: 1. Indexes in catalog after build: 18. Reinicie o serviço mongod após o reparo
[mongo@centos7 data]$ mongod --dbpath /opt/mongo/data/single --port 50001 --oplogSize 512 --fork --bind_ip 0.0.0.0 --logpath /opt/mongo/logs/single.log --logappend --journal --directoryperdb --profile=1
about to fork child process, waiting until server is ready for connections.
forked process: 102975
child process started successfully, parent exiting
[mongo@centos7 data]$ 9. Depois que o serviço mongod é iniciado, o serviço aceita consultas de dados normais, mas após o reparo, os dados de coleta que estão danificados pelo arquivo de dados foram perdidos
[mongo@centos7 data]$ mongo --port 50001
MongoDB shell version v4.2.3
connecting to: mongodb://127.0.0.1:50001/?compressors=disabled&gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("d88894c4-16bf-4013-a993-d29e2493fbdf") }
MongoDB server version: 4.2.3
Server has startup warnings:
> show dbs;
admin 0.000GB
config 0.000GB
dns_testdb 0.000GB
local 0.000GB
> use dns_testdb;
switched to db dns_testdb
> db.test_collection.find();
> 10. Resumo
O comando de reparo do banco de dados mongodb reparar, se não houver backup e o arquivo de dados estiver danificado, fará com que todos os dados de coleta relacionados ao arquivo de dados danificado sejam perdidos.
No entanto, após o reparo, isso não impedirá que o serviço mongod seja iniciado normalmente. Combinado com o log do processo de modificação, não é difícil ver que o reparo foi executado em arquivos de dados danificados e coleções relacionadas.
O arquivo de índice é reconstruído e o arquivo de dados reconstruído e o arquivo de coleção são reinicializados, portanto, os dados são perdidos. Então, usando o banco de dados mongodb, a maioria
Use o conjunto de réplicas do mongodb como uma estratégia de segurança de redundância de dados de uma maneira razoável. Ao usar o conjunto de réplicas do mongodb, você também pode ser um nó de sincronização atrasado para evitar
Falha de operação.