Mongodb

Tuning

• Limitance

  • Sort Operations : 32MB / order
    • https://docs.mongodb.com/manual/reference/limits/#Shard-Key-Size
  • Aggregation pipeline memory : 100MB
    • https://docs.mongodb.com/manual/reference/limits/#Sort-Operations
  • Members of a Replica Set : 50 members
    • https://docs.mongodb.com/manual/reference/limits/#Number-of-Members-of-a-Replica-Set
  • Voting Members of a Replica Set : 7 members
    • https://docs.mongodb.com/manual/reference/limits/#Number-of-Voting-Members-of-a-Replica-Set
  • Auto-Created Oplog : 50GB
    • https://docs.mongodb.com/manual/reference/limits/#Number-of-Voting-Members-of-a-Replica-Set
  • Sharding Existing Collection Data Size : see link table of below
    • https://docs.mongodb.com/manual/reference/limits/#Sharding-Existing-Collection-Data-Size
  • Maximum Number of Documents in a Capped Collection : 2^32 documents
    • https://docs.mongodb.com/manual/reference/limits/#Maximum-Number-of-Documents-in-a-Capped-Collection
  • The maximum BSON document size is 16 megabytes.
    • https://docs.mongodb.com/manual/reference/limits/#BSON-Document-Size
  • No more than 100 levels of nesting for BSON documents.
    • https://docs.mongodb.com/manual/reference/limits/#Nested-Depth-for-BSON-Documents
  • Shard Key Size : 512bytes
    • https://docs.mongodb.com/manual/reference/limits/#Shard-Key-Size
  • Number of Indexed Fields in a Compound Index : 32 fields
    • https://docs.mongodb.com/manual/reference/limits/#Number-of-Indexed-Fields-in-a-Compound-Index
  • Index Key Limit : 1024 bytes
    • https://docs.mongodb.com/manual/reference/limits/#Index-Key-Limit
  • Index per collection : 64 indexes.
    • https://docs.mongodb.com/manual/reference/limits/#Number-of-Indexes-per-Collection
  • Write Command Batch Limit Size = 100,000 writes (V3.6)
    • https://docs.mongodb.com/manual/reference/limits/#Write-Command-Batch-Limit-Size
  • Session idle timeout : 30 Min
    • https://docs.mongodb.com/manual/reference/limits/#Session-Idle-Timeout
  • The maximum length of the collection namespace, which includes the database name, the dot (.) separator, and the collection name (i.e. .), is 120 bytes.
    • https://docs.mongodb.com/manual/reference/limits/#Namespace-Length
  • 4095 code point each line by Cli
    • https://docs.mongodb.com/manual/reference/limits/#shell

• Recommend Memory

  • 50% of (RAM - 1 GB), or 256 MB.
  • https://docs.mongodb.com/manual/administration/production-notes/#prod-notes-ram

• RAID

  • For optimal performance in terms of the storage layer, use disks backed by RAID-10. RAID-5 and RAID-6 do not typically provide sufficient performance to support a MongoDB deployment.
  • https://docs.mongodb.com/manual/administration/production-notes/#raid

• Using WiredTiger Storage Engine(V3 ~)

  • Reduced lock range (DB Lock -> Row Lock)
  • Can limit cachesizeGB. (MMAP is fully used memory until dead process)
  • Auto defragment physical data(Auto compaction fragment block)
  • Separate index and data store.
  • Ref(ja) - https://qiita.com/oshou/items/03f8dfcedbd63e2a8353

• OS Configuration

  • Set THP(Transparent Huge Page) OFF

• Tips

  • know-how by experience(ja) : https://www.infoq.com/jp/articles/Starting-With-MongoDB/

• performance check

  • https://www.slideshare.net/tetsutarowatanabe/mongodb-70155001

Sharding(Replica set)

• Official best practice
  • https://www.mongodb.com/blog/post/mongodb-atlas-best-practices-part-3

Benchmark

• Mongodb insert performance test
  • best performance at 100 / 100 (session / goroutine) on AWS t2.2xlarge
    • https://qiita.com/toast-uz/items/0aad7cb5281b28fd2947

Links

• Auto generate mongo-QL aggregate editor : https://studio3t.com/