Packages

internal/ is MinIO's collection of reusable, dependency-light Go packages. They are imported by cmd/ (the runtime) and by each other; nothing outside this module can import them.

There are 34 directories under internal/. They fall into a handful of natural buckets:

Bucket	Packages
Auth and identity	auth/, jwt/, config/identity/{ldap,openid,plugin,tls}/, config/policy/{opa,plugin}/
Crypto and KMS	crypto/, kms/, hash/, etag/
HTTP and networking	http/, mountinfo/, net/, deadlineconn/, handlers/, mcontext/, rest/
Storage primitives	disk/, ioutil/, lock/, lsync/, dsync/, ringbuffer/, bpool/, bucket/{bandwidth,encryption,lifecycle,object,replication,versioning}/
Concurrency	pubsub/, once/, cachevalue/
Data and serialisation	arn/, s3select/, amztime/, color/, init/
Configuration	config/, config/api/, config/batch/, config/browser/, config/callhome/, config/compress/, config/dns/, config/drive/, config/etcd/, config/heal/, config/ilm/, config/lambda/, config/notify/, config/scanner/, config/storageclass/, config/subnet/
Eventing	event/, event/target/, store/
Logging	logger/, logger/audit/, logger/target/
Cluster RPC	grid/

Below is a short tour of the packages a contributor will reach for most often. Each one is intentionally small and well-bounded.

Highlights

Package	What it provides	Page
internal/auth	Access/secret key types, generation, validation.	auth-and-config
internal/config	The cluster-wide config registry consumed by every sub-system.	auth-and-config
internal/crypto	SSE-C / SSE-S3 / SSE-KMS scheme implementations.	crypto-and-kms
internal/kms	KMS interface + KES adapter.	crypto-and-kms
internal/hash	Pluggable content hashes (SHA-256, MD5, HighwayHash).	hash-and-etag
internal/etag	ETag arithmetic for multipart and SSE.	hash-and-etag
internal/event	Bucket event model + target multiplexer.	event-and-store
internal/store	On-disk FIFO queue used by every event/audit target.	event-and-store
internal/grid	Binary multiplex RPC protocol.	grid-and-rest
internal/rest	Lightweight HTTP-based RPC base used by storage REST and peer REST.	grid-and-rest
internal/dsync	Distributed RW mutex (DSync).	locks-and-sync
internal/lsync	Lightweight in-process sync helpers.	locks-and-sync
internal/lock	OS-level fcntl/flock primitives.	locks-and-sync
internal/logger	Operational + audit logging facade.	logger
internal/http	HTTP server + transport defaults.	http-and-net
internal/ioutil	I/O helpers (limited reader, copy with deadline, …).	http-and-net
internal/disk	Drive-level helpers (statfs, fdatasync, atime).	storage-primitives
internal/bucket/lifecycle, bucket/replication, bucket/encryption, bucket/versioning, bucket/object, bucket/bandwidth	Per-bucket models for ILM, replication, encryption, versioning, object lock, and bandwidth tracking.	bucket-models
internal/s3select	S3 Select SQL evaluator over CSV / JSON / Parquet.	s3select
internal/pubsub	In-process pub/sub used by trace and bandwidth telemetry.	pubsub-and-utilities
internal/cachevalue	TTL-backed cached value helper.	pubsub-and-utilities
internal/once	"Init once" helper variants.	pubsub-and-utilities
internal/ringbuffer	Lock-free ring buffer used in metrics and tracing.	pubsub-and-utilities
internal/init	Process-wide initialisation that must run before main().	pubsub-and-utilities
internal/handlers	Shared HTTP middleware used by the API router.	http-and-net
internal/mcontext	A context wrapper that carries metadata across HTTP boundaries.	http-and-net
internal/amztime	AWS-compatible time formats.	pubsub-and-utilities
internal/color	Terminal colour helpers used in the startup banner.	pubsub-and-utilities
internal/arn	AWS ARN parsing.	pubsub-and-utilities