Initial REPOSITORY_STRUCTURE.md document - describes util, library, c…

…ontrib, cloud/storage/core (#1332)

Will describe cloud/{blockstore,filestore,disk_manager,vm} in the upcoming PRs

doc/REPOSITORY_STRUCTURE.md

@@ -0,0 +1,78 @@
+# Repository structure
+
+## Common
+[util](/util) - the most basic things: collections, strings, smart pointers, basic cross-platform wrappers for OS primitives (like sockets), etc
+
+[library](/library) - common algorithms and data structures which are not directly related to a specific project
+
+[contrib](/contrib) - OSS libraries and tools imported into our repo - original LICENSE file and all other original files are kept together with the imported code
+
+## Cloud storage
+[cloud/storage/core](/cloud/storage/core) - common code used by NBS and Filestore
+
+[config](/cloud/storage/core/config) - config proto specs for common components
+
+[protos](/cloud/storage/core/protos) - proto specs for common entities like TError, EStorageMediaKind, etc
+
+[tests](/cloud/storage/core/tests) - scripts for launching the components used in both NBS and Filestore tests - e.g. qemu
+
+[tools](/cloud/storage/core/tools) - the tools not specific to only NBS or only Filestore
+
+### Cloud storage libs
+[cloud/storage/core/libs](/cloud/storage/core/libs) - the libraries used by both NBS and Filestore
+
+[actors](/cloud/storage/core/libs/actors) - some helpers for the code that uses ActorSystem
+
+[aio](/cloud/storage/core/libs/aio) - a more convenient wrapper around libaio (and, possibly, uring in the future)
+
+[api](/cloud/storage/core/libs/api) - Actor api for the actor-based components which are used both by NBS and Filestore
+
+[auth](/cloud/storage/core/libs/auth) - Authorized actor
+
+[common](/cloud/storage/core/libs/common) - Common structures and algorithms like ring buffer, error classification, scatter-gather list (sglist), etc.
+
+[coroutine](/cloud/storage/core/libs/coroutine) - Convenience wrappers for the coroutine library
+
+[daemon](/cloud/storage/core/libs/daemon) - Common code which is needed for daemon implementation - base classes for cmdline options, configs, signal handling, mlock, etc
+
+[diagnostics](/cloud/storage/core/libs/diagnostics) - Monitoring and tracing-related code - metrics aggregation, trace serialization/deserialization and analysis, histograms, some system stats monitoring code
+
+[features](/cloud/storage/core/libs/features) - Feature flags implementation
+
+[grpc](/cloud/storage/core/libs/grpc) - Helpers for nontrivial async grpc server/client implementation - executor, channel builders, credentials & auth, keepalive, etc.
+
+[hive_proxy](/cloud/storage/core/libs/hive_proxy) - Hive Tablet client actor which caches pipes to Hive
+
+[iam](/cloud/storage/core/libs/iam) - IAM client interface
+
+[keyring](/cloud/storage/core/libs/keyring) - Contains both the linux keyring-based endpoint storage (together with a convenience wrapper for linux keyring syscall api) and the file-based one 
+
+[kikimr](/cloud/storage/core/libs/kikimr) - YDB BlobStorage integration code - cluster registration, actorsystem configuration initialization, helpers
+
+[tablet](/cloud/storage/core/libs/tablet) - Some things common for the implementation of our tablets - TPartialBlobId, garbage collection logic
+
+[throttling](/cloud/storage/core/libs/throttling) - Request throttling implementation - leaky bucket implementation, throttler policy interface, throttler implementation for actor-based code
+
+[uds](/cloud/storage/core/libs/uds) - Unix socket listener, unix socket-based client wrapper with a TFuture-based interface
+
+[user_stats](/cloud/storage/core/libs/user_stats) - Some specific metrics-related code with serialization into json and spack formats
+
+[version](/cloud/storage/core/libs/version) - The code which can can extract build and repo-related info
+
+[version_ydb](/cloud/storage/core/libs/version_ydb) - The code which lets us register in the YDB BlobStorage cluster with the correct Application name
+
+[vhost-client](/cloud/storage/core/libs/vhost-client) - Our [vhost-blk](https://archive.fosdem.org/2023/schedule/event/sds_vhost_user_blk/) client implementation - used mostly in tests
+
+[viewer](/cloud/storage/core/libs/viewer) - Helpers for outputting some tablet-related info onto tablet monitoring pages
+
+## Blockstore (NBS)
+
+TODO
+
+## Filestore
+
+TODO
+
+## Disk Manager
+
+TODO