> ## Documentation Index
> Fetch the complete documentation index at: https://docs.springtail.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Code Structure

## Root directories

| Directory       | Description                                                                                     |
| --------------- | ----------------------------------------------------------------------------------------------- |
| src/            | Source tree by module                                                                           |
| include/        | Header tree by module                                                                           |
| external/       | Where `vcpkg` installs its packages                                                             |
| scripts/        | Helper scripts                                                                                  |
| python/         | Python libraries for testing; coordinator for deployment; localcluster controller and utilities |
| docker/         | Docker files, scripts                                                                           |
| cmake/          | CMake helper functions                                                                          |
| local\_cluster/ | Local cluster setup scripts for running cluster using containers on local machine               |
| debug/ \*       | Conditionally created by CMake for debug builds                                                 |
| release/ \*     | Conditionally created by CMake for production builds                                            |

## Important files

| Filename                         | Description                                                                                                                      |
| -------------------------------- | -------------------------------------------------------------------------------------------------------------------------------- |
| CMakeLists.txt                   | Top level CMake file for building code.  Add new modules/sub-dirs here.  Other configuration should be local to each module      |
| vcpkg.json                       | List of C++ vcpkg dependencies; See [list of packages](https://vcpkg.io/en/packages)                                             |
| clean.sh / debug.sh / release.sh | Helper scripts, wrapper around CMake to clean, build debug or build release                                                      |
| system.json                      | Properties JSON file for specifying hostnames, and other configuration info for modules                                          |
| python/testing/springtail.py     | Initialize redis with properties specified in system.json.\* file; bring up system, bring down system, run checks on system      |
| python/testing/test\_runner.py   | Run full system tests, uses [springtail.py](http://springtail.py) to bring up and down system, runs tests located in test\_cases |

## Modules

| Name          | Description                                                                                                                                                                                                                                                 |
| ------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| common        | Common utilities, springtail\_init() should be called in every main; logging, exceptions, concurrent queues, thread pool, etc.                                                                                                                              |
| storage       | Threaded storage layer; B-tree, extent and schema handling and definition                                                                                                                                                                                   |
| pg\_repl      | Low-level Postgres replication; connecting to primary and decoding replication messages                                                                                                                                                                     |
| pg\_log\_mgr  | Consumes Postgres replication stream to log, process log, extracts transaction start/commit, inserts commit records into a queue to be consumed by the committer.  The committer is responsible for applying log changes to the tables and committing them. |
| write\_cache  | Cache for holding dirty extents by XID; indexed by Table ID, Extent ID, XID and primary key value                                                                                                                                                           |
| xid\_mgr      | Persistently stores last committed XID                                                                                                                                                                                                                      |
| benchmarks    | Code for benchmarking file system performance (for distributed file systems)                                                                                                                                                                                |
| proto         | gRPC protocol definitions                                                                                                                                                                                                                                   |
| sys\_tbl\_mgr | System table service & cache; accessed via Thrift; centralizes management of system table metadata                                                                                                                                                          |
| proxy         | Postgres Proxy that handles read/write splitting sending writes to primary, and reads to FDWs                                                                                                                                                               |
| pg\_fdw       | Postgres frontend query nodes implemented using Postgres Foreign Data Wrapper (FDW) extension; also includes the ddl\_daemon for managing DDL changes for the FDW (to create/alter foreign tables)                                                          |
| redis         | Redis helper classes                                                                                                                                                                                                                                        |
| admin\_http   | Embedded internal http server                                                                                                                                                                                                                               |
| pg\_ext       | Postgres extension related                                                                                                                                                                                                                                  |