How to Efficiently Read Redis Source Code: A Step-by-Step Guide

01 Find the Map

Before diving into a large open‑source project like Redis, the author recommends first mapping the overall project structure, identifying modules and their corresponding source files (e.g., the src directory), so you have a clear macro view and avoid getting lost.

02 Prepare Prerequisite Knowledge

The author lists essential background topics needed to understand Redis code, including common data structures (arrays, linked lists, hash tables, skip lists), TCP networking, I/O models (reactor, non‑blocking), operating‑system concepts (copy‑on‑write, system calls, disk I/O), and basic C language constructs.

03 Start with Basic Modules

Reading should begin with the most fundamental modules—Redis’s data types such as String, List, Hash, Set, and Sorted Set—by examining files like t_string.c , t_list.c , t_hash.c , t_set.c , and t_zset.c . These rely on lower‑level structures (SDS, ziplist, quicklist, dict, intset) that are relatively independent and form the foundation for higher‑level functionality.

04 Identify the Core Execution Path

After mastering the basics, focus on the core logic that processes a client command—from server initialization, request parsing, command dispatch, to response writing. The author uses the example of a SET command to illustrate the sequence of modules involved (e.g., server.c , networking.c , data‑type files).

Redis Server initialization: load config, listen ports, register events, start event loop.

Receive and parse client request: create client, register read events, read socket.

Execute command: locate command function and run it.

Send response: write to client buffer, register write events, flush socket.

05 Overall First, Details Later

When encountering a complex function, first grasp its high‑level purpose and the sequence of major steps, building a mental framework before diving into each branch or line of code. This prevents getting stuck and maintains reading continuity.

06 Core Path First, Side Paths Later

After the main execution flow is clear, explore auxiliary features such as expiration, eviction, persistence, replication, sentinel failover, and clustering. Treat these as secondary goals; once the core is understood, the side‑paths become much easier to follow.

Expiration logic (expire.c, lazyfree.c)

Eviction strategy (evict.c)

Persistence (rdb.c, aof.c)

Replication (replication.c)

Sentinel failover (sentinel.c)

Cluster sharding (cluster.c)

07 Gap‑Filling

Finally, revisit the code with concrete problems encountered in work. Focus on the specific modules related to those issues (e.g., SDS expansion in sds.c ) to fill knowledge gaps and achieve a deeper, more complete understanding of the project.

Summary

The seven steps—find the map, prepare prerequisite knowledge, start from basic modules, locate the core path, read overall before details, handle side paths after the core, and perform targeted gap‑filling—constitute a universal approach for reading any large codebase, not just Redis.