How I Implemented the #1 Requested Feature In Redis In Less than 1 Hour with Modules
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The document provides instructions for building a Redis module that implements a ZPOP command to pop and remove the first element of a sorted set. It includes code for the ZPOP command implementation, registering the module and command, and compiling the module into a shared object library that can be loaded by Redis. The document also suggests some questions to consider before taking on developing a new module, such as whether the capability already exists or an open source module could be reused.
![int ZPop(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
if (argc != 2) {
RedisModule_WrongArity(ctx);
return REDISMODULE_OK;
}
RedisModule_AutoMemory(ctx);
RedisModuleCallReply *rep = RedisModule_Call(
ctx, "ZRANGE", "!sllc", argv[1], 0, 0, "WITHSCORES");
if (RedisModule_CallReplyType(rep) == REDISMODULE_REPLY_ERROR) {
RedisModule_ReplyWithCallReply(ctx, rep);
return REDISMODULE_OK;
}
RedisModuleString *ele =
RedisModule_CreateStringFromCallReply(
RedisModule_CallReplyArrayElement(arr, 0));
RedisModule_Call(ctx, "ZREM", "ss", key, ele);
RedisModule_ReplyWithCallReply(ctx, rep);
return REDISMODULE_OK;
}](https://image.slidesharecdn.com/day-1-modules-api-pt-2-180501122734/85/How-I-Implemented-the-1-Requested-Feature-In-Redis-In-Less-than-1-Hour-with-Modules-9-320.jpg)
How I Implemented the #1 Requested Feature In Redis In Less than 1 Hour with Modules
- 1. Day 1 Itamar Haber @itamarhaber #Redis #RedisConf
- 2. hello I am
- 3. ● ●
- 6. No Gave serious thought about what you need to solve? Is there a core Redis capability that does it? Do that! Can you do it in the app? Is Lua good enough? Is there an existing GA module that already does it? Yes No No No Honestly factored cost of taking on a new software project? Yes Yes Yes No Is it a valid feature request to the core? Yes Yes No mebi Roll out your own Try that first. Hackers love helping each other 3:-)
- 7. Found a really good name for it, something catchy and cool? Go back one diagram. Start at the beginning mebi
- 8. ctx argv argc #include "redismodule.h" int MyCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) { // My code here // ... return REDISMODULE_OK; }
- 9. int ZPop(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) { if (argc != 2) { RedisModule_WrongArity(ctx); return REDISMODULE_OK; } RedisModule_AutoMemory(ctx); RedisModuleCallReply *rep = RedisModule_Call( ctx, "ZRANGE", "!sllc", argv[1], 0, 0, "WITHSCORES"); if (RedisModule_CallReplyType(rep) == REDISMODULE_REPLY_ERROR) { RedisModule_ReplyWithCallReply(ctx, rep); return REDISMODULE_OK; } RedisModuleString *ele = RedisModule_CreateStringFromCallReply( RedisModule_CallReplyArrayElement(arr, 0)); RedisModule_Call(ctx, "ZREM", "ss", key, ele); RedisModule_ReplyWithCallReply(ctx, rep); return REDISMODULE_OK; }
- 10. // Registering the module and its commands int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) { if (RedisModule_Init(ctx, "zpop", 1, REDISMODULE_APIVER_1) == REDISMODULE_ERR) { return REDISMODULE_ERR; } if (RedisModule_CreateCommand(ctx, "z.pop", ZPop, "Write", 1, 1, 1) == REDISMODULE_ERR) { return REDISMODULE_ERR; } return REDISMODULE_OK; }
- 11. # Compile it on Linux: $ gcc -fPIC -std=gnu99 -c -o zpop.o zpop.c $ ld -o zpop.so zpop.o -shared -Bsymbolic -lc # Compile it on OSX: $ gcc -dynamic -fno-common -std=gnu99 -c -o zpop.o zpop.c $ ld -o zpop.so zpop.o -bundle -undefined dynamic_lookup -lc # Run it: $ redis-server --loadmodule ./zpop.so # Use it: $ redis-cli redis> ZADD z 0 a 1 b 3 c (integer) 3 redis> Z.POP z "a"
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