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Modules: block on keys: use a better interface.

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Using the is_key_ready() callback plus the reply callback later, creates
different issues AFAIK:

1. More complex API.
2. We need to call the reply callback() ASAP if the is_key_ready()
interface returned success, however the internals do not work in that
way, so when the reply callback is called the setup could be different.
To fix that, there is to break the current design that handles the
unblocked clients asyncrhonously, and run the list ASAP.
This commit is contained in:
antirez
2019-10-31 11:35:05 +01:00
parent 4534960b29
commit 91f4bdc9f9
5 changed files with 65 additions and 45 deletions
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26
src/modules/hellotype.c
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@ -193,26 +193,26 @@ int HelloTypeLen_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int
/* ====================== Example of a blocking command ==================== */
/* Is_key_ready callback for blocking command HELLOTYPE.BRANGE */
int HelloBlock_IsKeyReady(RedisModuleCtx *ctx, RedisModuleString *keyname, void *privdata) {
REDISMODULE_NOT_USED(privdata);
/* Reply callback for blocking command HELLOTYPE.BRANGE, this will get
* called when the key we blocked for is ready: we need to check if we
* can really serve the client, and reply OK or ERR accordingly. */
int HelloBlock_Reply(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
REDISMODULE_NOT_USED(argv);
REDISMODULE_NOT_USED(argc);
RedisModule_AutoMemory(ctx); /* Use automatic memory management. */
RedisModuleString *keyname = RedisModule_GetBlockedClientReadyKey(ctx);
RedisModuleKey *key = RedisModule_OpenKey(ctx,keyname,REDISMODULE_READ);
int type = RedisModule_KeyType(key);
if (type != REDISMODULE_KEYTYPE_MODULE ||
RedisModule_ModuleTypeGetType(key) != HelloType)
{
return 0;
} else {
return 1;
RedisModule_CloseKey(key);
return REDISMODULE_ERR;
}
}
/* Reply callback for blocking command HELLOTYPE.BRANGE */
int HelloBlock_Reply(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
REDISMODULE_NOT_USED(argv);
REDISMODULE_NOT_USED(argc);
/* In case the key is able to serve our blocked client, let's directly
* use our original command implementation to make this example simpler. */
RedisModule_CloseKey(key);
return HelloTypeRange_RedisCommand(ctx,argv,argc-1);
}
@ -251,7 +251,7 @@ int HelloTypeBRange_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv,
}
void *privdata = RedisModule_Alloc(100);
RedisModule_BlockClientOnKeys(ctx,HelloBlock_Reply,HelloBlock_Timeout,HelloBlock_FreeData,timeout,argv+1,1,HelloBlock_IsKeyReady,privdata);
RedisModule_BlockClientOnKeys(ctx,HelloBlock_Reply,HelloBlock_Timeout,HelloBlock_FreeData,timeout,argv+1,1,privdata);
return REDISMODULE_OK;
}