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本模块主要实现defrag回调机制，可以细看一下，还挺巧妙的：
/* A module that implements defrag callback mechanisms.*/#define REDISMODULE_EXPERIMENTAL_API
#include "redismodule.h"static RedisModuleType *FragType;struct FragObject {unsigned long len;void **values;int maxstep;
};/* Make sure we get the expected cursor */
unsigned long int last_set_cursor = 0;unsigned long int datatype_attempts = 0;
unsigned long int datatype_defragged = 0;
unsigned long int datatype_resumes = 0;
unsigned long int datatype_wrong_cursor = 0;
unsigned long int global_attempts = 0;
unsigned long int global_defragged = 0;int global_strings_len = 0;
RedisModuleString **global_strings = NULL;static void createGlobalStrings(RedisModuleCtx *ctx, int count)
{global_strings_len = count;global_strings = RedisModule_Alloc(sizeof(RedisModuleString *) * count);for (int i = 0; i < count; i++) {global_strings[i] = RedisModule_CreateStringFromLongLong(ctx, i);}
}static int defragGlobalStrings(RedisModuleDefragCtx *ctx)
{for (int i = 0; i < global_strings_len; i++) {RedisModuleString *new = RedisModule_DefragRedisModuleString(ctx, global_strings[i]);global_attempts++;if (new != NULL) {global_strings[i] = new;global_defragged++;}}return 0;
}static void FragInfo(RedisModuleInfoCtx *ctx, int for_crash_report) {REDISMODULE_NOT_USED(for_crash_report);RedisModule_InfoAddSection(ctx, "stats");RedisModule_InfoAddFieldLongLong(ctx, "datatype_attempts", datatype_attempts);RedisModule_InfoAddFieldLongLong(ctx, "datatype_defragged", datatype_defragged);RedisModule_InfoAddFieldLongLong(ctx, "datatype_resumes", datatype_resumes);RedisModule_InfoAddFieldLongLong(ctx, "datatype_wrong_cursor", datatype_wrong_cursor);RedisModule_InfoAddFieldLongLong(ctx, "global_attempts", global_attempts);RedisModule_InfoAddFieldLongLong(ctx, "global_defragged", global_defragged);
}struct FragObject *createFragObject(unsigned long len, unsigned long size, int maxstep) {struct FragObject *o = RedisModule_Alloc(sizeof(*o));o->len = len;o->values = RedisModule_Alloc(sizeof(RedisModuleString*) * len);o->maxstep = maxstep;for (unsigned long i = 0; i < len; i++) {o->values[i] = RedisModule_Calloc(1, size);}return o;
}/* FRAG.RESETSTATS */
static int fragResetStatsCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {REDISMODULE_NOT_USED(argv);REDISMODULE_NOT_USED(argc);datatype_attempts = 0;datatype_defragged = 0;datatype_resumes = 0;datatype_wrong_cursor = 0;global_attempts = 0;global_defragged = 0;RedisModule_ReplyWithSimpleString(ctx, "OK");return REDISMODULE_OK;
}/* FRAG.CREATE key len size maxstep */
static int fragCreateCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {if (argc != 5)return RedisModule_WrongArity(ctx);RedisModuleKey *key = RedisModule_OpenKey(ctx,argv[1],REDISMODULE_READ|REDISMODULE_WRITE);int type = RedisModule_KeyType(key);if (type != REDISMODULE_KEYTYPE_EMPTY){return RedisModule_ReplyWithError(ctx, "ERR key exists");}long long len;if ((RedisModule_StringToLongLong(argv[2], &len) != REDISMODULE_OK)) {return RedisModule_ReplyWithError(ctx, "ERR invalid len");}long long size;if ((RedisModule_StringToLongLong(argv[3], &size) != REDISMODULE_OK)) {return RedisModule_ReplyWithError(ctx, "ERR invalid size");}long long maxstep;if ((RedisModule_StringToLongLong(argv[4], &maxstep) != REDISMODULE_OK)) {return RedisModule_ReplyWithError(ctx, "ERR invalid maxstep");}struct FragObject *o = createFragObject(len, size, maxstep);RedisModule_ModuleTypeSetValue(key, FragType, o);RedisModule_ReplyWithSimpleString(ctx, "OK");RedisModule_CloseKey(key);return REDISMODULE_OK;
}void FragFree(void *value) {struct FragObject *o = value;for (unsigned long i = 0; i < o->len; i++)RedisModule_Free(o->values[i]);RedisModule_Free(o->values);RedisModule_Free(o);
}size_t FragFreeEffort(RedisModuleString *key, const void *value) {REDISMODULE_NOT_USED(key);const struct FragObject *o = value;return o->len;
}int FragDefrag(RedisModuleDefragCtx *ctx, RedisModuleString *key, void **value) {REDISMODULE_NOT_USED(key);unsigned long i = 0;int steps = 0;/* Attempt to get cursor, validate it's what we're exepcting */if (RedisModule_DefragCursorGet(ctx, &i) == REDISMODULE_OK) {if (i > 0) datatype_resumes++;/* Validate we're expecting this cursor */if (i != last_set_cursor) datatype_wrong_cursor++;} else {if (last_set_cursor != 0) datatype_wrong_cursor++;}/* Attempt to defrag the object itself */datatype_attempts++;struct FragObject *o = RedisModule_DefragAlloc(ctx, *value);if (o == NULL) {/* Not defragged */o = *value;} else {/* Defragged */*value = o;datatype_defragged++;}/* Deep defrag now */for (; i < o->len; i++) {datatype_attempts++;void *new = RedisModule_DefragAlloc(ctx, o->values[i]);if (new) {o->values[i] = new;datatype_defragged++;}if ((o->maxstep && ++steps > o->maxstep) ||((i % 64 == 0) && RedisModule_DefragShouldStop(ctx))){RedisModule_DefragCursorSet(ctx, i);last_set_cursor = i;return 1;}}last_set_cursor = 0;return 0;
}int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {REDISMODULE_NOT_USED(argv);REDISMODULE_NOT_USED(argc);if (RedisModule_Init(ctx, "defragtest", 1, REDISMODULE_APIVER_1)== REDISMODULE_ERR) return REDISMODULE_ERR;if (RedisModule_GetTypeMethodVersion() < REDISMODULE_TYPE_METHOD_VERSION) {return REDISMODULE_ERR;}long long glen;if (argc != 1 || RedisModule_StringToLongLong(argv[0], &glen) == REDISMODULE_ERR) {return REDISMODULE_ERR;}createGlobalStrings(ctx, glen);RedisModuleTypeMethods tm = {.version = REDISMODULE_TYPE_METHOD_VERSION,.free = FragFree,.free_effort = FragFreeEffort,.defrag = FragDefrag};FragType = RedisModule_CreateDataType(ctx, "frag_type", 0, &tm);if (FragType == NULL) return REDISMODULE_ERR;if (RedisModule_CreateCommand(ctx, "frag.create",fragCreateCommand, "write deny-oom", 1, 1, 1) == REDISMODULE_ERR)return REDISMODULE_ERR;if (RedisModule_CreateCommand(ctx, "frag.resetstats",fragResetStatsCommand, "write deny-oom", 1, 1, 1) == REDISMODULE_ERR)return REDISMODULE_ERR;RedisModule_RegisterInfoFunc(ctx, FragInfo);RedisModule_RegisterDefragFunc(ctx, defragGlobalStrings);return REDISMODULE_OK;
}
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