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CommandFilter API: REDISMODULE_CMDFILTER_NOSELF.

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Add a flag to automatically protect filters from being called
recursively by their own module.
This commit is contained in:
Yossi Gottlieb
2019-03-21 19:47:43 +02:00
parent 4ea3ed896b
commit 6c0a5fde3d
4 changed files with 62 additions and 15 deletions
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28
src/module.c
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@ -50,6 +50,7 @@ struct RedisModule {
list *usedby; /* List of modules using APIs from this one. */
list *using; /* List of modules we use some APIs of. */
list *filters; /* List of filters the module has registered. */
int in_call; /* RM_Call() nesting level */
};
typedef struct RedisModule RedisModule;
@ -283,6 +284,8 @@ typedef struct RedisModuleCommandFilter {
RedisModule *module;
/* Filter callback function */
RedisModuleCommandFilterFunc callback;
/* REDISMODULE_CMDFILTER_* flags */
int flags;
} RedisModuleCommandFilter;
/* Registered filters */
@ -2756,6 +2759,8 @@ RedisModuleCallReply *RM_Call(RedisModuleCtx *ctx, const char *cmdname, const ch
c->db = ctx->client->db;
c->argv = argv;
c->argc = argc;
if (ctx->module) ctx->module->in_call++;
/* We handle the above format error only when the client is setup so that
* we can free it normally. */
if (argv == NULL) goto cleanup;
@ -2822,6 +2827,7 @@ RedisModuleCallReply *RM_Call(RedisModuleCtx *ctx, const char *cmdname, const ch
autoMemoryAdd(ctx,REDISMODULE_AM_REPLY,reply);
cleanup:
if (ctx->module) ctx->module->in_call--;
freeClient(c);
return reply;
}
@ -4857,17 +4863,27 @@ int moduleUnregisterFilters(RedisModule *module) {
*
* Note that in the above use case, if `MODULE.SET` itself uses
* `RedisModule_Call()` the filter will be applied on that call as well. If
* that is not desired, the module itself is responsible for maintaining a flag
* to identify and avoid this form of re-entrancy.
* that is not desired, the `REDISMODULE_CMDFILTER_NOSELF` flag can be set when
* registering the filter.
*
* The `REDISMODULE_CMDFILTER_NOSELF` flag prevents execution flows that
* originate from the module's own `RM_Call()` from reaching the filter. This
* flag is effective for all execution flows, including nested ones, as long as
* the execution begins from the module's command context or a thread-safe
* context that is associated with a blocking command.
*
* Detached thread-safe contexts are *not* associated with the module and cannot
* be protected by this flag.
*
* If multiple filters are registered (by the same or different modules), they
* are executed in the order of registration.
*/
RedisModuleCommandFilter *RM_RegisterCommandFilter(RedisModuleCtx *ctx, RedisModuleCommandFilterFunc callback) {
RedisModuleCommandFilter *RM_RegisterCommandFilter(RedisModuleCtx *ctx, RedisModuleCommandFilterFunc callback, int flags) {
RedisModuleCommandFilter *filter = zmalloc(sizeof(*filter));
filter->module = ctx->module;
filter->callback = callback;
filter->flags = flags;
listAddNodeTail(moduleCommandFilters, filter);
listAddNodeTail(ctx->module->filters, filter);
@ -4908,6 +4924,12 @@ void moduleCallCommandFilters(client *c) {
while((ln = listNext(&li))) {
RedisModuleCommandFilter *f = ln->value;
/* Skip filter if REDISMODULE_CMDFILTER_NOSELF is set and module is
* currently processing a command.
*/
if ((f->flags & REDISMODULE_CMDFILTER_NOSELF) && f->module->in_call) continue;
/* Call filter */
f->callback(&filter);
}