Initial command filter experiment.

src/module.c

@@ -270,6 +270,28 @@ typedef struct RedisModuleDictIter {
     raxIterator ri;
 } RedisModuleDictIter;
 
+/* Information about the command to be executed, as passed to and from a
+ * filter. */
+typedef struct RedisModuleFilteredCommand {
+    RedisModuleString **argv;
+    int argc;
+} RedisModuleFilteredCommand;
+
+typedef void (*RedisModuleCommandFilterFunc) (RedisModuleCtx *ctx, RedisModuleFilteredCommand *cmd);
+
+typedef struct RedisModuleCommandFilter {
+    /* The module that registered the filter */
+    RedisModule *module;
+    /* Filter callback function */
+    RedisModuleCommandFilterFunc callback;
+    /* Indicates a filter is active, avoid reentrancy */
+    int active;
+} RedisModuleCommandFilter;
+
+/* Registered filters */
+static list *moduleCommandFilters;
+
+
 /* --------------------------------------------------------------------------
  * Prototypes
  * -------------------------------------------------------------------------- */
@@ -4772,6 +4794,56 @@ int moduleUnregisterUsedAPI(RedisModule *module) {
     return count;
 }
 
+/* --------------------------------------------------------------------------
+ * Module Command Filter API
+ * -------------------------------------------------------------------------- */
+
+/* Register a new command filter function.  Filters get executed by Redis
+ * before processing an inbound command and can be used to manipulate the
+ * behavior of standard Redis commands.  Filters must not attempt to
+ * perform Redis commands or operate on the dataset, and must restrict
+ * themselves to manipulation of the arguments.
+ */
+
+int RM_RegisterCommandFilter(RedisModuleCtx *ctx, RedisModuleCommandFilterFunc callback) {
+    RedisModuleCommandFilter *filter = zmalloc(sizeof(*filter));
+    filter->module = ctx->module;
+    filter->callback = callback;
+    filter->active = 0;
+
+    listAddNodeTail(moduleCommandFilters, filter);
+    return REDISMODULE_OK;
+}
+
+void moduleCallCommandFilters(client *c) {
+    if (listLength(moduleCommandFilters) == 0) return;
+
+    listIter li;
+    listNode *ln;
+    listRewind(moduleCommandFilters,&li);
+
+    RedisModuleFilteredCommand cmd = {
+        .argv = c->argv,
+        .argc = c->argc
+    };
+
+    while((ln = listNext(&li))) {
+        RedisModuleCommandFilter *filter = ln->value;
+        if (filter->active) continue;
+
+        RedisModuleCtx ctx = REDISMODULE_CTX_INIT;
+        ctx.module = filter->module;
+
+        filter->active = 1;
+        filter->callback(&ctx, &cmd);
+        filter->active = 0;
+        moduleFreeContext(&ctx);
+    }
+
+    c->argv = cmd.argv;
+    c->argc = cmd.argc;
+}
+
 /* --------------------------------------------------------------------------
  * Modules API internals
  * -------------------------------------------------------------------------- */
@@ -4817,6 +4889,9 @@ void moduleInitModulesSystem(void) {
     moduleFreeContextReusedClient = createClient(-1);
     moduleFreeContextReusedClient->flags |= CLIENT_MODULE;
 
+    /* Set up filter list */
+    moduleCommandFilters = listCreate();
+
     moduleRegisterCoreAPI();
     if (pipe(server.module_blocked_pipe) == -1) {
         serverLog(LL_WARNING,
@@ -5215,4 +5290,5 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(DictCompare);
     REGISTER_API(ExportSharedAPI);
     REGISTER_API(GetSharedAPI);
+    REGISTER_API(RegisterCommandFilter);
 }

src/modules/Makefile

@@ -13,7 +13,7 @@ endif
 
 .SUFFIXES: .c .so .xo .o
 
-all: helloworld.so hellotype.so helloblock.so testmodule.so hellocluster.so hellotimer.so hellodict.so
+all: helloworld.so hellotype.so helloblock.so testmodule.so hellocluster.so hellotimer.so hellodict.so hellofilter.so
 
 .c.xo:
 	$(CC) -I. $(CFLAGS) $(SHOBJ_CFLAGS) -fPIC -c $< -o $@
@@ -46,6 +46,10 @@ hellotimer.so: hellotimer.xo
 hellodict.xo: ../redismodule.h
 
 hellodict.so: hellodict.xo
+
+hellofilter.xo: ../redismodule.h
+
+hellofilter.so: hellofilter.xo
 	$(LD) -o $@ $< $(SHOBJ_LDFLAGS) $(LIBS) -lc
 
 testmodule.xo: ../redismodule.h

src/modules/hellofilter.c

+#define REDISMODULE_EXPERIMENTAL_API
+#include "../redismodule.h"
+
+static RedisModuleString *log_key_name;
+
+static const char log_command_name[] = "hellofilter.log";
+
+int HelloFilter_LogCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
+{
+    RedisModuleString *s = RedisModule_CreateStringFromString(ctx, argv[0]);
+
+    int i;
+    for (i = 1; i < argc; i++) {
+        size_t arglen;
+        const char *arg = RedisModule_StringPtrLen(argv[i], &arglen);
+
+        RedisModule_StringAppendBuffer(ctx, s, " ", 1);
+        RedisModule_StringAppendBuffer(ctx, s, arg, arglen);
+    }
+
+    RedisModuleKey *log = RedisModule_OpenKey(ctx, log_key_name, REDISMODULE_WRITE|REDISMODULE_READ);
+    RedisModule_ListPush(log, REDISMODULE_LIST_HEAD, s);
+    RedisModule_CloseKey(log);
+    RedisModule_FreeString(ctx, s);
+
+    size_t cmdlen;
+    const char *cmdname = RedisModule_StringPtrLen(argv[1], &cmdlen);
+    RedisModuleCallReply *reply = RedisModule_Call(ctx, cmdname, "v", &argv[2], argc - 2);
+    if (reply) {
+        RedisModule_ReplyWithCallReply(ctx, reply);
+        RedisModule_FreeCallReply(reply);
+    } else {
+        RedisModule_ReplyWithSimpleString(ctx, "Unknown command or invalid arguments");
+    }
+    return REDISMODULE_OK;
+}
+
+void HelloFilter_CommandFilter(RedisModuleCtx *ctx, RedisModuleFilteredCommand *cmd)
+{
+    cmd->argv = RedisModule_Realloc(cmd->argv, (cmd->argc+1)*sizeof(RedisModuleString *));
+    int i;
+
+    for (i = cmd->argc; i > 0; i--) {
+        cmd->argv[i] = cmd->argv[i-1];
+    }
+    cmd->argv[0] = RedisModule_CreateString(ctx, log_command_name, sizeof(log_command_name)-1);
+    cmd->argc++;
+}
+
+int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    if (RedisModule_Init(ctx,"hellofilter",1,REDISMODULE_APIVER_1)
+            == REDISMODULE_ERR) return REDISMODULE_ERR;
+
+    if (argc != 1) {
+        RedisModule_Log(ctx, "warning", "Log key name not specified");
+        return REDISMODULE_ERR;
+    }
+
+    log_key_name = RedisModule_CreateStringFromString(ctx, argv[0]);
+
+    if (RedisModule_CreateCommand(ctx,log_command_name,
+                HelloFilter_LogCommand,"write deny-oom",1,1,1) == REDISMODULE_ERR)
+            return REDISMODULE_ERR;
+
+    if (RedisModule_RegisterCommandFilter(ctx, HelloFilter_CommandFilter)
+            == REDISMODULE_ERR) return REDISMODULE_ERR;
+
+    return REDISMODULE_OK;
+}

src/redismodule.h

@@ -163,6 +163,12 @@ typedef void (*RedisModuleTypeFreeFunc)(void *value);
 typedef void (*RedisModuleClusterMessageReceiver)(RedisModuleCtx *ctx, const char *sender_id, uint8_t type, const unsigned char *payload, uint32_t len);
 typedef void (*RedisModuleTimerProc)(RedisModuleCtx *ctx, void *data);
 
+typedef struct RedisModuleFilteredCommand {
+    RedisModuleString **argv;
+    int argc;
+} RedisModuleFilteredCommand;
+typedef void (*RedisModuleCommandFilterFunc) (RedisModuleCtx *ctx, RedisModuleFilteredCommand *cmd);
+
 #define REDISMODULE_TYPE_METHOD_VERSION 1
 typedef struct RedisModuleTypeMethods {
     uint64_t version;
@@ -338,6 +344,7 @@ void REDISMODULE_API_FUNC(RedisModule_SetDisconnectCallback)(RedisModuleBlockedC
 void REDISMODULE_API_FUNC(RedisModule_SetClusterFlags)(RedisModuleCtx *ctx, uint64_t flags);
 int REDISMODULE_API_FUNC(RedisModule_ExportSharedAPI)(RedisModuleCtx *ctx, const char *apiname, void *func);
 void *REDISMODULE_API_FUNC(RedisModule_GetSharedAPI)(RedisModuleCtx *ctx, const char *apiname);
+int REDISMODULE_API_FUNC(RedisModule_RegisterCommandFilter)(RedisModuleCtx *ctx, RedisModuleCommandFilterFunc cb);
 #endif
 
 /* This is included inline inside each Redis module. */
@@ -501,6 +508,7 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(SetClusterFlags);
     REDISMODULE_GET_API(ExportSharedAPI);
     REDISMODULE_GET_API(GetSharedAPI);
+    REDISMODULE_GET_API(RegisterCommandFilter);
 #endif
 
     if (RedisModule_IsModuleNameBusy && RedisModule_IsModuleNameBusy(name)) return REDISMODULE_ERR;

src/server.c

@@ -2541,6 +2541,8 @@ void call(client *c, int flags) {
  * other operations can be performed by the caller. Otherwise
  * if C_ERR is returned the client was destroyed (i.e. after QUIT). */
 int processCommand(client *c) {
+    moduleCallCommandFilters(c);
+
     /* The QUIT command is handled separately. Normal command procs will
      * go through checking for replication and QUIT will cause trouble
      * when FORCE_REPLICATION is enabled and would be implemented in

src/server.h

@@ -1410,7 +1410,7 @@ size_t moduleCount(void);
 void moduleAcquireGIL(void);
 void moduleReleaseGIL(void);
 void moduleNotifyKeyspaceEvent(int type, const char *event, robj *key, int dbid);
-
+void moduleCallCommandFilters(client *c);
 
 /* Utils */
 long long ustime(void);