Split error message so dependandent callers give a useful result

src/cluster.c

@@ -5476,8 +5476,8 @@ void readwriteCommand(client *c) {
  * already "down" but it is fragile to rely on the update of the global state,
  * so we also handle it here.
  *
- * CLUSTER_REDIR_DOWN_STATE if the cluster is down but the user attempts to
- * execute a command that addresses one or more keys. */
+ * CLUSTER_REDIR_DOWN_STATE and CLUSTER_REDIR_DOWN_RO_STATE if the cluster is 
+ * down but the user attempts to execute a command that addresses one or more keys. */
 clusterNode *getNodeByQuery(client *c, struct redisCommand *cmd, robj **argv, int argc, int *hashslot, int *error_code) {
     clusterNode *n = NULL;
     robj *firstkey = NULL;
@@ -5597,12 +5597,17 @@ clusterNode *getNodeByQuery(client *c, struct redisCommand *cmd, robj **argv, in
 
     /* Cluster is globally down but we got keys? We only serve the request
      * if it is a read command and when allow_reads_when_down is enabled. */
-    if ((server.cluster->state != CLUSTER_OK) &&
-        !(server.cluster_allow_reads_when_down && ((cmd->flags & CMD_READONLY)
-        || (cmd->proc == evalCommand) || (cmd->proc == evalShaCommand)))) 
-    {
-        if (error_code) *error_code = CLUSTER_REDIR_DOWN_STATE;
-        return NULL;
+    if (server.cluster->state != CLUSTER_OK) {
+        if (!server.cluster_allow_reads_when_down) {
+            if (error_code) *error_code = CLUSTER_REDIR_DOWN_STATE;
+            return NULL;
+        }
+
+        if (!(cmd->flags & CMD_READONLY) && !(cmd->proc == evalCommand) 
+                && !(cmd->proc == evalShaCommand)) {
+            if (error_code) *error_code = CLUSTER_REDIR_DOWN_RO_STATE;
+            return NULL;
+        }
     }
 
     /* Return the hashslot by reference. */
@@ -5671,6 +5676,8 @@ void clusterRedirectClient(client *c, clusterNode *n, int hashslot, int error_co
         addReplySds(c,sdsnew("-TRYAGAIN Multiple keys request during rehashing of slot\r\n"));
     } else if (error_code == CLUSTER_REDIR_DOWN_STATE) {
         addReplySds(c,sdsnew("-CLUSTERDOWN The cluster is down\r\n"));
+    } else if (error_code == CLUSTER_REDIR_DOWN_RO_STATE) {
+        addReplySds(c,sdsnew("-CLUSTERDOWN The cluster is down and only accepts read commands\r\n"));
     } else if (error_code == CLUSTER_REDIR_DOWN_UNBOUND) {
         addReplySds(c,sdsnew("-CLUSTERDOWN Hash slot not served\r\n"));
     } else if (error_code == CLUSTER_REDIR_MOVED ||

src/cluster.h

@@ -29,6 +29,7 @@
 #define CLUSTER_REDIR_MOVED 4         /* -MOVED redirection required. */
 #define CLUSTER_REDIR_DOWN_STATE 5    /* -CLUSTERDOWN, global state. */
 #define CLUSTER_REDIR_DOWN_UNBOUND 6  /* -CLUSTERDOWN, unbound slot. */
+#define CLUSTER_REDIR_DOWN_RO_STATE 7 /* -CLUSTERDOWN, allow reads. */
 
 struct clusterNode;
 

src/module.c

@@ -3176,6 +3176,7 @@ fmterr:
  * EPERM:  operation in Cluster instance with key in non local slot.
  * EROFS:  operation in Cluster instance when a write command is sent
  *         in a readonly state.
+ * ENETDOWN: operation in Cluster instance when cluster is down.
  *
  * This API is documented here: https://redis.io/topics/modules-intro
  */
@@ -3240,8 +3241,10 @@ RedisModuleCallReply *RM_Call(RedisModuleCtx *ctx, const char *cmdname, const ch
         if (getNodeByQuery(c,c->cmd,c->argv,c->argc,NULL,&error_code) !=
                            server.cluster->myself)
         {
-            if (error_code == CLUSTER_REDIR_DOWN_STATE) { 
+            if (error_code == CLUSTER_REDIR_DOWN_RO_STATE) { 
                 errno = EROFS;
+            } else if (error_code == CLUSTER_REDIR_DOWN_STATE) { 
+                errno = ENETDOWN;
             } else {
                 errno = EPERM;
             }

src/scripting.c

@@ -686,11 +686,15 @@ int luaRedisGenericCommand(lua_State *lua, int raise_error) {
         if (getNodeByQuery(c,c->cmd,c->argv,c->argc,NULL,&error_code) !=
                            server.cluster->myself)
         {
-            if (error_code == CLUSTER_REDIR_DOWN_STATE) { 
+            if (error_code == CLUSTER_REDIR_DOWN_RO_STATE) { 
                 luaPushError(lua,
-                    "Lua script attempted execute a write command while "
+                    "Lua script attempted to execute a write command while the"
+                    "cluster is down and readonly");
+            } else if (error_code == CLUSTER_REDIR_DOWN_STATE) { 
+                luaPushError(lua,
+                    "Lua script attempted to execute a command while the"
                     "cluster is down");
-            } else {
+            } else {}
                 luaPushError(lua,
                     "Lua script attempted to access a non local key in a "
                     "cluster node");