Function afterErrorReply

app/redis-6.2.6/src/networking.c:419–475

Do some actions after an error reply was sent (Log if needed, updates stats, etc.) */

/* Do some actions after an error reply was sent (Log if needed, updates stats, etc.) */
void afterErrorReply(client *c, const char *s, size_t len) {
    /* Increment the global error counter */
    server.stat_total_error_replies++;
    /* Increment the error stats
     * If the string already starts with "-..." then the error prefix
     * is provided by the caller ( we limit the search to 32 chars). Otherwise we use "-ERR". */
    if (s[0] != '-') {
        incrementErrorCount("ERR", 3);
    } else {
        char *spaceloc = memchr(s, ' ', len < 32 ? len : 32);
        if (spaceloc) {
            const size_t errEndPos = (size_t)(spaceloc - s);
            incrementErrorCount(s+1, errEndPos-1);
        } else {
            /* Fallback to ERR if we can't retrieve the error prefix */
            incrementErrorCount("ERR", 3);
        }
    }

    /* Sometimes it could be normal that a slave replies to a master with
     * an error and this function gets called. Actually the error will never
     * be sent because addReply*() against master clients has no effect...
     * A notable example is:
     *
     *    EVAL 'redis.call("incr",KEYS[1]); redis.call("nonexisting")' 1 x
     *
     * Where the master must propagate the first change even if the second
     * will produce an error. However it is useful to log such events since
     * they are rare and may hint at errors in a script or a bug in Redis. */
    int ctype = getClientType(c);
    if (ctype == CLIENT_TYPE_MASTER || ctype == CLIENT_TYPE_SLAVE || c->id == CLIENT_ID_AOF) {
        char *to, *from;

        if (c->id == CLIENT_ID_AOF) {
            to = "AOF-loading-client";
            from = "server";
        } else if (ctype == CLIENT_TYPE_MASTER) {
            to = "master";
            from = "replica";
        } else {
            to = "replica";
            from = "master";
        }

        if (len > 4096) len = 4096;
        char *cmdname = c->lastcmd ? c->lastcmd->name : "<unknown>";
        serverLog(LL_WARNING,"== CRITICAL == This %s is sending an error "
                             "to its %s: '%.*s' after processing the command "
                             "'%s'", from, to, (int)len, s, cmdname);
        if (ctype == CLIENT_TYPE_MASTER && server.repl_backlog &&
            server.repl_backlog_histlen > 0)
        {
            showLatestBacklog();
        }
        server.stat_unexpected_error_replies++;
    }
}