Escape the special chars in the monitor command output

[w4096]

fix the format error in monitor response

If the payload of a request has \r\n, the response forwarded to monitoring client is in bad format since simple string can't contains CRLF in RESP.

I found this issue when I execute monitor command in redis-cli and set content of a .c file as value in another redis-cli:

$ redis-cli -p 6666
127.0.0.1:6666> monitor
OK
1685165694.988910 [__namespace 127.0.0.1:55614] "set" "a" "#include <stdio.h>
Error: Protocol error, got "\r" as reply type byte

$ redis-cli -p 6666 -x set a < ./main.c

In the redis code the monitor response sending to client has been escaped by sdscatrepr:

https://github.com/redis/redis/blob/e775b34e813654ead5be899faa065f1c31753040/src/replication.c#L560
https://github.com/redis/redis/blob/e775b34e813654ead5be899faa065f1c31753040/src/sds.c#L986

I implement a function StringRepr in string_util to do the escap which did the same escape with sdscatrepr.

improve the performance of monitor

the content of monitor response is formated in worker, if more than one worker exists, the content will be formated several times.

We can format the response in Server::FeedMonitorConns and pass the response to Worker::FeedMonitorConns.

[git-hulk]

@wy-ei Cool, thanks

[PragmaTwice]

IMHO I think maybe we should just use bulk string reply rather than simple string to solve this problem, and for me these string escaping in this patch is just like a workaround.

[PragmaTwice]

https://redis.io/commands/monitor/

Seems redis itself already has some bad practice in solving these escaping problem, which is sad since we need to be compatible to redis.

For me, escaping is not need at all, we can just send an arrays with bulk strings, all in RESP.

[w4096]

@PragmaTwice If redis use bulk string as the monitor response format, this issue does't exists any more. But the simple string is used and the issue is exists. This change is a workaround and it has fix the bad case and make it compatible with redis.

It's easy to change the format as bulk string or array, but client SDK may not work.

For example, in redis-py, unescaping is applyed on monitor response:

https://github.com/redis/redis-py/blob/2d9b5ac6fe03fdc572b8ca47f7134082bae2a5e2/redis/client.py#L1337

[torwig]

LGTM

[git-hulk]

Thanks all, merging...