wait_until_loaded option

[melo]

An attempt at solving #93.

Not a perfect solution by large, and on top of that I don't have a large enough dataset on my laptop to test this.

Also, not sure about the placement of the "fix", the auth() command is used before-hand, not sure if that command works while LOADING.

Anyway, if someone has large datasets, see if this works for you.

[vsespb]

Anyway, if someone has large datasets, see if this works for you.

I'll test a bit later

Also, not sure about the placement of the "fix", the auth() command is used before-hand, not sure if that command works while LOADING.

not sure either

if someone has large datasets

btw there is a great test in R:F

https://github.com/shogo82148/Redis-Fast/pull/23/files#diff-1

[vsespb]

also I am thinking maybe it should stop trying after some timeout.. (maybe use reconnect option as timeout?)

[vsespb]

1. In order to test fix I had to fix another problem. I was getting "Connection reset by peer" from here:

diff --git a/lib/Redis.pm b/lib/Redis.pm
index eade528..42840af 100644
--- a/lib/Redis.pm
+++ b/lib/Redis.pm
@@ -772,7 +772,7 @@ sub __read_line {
   my $sock = $self->{sock};

   my $data = $self->__read_line_raw;
-  croak("Error while reading from Redis server: $!")
+  $self->__throw_reconnect("Error while reading from Redis server: $!")
     unless defined $data;

   chomp $data;

when I restarted redis server (most of time, LOADING error was less frequent).

Then I tested fix - yes it works.

2. About AUTH command. Seems it should be OK:

https://github.com/antirez/redis/blob/38a5db6c9ac21812e4942d7016e4e58429f9ab09/src/redis.c#L2236
https://github.com/antirez/redis/blob/38a5db6c9ac21812e4942d7016e4e58429f9ab09/src/redis.c#L110
https://github.com/antirez/redis/blob/38a5db6c9ac21812e4942d7016e4e58429f9ab09/src/redis.c#L225

3. I propose to add additional wait_until_loaded_timeout option to control max possible wait period.
   I can send PR, if it's ok

So:
wait_until_loaded => TRUE|FALSE
if wait_until_loaded is TRUE, then wait_until_loaded_timeout is timeout in seconds. Defaults to 120.

OK?

note that I have filing that names wait_until_loaded and wait_until_loaded_timeout are not consistent with other option names. But I cannot suggest anything. It's up to you.

4. Sad that the test is missing.

[dams]

coming back to this issue, it seems that

-  croak("Error while reading from Redis server: $!")
+  $self->__throw_reconnect("Error while reading from Redis server: $!")

would invalidate the documentation about reconnect:

Be aware that read errors will always thrown an exception, and will not trigger
a retry until the new command is sent.

It seems that in most of the case (so not in wait_until_loaded), we want it to croak and not retry. So the code should realize that it's in specific case of wait_until_loaded