xadd with id * generates random stream id
xadd & xtrim with approximate maxlen count may
trim stream randomly
xinfo may get random radix-tree-keys/nodes
xpending may get random idletime
xclaim: master and slave may have different
idletime in stream
xadd with id * generates random stream id
xadd & xtrim with approximate maxlen count may
trim stream randomly
xinfo may get random radix-tree-keys/nodes
xpending may get random idletime
xclaim: master and slave may have different
idletime in stream
Here the idea is that we do not want freeMemoryIfNeeded() to propagate a
DEL command before the script and change what happens in the script
execution once it reaches the slave. For example see this potential
issue (in the words of @soloestoy):
On master, we run the following script:
if redis.call('get','key')
then
redis.call('set','xxx','yyy')
end
redis.call('set','c','d')
Then when redis attempts to execute redis.call('set','xxx','yyy'), we call freeMemoryIfNeeded(), and the key may get deleted, and because redis.call('set','xxx','yyy') has already been executed on master, this script will be replicated to slave.
But the slave received "DEL key" before the script, and will ignore maxmemory, so after that master has xxx and c, slave has only one key c.
Note that this patch (and other related work) was authored collaboratively in
issue #5250 with the help of @soloestoy and @oranagra.
Related to issue #5250.
Here the idea is that we do not want freeMemoryIfNeeded() to propagate a
DEL command before the script and change what happens in the script
execution once it reaches the slave. For example see this potential
issue (in the words of @soloestoy):
On master, we run the following script:
if redis.call('get','key')
then
redis.call('set','xxx','yyy')
end
redis.call('set','c','d')
Then when redis attempts to execute redis.call('set','xxx','yyy'), we call freeMemoryIfNeeded(), and the key may get deleted, and because redis.call('set','xxx','yyy') has already been executed on master, this script will be replicated to slave.
But the slave received "DEL key" before the script, and will ignore maxmemory, so after that master has xxx and c, slave has only one key c.
Note that this patch (and other related work) was authored collaboratively in
issue #5250 with the help of @soloestoy and @oranagra.
Related to issue #5250.
The conclusion, that a xread request can be answered syncronously in
case that the stream's last_id is larger than the passed last-received-id
parameter, assumes, that there must be entries present, which could be
returned immediately.
This assumption fails for empty streams that actually contained some
entries which got removed by xdel, ... .
As result, the client is answered synchronously with an empty result,
instead of blocking for new entries to arrive.
An additional check for a non-empty stream is required.
The conclusion, that a xread request can be answered syncronously in
case that the stream's last_id is larger than the passed last-received-id
parameter, assumes, that there must be entries present, which could be
returned immediately.
This assumption fails for empty streams that actually contained some
entries which got removed by xdel, ... .
As result, the client is answered synchronously with an empty result,
instead of blocking for new entries to arrive.
An additional check for a non-empty stream is required.
If we are going to read a large object from network
try to make it likely that it will start at c->querybuf
boundary so that we can optimize object creation
avoiding a large copy of data.
But only when the data we have not parsed is less than
or equal to ll+2. If the data length is greater than
ll+2, trimming querybuf is just a waste of time, because
at this time the querybuf contains not only our bulk.
It's easy to reproduce the that:
Time1: call `client pause 10000` on slave.
Time2: redis-benchmark -t set -r 10000 -d 33000 -n 10000.
Then slave hung after 10 seconds.
If we are going to read a large object from network
try to make it likely that it will start at c->querybuf
boundary so that we can optimize object creation
avoiding a large copy of data.
But only when the data we have not parsed is less than
or equal to ll+2. If the data length is greater than
ll+2, trimming querybuf is just a waste of time, because
at this time the querybuf contains not only our bulk.
It's easy to reproduce the that:
Time1: call `client pause 10000` on slave.
Time2: redis-benchmark -t set -r 10000 -d 33000 -n 10000.
Then slave hung after 10 seconds.
