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47c51d0c78
Current implementation simple idle client which serves no traffic still
use ~17Kb of memory. this is mainly due to a fixed size reply buffer
currently set to 16kb.
We have encountered some cases in which the server operates in a low memory environments.
In such cases a user who wishes to create large connection pools to support potential burst period,
will exhaust a large amount of memory to maintain connected Idle clients.
Some users may choose to "sacrifice" performance in order to save memory.
This commit introduce a dynamic mechanism to shrink and expend the client reply buffer based on
periodic observed peak.
the algorithm works as follows:
1. each time a client reply buffer has been fully written, the last recorded peak is updated:
new peak = MAX( last peak, current written size)
2. during clients cron we check for each client if the last observed peak was:
a. matching the current buffer size - in which case we expend (resize) the buffer size by 100%
b. less than half the buffer size - in which case we shrink the buffer size by 50%
3. In any case we will **not** resize the buffer in case:
a. the current buffer peak is less then the current buffer usable size and higher than 1/2 the
current buffer usable size
b. the value of (current buffer usable size/2) is less than 1Kib
c. the value of (current buffer usable size*2) is larger than 16Kib
4. the peak value is reset to the current buffer position once every **5** seconds. we maintain a new
field in the client structure (buf_peak_last_reset_time) which is used to keep track of how long it
passed since the last buffer peak reset.
### **Interface changes:**
**CIENT LIST** - now contains 2 new extra fields:
rbs= < the current size in bytes of the client reply buffer >
rbp=< the current value in bytes of the last observed buffer peak position >
**INFO STATS** - now contains 2 new statistics:
reply_buffer_shrinks = < total number of buffer shrinks performed >
reply_buffer_expends = < total number of buffer expends performed >
Co-authored-by: Oran Agra <oran@redislabs.com>
Co-authored-by: Yoav Steinberg <yoav@redislabs.com>
47 lines
1.6 KiB
Tcl
47 lines
1.6 KiB
Tcl
proc get_reply_buffer_size {cname} {
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set clients [split [string trim [r client list]] "\r\n"]
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set c [lsearch -inline $clients *name=$cname*]
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if {![regexp rbs=(\[a-zA-Z0-9-\]+) $c - rbufsize]} {
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error "field rbus not found in $c"
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}
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return $rbufsize
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}
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start_server {tags {"replybufsize"}} {
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test {verify reply buffer limits} {
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# In order to reduce test time we can set the peak reset time very low
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r debug replybuffer-peak-reset-time 100
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# Create a simple idle test client
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variable tc [redis_client]
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$tc client setname test_client
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# make sure the client is idle for 1 seconds to make it shrink the reply buffer
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wait_for_condition 10 100 {
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[get_reply_buffer_size test_client] >= 1024 && [get_reply_buffer_size test_client] < 2046
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} else {
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set rbs [get_reply_buffer_size test_client]
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fail "reply buffer of idle client is $rbs after 1 seconds"
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}
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r set bigval [string repeat x 32768]
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# In order to reduce test time we can set the peak reset time very low
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r debug replybuffer-peak-reset-time never
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wait_for_condition 10 100 {
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[$tc get bigval ; get_reply_buffer_size test_client] >= 16384 && [get_reply_buffer_size test_client] < 32768
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} else {
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set rbs [get_reply_buffer_size test_client]
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fail "reply buffer of busy client is $rbs after 1 seconds"
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}
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# Restore the peak reset time to default
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r debug replybuffer-peak-reset-time reset
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$tc close
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} {0} {needs:debug}
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}
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