<div dir="ltr">Hi Simon,<div><br></div><div>That pages says this:</div><div><br></div><div><span style="color:rgb(85,85,85);font-family:Verdana,sans-serif;font-size:13px;line-height:18px">It is possible to set�</span><span class="" style="color:rgb(51,51,51);font-family:'Courier New',Courier,monospace;font-size:13px;white-space:nowrap;line-height:18px">vm_memory_high_watermark_paging_ratio</span><span style="color:rgb(85,85,85);font-family:Verdana,sans-serif;font-size:13px;line-height:18px">�to a greater value than�</span><span class="" style="color:rgb(51,51,51);font-family:'Courier New',Courier,monospace;font-size:13px;white-space:nowrap;line-height:18px">1.0</span><span style="color:rgb(85,85,85);font-family:Verdana,sans-serif;font-size:13px;line-height:18px">. In this case queues will not page their contents to disc.</span><br>
</div><div><br></div><div>What would happen then? Will RabbitMQ stop receiving messages? Drop messages?<br></div><div><br></div><div>Cheers,</div><div><br></div><div>Alvaro</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">
On Thu, Sep 26, 2013 at 3:39 AM, Simon MacMullen <span dir="ltr"><<a href="mailto:simon@rabbitmq.com" target="_blank">simon@rabbitmq.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On 26/09/2013 4:37AM, Peter Wright wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
i was hoping someone could help explain to me under what circumstances<br>
messages are written to the msg_store_transient directory. �i have been<br>
witnessing this directory grow to 10's of GB - infact it spun out of<br>
control at one point consuming almost 100G of space. �i do have a queue<br>
with quite a few messages ready for consumption, yet when i monitor<br>
memory utilization for this queue it rarely spikes above 20MB.<br>
</blockquote>
<br></div>
The memory use reported by the queue does not include message bodies (since these are shared across queues). Also it does not include anything that's been paged out, so if messages are paging out it can be quite low anyway.<br>
<br>
The decision as to whether to page messages is made globally based on how much memory is in use. All released versions of RabbitMQ (since 2.0.0 when the persister was rewritten) will start to page out when 20% of the way to the high watermark. By default the high watermark is at 40% of physical memory, so paging will start at 8% memory used.<br>
<br>
That's probably too cautious, so the next release (3.2.x) will raise the paging ratio from 20% to 50% (so paging will start at 20% memory used by default) and also make it configurable. See <a href="http://next.rabbitmq.com/memory.html#memsup-paging" target="_blank">http://next.rabbitmq.com/<u></u>memory.html#memsup-paging</a><br>
<br>
Having said that, if msg_store_transient grows to 100GB of space, I suspect you probably have 100GB of messages. If you don't have 100GB of RAM, you're going to page out...<br>
<br>
Hope this helps.<br>
<br>
Cheers, Simon<span class="HOEnZb"><font color="#888888"><br>
<br>
-- <br>
Simon MacMullen<br>
RabbitMQ, Pivotal<br>
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</font></span></blockquote></div><br></div>