[Openstack] Download file from swift extremely slow
rick.jones2 at hpe.com
Fri Jan 6 17:39:15 UTC 2017
On 01/05/2017 11:52 PM, dongjh at ahope.com.cn wrote:
> *Also, i can put/get files via dashboard/swift-CLI very quickly.*
> *So it is strange why 'openstack object save' so slowly...*
Well, two additional ways to compare might be to run both the openstack
and swift CLI versions under an strace and compare the system calls they
strace -v -f -ttt -o <something> cli command ...
where -v tells strace to be verbose, the -ttt tells it to timestamp each
system call with seconds.microseconds since the epoch, the -f tells it
to follow forks and the -o option gives a filename into which the trace
The second comparison would be to take a packet trace for each using
tcpdump. So, on the client something like:
tcpdump -s 96 -w <filename>.pcap -i <interface> "port <swift port> and
host <swift proxy>"
The -s says to capture no more than 96 bytes per packet, the -w puts the
capture to the named file, the -i selects the network interface on the
client, and then the last bit is a filter expression to select only
those packets which are swift and to/from the proxy.
That file can be post-processed in a number of ways, one of which is:
tcpdump -r <filename>.pcap -n -ttt > <filename>.cooked
where -r selects the file from which to read captured packets, the -n
says to disable looking up hostnames for IP addresses, and the -ttt says
to print the time delta for each packet compared to the one before. I
happen to follow a convention of calling the resulting output a
".cooked" file - as in it is a cooked version of a raw (binary) capture.
In both cases, you would be looking for large gaps in time -
particularly the openstack cli traces.
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