[Openstack] Download file from swift extremely slow

Clay Gerrard clay.gerrard at gmail.com
Fri Jan 6 19:03:33 UTC 2017

Is this *really* the default chunk_size?


Because, that'd be like a *lot* of read calls for a large object ;)


Maybe try like, idk, chunk_size=None or 64 * 2 ** 10?


On Fri, Jan 6, 2017 at 9:39 AM, Rick Jones <rick.jones2 at hpe.com> wrote:

> 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
> are making:
> 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 should
> go.
> 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.
> happy benchmarking,
> rick jones
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