2019-07-20 13:14:00 -04:00
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# Parallel transfers
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2019-07-20 13:19:56 -04:00
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curl 7.66.0 introduces support for doing multiple transfers simultaneously; in
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2019-07-20 13:14:00 -04:00
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parallel.
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## -Z, --parallel
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When this command line option is used, curl will perform the transfers given
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to it at the same time. It will do up to `--parallel-max` concurrent
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transfers, with a default value of 50.
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## Progress meter
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The progress meter that is displayed when doing parallel transfers is
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completely different than the regular one used for each single transfer.
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It shows:
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o percent download (if known, which means *all* transfers need to have a
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known size)
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o precent upload (if known, with the same caveat as for download)
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o total amount of downloaded data
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o total amount of uploaded data
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o number of transfers to perform
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o number of concurrent transfers being transferred right now
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o number of transfers queued up waiting to start
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o total time all transfers are expected to take (if sizes are known)
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o current time the transfers have spent so far
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o estimated time left (if sizes are known)
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o current transfer speed (the faster of UL/DL speeds measured over the last
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few seconds)
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Example:
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DL% UL% Dled Uled Xfers Live Qd Total Current Left Speed
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72 -- 37.9G 0 101 30 23 0:00:55 0:00:34 0:00:22 2752M
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## Behavior differences
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Connections are shared fine between different easy handles, but the
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"authentication contexts" are not. So for example doing HTTP Digest auth with
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one handle for a particular transfer and then continue on with another handle
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that reuses the same connection, the second handle can't send the necessary
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Authorization header at once since the context is only kept in the original
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easy handle.
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To fix this, the authorization state could be made possible to share with the
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share API as well, as a context per origin + path (realm?) basically.
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Visible in test 153, 1412 and more.
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## Feedback!
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This is early days for parallel transfer support. Keep your eyes open for
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unintended side effects or downright bugs.
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Tell us what you think and how you think we could improve this feature!
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