Background:
I am using wget (version 1.14-15.el7) on RedHat Linux (version 7.3 (Maipo)), in a Bash (version 4.2.46(1)) terminal.
Unfortunately, I am limited to this particular RHEL image, so I can't upgrade to a newer version of wget.
Goal:
I am trying to configure wget so that, if a download attempt fails, it does the following:
1) Retries the download 4 more times (total of 5 attempts)
2) Waits a FIXED amount of time (30 seconds) between download attempts ('retries')
For context, here is a relevant snippet of the wget manual:
-w seconds
--wait=seconds
Wait the specified number of seconds between the retrievals. Use of this option is
recommended, as it lightens the server load by making the requests less frequent.
Instead of in seconds, the time can be specified in minutes using the "m" suffix, in
hours using "h" suffix, or in days using "d" suffix.
Specifying a large value for this option is useful if the network or the destination
host is down, so that Wget can wait long enough to reasonably expect the network error
to be fixed before the retry. The waiting interval specified by this function is
influenced by "--random-wait", which see.
--waitretry=seconds
If you don't want Wget to wait between every retrieval, but only between retries of
failed downloads, you can use this option. Wget will use linear backoff, waiting 1
second after the first failure on a given file, then waiting 2 seconds after the second
failure on that file, up to the maximum number of seconds you specify.
By default, Wget will assume a value of 10 seconds.
To be clear, I am using the --wait flag, NOT the --waitretry flag.
Process:
First, I export/set a wrong http_proxy and https_proxy, to ensure any download attempt will time out.
I run the following command:
wget --tries=5 --wait=30 <url> -O <output_filename>
At this point, the --wait functionality does NOT work as expected. Specifically, it does NOT wait 30s after each download attempt.
Instead:
1) After the first attempt, it waits 1s.
2) After the 2nd attempt, it waits 2s.
3) After the 3rd attempt, it waits 3s.
and so on ...
In other words, despite using the --wait flag (which should result in a fixed waiting time between download attempts), wget seems to be performing a 'linear backoff' as described in the --waitretry flag section.
PROBLEM:
I want the functionality of the --wait flag, NOT the --waitretry flag.
Unfortunately, the --wait flag seems to be acting like the --waitretry flag -- is there any way to fix this apparent bug in wget, so that using the --wait flag results in the expected fixed waiting time between download attempts?
--waitis only for waiting between downloading different files, it's not related at all to retrying failed downloads. – Barmar Aug 18 '17 at 19:29