Follow-up from bug 1197720. The current version of the DownloadContentService discards partially downloaded content on error. Instead we could keep the temporary file and continue downloading using the "Range" header field. Some things to consider: * If an item in the catalog is updated (bug 1201059) we want to discard an existing temporary file. * The server side component needs to support Range headers.

Review commit: https://reviewboard.mozilla.org/r/28251/diff/#index_header See other reviews: https://reviewboard.mozilla.org/r/28251/

Comment on attachment 8699431 [details] MozReview Request: Bug 1209513 - DownloadContentService: Add support for resuming downloads. r?rnewman https://reviewboard.mozilla.org/r/28251/#review25777 Well, that was dramatically simpler than expected. My main concern here is that if the catalog is wrong, reporting a larger file than we host, we'll try to resume downloading over and over. Think about that for a minute.

(In reply to Richard Newman [:rnewman] from comment #2) > My main concern here is that if the catalog is wrong, reporting a larger > file than we host, we'll try to resume downloading over and over. Think > about that for a minute. That's a good point. However after a successful download (no exceptions etc.) I do not check the file size again and just do a checksum validation. So in the worst case we'd do one unnecessary resume but then continue normally. With the current implementation of failure counters we should avoid running into this too often. I'll add this as task for the online catalog story: How do we verify the correctness of the catalog and monitor that it remains correct?

https://hg.mozilla.org/integration/fx-team/rev/154b78cbac4a2db1e6a5128bcd30650c5d158d46 Bug 1209513 - DownloadContentService: Add support for resuming downloads. r=rnewman

Might this make a good release note for 46? Can you suggest wording?

(In reply to Liz Henry (:lizzard) (needinfo? me) from comment #6) > Might this make a good release note for 46? Can you suggest wording? All this is behind (disabled) flags for now. The only "visible" change for users (bug 1197720) will be a reduced app size but this is probably only going to affect Fx47.