Transmission 4.0.0

Highlights

This is a major release, both in numbering and in effort! It's been in active development for over a year and has a huge list of changes -- over a thousand commits -- since Transmission 3.00. Some of the highlights include:

• Resource Efficiency - Use less memory and fewer CPU cycles
• Better Community - Pull requests welcomed and used
• Code Modernization - Migrated from C90 to modern C++
• New Features - What would a major release be without them?

Resource Efficiency

• The code has been extensively profiled and improved to fix inefficient code and memory use. For example, a stress test of starting transmission-daemon with 25,000 torrents is almost entirely IO-bound, using 50% fewer CPU cycles and 70% fewer memory allocations than Transmission 3.00.

• The remote control GUIs (transmission-qt and transmission-web) now use the RPC API "table" mode, resulting in smaller payloads / less bandwidth use.

• RPC payloads are now compressed using libdeflate, a "heavily optimized [library that is] significantly faster than the zlib library."

Community

• The project is much more responsive to bug reports and code submissions than it has been in the past.
• There is a new group of volunteer contributors who are working on Transmission!
• Transmission 4.0.0 includes over 350 new community commits (see the Thank You section below and in the previous 4.0.0 betas) since 3.00 and welcomes new contributors.
• Documentation has been moved into the transmission/transmission so that contributors can submit PRs to improve it.

Code Modernization

• The entire codebase has been migrated from C to C++. In the process, we've removed thousands of lines of custom code and used standard C++ tools instead. The core's code has shrunk by 18%. The core codebase has been extensively refactored to be more testable and maintainable.
• The GTK client has been ported to gtkmm.
• The Web client has been rewritten in modern JavaScript and no longer uses jQuery. The entire gzipped bundle is now 68K.
• The unit tests have been expanded and ported to Google Test. Clang sanitizer builds are run during CI.
• The core library is now fuzz tested.
• Transmission now uses Sonarcloud, Coverity, LGTM, and clang-tidy static analysis on new code. Several hundred code warnings have been fixed compared to Transmission 3.00.

New Features

• Support for using BitTorrent v2 torrents and hybrid torrents. (Support for creating v2 and hybrid torrents is slated for an upcoming release.)
• Users can now set "default" trackers that can be used to announce all public torrents.
• Newly-added seeds can start immediately and verify pieces on demand, instead of needing a full verify before seeding can begin. (#2626)
• Added an option to omit potentially-identifying information (e.g. User-Agent and date created) when creating new torrents. (#3452)
• The Web client has been rewritten and now supports mobile use.
• When creating new torrents, users can now specify the piece size. (#3768, #3145, #2805)
• IPv6 blocklists are now supported. (#3835)
• Beginning with 4.0.0-beta.1, Transmission releases now use semver versioning.
• Dozens of other new features -- too many to list here! We've been working on this for a year!

What's New Since 4.0.0-beta.3

libtransmission (All Platforms)

• Added a new setting, torrent-added-verify-mode, to force-verify added torrents. (#4611)
• Improved handling of webseed servers that do not support Range requests or 206 Partial Content. (#4601)
• Improved handling of webseed servers that return a content-encoding that was not requested. (#4609)
• Fixed 4.0.0-beta.3 potential socket leak. (#4616)
• Fixed 4.0.0-beta.3 regression that failed to detect largefile build flags on 32bit systems. (#4627)
• Fixed 4.0.0-beta.1 UI bug when removing a tracker from the announce list. (#4635)
• Improved error handling when receiving corrupt piece data from peers. (#4665)
• Fixed 4.0.0-beta.1 FTBFS error on CentOS 7. (#4673, #4675)
• Made small performance improvements in libtransmission. (#4577, #4679)
• Dropped libiconv dependency in libtransmission. (#4565)
• Updated 403 RPC error message. (#4567)
• Bumped libdeflate snapshot to 1.17. (#4596)

macOS Client

• Fixed two Help menus in macOS. (#4500)
• Fixed bug that caused magnet links to always be paused when added. (#4528)
• Fixed 4.0.0-beta.1 regression that broke the Piece View "blinking" when a piece completes. (#4587)
• Ensured that the preferences window is centered the first time it is shown. (#4659)
• Fixed 4.0.0-beta.1 regression that incorrectly handled corrupt blocklists. (#4705)
• Increased the font size in the main window's torrent list. (#4557)
• Fixed libpsl dependency build issue on macOS. (#4642)

Qt Client

• Made display order of speed limits consistent between Properties, Details dialogs. (#4677)

GTK Client

• Fixed 4.0.0-beta.1 regression making it impossible to close "Set location" dialog (GTK 3 only). (#4625)
• Fixed 4.0.0-beta.2 regression leading to crash during progress bars rendering on some systems. (#4688)

Web Client

• Fixed 4.0.0-beta.1 potential crash when detecting mime-types. (#4569)
• Fixed 4.0.0-beta.1 regression that broke file priority buttons in the web client. (#4610)

Daemon

• Fixed stderr logging issue when running as a systemd unit. (#4612)

transmission-remote

• Fixed 4.0.0-beta.1 regression when displaying session info. (#4624)
• Fixed 4.0.0-beta.1 regression when displaying tracker info. (#4633)

Thank You!

Last but certainly not least, a big Thank You to these people who contributed after 4.0.0-beta.3:

Contributions to libtransmission (All Platforms):

• @dmantipov (Dmitry Antipov):
  • Chore: simplify announcer add callback. (#4573)
  • Refactor: use std::function for announcer callback. (#4575)
  • Refactor: switch to C++11-compatible tr_wait() from tr_wait_msec(). (#4576)
  • Made small performance improvements in libtransmission. (#4577)
  • Made small performance improvements in libtransmission. (#4679)
• @InsaneKnight:
  • Fixed 4.0.0-beta.3 potential socket leak. (#4616)
• @nevack (Dzmitry Neviadomski):
  • Code review for #4576

Contributions to macOS Client:

• @cfauchereau (Clément Fauchereau):
  • Fixed two Help menus in macOS. (#4500)
• @DevilDimon (Dmitry Serov):
  • Code review for #4500, #4692
• @GaryElshaw (Gary Elshaw):
  • Increased the font size in the main window's torrent list. (#4557)
• @nevack (Dzmitry Neviadomski):
  • Code review for #4500, #4692
  • Fixed 4.0.0-beta.1 regression that incorrectly handled corrupt blocklists. (#4705)
• @sweetppro (SweetPPro):
  • Fixed bug that caused magnet links to always be paused when added. (#4528)

Contributions to Qt Client:

• @anarcat (anarcat):
  • Added remote HTTPS support to Qt GUI. (#4622)
• @GaryElshaw (Gary Elshaw):
  • Removed 'Message Log' item from Qt sys tray. (#4656)
• @Schlossgeist (Nick):
  • Quick fix: changed order of some session prefs. (#4676)

Contributions to Web Client:

• @dareiff (Derek Reiff):
  • Fixed 4.0.0-beta.1 regression that broke file priority buttons in the web client. (#4610)

Contributions to Daemon:

• @dmantipov (Dmitry Antipov):
  • Fixed stderr logging issue when running as a systemd unit. (#4612)

Contributions to transmission-remote:

• @lajp (Luukas Pörtfors):
  • Fixed 4.0.0-beta.1 regression when displaying session info. (#4624)
  • Fixed 4.0.0-beta.1 regression when displaying tracker info. (#4633)

Contributions to Everything Else:

• @progiv (progiv):
  • Fixed GitHub CI actions warning for set-output. (#4564)
• @t-8ch (Thomas Weißschuh):
  • Code review for #4637

New Contributors since 3.00

• @1100101 made their first contribution in #2040
• @acchang made their first contribution in #3729
• @anacrolix made their first contribution in #2275
• @anarcat made their first contribution in #4622
• @AndreyPavlenko made their first contribution in #585
• @azy5030 made their first contribution in #2805
• @BENICHN made their first contribution in #1760
• @Berbe made their first contribution in #1417
• @bexnoss made their first contribution in #2201
• @bkuhls made their first contribution in #2576
• @buckmelanoma made their first contribution in #2179
• @BunioFH made their first contribution in #2284
• @candrews made their first contribution in #2573
• @carandraug made their first contribution in #3452
• @cfauchereau made their first contribution in #4500
• @Chrool made their first contribution in #1447
• @CodeWitchBella made their first contribution in #2874
• @cpba made their first contribution in #1487
• @Dachtire made their first contribution in #3736
• @dareiff made their first contribution in #3985
• @dbeinder made their first contribution in #2799
• @deepwell made their first contribution in #1681
• @dependabot made their first contribution in #1559
• @depler made their first contribution in #2066
• @dmantipov made their first contribution in #3766
• @evils made their first contribution in #2204
• @ewtoombs made their first contribution in #3049
• @FallenWarrior2k made their first contribution in #2721
• @federicobond made their first contribution in #1441
• @FluxState made their first contribution in #2586
• @foobar-d made their first contribution in #2847
• @fxcoudert made their first contribution in #2234
• @GaryElshaw made their first contribution in #2779
• @GermanAizek made their first contribution in #4172
• @ghazel made their first contribution in #3447
• @github-actions made their first contribution in #4664
• @goldsteinn made their first contribution in #2933
• @guidocella made their first contribution in #1080
• @guidovranken made their first contribution in #3600
• @Harm133 made their first contribution in #3835
• @ile6695 made their first contribution in #2508
• @IMurzich made their first contribution in #3739
• @InsaneKnight made their first contribution in #4616
• @johman10 made their first contribution in #1682
• @jonasmalacofilho made their first contribution in #2232
• @JP-Ellis made their first contribution in #2812
• @kakuhen made their first contribution in #2690
• @Kobaxidze256 made their first contribution in #3552
• @koro666 made their first contribution in #1405
• @kvakvs made their first contribution in #1799
• @Kwstubbs made their first contribution in #4125
• @L2501 made their first contribution in #3750
• @lajp made their first contribution in #2905
• @Lanzaa made their first contribution in #3380
• @lucaxvi made their first contribution in #3655
• @luzpaz made their first contribution in #3743
• @lvella made their first contribution in #1660
• @MatanZ made their first contribution in #2761
• @maxz made their first contribution in #2875
• @meskobalazs made their first contribution in #3210
• @mickaelifs made their first contribution in #1602
• @mlopezfm made their first contribution in #2549
• @mymedia2 made their first contribution in #1354
• @Narthorn made their first contribution in #1638
• @npapke made their first contribution in #1619
• @Oleg-Chashko made their first contribution in #1923
• @orbital-mango made their first contribution in #3124
• @OscarCunningham made their first contribution in #3814
• @pborzenkov made their first contribution in #1251
• @pedrinho made their first contribution in #1313
• @piec made their first contribution in #1328
• @progiv made their first contribution in #4564
• @pudymody made their first contribution in #3927
• @pyrovski made their first contribution in #715
• @razaqq made their first contribution in #2053
• @robd003 made their first contribution in #3669
• @rsekman made their first contribution in #3201
• @saidinesh5 made their first contribution in #1161
• @sammarcus made their first contribution in #459
• @sandervankasteel made their first contribution in #1885
• @Schlossgeist made their first contribution in #4676
• @sewe2000 made their first contribution in #3121
• @shelvacu made their first contribution in #1900
• @shenhanc78 made their first contribution in #1282
• @shric made their first contribution in #1326
• @sio made their first contribution in #893
• @sir-sigurd made their first contribution in #1040
• @smrtrfszm made their first contribution in #4363
• @stefantalpalaru made their first contribution in #4343
• @subdan made their first contribution in #4245
• @sweetppro made their first contribution in #2654
• @tinselcity made their first contribution in #4409
• @ToKe79 made their first contribution in #2071
• @trainto made their first contribution in #1489
• @tylergibbs2 made their first contribution in #1808
• @uiryuu made their first contribution in #3962
• @uprt made their first contribution in #857
• @varesa made their first contribution in #1633
• @vchimishuk made their first contribution in #1364
• @ViktorOn made their first contribution in #3710
• @vuori made their first contribution in #265
• @wiz78 made their first contribution in #874
• @wsy2220 made their first contribution in #4684
• @xavery made their first contribution in #851
• @Xist12gh made their first contribution in #3756
• @yarons made their first contribution in #3996