view tests/test-narrow-clone-no-ellipsis.t @ 36426:23d12524a202

http: drop custom http client logic

Eight and a half years ago, as my starter bug on code.google.com, I
investigated a mysterious "broken pipe" error from seemingly random
clients[0]. That investigation revealed a tragic story: the Python
standard library's httplib was (and remains) barely functional. During
large POSTs, if a server responds early with an error (even a
permission denied error!) the client only notices that the server
closed the connection and everything breaks. Such server behavior is
implicitly legal under RFC 2616 (the latest HTTP RFC as of when I was
last working on this), and my understanding is that later RFCs have
made it explicitly legal to respond early with any status code outside
the 2xx range.

I embarked, probably foolishly, on a journey to write a new http
library with better overall behavior. The http library appears to work
well in most cases, but it can get confused in the presence of
proxies, and it depends on select(2) which limits its utility if a lot
of file descriptors are open. I haven't touched the http library in
almost two years, and in the interim the Python community has
discovered a better way[1] of writing network code. In theory some day
urllib3 will have its own home-grown http library built on h11[2], or
we could do that. Either way, it's time to declare our current
confusingly-named "http2" client logic and move on. I do hope to
revisit this some day: it's still garbage that we can't even respond
with a 401 or 403 without reading the entire POST body from the
client, but the goalposts on writing a new http client library have
moved substantially. We're almost certainly better off just switching
to requests and eventually picking up their http fixes than trying to
live with something that realistically only we'll ever use. Another
approach would be to write an adapter so that Mercurial can use pycurl
if it's installed. Neither of those approaches seem like they should
be investigated prior to a release of Mercurial that works on Python
3: that's where the mindshare is going to be for any improvements to
the state of the http client art.

0: http://web.archive.org/web/20130501031801/http://code.google.com/p/support/issues/detail?id=2716
1: http://sans-io.readthedocs.io/
2: https://github.com/njsmith/h11

Differential Revision: https://phab.mercurial-scm.org/D2444

  $ . "$TESTDIR/narrow-library.sh"

  $ hg init master
  $ cd master
  $ mkdir dir
  $ mkdir dir/src
  $ cd dir/src
  $ for x in `$TESTDIR/seq.py 20`; do echo $x > "f$x"; hg add "f$x"; hg commit -m "Commit src $x"; done
  $ cd ..
  $ mkdir tests
  $ cd tests
  $ for x in `$TESTDIR/seq.py 20`; do echo $x > "t$x"; hg add "t$x"; hg commit -m "Commit test $x"; done
  $ cd ../../..

narrow clone a file, f10

  $ hg clone --narrow ssh://user@dummy/master narrow --noupdate --include "dir/src/f10"
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 40 changesets with 1 changes to 1 files
  new changesets *:* (glob)
  $ cd narrow
  $ cat .hg/requires | grep -v generaldelta
  dotencode
  fncache
  narrowhg-experimental
  revlogv1
  store

  $ cat .hg/narrowspec
  [includes]
  path:dir/src/f10
  [excludes]
  $ hg update
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ find * | sort
  dir
  dir/src
  dir/src/f10
  $ cat dir/src/f10
  10

  $ cd ..

narrow clone a directory, tests/, except tests/t19

  $ hg clone --narrow ssh://user@dummy/master narrowdir --noupdate --include "dir/tests/" --exclude "dir/tests/t19"
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 40 changesets with 19 changes to 19 files
  new changesets *:* (glob)
  $ cd narrowdir
  $ cat .hg/narrowspec
  [includes]
  path:dir/tests
  [excludes]
  path:dir/tests/t19
  $ hg update
  19 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ find * | sort
  dir
  dir/tests
  dir/tests/t1
  dir/tests/t10
  dir/tests/t11
  dir/tests/t12
  dir/tests/t13
  dir/tests/t14
  dir/tests/t15
  dir/tests/t16
  dir/tests/t17
  dir/tests/t18
  dir/tests/t2
  dir/tests/t20
  dir/tests/t3
  dir/tests/t4
  dir/tests/t5
  dir/tests/t6
  dir/tests/t7
  dir/tests/t8
  dir/tests/t9

  $ cd ..

narrow clone everything but a directory (tests/)

  $ hg clone --narrow ssh://user@dummy/master narrowroot --noupdate --exclude "dir/tests"
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 40 changesets with 20 changes to 20 files
  new changesets *:* (glob)
  $ cd narrowroot
  $ cat .hg/narrowspec
  [includes]
  path:.
  [excludes]
  path:dir/tests
  $ hg update
  20 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ find * | sort
  dir
  dir/src
  dir/src/f1
  dir/src/f10
  dir/src/f11
  dir/src/f12
  dir/src/f13
  dir/src/f14
  dir/src/f15
  dir/src/f16
  dir/src/f17
  dir/src/f18
  dir/src/f19
  dir/src/f2
  dir/src/f20
  dir/src/f3
  dir/src/f4
  dir/src/f5
  dir/src/f6
  dir/src/f7
  dir/src/f8
  dir/src/f9

  $ cd ..