view tests/test-censor.t @ 26623:5a95fe44121d

clonebundles: support for seeding clones from pre-generated bundles

Cloning can be an expensive operation for servers because the server
generates a bundle from existing repository data at request time. For
a large repository like mozilla-central, this consumes 4+ minutes
of CPU time on the server. It also results in significant network
utilization. Multiplied by hundreds or even thousands of clients and
the ensuing load can result in difficulties scaling the Mercurial server.

Despite generation of bundles being deterministic until the next
changeset is added, the generation of bundles to service a clone request
is not cached. Each clone thus performs redundant work. This is
wasteful.

This patch introduces the "clonebundles" extension and related
client-side functionality to help alleviate this deficiency. The
client-side feature is behind an experimental flag and is not enabled by
default.

It works as follows:

1) Server operator generates a bundle and makes it available on a
   server (likely HTTP).
2) Server operator defines the URL of a bundle file in a
   .hg/clonebundles.manifest file.
3) Client `hg clone`ing sees the server is advertising bundle URLs.
4) Client fetches and applies the advertised bundle.
5) Client performs equivalent of `hg pull` to fetch changes made since
   the bundle was created.

Essentially, the server performs the expensive work of generating a
bundle once and all subsequent clones fetch a static file from
somewhere. Scaling static file serving is a much more manageable
problem than scaling a Python application like Mercurial. Assuming your
repository grows less than 1% per day, the end result is 99+% of CPU
and network load from clones is eliminated, allowing Mercurial servers
to scale more easily. Serving static files also means data can be
transferred to clients as fast as they can consume it, rather than as
fast as servers can generate it. This makes clones faster.

Mozilla has implemented similar functionality of this patch on
hg.mozilla.org using a custom extension. We are hosting bundle files in
Amazon S3 and CloudFront (a CDN) and have successfully offloaded
>1 TB/day in data transfer from hg.mozilla.org, freeing up significant
bandwidth and CPU resources. The positive impact has been stellar and
I believe it has proved its value to be included in Mercurial core. I
feel it is important for the client-side support to be enabled in core
by default because it means that clients will get faster, more reliable
clones and will enable server operators to reduce load without
requiring any client-side configuration changes (assuming clients are
up to date, of course).

The scope of this feature is narrowly and specifically tailored to
cloning, despite "serve pulls from pre-generated bundles" being a valid
and useful feature. I would eventually like for Mercurial servers to
support transferring *all* repository data via statically hosted files.
You could imagine a server that siphons all pushed data to bundle files
and instructs clients to apply a stream of bundles to reconstruct all
repository data. This feature, while useful and powerful, is
significantly more work to implement because it requires the server
component have awareness of discovery and a mapping of which changesets
are in which files. Full, clone bundles, by contrast, are much simpler.

The wire protocol command is named "clonebundles" instead of something
more generic like "staticbundles" to leave the door open for a new, more
powerful and more generic server-side component with minimal backwards
compatibility implications. The name "bundleclone" is used by Mozilla's
extension and would cause problems since there are subtle differences
in Mozilla's extension.

Mozilla's experience with this idea has taught us that some form of
"content negotiation" is required. Not all clients will support all
bundle formats or even URLs (advanced TLS requirements, etc). To ensure
the highest uptake possible, a server needs to advertise multiple
versions of bundles and clients need to be able to choose the most
appropriate from that list one. The "attributes" in each
server-advertised entry facilitate this filtering and sorting. Their
use will become apparent in subsequent patches.

Initial inspiration and credit for the idea of cloning from static files
belongs to Augie Fackler and his "lookaside clone" extension proof of
concept.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > censor=
  > EOF
  $ cp $HGRCPATH $HGRCPATH.orig

Create repo with unimpeachable content

  $ hg init r
  $ cd r
  $ echo 'Initially untainted file' > target
  $ echo 'Normal file here' > bystander
  $ hg add target bystander
  $ hg ci -m init

Clone repo so we can test pull later

  $ cd ..
  $ hg clone r rpull
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd r

Introduce content which will ultimately require censorship. Name the first
censored node C1, second C2, and so on

  $ echo 'Tainted file' > target
  $ echo 'Passwords: hunter2' >> target
  $ hg ci -m taint target
  $ C1=`hg id --debug -i`

  $ echo 'hunter3' >> target
  $ echo 'Normal file v2' > bystander
  $ hg ci -m moretaint target bystander
  $ C2=`hg id --debug -i`

Add a new sanitized versions to correct our mistake. Name the first head H1,
the second head H2, and so on

  $ echo 'Tainted file is now sanitized' > target
  $ hg ci -m sanitized target
  $ H1=`hg id --debug -i`

  $ hg update -r $C2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo 'Tainted file now super sanitized' > target
  $ hg ci -m 'super sanitized' target
  created new head
  $ H2=`hg id --debug -i`

Verify target contents before censorship at each revision

  $ hg cat -r $H1 target
  Tainted file is now sanitized
  $ hg cat -r $H2 target
  Tainted file now super sanitized
  $ hg cat -r $C2 target
  Tainted file
  Passwords: hunter2
  hunter3
  $ hg cat -r $C1 target
  Tainted file
  Passwords: hunter2
  $ hg cat -r 0 target
  Initially untainted file

Try to censor revision with too large of a tombstone message

  $ hg censor -r $C1 -t 'blah blah blah blah blah blah blah blah bla' target
  abort: censor tombstone must be no longer than censored data
  [255]

Censor revision with 2 offenses

(this also tests file pattern matching: path relative to cwd case)

  $ mkdir -p foo/bar/baz
  $ hg --cwd foo/bar/baz censor -r $C2 -t "remove password" ../../../target
  $ hg cat -r $H1 target
  Tainted file is now sanitized
  $ hg cat -r $H2 target
  Tainted file now super sanitized
  $ hg cat -r $C2 target
  abort: censored node: 1e0247a9a4b7
  (set censor.policy to ignore errors)
  [255]
  $ hg cat -r $C1 target
  Tainted file
  Passwords: hunter2
  $ hg cat -r 0 target
  Initially untainted file

Censor revision with 1 offense

(this also tests file pattern matching: with 'path:' scheme)

  $ hg --cwd foo/bar/baz censor -r $C1 path:target
  $ hg cat -r $H1 target
  Tainted file is now sanitized
  $ hg cat -r $H2 target
  Tainted file now super sanitized
  $ hg cat -r $C2 target
  abort: censored node: 1e0247a9a4b7
  (set censor.policy to ignore errors)
  [255]
  $ hg cat -r $C1 target
  abort: censored node: 613bc869fceb
  (set censor.policy to ignore errors)
  [255]
  $ hg cat -r 0 target
  Initially untainted file

Can only checkout target at uncensored revisions, -X is workaround for --all

  $ hg revert -r $C2 target
  abort: censored node: 1e0247a9a4b7
  (set censor.policy to ignore errors)
  [255]
  $ hg revert -r $C1 target
  abort: censored node: 613bc869fceb
  (set censor.policy to ignore errors)
  [255]
  $ hg revert -r $C1 --all
  reverting bystander
  reverting target
  abort: censored node: 613bc869fceb
  (set censor.policy to ignore errors)
  [255]
  $ hg revert -r $C1 --all -X target
  $ cat target
  Tainted file now super sanitized
  $ hg revert -r 0 --all
  reverting target
  $ cat target
  Initially untainted file
  $ hg revert -r $H2 --all
  reverting bystander
  reverting target
  $ cat target
  Tainted file now super sanitized

Uncensored file can be viewed at any revision

  $ hg cat -r $H1 bystander
  Normal file v2
  $ hg cat -r $C2 bystander
  Normal file v2
  $ hg cat -r $C1 bystander
  Normal file here
  $ hg cat -r 0 bystander
  Normal file here

Can update to children of censored revision

  $ hg update -r $H1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Tainted file is now sanitized
  $ hg update -r $H2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Tainted file now super sanitized

Set censor policy to abort in trusted $HGRC so hg verify fails

  $ cp $HGRCPATH.orig $HGRCPATH
  $ cat >> $HGRCPATH <<EOF
  > [censor]
  > policy = abort
  > EOF

Repo fails verification due to censorship

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
   target@1: censored file data
   target@2: censored file data
  2 files, 5 changesets, 7 total revisions
  2 integrity errors encountered!
  (first damaged changeset appears to be 1)
  [1]

Cannot update to revision with censored data

  $ hg update -r $C2
  abort: censored node: 1e0247a9a4b7
  (set censor.policy to ignore errors)
  [255]
  $ hg update -r $C1
  abort: censored node: 613bc869fceb
  (set censor.policy to ignore errors)
  [255]
  $ hg update -r 0
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg update -r $H2
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

Set censor policy to ignore in trusted $HGRC so hg verify passes

  $ cp $HGRCPATH.orig $HGRCPATH
  $ cat >> $HGRCPATH <<EOF
  > [censor]
  > policy = ignore
  > EOF

Repo passes verification with warnings with explicit config

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 5 changesets, 7 total revisions

May update to revision with censored data with explicit config

  $ hg update -r $C2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  $ hg update -r $C1
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  $ hg update -r 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Initially untainted file
  $ hg update -r $H2
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Tainted file now super sanitized

Can merge in revision with censored data. Test requires one branch of history
with the file censored, but we can't censor at a head, so advance H1.

  $ hg update -r $H1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ C3=$H1
  $ echo 'advanced head H1' > target
  $ hg ci -m 'advance head H1' target
  $ H1=`hg id --debug -i`
  $ hg censor -r $C3 target
  $ hg update -r $H2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge -r $C3
  merging target
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

Revisions present in repository heads may not be censored

  $ hg update -C -r $H2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg censor -r $H2 target
  abort: cannot censor file in heads (78a8fc215e79)
  (clean/delete and commit first)
  [255]
  $ echo 'twiddling thumbs' > bystander
  $ hg ci -m 'bystander commit'
  $ H2=`hg id --debug -i`
  $ hg censor -r "$H2^" target
  abort: cannot censor file in heads (efbe78065929)
  (clean/delete and commit first)
  [255]

Cannot censor working directory

  $ echo 'seriously no passwords' > target
  $ hg ci -m 'extend second head arbitrarily' target
  $ H2=`hg id --debug -i`
  $ hg update -r "$H2^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg censor -r . target
  abort: cannot censor working directory
  (clean/delete/update first)
  [255]
  $ hg update -r $H2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Can re-add file after being deleted + censored

  $ C4=$H2
  $ hg rm target
  $ hg ci -m 'delete target so it may be censored'
  $ H2=`hg id --debug -i`
  $ hg censor -r $C4 target
  $ hg cat -r $C4 target
  $ hg cat -r "$H2^^" target
  Tainted file now super sanitized
  $ echo 'fresh start' > target
  $ hg add target
  $ hg ci -m reincarnated target
  $ H2=`hg id --debug -i`
  $ hg cat -r $H2 target
  fresh start
  $ hg cat -r "$H2^" target
  target: no such file in rev 452ec1762369
  [1]
  $ hg cat -r $C4 target
  $ hg cat -r "$H2^^^" target
  Tainted file now super sanitized

Can censor after revlog has expanded to no longer permit inline storage

  $ for x in `python $TESTDIR/seq.py 0 50000`
  > do
  >   echo "Password: hunter$x" >> target
  > done
  $ hg ci -m 'add 100k passwords'
  $ H2=`hg id --debug -i`
  $ C5=$H2
  $ hg revert -r "$H2^" target
  $ hg ci -m 'cleaned 100k passwords'
  $ H2=`hg id --debug -i`
  $ hg censor -r $C5 target
  $ hg cat -r $C5 target
  $ hg cat -r $H2 target
  fresh start

Repo with censored nodes can be cloned and cloned nodes are censored

  $ cd ..
  $ hg clone r rclone
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd rclone
  $ hg cat -r $H1 target
  advanced head H1
  $ hg cat -r $H2~5 target
  Tainted file now super sanitized
  $ hg cat -r $C2 target
  $ hg cat -r $C1 target
  $ hg cat -r 0 target
  Initially untainted file
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 12 changesets, 13 total revisions

Repo cloned before tainted content introduced can pull censored nodes

  $ cd ../rpull
  $ hg cat -r tip target
  Initially untainted file
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 1 changesets, 2 total revisions
  $ hg pull -r $H1 -r $H2
  pulling from $TESTTMP/r (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 11 changesets with 11 changes to 2 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg update 4
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Tainted file now super sanitized
  $ hg cat -r $H1 target
  advanced head H1
  $ hg cat -r $H2~5 target
  Tainted file now super sanitized
  $ hg cat -r $C2 target
  $ hg cat -r $C1 target
  $ hg cat -r 0 target
  Initially untainted file
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 12 changesets, 13 total revisions

Censored nodes can be pushed if they censor previously unexchanged nodes

  $ echo 'Passwords: hunter2hunter2' > target
  $ hg ci -m 're-add password from clone' target
  created new head
  $ H3=`hg id --debug -i`
  $ REV=$H3
  $ echo 'Re-sanitized; nothing to see here' > target
  $ hg ci -m 're-sanitized' target
  $ H2=`hg id --debug -i`
  $ CLEANREV=$H2
  $ hg cat -r $REV target
  Passwords: hunter2hunter2
  $ hg censor -r $REV target
  $ hg cat -r $REV target
  $ hg cat -r $CLEANREV target
  Re-sanitized; nothing to see here
  $ hg push -f -r $H2
  pushing to $TESTTMP/r (glob)
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files (+1 heads)

  $ cd ../r
  $ hg cat -r $REV target
  $ hg cat -r $CLEANREV target
  Re-sanitized; nothing to see here
  $ hg update $CLEANREV
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Re-sanitized; nothing to see here

Censored nodes can be bundled up and unbundled in another repo

  $ hg bundle --base 0 ../pwbundle
  13 changesets found
  $ cd ../rclone
  $ hg unbundle ../pwbundle
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files (+1 heads)
  (run 'hg heads .' to see heads, 'hg merge' to merge)
  $ hg cat -r $REV target
  $ hg cat -r $CLEANREV target
  Re-sanitized; nothing to see here
  $ hg update $CLEANREV
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Re-sanitized; nothing to see here
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 14 changesets, 15 total revisions

Censored nodes can be imported on top of censored nodes, consecutively

  $ hg init ../rimport
  $ hg bundle --base 1 ../rimport/splitbundle
  12 changesets found
  $ cd ../rimport
  $ hg pull -r $H1 -r $H2 ../r
  pulling from ../r
  adding changesets
  adding manifests
  adding file changes
  added 8 changesets with 10 changes to 2 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg unbundle splitbundle
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 5 changes to 2 files (+1 heads)
  (run 'hg heads .' to see heads, 'hg merge' to merge)
  $ hg update $H2
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat target
  Re-sanitized; nothing to see here
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 14 changesets, 15 total revisions
  $ cd ../r

Can import bundle where first revision of a file is censored

  $ hg init ../rinit
  $ hg censor -r 0 target
  $ hg bundle -r 0 --base null ../rinit/initbundle
  1 changesets found
  $ cd ../rinit
  $ hg unbundle initbundle
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 2 changes to 2 files
  (run 'hg update' to get a working copy)
  $ hg cat -r 0 target