tests/test-censor.t

changegroup: remove reordering control (BC)

This logic - including the experimental bundle.reorder option -
was originally added in a8e3931e3fb5 in 2011 and then later ported
to changegroup.py.

The intent of this option and associated logic is to control
the ordering of revisions in deltagroups in changegroups. At the
time it was implemented, only changegroup version 1 existed
and generaldelta revlogs were just coming into the world. Changegroup
version 1 requires that deltas be made against the last revision
sent over the wire. Used with generaldelta, this created an
impedance mismatch of sorts and resulted in changegroup producers
spending a lot of time recomputing deltas.

Revision reordering was introduced so outgoing revisions would be
sent in "generaldelta order" and producers would be able to
reuse internal deltas from storage.

Later on, we introduced changegroup version 2. It supported denoting
which revision a delta was against. So we no longer needed to
sort outgoing revisions to ensure optimal delta generation from the
producer. So, subsequent changegroup versions disabled reordering.

We also later made the changelog not store deltas by default. And
we also made the changelog send out deltas in storage order. Why we
do this for changelog, I'm not sure. Maybe we want to preserve revision
order across clones? It doesn't really matter for this commit.

Fast forward to 2018. We want to abstract storage backends. And having
changegroup code require knowledge about how deltas are stored
internally interferes with that goal.

This commit removes reordering control from changegroup generation.
After this commit, the reordering behavior is:

* The changelog is always sent out in storage order (no behavior
  change).
* Non-changelog generaldelta revlogs are reordered to always be in DAG
  topological order (previously, generaldelta revlogs would be emitted
  in storage order for version 2 and 3 changegroups).
* Non-changelog non-generaldelta revlogs are sent in storage order (no
  behavior change).
* There exists no config option to override behavior.

The big difference here is that generaldelta revlogs now *always* have
their revisions sorted in DAG order before going out over the wire. This
behavior was previously only done for changegroup version 1. Version 2
and version 3 changegroups disabled reordering because the interchange
format supported encoding arbitrary delta parents, so reordering wasn't
strictly necessary.

I can think of a few significant implications for this change.

Because changegroup receivers will now see non-changelog revisions
in DAG order instead of storage order, the internal storage order of
manifests and files may differ substantially between producer and
consumer. I don't think this matters that much, since the storage
order of manifests and files is largely hidden from users. Only
the storage order of changelog matters (because `hg log` shows the
changelog in storage order). I don't think there should be any
controversy here.

The reordering of revisions has implications for changegroup producers.
Previously, generaldelta revlogs would be emitted in storage order.
And in the common case, the internally-stored delta could effectively
be copied from disk into the deltagroup delta. This meant that emitting
delta groups for generaldelta revlogs would be mostly linear read I/O.
This is desirable for performance. With us now reordering generaldelta
revlog revisions in DAG order, the read operations may use more random
I/O instead of sequential I/O. This could result in performance
loss. But with the prevalence of SSDs and fast random I/O, I'm not
too worried. (Note: the optimal emission order for revlogs is actually
delta encoding order. But the changegroup code wasn't doing that before
or after this change. We could potentially implement that in a later
commit.)

Changegroups in DAG order will have implications for receivers.
Previously, receiving storage order might mean seeing a number of
interleaved branches. This would mean long delta chains, sparse
I/O, and possibly more fulltext revisions instead of deltas, blowing
up storage storage. (This is the same set of problems that sparse
revlogs aims to address.) With the producer now sending revisions in DAG
order, the receiver also stores revisions in DAG order. That means
revisions for the same DAG branch are all grouped together. And this
should yield better storage outcomes. In other words, sending the
reordered changegroup allows the receiver to have better storage
order and for the producer to not propagate its (possibly sub-optimal)
internal storage order.

On the mozilla-unified repository, this change influences bundle
generation:

$ hg bundle -t none-v2 -a
before: time: real 355.680 secs (user 256.790+0.000 sys 16.820+0.000)
after:  time: real 382.950 secs (user 281.700+0.000 sys 17.690+0.000)

before: 7,150,228,967 bytes (uncompressed)
after:  7,041,556,273 bytes (uncompressed)

before: 1,669,063,234 bytes (zstd l=3)
after:  1,628,598,830 bytes (zstd l=3)

$ hg unbundle
before: time: real 511.910 secs (user 466.750+0.000 sys 32.680+0.000)
after:  time: real 487.790 secs (user 443.940+0.000 sys 30.840+0.000)

00manifest.d size:
source: 274,924,292 bytes
before: 304,741,626 bytes
after:  245,252,087 bytes

.hg/store total file size:
source: 2,649,133,490
before: 2,680,888,130
after:  2,627,875,673

We see the bundle size drop. That's probably because if a revlog
internally isn't storing a delta, it will choose to delta against
the last emitted revision. And on repos with interleaved branches
(like mozilla-unified), the previous revision could be an unrelated
branch and therefore be a large delta. But with this patch, the
previous revision is likely p1 or p2 and a delta should be small.

We also see the manifest size drop by ~50 MB. It's worth noting that
the manifest actually *increased* in size by ~25 MB in the old
strategy and decreased ~25 MB from its source in the new strategy.
Again, my explanation for this is that the DAG ordering in the
changegroup is resulting in better grouping of revisions in the
receiver, which results in more compact delta chains and higher
storage efficiency.

Unbundle time also dropped. I suspect this is due to the revlog having
to work less to compute deltas since the incoming deltas are more
optimal. i.e. the receiver spends less time resolving fulltext
revisions as incoming deltas bounce around between DAG branches and
delta chains.

We also see bundle generation time increase. This is not desirable.
However, the regression is only significant on the original repository:
if we generate a bundle from the repository created from the new,
always reordered bundles, we're close to baseline (if not at it with
expected noise):

$ hg bundle -t none-v2 -a
before (original): time: real 355.680 secs (user 256.790+0.000 sys 16.820+0.000)
after (original):  time: real 382.950 secs (user 281.700+0.000 sys 17.690+0.000)
after (new repo):  time: real 362.280 secs (user 260.300+0.000 sys 17.700+0.000)

This regression is a bit worrying because it will impact serving
canonical repositories (that don't have optimal internal storage
unless they are reordered - possibly as part of running
`hg debugupgraderepo`). However, this regression will only be
noticed by very large changegroups. And I'm guessing/hoping that
any repository that large is using clonebundles to mitigate server
load.

Again, sending DAG order isn't the optimal send order for servers:
sending in storage-delta order is. But in order to enable
storage-optimal send order, we'll need a storage API that handles
sorting. Future commits will introduce such an API.

Differential Revision: https://phab.mercurial-scm.org/D4721

#require no-reposimplestore

  $ 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
  checked 5 changesets with 7 changes to 2 files
  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
  checked 5 changesets with 7 changes to 2 files

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
  checked 12 changesets with 13 changes to 2 files

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
  checked 1 changesets with 2 changes to 2 files
  $ hg pull -r $H1 -r $H2
  pulling from $TESTTMP/r
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 11 changesets with 11 changes to 2 files (+1 heads)
  new changesets 186fb27560c3:683e4645fded
  (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
  checked 12 changesets with 13 changes to 2 files

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
  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)
  new changesets 075be80ac777:dcbaf17bf3a1 (2 drafts)
  (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
  checked 14 changesets with 15 changes to 2 files

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)
  new changesets e97f55b2665a:dcbaf17bf3a1
  (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)
  new changesets efbe78065929:683e4645fded (6 drafts)
  (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
  checked 14 changesets with 15 changes to 2 files
  $ 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
  new changesets e97f55b2665a (1 drafts)
  (run 'hg update' to get a working copy)
  $ hg cat -r 0 target