wireproto: add request IDs to frames
One of my primary goals with the new wire protocol is to make
operations faster and enable both client and server-side
operations to scale to multiple CPU cores.
One of the ways we make server interactions faster is by reducing
the number of round trips to that server.
With the existing wire protocol, the "batch" command facilitates
executing multiple commands from a single request payload. The way
it works is the requests for multiple commands are serialized. The
server executes those commands sequentially then serializes all
their results. As an optimization for reducing round trips, this
is very effective. The technical implementation, however, is pretty
bad and suffers from a number of deficiencies. For example, it
creates a new place where authorization to run a command must be
checked. (The lack of this checking in older Mercurial releases
was CVE-2018-1000132.)
The principles behind the "batch" command are sound. However, the
execution is not. Therefore, I want to ditch "batch" in the
new wire protocol and have protocol level support for issuing
multiple requests in a single round trip.
This commit introduces support in the frame-based wire protocol to
facilitate this. We do this by adding a "request ID" to each frame.
If a server sees frames associated with different "request IDs," it
handles them as separate requests. All of this happening possibly
as part of the same message from client to server (the same request
body in the case of HTTP).
We /could/ model the exchange the way pipelined HTTP requests do,
where the server processes requests in order they are issued and
received. But this artifically constrains scalability. A better
model is to allow multi-requests to be executed concurrently and
for responses to be sent and handled concurrently. So the
specification explicitly allows this. There is some work to be done
around specifying dependencies between multi-requests. We take
the easy road for now and punt on this problem, declaring that
if order is important, clients must not issue the request until
responses to dependent requests have been received.
This commit focuses on the boilerplate of implementing the request
ID. The server reactor still can't manage multiple, in-flight
request IDs. This will be addressed in a subsequent commit.
Because the wire semantics have changed, we bump the version of the
media type.
Differential Revision: https://phab.mercurial-scm.org/D2869
Test the EOL hook
$ hg init main
$ cat > main/.hg/hgrc <<EOF
> [hooks]
> pretxnchangegroup = python:hgext.eol.hook
> EOF
$ hg clone main fork
updating to branch default
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd fork
Create repo
$ cat > .hgeol <<EOF
> [patterns]
> mixed.txt = BIN
> crlf.txt = CRLF
> **.txt = native
> EOF
$ hg add .hgeol
$ hg commit -m 'Commit .hgeol'
$ printf "first\nsecond\nthird\n" > a.txt
$ hg add a.txt
$ hg commit -m 'LF a.txt'
$ hg push ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files
$ printf "first\r\nsecond\r\nthird\n" > a.txt
$ hg commit -m 'CRLF a.txt'
$ hg push ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
error: pretxnchangegroup hook failed: end-of-line check failed:
a.txt in a8ee6548cd86 should not have CRLF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
a.txt in a8ee6548cd86 should not have CRLF line endings
[255]
$ printf "first\nsecond\nthird\n" > a.txt
$ hg commit -m 'LF a.txt (fixed)'
$ hg push ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
$ printf "first\nsecond\nthird\n" > crlf.txt
$ hg add crlf.txt
$ hg commit -m 'LF crlf.txt'
$ hg push ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
error: pretxnchangegroup hook failed: end-of-line check failed:
crlf.txt in 004ba2132725 should not have LF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
crlf.txt in 004ba2132725 should not have LF line endings
[255]
$ printf "first\r\nsecond\r\nthird\r\n" > crlf.txt
$ hg commit -m 'CRLF crlf.txt (fixed)'
$ hg push ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
$ printf "first\r\nsecond" > b.txt
$ hg add b.txt
$ hg commit -m 'CRLF b.txt'
$ hg push ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
error: pretxnchangegroup hook failed: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
[255]
$ hg up -r -2
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ printf "some\nother\nfile" > c.txt
$ hg add c.txt
$ hg commit -m "LF c.txt, b.txt doesn't exist here"
created new head
$ hg push -f ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files (+1 heads)
error: pretxnchangegroup hook failed: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
[255]
Test checkheadshook alias
$ cat > ../main/.hg/hgrc <<EOF
> [hooks]
> pretxnchangegroup = python:hgext.eol.checkheadshook
> EOF
$ hg push -f ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files (+1 heads)
error: pretxnchangegroup hook failed: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
[255]
We can fix the head and push again
$ hg up 6
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ printf "first\nsecond" > b.txt
$ hg ci -m "remove CRLF from b.txt"
$ hg push -f ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 2 files (+1 heads)
$ hg -R ../main rollback
repository tip rolled back to revision 5 (undo push)
Test it still fails with checkallhook
$ cat > ../main/.hg/hgrc <<EOF
> [hooks]
> pretxnchangegroup = python:hgext.eol.checkallhook
> EOF
$ hg push -f ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 2 files (+1 heads)
error: pretxnchangegroup hook failed: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
[255]
But we can push the clean head
$ hg push -r7 -f ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
Test multiple files/revisions output
$ printf "another\r\nbad\r\none" > d.txt
$ hg add d.txt
$ hg ci -m "add d.txt"
$ hg push -f ../main
pushing to ../main
searching for changes
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 2 files (+1 heads)
error: pretxnchangegroup hook failed: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
d.txt in a7040e68714f should not have CRLF line endings
transaction abort!
rollback completed
abort: end-of-line check failed:
b.txt in fbcf9b1025f5 should not have CRLF line endings
d.txt in a7040e68714f should not have CRLF line endings
[255]
$ cd ..