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changegroup: introduce requests to define delta generation...
changegroup: introduce requests to define delta generation Currently, we iterate through each revision we will be producing a delta for then call into 1 of 2 functions for generating that delta. Deltas are emitted as we iterate. A problem with this model is that revision generation is tightly coupled to the changegroup code. And the storage layer needs to expose APIs like deltaparent() so changegroup delta generation can produce a delta with that knowledge. Another problem is that in this model, deltas can only be produced sequentially after the previous delta was produced and emitted. Some storage backends might be capable of producing deltas in parallel (e.g. if the changegroup deltas are cached somewhere). This commit aims to solve these problems by turning delta generation into a 2 phase implementation where the first phase determines info about all the deltas that need to be generated and the 2nd phase resolves those deltas. We introduce a "revisiondeltarequest" object that holds data about a to-be-generated delta. We perform a full pass over all revisions whose delta is to be generated and generate a "revisiondeltarequest" for each. Then we iterate over the "revisiondeltarequest" instances and derive a "revisiondelta" for each. This patch was quite large. In order to avoid even more churn, aspects of the implementation are less than ideal. e.g. we're recording revision numbers instead of nodes in a few places and we don't yet have a formal API for resolving an iterable of revisiondeltarequest instances. Things will be improved in subsequent commits. Unfortunately, this commit reduces performance substantially. For `hg perfchangegroupchangelog` on my hg repo: ! wall 1.512607 comb 1.510000 user 1.490000 sys 0.020000 (best of 7) ! wall 2.150863 comb 2.150000 user 2.150000 sys 0.000000 (best of 5) And for `hg bundle -t none-v2 -a` for the mozilla-unified repo: 178.32user 4.22system 3:02.59elapsed 190.97user 4.17system 3:15.19elapsed Some of this was attributed to changelog slowdown. `hg perfchangegroupchangelog` on mozilla-unified: ! wall 21.688715 comb 21.690000 user 21.570000 sys 0.120000 (best of 3) ! wall 25.683659 comb 25.680000 user 25.540000 sys 0.140000 (best of 3) Profiling seems to reveal that the changelog slowdown is due to reading changelog revisions multiple times. First in the linknode callback to resolve the set of files changed. Second in the delta generation. Before, we likely had hit the last revision cache in the revlog when doing delta generation since we performed that immediately after performing the linknode callback. I'm not exactly sure where the other ~8s are being spent. It might be from overhead of constructing a few million revisiondeltarequest objects. I'm OK with the regression for now because it is in service of a larger cause (storage abstraction). I'll try to profile later and claw back the performance. Differential Revision: https://phab.mercurial-scm.org/D4215
Gregory Szorc -
r39054:e793e11e default
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Apache Docker Server

This directory contains code for running a Mercurial hgweb server via mod_wsgi with the Apache HTTP Server inside a Docker container.

Important

This container is intended for testing purposes only: it is not meant to be suitable for production use.

Building Image

The first step is to build a Docker image containing Apache and mod_wsgi:

$ docker build -t hg-apache .

Important

You should rebuild the image whenever the content of this directory changes. Rebuilding after pulling or when you haven't run the container in a while is typically a good idea.

Running the Server

To run the container, you'll execute something like:

$ docker run --rm -it -v `pwd`/../../..:/var/hg/source -p 8000:80 hg-apache

If you aren't a Docker expert:

  • --rm will remove the container when it stops (so it doesn't clutter your system)
  • -i will launch the container in interactive mode so stdin is attached
  • -t will allocate a pseudo TTY
  • -v src:dst will mount the host filesystem at src into dst in the container. In our example, we assume you are running from this directory and use the source code a few directories up.
  • -p 8000:80 will publish port 80 on the container to port 8000 on the host, allowing you to access the HTTP server on the host interface.
  • hg-apache is the container image to run. This should correspond to what we build with docker build.

Important

The container requires that /var/hg/source contain the Mercurial source code.

Upon start, the container will attempt an install of the source in that directory. If the architecture of the host machine doesn't match that of the Docker host (e.g. when running Boot2Docker under OS X), Mercurial's Python C extensions will fail to run. Be sure to make clean your host's source tree before mounting it in the container to avoid this.

When starting the container, you should see some start-up actions (including a Mercurial install) and some output saying Apache has started:

Now if you load http://localhost:8000/ (or whatever interface Docker is using), you should see hgweb running!

For your convenience, we've created an empty repository available at /repo. Feel free to populate it with hg push.

Customizing the Server

By default, the Docker container installs a basic hgweb config and an empty dummy repository. It also uses some reasonable defaults for mod_wsgi.

Customizing the WSGI Dispatcher And Mercurial Config

By default, the Docker environment installs a custom hgweb.wsgi file (based on the example in contrib/hgweb.wsgi). The file is installed into /var/hg/htdocs/hgweb.wsgi.

A default hgweb configuration file is also installed. The hgwebconfig file from this directory is installed into /var/hg/htdocs/config.

You have a few options for customizing these files.

The simplest is to hack up hgwebconfig and entrypoint.sh in this directory and to rebuild the Docker image. This has the downside that the Mercurial working copy is modified and you may accidentally commit unwanted changes.

The next simplest is to copy this directory somewhere, make your changes, then rebuild the image. No working copy changes involved.

The preferred solution is to mount a host file into the container and overwrite the built-in defaults.

For example, say we create a custom hgweb config file in ~/hgweb. We can start the container like so to install our custom config file:

$ docker run -v ~/hgweb:/var/hg/htdocs/config ...

You can do something similar to install a custom WSGI dispatcher:

$ docker run -v ~/hgweb.wsgi:/var/hg/htdocs/hgweb.wsgi ...

Managing Repositories

Repositories are served from /var/hg/repos by default. This directory is configured as a Docker volume. This means you can mount an existing data volume container in the container so repository data is persisted across container invocations. See https://docs.docker.com/userguide/dockervolumes/ for more.

Alternatively, if you just want to perform lightweight repository manipulation, open a shell in the container:

$ docker exec -it <container> /bin/bash

Then run hg init, etc to manipulate the repositories in /var/hg/repos.

mod_wsgi Configuration Settings

mod_wsgi settings can be controlled with the following environment variables.

WSGI_PROCESSES
Number of WSGI processes to run.
WSGI_THREADS
Number of threads to run in each WSGI process
WSGI_MAX_REQUESTS
Maximum number of requests each WSGI process may serve before it is reaped.

See https://code.google.com/p/modwsgi/wiki/ConfigurationDirectives#WSGIDaemonProcess for more on these settings.

Note

The default is to use 1 thread per process. The reason is that Mercurial doesn't perform well in multi-threaded mode due to the GIL. Most people run a single thread per process in production for this reason, so that's what we default to.