Version Control
CFEngine is policy is stored in /var/cfengine/masterfiles
on the policy
server. It is common that this directory is backed by a version control system
(VCS), such as git or subversion. In this document we will focus on git, but
CFEngine is VCS agnostic.
Repository synchronization
When /var/cfengine/masterfiles
is backed by VCS, it may be useful to have an
agent policy that periodically checks the VCS server for the latest version
fetches any updates.
After installing CFEngine on the policy server, before bootstrapping the agent to itself, we create a git clone of our masterfiles.
$ git clone git@github.com:upstream/masterfiles.git /var/cfengine/masterfiles/
The following policy uses git pull
with the --ff-only flag to avoid
potentially bad merges. This assumes that no development takes place in
/var/cfengine/masterfiles
itself.
bundle agent vcs_update
{
commands:
"/usr/bin/git"
args => "pull --ff-only origin master",
contain => masterfiles_contain;
}
body contain masterfiles_contain
{
chdir => "/var/cfengine/masterfiles";
}
Commit hooks
Commit hooks are scripts that are run when a repository is updated. We can use
a hook to notify a policy developer if an update causes a syntax error. While
the agent on the policy server should not copy from
/var/cfengine/masterfiles
to /var/cfengine/inputs
if the new policy does
not pass validation, it can nevertheless be helpful to employ VCS commit
hooks. A hook needs to be installed on the VCS server. Git and subversion
store their hooks on the server, under directories .git/hooks
and hooks
,
respectively.
Example git update hook
We can use a git update hook to prevent a change from being made unless it
passes syntax checking. The idea is to check out the revision in a temporary
directory and run cf-promises
on it. Here is an example hook.
#!/bin/sh
# --- Command line
REF_NAME="$1"
OLD_REV="$2"
NEW_REV="$3"
GIT=/usr/bin/git
TAR=/bin/tar
CF_PROMISES=/home/a10021/Source/core/cf-promises/cf-promises
TMP_CHECKOUT_DIR=/tmp/cfengine-post-commit-syntax-check/
MAIN_POLICY_FILE=promises.cf
echo "Creating temporary checkout directory at ${TMP_CHECKOUT_DIR}"
mkdir -p ${TMP_CHECKOUT_DIR}
echo "Clearing potential data in temporary checkout directory"
rm -rf ${TMP_CHECKOUT_DIR}/*
rm -rf ${TMP_CHECKOUT_DIR}/.svn
echo "Checking out revision ${REV} from ${REPOS} to file://${TMP_CHECKOUT_DIR}"
${GIT} archive ${NEW_REV} | tar -x -C ${TMP_CHECKOUT_DIR}
if [ $? -ne 0 ]; then
echo "Error checking out repository to temporary folder during post-commit syntax checking!" >&2
return 1
fi
echo "Running cf-promises -cf on ${TMP_CHECKOUT_DIR}/${MAIN_POLICY_FILE}"
${CF_PROMISES} -cf ${TMP_CHECKOUT_DIR}/${MAIN_POLICY_FILE}
if [ $? -ne 0 ]; then
echo "There were policy errors in pushed revision ${REV}" >&2
return 1
else
echo "Policy check completed successfully!"
return 0
fi
Example subversion post-commit hook
For subversion, the principle is essentially the same. Note that for a post-commit hook the check is run after update, so the repository may be left with a syntax error, but the committer is notified.
#!/bin/sh
REPOS="$1"
REV="$2"
SVN=/usr/bin/svn
CF_PROMISES=/home/a10021/Source/core/cf-promises/cf-promises
TMP_CHECKOUT_DIR=/tmp/cfengine-post-commit-syntax-check/
MAIN_POLICY_FILE=trunk/promises.cf
echo "Creating temporary checkout directory at ${TMP_CHECKOUT_DIR}"
mkdir -p ${TMP_CHECKOUT_DIR}
echo "Clearing potential data in temporary checkout directory"
rm -rf ${TMP_CHECKOUT_DIR}/*
rm -rf ${TMP_CHECKOUT_DIR}/.svn
echo "Checking out revision ${REV} from ${REPOS} to file://${TMP_CHECKOUT_DIR}"
${SVN} co -r ${REV} file://${REPOS} ${TMP_CHECKOUT_DIR}
if [ $? -ne 0 ]; then
echo "Error checking out repository to temporary folder during post-commit syntax checking!" >&2
return 1
fi
echo "Running cf-promises -cf on ${TMP_CHECKOUT_DIR}/${MAIN_POLICY_FILE}"
${CF_PROMISES} -cf ${TMP_CHECKOUT_DIR}/${MAIN_POLICY_FILE}
if [ $? -ne 0 ]; then
echo "There were policy errors in committed revision ${REV}" >&2
return 1
else
echo "Policy check completed successfully!"
return 0
fi