Pivotal Engineering Journal

Technical articles from Pivotal engineers.

Updating a BOSH Release

Authors of a BOSH Release may want to release a new version when the upstream application is updated. This blog post describes the process of updating a BOSH Release while avoiding common pitfalls.

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When PowerDNS released version 4.0.1 of their authoritative nameserver, we rushed to update our BOSH Release (which was at version 4.0.0). We thought it would be a walk in the park, but instead it was an epic fail (a final release which couldn’t be deployed because the blobs were broken).

In this blog post we describe the procedure we ultimately followed to successfully create an updated BOSH final release of version 4.0.1 of the PowerDNS authoritative nameserver, highlighting some of the tricky and non-obvious steps.

Updating a BOSH Release

0. Ensure Our Git Repo is Up-to-date

We clone our release’s git repo:

cd ~/workspace
git clone git@github.com:cloudfoundry-community/pdns-release.git

Alternatively, if we’ve already cloned, we make sure we have the latest version of our release’s code:

cd ~/workspace/pdns-release
git checkout master # assuming 'master' is the default branch
git pull -r

1. Download the Application’s Updated Source Code

We download version PowerDNS’s 4.0.1 source code to our Downloads/ folder:

curl -L https://downloads.powerdns.com/releases/pdns-4.0.1.tar.bz2 \
  -o ~/Downloads/pdns-4.0.1.tar.bz2

2. Update BOSH Release to use New version

We’re lazy — we use a Perl one-liner to update our release to use the new version:

find packages/pdns -type f -print0 |
  xargs -0 perl -pi -e 's/pdns-4.0.0/pdns-4.0.1/g'

We’re careful — we use git diff to double-check the changes:

git diff

3. Blobs: Out with the Old, In with the new

We add our new blob.

bosh add-blob ~/Downloads/pdns-4.0.1.tar.bz2 pdns/pdns-4.0.1.tar.bz2

We remove the old blob (4.0.0) by manually editing blobs.yml:

vim config/blobs.yml # delete `pdns-4.0.0.tar.bz2` stanza
 # we take this opportunity to fix a broken path in our previous release:
 # we change `boost_1_61_0.tar.bz2:` to `boost/boost_1_61_0.tar.bz2:`

4. Create Development Release and Deploy

We create our development release:

bosh create-release --force

In our case, we use BOSH Lite to deploy and test because BOSH Lite is wonderfully convenient; however, any BOSH director will do. We assume the BOSH Lite Director is running and targeted:

bosh upload-release

We take advantage of our existing BOSH Lite manifest for our PowerDNS release, making sure to recreate the deployment if it already exists:

bosh -n -d pdns deploy manifests/bosh-lite.yml --recreate

5. Test the Development Release

Our compile should work. If there are compilation issues, we resolve them and redeploy.

We use a simple test to ensure our new PowerDNS release is functioning properly — we look up the SOA record of the domain example.com. The PowerDNS default configuration will return a different record than the one returned by the Internet DNS servers:

dig +short SOA example.com @10.244.8.64
  ns1.example.com. ahu.example.com. 2008080300 1800 3600 604800 3600

6. Upload the Blobs

Copy the private.yml into place:

cp ~/some-dir/private.yml config/

We upload the blob:

bosh upload-blobs

7. Create the Final Release

We assign the version number ‘4.0.1’ to our BOSH release (in order to track our upstream’s version).

bosh create-release --final --tarball ~/Downloads/pdns-4.0.1.tgz --version 4.0.1 --force

8. Commit but do NOT Push

We do not push our commit yet — if we discover a mistake, we won’t suffer the embarrassment of reverting the commit, unlike last time.

git add -N .
git add -p
git commit -m 'PowerDNS release 4.0.1'
git tag v4.0.1

9. Clean the Release Directory

We git clean our release the directory — this will force the blobs to be downloaded, and uncover any errors in the blob configuration (config/blobs.yml).

git clean -xfd

10. Clean out the BOSH Lite Director

We want to force our BOSH director to recompile the packages (and not be contaminated by caches). The most surefire way? We destroy and recreate our director, and clean out the compiled package cache, too:

pushd ~/workspace/bosh-lite
vagrant destroy -f
rm tmp/compiled_package_cache/*
vagrant up
popd

We re-upload our stemcell:

bosh upload-stemcell https://bosh.io/d/stemcells/bosh-warden-boshlite-ubuntu-trusty-go_agent

11. Deploy and Test the Final Release

bosh upload-release
bosh -n -d pdns deploy manifests/bosh-lite.yml
dig +short SOA example.com @10.244.8.64
  ns1.example.com. ahu.example.com. 2008080300 1800 3600 604800 3600

12. Push the Final Release’s Commits

git push
git push --tags

13. (Optional) Publish the Release on GitHub and Update README.md

Upload the tarball to GitHub to create a new GitHub Release. Update README.md if it refers to uploading the release’s tarball.

Footnotes

[Golang CLI] We are using an experimental Golang-based BOSH command line interface (CLI), and the arguments are slightly different than those of canonical Ruby-based BOSH CLI; however, the arguments are similar enough to be readily adapted to the Ruby CLI (e.g. the Golang CLI’s bosh upload-stemcell equivalent to the Ruby CLI’s bosh upload stemcell (no dash)).

The new CLI also allows variable interpolation, with the value of the variables to interpolate passed in via YAML file on the command line. This feature allows the redaction of sensitive values (e.g. SSL keys) from the manifest. The format is similar to Concourse’s interpolation, except that interpolated values are bracketed by double parentheses “((key))”, whereas Concourse uses double curly braces “{{key}}”.

Similar to Concourse, the experimental BOSH CLI allows the YAML file containing the secrets to be passed via the command line, e.g. -l ~/secrets.yml or -l <(lpass show --note secrets)

The Golang CLI is in alpha and should not be used on production systems.

Correction: December 17, 2016

The blog post has been updated to reflect the bosh create-release command’s option --tarball now requires an argument (the pathname of the release file to create). Previous versions of the BOSH CLI did not expect an argument passed to the --tarball option.