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Transitioning to BPM

Update the monit File

You need to convert the job's monit file to use bpm to start and stop the process. In order to allow monit to accurately track the status of the process, you will also need to update the location of the pidfile to the standard bpm location, like so:

# jobs/<job>/monit
check process <job>
  with pidfile /var/vcap/sys/run/bpm/<job>/<job>.pid
  start program "/var/vcap/jobs/bpm/bin/bpm start <job>"
  stop program "/var/vcap/jobs/bpm/bin/bpm stop <job>"
  group vcap

Note: You should use bpm from the canonical location of /var/vcap/jobs/bpm/bin/bpm.

Create bpm.yml Configuration File

In order for bpm to successfully start your process, you will need to create a bpm configuration file in the canonical location: /var/vcap/jobs/<job>/config/bpm.yml. This can be done by adding a template in your job definition with the following structure:

# jobs/<job>/templates/bpm.yml.erb
processes:
  - name: <job>
    executable: /path/to/executable
    args:
    - --port
    - 2424
    env:
      FOO: BAR

Also you will need to add the following to the list of templates in the job's spec file:

# jobs/<job>/spec
templates:
  bpm.yml.erb: config/bpm.yml

Converting _ctl Scripts to bpm.yml

A common pattern in BOSH releases is to use a _ctl bash script to control the execution of a process. Because bpm handles process execution, you will need to move functionality from the _ctl script to bpm.yml. We have found the following patterns useful:

Executable

Most _ctl scripts exec a binary as their last step with de-escalated privileges. Because bpm will always execute your process with de-escalated privileges, it is no longer necessary to manually de-escalate. Thus the executable and its corresponding arguments can be moved into bpm.yml as follows:

executable: /path/to/executable
args:
- arg1
- -flag
- arg2

Environment Variables

Any necessary environment variables that are set in the _ctl script can be moved into the env: block of bpm.yml. The format of this configuration is as follows:

env:
  KEY: VALUE

Note: that it is not currently possible for one value to interpolate values from another. If this is required, perform the interpolation earlier in the erb rendering, or later in a shell script that is called by BPM.

Runtime Configuration

Often times _ctl scripts need to modify runtime configuration, such as the $PATH environment variable. This functionality is not currently supported in the static bpm.yml configuration file, so we have found it useful to extract runtime configuration into smaller, more auditable, bash scripts. An example bpm.yml and bash script would work as follows:

# jobs/<job>/templates/bpm.yml.erb
executable: /path/to/helper/bash/script
# jobs/<job>/templates/script.erb
#!/bin/bash

export PATH=$PATH:/path/to/runtime/config

/path/to/executable arg1 -flag arg2

Stop / Usage Blocks

Many _ctl scripts provide implementations for monit stop and usage. Due to the fact that bpm manages stopping processes, these blocks are no longer necessary.

Complex BOSH Property Templating

Oftentimes releases will consume configuration from BOSH properties. A good pattern for templating these properties into the bpm.yml.erb is to use a Ruby hash and then perform a YAML.dump() to format and escape it correctly. For example:

# jobs/<job>/templates/bpm.yml.erb
<%=

config= {}
config["executable"] = /path/to/executable
config["args"] = []
config["args"] << p("example.property")
config["env"] = { "KEY" => "#{p("another.example.property")}" }

YAML.dump(config)
%>

Errands

The bpm run command can be used to run short-lived processes in the same environment as other long-lived processes. Each errand's conversion is going to be slightly different but most will follow these approximate steps.

  1. Rename the run script to describe what it does. e.g. drop_database.sh
  2. Add a bpm.yml file by following the other advice in this file. The executable: should be the script from step one.
  3. Re-add the run script but change the contents to include the snippet from below.
  4. Update the templates in the spec for all your new files.
#!/bin/bash

set -e

/var/vcap/jobs/bpm/bin/bpm run <job> [-p <process>]"

The bpm run command will exit with the same exit status as the internal executable. It will tee logs to both standard out and standard error as well as the typical log files.

Feature Flagging

We have found that in order to integrate bpm into certain releases, it needs to be introduced under a feature flag. If that is the case with your release, we recommend the following pattern.

# jobs/<job>/spec
properties:
  bpm.enabled:
    description: "Enable Bosh Process Manager"
    default: false
# jobs/<job>/monit
<% if p("bpm.enabled") %>
check process <job>
  with pidfile /var/vcap/sys/run/bpm/<job>/<job>.pid
  start program "/var/vcap/jobs/bpm/bin/bpm start <job>"
  stop program "/var/vcap/jobs/bpm/bin/bpm stop <job>"
  group vcap
<% else %>
check process <job>
  with pidfile /var/vcap/sys/run/<job>/<job>.pid
  start program "/var/vcap/jobs/<job>/bin/<job>_ctl start"
  stop program "/var/vcap/jobs/<job>/bin/<job>_ctl stop"
  group vcap
<% end %>

In most cases, when feature flagging, the _ctl script will not need to be modified, as the bpm.yml can replace it entirely if the flag is active.

If a helper script is necessary to provide functionality missing from bpm, the same pattern as described in the "Runtime Configuration" section above still applies. In addition, we have found it useful to modify the _ctl script to call this helper function as it unifies the execution path between bpm and the _ctl script.

Updating Deployment Manifest

In order to successfully deploy your release using BPM, you will need to add the BPM release to the list of releases in your deployment manifest. As of right now, there is not a canonical location to consume final releases of BPM from, thus you will need to create and upload the release to your BOSH director. This should look as follows:

releases:
- name: bpm
  version: latest

You can also add bpm using the following operation file:

- type: replace
  path: /releases/-
  value:
    name: bpm
    version: create
    url: file:///path/to/bpm-release

Note: This operation file takes advantage of the version: create syntax which will create and upload the release for you.

Once you have added bpm to the list of releases, you will also need to colocate the bpm job on any instance_groups that utilize it. This can be done by adding the following to your templates configuration for the instance_group in the deployment manifest:

templates:
- name: bpm
  release: bpm

This also can be achieved using an operation file similar to the following:

- type: replace
  path: /instance_groups/name=<job>/jobs/-
  value:
    name: bpm
    release: bpm

- type: replace
  path: /instance_groups/name=<job>/jobs/name=<job>/properties/bpm?/enabled?
  value: true

Using an Addon

Instead of manually weaving BPM onto each instance group on the system you can use addons in the BOSH runtime configuration to deploy with BPM.

releases:
- name: bpm
  version: latest

- name: bpm
  jobs:
  - name: bpm
    release: bpm

Log Forwarding

Some _ctl scripts forward the output and error streams from their server to the logger program which sends those logs to syslog.

For example, your job's _ctl script may look like this:

log_dir=/var/vcap/sys/log/<job>

/var/vcap/packages/<package>/bin/<job> \
  -config=$conf_dir/<job>.json \
  2> >(tee -a $log_dir/<job>.stderr.log | logger -p user.error -t vcap.<job>) \
  1> >(tee -a $log_dir/<job>.stdout.log | logger -p user.info -t vcap.<job>) & echo $! > $pidfile

BPM does not forward logs and so you should use something like the syslog release to send your logs from the machine to an external log aggregator and store:

 jobs:
  - name: syslog_forwarder
    properties:
      syslog:
        address: ((syslog_address))
        custom_rule: |
          if ($programname startswith "vcap.") then stop
        port: ((syslog_port))
        transport: ((syslog_transport))
    release: syslog
  - name: <job>
    ...

This decision was made to encourage consistency and to keep features in one place: BPM puts logs in the BOSH log directory and the syslog release takes those logs and puts them somewhere else. This means this if we need to fix a bug in the syslog forwarding then we don't need to bump every release.

If you have some jobs using bpm, but they are co-located with other jobs using _ctl scripts, avoid double logs by adding providing a custom_rule argument to filter out messages originating from logger. _ctl scripts write to logger with the program name vcap.[JOB_NAME], so we can filter out logs where the program name starts with vcap.

Post Deployment Checklist

You can use the bpm list command to verify that your jobs are all running as expected. If you'd like to tail the logs for a particular job then you can run bpm logs --all -f JOB.