Operation

Nodepool has two components which run as daemons. The nodepool-builder daemon is responsible for building diskimages and uploading them to providers, and the nodepool-launcher daemon is responsible for launching and deleting nodes.

Both daemons frequently re-read their configuration file after starting to support adding or removing new images and providers, or otherwise altering the configuration.

These daemons communicate with each other via a Zookeeper database. You must run Zookeeper and at least one of each of these daemons to have a functioning Nodepool installation.

Nodepool-builder

The nodepool-builder daemon builds and uploads images to providers. It may be run on the same or a separate host as the main nodepool daemon. Multiple instances of nodepool-builder may be run on the same or separate hosts in order to speed up image builds across many machines, or supply high-availability or redundancy. However, since nodepool-builder allows specification of the number of both build and upload threads, it is usually not advantageous to run more than a single instance on one machine. Note that while diskimage-builder (which is responsible for building the underlying images) generally supports executing multiple builds on a single machine simultaneously, some of the elements it uses may not. To be safe, it is recommended to run a single instance of nodepool-builder on a machine, and configure that instance to run only a single build thread (the default).

Nodepool-launcher

The main nodepool daemon is named nodepool-launcher and is responsible for managing cloud instances launched from the images created and uploaded by nodepool-builder.

When a new image is created and uploaded, nodepool-launcher will immediately start using it when launching nodes (Nodepool always uses the most recent image for a given provider in the ready state). Nodepool will delete images if they are not the most recent or second most recent ready images. In other words, Nodepool will always make sure that in addition to the current image, it keeps the previous image around. This way if you find that a newly created image is problematic, you may simply delete it and Nodepool will revert to using the previous image.

Daemon usage

To start the main Nodepool daemon, run nodepool-launcher:

usage: nodepool-launcher [-h] [-l LOGCONFIG] [--version] [-p PIDFILE] [-d]
                         [-c CONFIG] [-s SECURE] [--no-webapp]

Node pool.

optional arguments:
  -h, --help    show this help message and exit
  -l LOGCONFIG  path to log config file (default: None)
  --version     show program's version number and exit
  -p PIDFILE    path to pid file (default: /var/run/nodepool/nodepool.pid)
  -d            do not run as a daemon (default: False)
  -c CONFIG     path to config file (default: /etc/nodepool/nodepool.yaml)
  -s SECURE     path to secure file (default: None)
  --no-webapp

To start the nodepool-builder daemon, run nodepool–builder:

usage: nodepool-builder [-h] [-l LOGCONFIG] [--version] [-p PIDFILE] [-d]
                        [-c CONFIG] [-s SECURE]
                        [--build-workers BUILD_WORKERS]
                        [--upload-workers UPLOAD_WORKERS] [--fake]

NodePool Image Builder.

optional arguments:
  -h, --help            show this help message and exit
  -l LOGCONFIG          path to log config file (default: None)
  --version             show program's version number and exit
  -p PIDFILE            path to pid file (default: /var/run/nodepool/nodepool-
                        builder.pid)
  -d                    do not run as a daemon (default: False)
  -c CONFIG             path to config file (default:
                        /etc/nodepool/nodepool.yaml)
  -s SECURE             path to secure config file (default: None)
  --build-workers BUILD_WORKERS
                        number of build workers (default: 1)
  --upload-workers UPLOAD_WORKERS
                        number of upload workers (default: 4)
  --fake                Do not actually run diskimage-builder (used for
                        testing) (default: False)

To stop a daemon, send SIGINT to the process.

When yappi (Yet Another Python Profiler) is available, additional functions’ and threads’ stats are emitted as well. The first SIGUSR2 will enable yappi, on the second SIGUSR2 it dumps the information collected, resets all yappi state and stops profiling. This is to minimize the impact of yappi on a running system.

Metadata

When Nodepool creates instances, it will assign the following nova metadata:

groups
A comma separated list containing the name of the image and the name of the provider. This may be used by the Ansible OpenStack inventory plugin.
nodepool_image_name
The name of the image as a string.
nodepool_provider_name
The name of the provider as a string.
nodepool_node_id
The nodepool id of the node as an integer.

Common Management Tasks

In the course of running a Nodepool service you will find that there are some common operations that will be performed. Like the services themselves these are split into two groups, image management and instance management.

Image Management

Before Nodepool can launch any cloud instances it must have images to boot off of. nodepool dib-image-list will show you which images are available locally on disk. These images on disk are then uploaded to clouds, nodepool image-list will show you what images are bootable in your various clouds.

If you need to force a new image to be built to pick up a new feature more quickly than the normal rebuild cycle (which defaults to 24 hours) you can manually trigger a rebuild. Using nodepool image-build you can tell Nodepool to begin a new image build now. Note that depending on work that the nodepool-builder is already performing this may queue the build. Check nodepool dib-image-list to see the current state of the builds. Once the image is built it is automatically uploaded to all of the clouds configured to use that image.

At times you may need to stop using an existing image because it is broken. Your two major options here are to build a new image to replace the existing image or to delete the existing image and have Nodepool fall back on using the previous image. Rebuilding and uploading can be slow so typically the best option is to simply nodepool image-delete the most recent image which will cause Nodepool to fallback on using the previous image. Howevever, if you do this without “pausing” the image it will be immediately reuploaded. You will want to pause the image if you need to further investigate why the image is not being built correctly. If you know the image will be built correctly you can simple delete the built image and remove it from all clouds which will cause it to be rebuilt using nodepool dib-image-delete.

Command Line Tools

Usage

The general options that apply to all subcommands are:

usage: nodepool [-h] [-l LOGCONFIG] [--version] [-c CONFIG] [-s SECURE]
                [--debug]
                {list,image-list,dib-image-list,image-build,alien-image-list,delete,image-delete,dib-image-delete,config-validate,request-list,info,erase}
                ...

Node pool.

optional arguments:
  -h, --help            show this help message and exit
  -l LOGCONFIG          path to log config file (default: None)
  --version             show program's version number and exit
  -c CONFIG             path to config file (default:
                        /etc/nodepool/nodepool.yaml)
  -s SECURE             path to secure file (default: None)
  --debug               show DEBUG level logging (default: False)

commands:
  valid commands

  {list,image-list,dib-image-list,image-build,alien-image-list,delete,image-delete,dib-image-delete,config-validate,request-list,info,erase}
                        additional help
    list                list nodes
    image-list          list images from providers
    dib-image-list      list images built with diskimage-builder
    image-build         build image using diskimage-builder
    alien-image-list    list images not accounted for by nodepool
    delete              place a node in the DELETE state
    image-delete        delete an image
    dib-image-delete    Delete a dib built image from disk along with all
                        cloud uploads of this image
    config-validate     Validate configuration file
    request-list        list the current node requests
    info                Show provider data from zookeeper
    erase               Erase provider data from zookeeper

The following subcommands deal with nodepool images:

dib-image-list

usage: nodepool dib-image-list [-h]

optional arguments:
  -h, --help  show this help message and exit

image-list

usage: nodepool image-list [-h]

optional arguments:
  -h, --help  show this help message and exit

image-build

usage: nodepool image-build [-h] image

positional arguments:
  image       image name

optional arguments:
  -h, --help  show this help message and exit

dib-image-delete

usage: nodepool dib-image-delete [-h] id

positional arguments:
  id          dib image id

optional arguments:
  -h, --help  show this help message and exit

image-delete

usage: nodepool image-delete [-h] --provider PROVIDER --image IMAGE
                             --upload-id UPLOAD_ID --build-id BUILD_ID

optional arguments:
  -h, --help            show this help message and exit
  --provider PROVIDER   provider name
  --image IMAGE         image name
  --upload-id UPLOAD_ID
                        image upload id
  --build-id BUILD_ID   image build id

The following subcommands deal with nodepool nodes:

list

usage: nodepool list [-h] [--detail]

optional arguments:
  -h, --help  show this help message and exit
  --detail    Output detailed node info

delete

usage: nodepool delete [-h] [--now] id

positional arguments:
  id          node id

optional arguments:
  -h, --help  show this help message and exit
  --now       delete the node in the foreground

The following subcommands deal with ZooKeeper data management:

info

usage: nodepool info [-h] PROVIDER

positional arguments:
  PROVIDER    Provider name

optional arguments:
  -h, --help  show this help message and exit

erase

usage: nodepool erase [-h] [--force] PROVIDER

positional arguments:
  PROVIDER    Provider name

optional arguments:
  -h, --help  show this help message and exit
  --force     Bypass the warning prompt

If Nodepool’s database gets out of sync with reality, the following commands can help identify compute instances or images that are unknown to Nodepool:

alien-image-list

usage: nodepool alien-image-list [-h] [provider]

positional arguments:
  provider    provider name

optional arguments:
  -h, --help  show this help message and exit

Removing a Provider

To remove a provider, remove all of the images from that provider`s configuration (and remove all instances of that provider from any labels) and set that provider’s max-servers to -1. This will instruct Nodepool to delete any images uploaded to that provider, not upload any new ones, and stop booting new nodes on the provider. You can then let the nodes go through their normal lifecycle. Once all nodes have been deleted you remove the config from nodepool for that provider entirely (though leaving it in this state is effectively the same and makes it easy to turn the provider back on).

If urgency is required you can delete the nodes directly instead of waiting for them to go through their normal lifecycle but the effect is the same.

Web interface

If configured (see webapp-conf), a nodepool-launcher instance can provide a range of end-points that can provide information in text and json format. Note if there are multiple launchers, all will provide the same information.

GET /image-list

The status of uploaded images

Query Parameters:
 
  • fields – comma-separated list of fields to display
Request Headers:
 
  • Acceptapplication/json or text/*
Response Headers:
 
GET /dib-image-list

The status of images built by diskimage-builder

Query Parameters:
 
  • fields – comma-separated list of fields to display
Request Headers:
 
  • Acceptapplication/json or text/*
Response Headers:
 
GET /node-list

The status of currently active nodes

Query Parameters:
 
  • node_id – restrict to a specific node
  • fields – comma-separated list of fields to display
Request Headers:
 
  • Acceptapplication/json or text/*
Response Headers:
 
GET /request-list

Outstanding requests

Query Parameters:
 
  • fields – comma-separated list of fields to display
Request Headers:
 
  • Acceptapplication/json or text/*
Response Headers:
 
GET /label-list

All available labels as reported by all launchers

Query Parameters:
 
  • fields – comma-separated list of fields to display
Request Headers:
 
  • Acceptapplication/json or text/*
Response Headers:
 

Monitoring

Nodepool provides monitoring information to statsd. See Statsd and Graphite to learn how to enable statsd support. Currently, these metrics are supported:

Nodepool builder

nodepool.dib_image_build.<diskimage_name>.<ext>.size (gauge)

This stat reports the size of the built image in bytes.

nodepool.image_update.<image name>.<provider name> (counter, timer)

Number of image uploads to a specific provider in the cloud plus the time in seconds spent to upload the image.

nodepool.builder.dib_image_build.<diskimage_name>.<ext>.rc (gauge)

Return code of the DIB.

nodepool.builder.dib_image_build.<diskimage_name>.<ext>.duration (timer)

Time the DIB run took.

Nodepool launcher

nodepool.provider.<provider>.max_servers (gauge)

Current setting of the max-server configuration parameter for the respective provider.

nodepool.nodes.<state> (counter)

Number of nodes in a specific state.

state can be:

  • building
  • deleting
  • failed
  • in-use
  • ready
  • used
nodepool.provider.<provider>.downPorts (counter)

Number of ports in the DOWN state that have been removed automatically in the cleanup resources phase of the OpenStack driver.

nodepool.provider.<provider>.nodes.<state> (gauge)

Number of nodes per provider that are in one specific state. See nodepool.nodes for a list of possible states.

nodepool.label.<label>.nodes.<state> (counter)

Number of nodes with a specific label in a specific state. See nodepool.nodes for a list of possible states.

nodepool.task.<provider>.<task> (counter, timer)

Number of tasks executed per provider plus the duration of the task execution.

nodepool.launch.<result> (counter, timer)

Number of launches, categorized by the launch result plus the duration of the launch.

result can be:

  • ready: launch was successful
  • error.zksession: Zookeeper session was lost
  • error.quota: Quota of the provider was reached
  • error.unknown: Some other error during launch
nodepool.launch.provider.<provider>.<az>.<result> (counter, timer)

Number of launches per provider per availability zone, categorized by the launch result plus duration of the launch.

See nodepool.launch for a list of possible results.

nodepool.launch.image.<image>.<result> (counter, timer)

Number of launches per image, categorized by the launch result plus duration of the launch.

See nodepool.launch for a list of possible results.

nodepool.launch.requestor.<requestor>.<result> (counter, timer)

Number of launches per requestor, categorized by the launch result plus the duration of the launch.

See nodepool.launch for a list of possible results.

OpenStack API stats

Low level details on the timing of OpenStack API calls will be logged by the API task manager. These calls are logged under nodepool.task.<provider>.<api-call>. The API call name is of the generic format <endpoint><method><operation> transformed into a CamelCase value with no deliminators; for example the compute.GET.servers call becomes ComputeGetServers and compute.POST.os-volumes_boot becomes ComputePostOsVolumesBoot.

Since these calls reflect the internal operations of the openstacksdk, the exact keys logged may vary across providers and releases.