Ganeti customisation using hooks

Documents Ganeti version 2.16

Introduction

In order to allow customisation of operations, Ganeti runs scripts in sub-directories of @SYSCONFDIR@/ganeti/hooks. These sub-directories are named $hook-$phase.d, where $phase is either pre or post and $hook matches the directory name given for a hook (e.g. cluster-verify-post.d or node-add-pre.d).

This is similar to the /etc/network/ structure present in Debian for network interface handling.

Organisation

For every operation, two sets of scripts are run:

  • pre phase (for authorization/checking)
  • post phase (for logging)

Also, for each operation, the scripts are run on one or more nodes, depending on the operation type.

Note that, even though we call them scripts, we are actually talking about any executable.

pre scripts

The pre scripts have a definite target: to check that the operation is allowed given the site-specific constraints. You could have, for example, a rule that says every new instance is required to exists in a database; to implement this, you could write a script that checks the new instance parameters against your database.

The objective of these scripts should be their return code (zero or non-zero for success and failure). However, if they modify the environment in any way, they should be idempotent, as failed executions could be restarted and thus the script(s) run again with exactly the same parameters.

Note that if a node is unreachable at the time a hooks is run, this will not be interpreted as a deny for the execution. In other words, only an actual error returned from a script will cause abort, and not an unreachable node.

Therefore, if you want to guarantee that a hook script is run and denies an action, it’s best to put it on the master node.

post scripts

These scripts should do whatever you need as a reaction to the completion of an operation. Their return code is not checked (but logged), and they should not depend on the fact that the pre scripts have been run.

Naming

The allowed names for the scripts consist of (similar to run-parts) upper and lower case, digits, underscores and hyphens. In other words, the regexp ^[a-zA-Z0-9_-]+$. Also, non-executable scripts will be ignored.

Order of execution

On a single node, the scripts in a directory are run in lexicographic order (more exactly, the python string comparison order). It is advisable to implement the usual NN-name convention where NN is a two digit number.

For an operation whose hooks are run on multiple nodes, there is no specific ordering of nodes with regard to hooks execution; you should assume that the scripts are run in parallel on the target nodes (keeping on each node the above specified ordering). If you need any kind of inter-node synchronisation, you have to implement it yourself in the scripts.

Execution environment

The scripts will be run as follows:

  • no command line arguments
  • no controlling tty
  • stdin is actually /dev/null
  • stdout and stderr are directed to files
  • PATH is reset to /sbin:/bin:/usr/sbin:/usr/bin
  • the environment is cleared, and only ganeti-specific variables will be left

All information about the cluster is passed using environment variables. Different operations will have sligthly different environments, but most of the variables are common.

Operation list

Node operations

OP_NODE_ADD

Adds a node to the cluster.

directory:node-add
env. vars:NODE_NAME, NODE_PIP, NODE_SIP, MASTER_CAPABLE, VM_CAPABLE
pre-execution:all existing nodes
post-execution:all nodes plus the new node

OP_NODE_REMOVE

Removes a node from the cluster. On the removed node the hooks are called during the execution of the operation and not after its completion.

directory:node-remove
env. vars:NODE_NAME
pre-execution:all existing nodes except the removed node
post-execution:all existing nodes

OP_NODE_SET_PARAMS

Changes a node’s parameters.

directory:node-modify
env. vars:MASTER_CANDIDATE, OFFLINE, DRAINED, MASTER_CAPABLE, VM_CAPABLE
pre-execution:master node, the target node
post-execution:master node, the target node

OP_NODE_MIGRATE

Relocate secondary instances from a node.

directory:node-migrate
env. vars:NODE_NAME
pre-execution:master node
post-execution:master node

Node group operations

OP_GROUP_ADD

Adds a node group to the cluster.

directory:group-add
env. vars:GROUP_NAME
pre-execution:master node
post-execution:master node

OP_GROUP_SET_PARAMS

Changes a node group’s parameters.

directory:group-modify
env. vars:GROUP_NAME, NEW_ALLOC_POLICY
pre-execution:master node
post-execution:master node

OP_GROUP_REMOVE

Removes a node group from the cluster. Since the node group must be empty for removal to succeed, the concept of “nodes in the group” does not exist, and the hook is only executed in the master node.

directory:group-remove
env. vars:GROUP_NAME
pre-execution:master node
post-execution:master node

OP_GROUP_RENAME

Renames a node group.

directory:group-rename
env. vars:OLD_NAME, NEW_NAME
pre-execution:master node and all nodes in the group
post-execution:master node and all nodes in the group

OP_GROUP_EVACUATE

Evacuates a node group.

directory:group-evacuate
env. vars:GROUP_NAME, TARGET_GROUPS
pre-execution:master node and all nodes in the group
post-execution:master node and all nodes in the group

Network operations

OP_NETWORK_ADD

Adds a network to the cluster.

directory:network-add
env. vars:NETWORK_NAME, NETWORK_SUBNET, NETWORK_GATEWAY, NETWORK_SUBNET6, NETWORK_GATEWAY6, NETWORK_MAC_PREFIX, NETWORK_TAGS
pre-execution:master node
post-execution:master node

OP_NETWORK_REMOVE

Removes a network from the cluster.

directory:network-remove
env. vars:NETWORK_NAME
pre-execution:master node
post-execution:master node

OP_NETWORK_CONNECT

Connects a network to a nodegroup.

directory:network-connect
env. vars:GROUP_NAME, NETWORK_NAME, GROUP_NETWORK_MODE, GROUP_NETWORK_LINK, GROUP_NETWORK_VLAN, NETWORK_SUBNET, NETWORK_GATEWAY, NETWORK_SUBNET6, NETWORK_GATEWAY6, NETWORK_MAC_PREFIX, NETWORK_TAGS
pre-execution:nodegroup nodes
post-execution:nodegroup nodes

OP_NETWORK_DISCONNECT

Disconnects a network from a nodegroup.

directory:network-disconnect
env. vars:GROUP_NAME, NETWORK_NAME, GROUP_NETWORK_MODE, GROUP_NETWORK_LINK, GROUP_NETWORK_VLAN, NETWORK_SUBNET, NETWORK_GATEWAY, NETWORK_SUBNET6, NETWORK_GATEWAY6, NETWORK_MAC_PREFIX, NETWORK_TAGS
pre-execution:nodegroup nodes
post-execution:nodegroup nodes

OP_NETWORK_SET_PARAMS

Modifies a network.

directory:network-modify
env. vars:NETWORK_NAME, NETWORK_SUBNET, NETWORK_GATEWAY, NETWORK_SUBNET6, NETWORK_GATEWAY6, NETWORK_MAC_PREFIX, NETWORK_TAGS
pre-execution:master node
post-execution:master node

Instance operations

All instance operations take at least the following variables: INSTANCE_NAME, INSTANCE_PRIMARY, INSTANCE_SECONDARY, INSTANCE_OS_TYPE, INSTANCE_DISK_TEMPLATE, INSTANCE_MEMORY, INSTANCE_DISK_SIZES, INSTANCE_VCPUS, INSTANCE_NIC_COUNT, INSTANCE_NICn_IP, INSTANCE_NICn_BRIDGE, INSTANCE_NICn_MAC, INSTANCE_NICn_NETWORK, INSTANCE_NICn_NETWORK_UUID, INSTANCE_NICn_NETWORK_SUBNET, INSTANCE_NICn_NETWORK_GATEWAY, INSTANCE_NICn_NETWORK_SUBNET6, INSTANCE_NICn_NETWORK_GATEWAY6, INSTANCE_NICn_NETWORK_MAC_PREFIX, INSTANCE_DISK_COUNT, INSTANCE_DISKn_SIZE, INSTANCE_DISKn_MODE, INSTANCE_DISKn_NAME, INSTANCE_DISKn_UUID, INSTANCE_DISKn_DEV_TYPE.

The INSTANCE_NICn_* and INSTANCE_DISKn_* variables represent the properties of the n -th NIC and disk, and are zero-indexed. Depending on the disk template, Ganeti exports some info related to the logical id of the disk, that is basically its driver and id.

The INSTANCE_NICn_NETWORK_* variables are only passed if a NIC’s network parameter is set (that is if the NIC is associated to a network defined via gnt-network)

OP_INSTANCE_CREATE

Creates a new instance.

directory:instance-add
env. vars:ADD_MODE, SRC_NODE, SRC_PATH, SRC_IMAGES
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_REINSTALL

Reinstalls an instance.

directory:instance-reinstall
env. vars:only the standard instance vars
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_BACKUP_EXPORT

Exports the instance.

directory:instance-export
env. vars:EXPORT_MODE, EXPORT_NODE, EXPORT_DO_SHUTDOWN, REMOVE_INSTANCE
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_STARTUP

Starts an instance.

directory:instance-start
env. vars:FORCE
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_SHUTDOWN

Stops an instance.

directory:instance-stop
env. vars:TIMEOUT
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_REBOOT

Reboots an instance.

directory:instance-reboot
env. vars:IGNORE_SECONDARIES, REBOOT_TYPE, SHUTDOWN_TIMEOUT
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_SET_PARAMS

Modifies the instance parameters.

directory:instance-modify
env. vars:NEW_DISK_TEMPLATE, RUNTIME_MEMORY
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_FAILOVER

Failovers an instance. In the post phase INSTANCE_PRIMARY and INSTANCE_SECONDARY refer to the nodes that were repectively primary and secondary before failover.

directory:instance-failover
env. vars:IGNORE_CONSISTENCY, SHUTDOWN_TIMEOUT, OLD_PRIMARY, OLD_SECONDARY, NEW_PRIMARY, NEW_SECONDARY
pre-execution:master node, secondary (target) node
post-execution:master node, primary (source) and secondary (target) nodes

OP_INSTANCE_MIGRATE

Migrates an instance. In the post phase INSTANCE_PRIMARY and INSTANCE_SECONDARY refer to the nodes that were repectively primary and secondary before migration.

directory:instance-migrate
env. vars:MIGRATE_LIVE, MIGRATE_CLEANUP, OLD_PRIMARY, OLD_SECONDARY, NEW_PRIMARY, NEW_SECONDARY
pre-execution:master node, primary (source) and secondary (target) nodes
post-execution:master node, primary (source) and secondary (target) nodes

OP_INSTANCE_REMOVE

Remove an instance.

directory:instance-remove
env. vars:SHUTDOWN_TIMEOUT
pre-execution:master node
post-execution:master node, primary and secondary nodes

OP_INSTANCE_GROW_DISK

Grows the disk of an instance.

directory:disk-grow
env. vars:DISK, AMOUNT
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_RENAME

Renames an instance.

directory:instance-rename
env. vars:INSTANCE_NEW_NAME
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_MOVE

Move an instance by data-copying.

directory:instance-move
env. vars:TARGET_NODE, SHUTDOWN_TIMEOUT
pre-execution:master node, primary and target nodes
post-execution:master node, primary and target nodes

OP_INSTANCE_RECREATE_DISKS

Recreate an instance’s missing disks.

directory:instance-recreate-disks
env. vars:only the standard instance vars
pre-execution:master node, primary and secondary nodes
post-execution:master node, primary and secondary nodes

OP_INSTANCE_REPLACE_DISKS

Replace the disks of an instance.

directory:mirrors-replace
env. vars:MODE, NEW_SECONDARY, OLD_SECONDARY
pre-execution:master node, primary and new secondary nodes
post-execution:master node, primary and new secondary nodes

OP_INSTANCE_CHANGE_GROUP

Moves an instance to another group.

directory:instance-change-group
env. vars:TARGET_GROUPS
pre-execution:master node
post-execution:master node

Cluster operations

OP_CLUSTER_POST_INIT

This hook is called via a special “empty” LU right after cluster initialization.

directory:cluster-init
env. vars:none
pre-execution:none
post-execution:master node

OP_CLUSTER_DESTROY

The post phase of this hook is called during the execution of destroy operation and not after its completion.

directory:cluster-destroy
env. vars:none
pre-execution:none
post-execution:master node

OP_CLUSTER_VERIFY_GROUP

Verifies all nodes in a group. This is a special LU with regard to hooks, as the result of the opcode will be combined with the result of post-execution hooks, in order to allow administrators to enhance the cluster verification procedure.

directory:cluster-verify
env. vars:CLUSTER, MASTER, CLUSTER_TAGS, NODE_TAGS_<name>
pre-execution:none
post-execution:all nodes in a group

OP_CLUSTER_RENAME

Renames the cluster.

directory:cluster-rename
env. vars:NEW_NAME
pre-execution:master-node
post-execution:master-node

OP_CLUSTER_SET_PARAMS

Modifies the cluster parameters.

directory:cluster-modify
env. vars:NEW_VG_NAME
pre-execution:master node
post-execution:master node

Virtual operation OP_CLUSTER_IP_TURNUP

This doesn’t correspond to an actual op-code, but it is called when the master IP is activated.

directory:master-ip-turnup
env. vars:MASTER_NETDEV, MASTER_IP, MASTER_NETMASK, CLUSTER_IP_VERSION
pre-execution:master node
post-execution:master node

Virtual operation OP_CLUSTER_IP_TURNDOWN

This doesn’t correspond to an actual op-code, but it is called when the master IP is deactivated.

directory:master-ip-turndown
env. vars:MASTER_NETDEV, MASTER_IP, MASTER_NETMASK, CLUSTER_IP_VERSION
pre-execution:master node
post-execution:master node

Obsolete operations

The following operations are no longer present or don’t execute hooks anymore in Ganeti 2.0:

  • OP_INIT_CLUSTER
  • OP_MASTER_FAILOVER
  • OP_INSTANCE_ADD_MDDRBD
  • OP_INSTANCE_REMOVE_MDDRBD

Environment variables

Note that all variables listed here are actually prefixed with GANETI_ in order to provide a clear namespace. In addition, post-execution scripts receive another set of variables, prefixed with GANETI_POST_, representing the status after the opcode executed.

Common variables

This is the list of environment variables supported by all operations:

HOOKS_VERSION
Documents the hooks interface version. In case this doesnt match what the script expects, it should not run. The documents conforms to the version 2.
HOOKS_PHASE
One of PRE or POST denoting which phase are we in.
CLUSTER
The cluster name.
MASTER
The master node.
OP_CODE
One of the OP_ values from the list of operations.
OBJECT_TYPE
One of INSTANCE, NODE, CLUSTER.
DATA_DIR
The path to the Ganeti configuration directory (to read, for example, the ssconf files).

Specialised variables

This is the list of variables which are specific to one or more operations.

CLUSTER_IP_VERSION
IP version of the master IP (4 or 6)
INSTANCE_NAME
The name of the instance which is the target of the operation.
INSTANCE_BE_x,y,z,...
Instance BE params. There is one variable per BE param. For instance, GANETI_INSTANCE_BE_auto_balance
INSTANCE_DISK_TEMPLATE
The disk type for the instance.
NEW_DISK_TEMPLATE
The new disk type for the instance.
INSTANCE_DISK_COUNT
The number of disks for the instance.
INSTANCE_DISKn_SIZE
The size of disk n for the instance.
INSTANCE_DISKn_MODE
Either rw for a read-write disk or ro for a read-only one.
INSTANCE_HV_x,y,z,...
Instance hypervisor options. There is one variable per option. For instance, GANETI_INSTANCE_HV_use_bootloader
INSTANCE_HYPERVISOR
The instance hypervisor.
INSTANCE_NIC_COUNT
The number of NICs for the instance.
INSTANCE_NICn_BRIDGE
The bridge to which the n -th NIC of the instance is attached.
INSTANCE_NICn_IP
The IP (if any) of the n -th NIC of the instance.
INSTANCE_NICn_MAC
The MAC address of the n -th NIC of the instance.
INSTANCE_NICn_MODE
The mode of the n -th NIC of the instance.
INSTANCE_OS_TYPE
The name of the instance OS.
INSTANCE_PRIMARY
The name of the node which is the primary for the instance. Note that for migrations/failovers, you shouldn’t rely on this variable since the nodes change during the exectution, but on the OLD_PRIMARY/NEW_PRIMARY values.
INSTANCE_SECONDARY
Space-separated list of secondary nodes for the instance. Note that for migrations/failovers, you shouldn’t rely on this variable since the nodes change during the exectution, but on the OLD_SECONDARY/NEW_SECONDARY values.
INSTANCE_MEMORY
The memory size (in MiBs) of the instance.
INSTANCE_VCPUS
The number of virtual CPUs for the instance.
INSTANCE_STATUS
The run status of the instance.
MASTER_CAPABLE
Whether a node is capable of being promoted to master.
VM_CAPABLE
Whether the node can host instances.
MASTER_NETDEV
Network device of the master IP
MASTER_IP
The master IP
MASTER_NETMASK
Netmask of the master IP
INSTANCE_TAGS
A space-delimited list of the instance’s tags.
NODE_NAME
The target node of this operation (not the node on which the hook runs).
NODE_PIP
The primary IP of the target node (the one over which inter-node communication is done).
NODE_SIP
The secondary IP of the target node (the one over which drbd replication is done). This can be equal to the primary ip, in case the cluster is not dual-homed.
FORCE
This is provided by some operations when the user gave this flag.
IGNORE_CONSISTENCY
The user has specified this flag. It is used when failing over instances in case the primary node is down.
ADD_MODE
The mode of the instance create: either create for create from scratch or import for restoring from an exported image.
SRC_NODE, SRC_PATH, SRC_IMAGE
In case the instance has been added by import, these variables are defined and point to the source node, source path (the directory containing the image and the config file) and the source disk image file.
NEW_SECONDARY
The name of the node on which the new mirror component is being added (for replace disk). This can be the name of the current secondary, if the new mirror is on the same secondary. For migrations/failovers, this is the old primary node.
OLD_SECONDARY
The name of the old secondary in the replace-disks command. Note that this can be equal to the new secondary if the secondary node hasn’t actually changed. For migrations/failovers, this is the new primary node.
OLD_PRIMARY, NEW_PRIMARY
For migrations/failovers, the old and respectively new primary nodes. These two mirror the NEW_SECONDARY/OLD_SECONDARY variables
EXPORT_MODE
The instance export mode. Either “remote” or “local”.
EXPORT_NODE
The node on which the exported image of the instance was done.
EXPORT_DO_SHUTDOWN
This variable tells if the instance has been shutdown or not while doing the export. In the “was shutdown” case, it’s likely that the filesystem is consistent, whereas in the “did not shutdown” case, the filesystem would need a check (journal replay or full fsck) in order to guarantee consistency.
REMOVE_INSTANCE
Whether the instance was removed from the node.
SHUTDOWN_TIMEOUT
Amount of time to wait for the instance to shutdown.
TIMEOUT
Amount of time to wait before aborting the op.
OLD_NAME, NEW_NAME
Old/new name of the node group.
GROUP_NAME
The name of the node group.
NEW_ALLOC_POLICY
The new allocation policy for the node group.
CLUSTER_TAGS
The list of cluster tags, space separated.
NODE_TAGS_<name>
The list of tags for node <name>, space separated.

Examples

The startup of an instance will pass this environment to the hook script:

GANETI_CLUSTER=cluster1.example.com
GANETI_DATA_DIR=/var/lib/ganeti
GANETI_FORCE=False
GANETI_HOOKS_PATH=instance-start
GANETI_HOOKS_PHASE=post
GANETI_HOOKS_VERSION=2
GANETI_INSTANCE_DISK0_MODE=rw
GANETI_INSTANCE_DISK0_SIZE=128
GANETI_INSTANCE_DISK_COUNT=1
GANETI_INSTANCE_DISK_TEMPLATE=drbd
GANETI_INSTANCE_MEMORY=128
GANETI_INSTANCE_NAME=instance2.example.com
GANETI_INSTANCE_NIC0_BRIDGE=xen-br0
GANETI_INSTANCE_NIC0_IP=
GANETI_INSTANCE_NIC0_MAC=aa:00:00:a5:91:58
GANETI_INSTANCE_NIC_COUNT=1
GANETI_INSTANCE_OS_TYPE=debootstrap
GANETI_INSTANCE_PRIMARY=node3.example.com
GANETI_INSTANCE_SECONDARY=node5.example.com
GANETI_INSTANCE_STATUS=down
GANETI_INSTANCE_VCPUS=1
GANETI_MASTER=node1.example.com
GANETI_OBJECT_TYPE=INSTANCE
GANETI_OP_CODE=OP_INSTANCE_STARTUP
GANETI_OP_TARGET=instance2.example.com