-
Michael Hanselmann authored
Signed-off-by:
Michael Hanselmann <hansmi@google.com> Reviewed-by:
Luca Bigliardi <shammash@google.com>
6c6b7f8a
Ganeti customisation using hooks
Documents ganeti version 2.0
Contents
- Introduction
- Organisation
-
Operation list
- Node operations
-
Instance operations
- OP_INSTANCE_ADD
- OP_INSTANCE_REINSTALL
- OP_BACKUP_EXPORT
- OP_INSTANCE_START
- OP_INSTANCE_SHUTDOWN
- OP_INSTANCE_REBOOT
- OP_INSTANCE_MODIFY
- OP_INSTANCE_FAILOVER
- OP_INSTANCE_MIGRATE
- OP_INSTANCE_REMOVE
- OP_INSTANCE_REPLACE_DISKS
- OP_INSTANCE_GROW_DISK
- OP_INSTANCE_RENAME
- OP_INSTANCE_MOVE
- OP_INSTANCE_RECREATE_DISKS
- OP_INSTANCE_REPLACE_DISKS
- Cluster operations
- Obsolete operations
- Environment variables
- Examples
Introduction
In order to allow customisation of operations, ganeti runs scripts
under /etc/ganeti/hooks based on certain rules.
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_ADD_NODE
Adds a node to the cluster.
| directory: | node-add |
|---|---|
| env. vars: | NODE_NAME, NODE_PIP, NODE_SIP |
| pre-execution: | all existing nodes |
| post-execution: | all nodes plus the new node |
OP_REMOVE_NODE
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 |
| pre-execution: | master node, the target node |
| post-execution: | master node, the target node |
OP_NODE_EVACUATE
Relocate secondary instances from a node.
| directory: | node-evacuate |
|---|---|
| env. vars: | NEW_SECONDARY, NODE_NAME |
| pre-execution: | master node, target node |
| post-execution: | master node, 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 |
Instance operations
All instance operations take at least the following variables: INSTANCE_NAME, INSTANCE_PRIMARY, INSTANCE_SECONDARIES, 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_DISK_COUNT, INSTANCE_DISKn_SIZE, INSTANCE_DISKn_MODE.
The INSTANCE_NICn_* and INSTANCE_DISKn_* variables represent the properties of the n -th NIC and disk, and are zero-indexed.
OP_INSTANCE_ADD
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_NODE, EXPORT_DO_SHUTDOWN |
| pre-execution: | master node, primary and secondary nodes |
| post-execution: | master node, primary and secondary nodes |
OP_INSTANCE_START
Starts an instance.
| directory: | instance-start |
|---|---|
| env. vars: | INSTANCE_NAME, INSTANCE_PRIMARY, INSTANCE_SECONDARIES, 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: | INSTANCE_NAME, INSTANCE_PRIMARY, INSTANCE_SECONDARIES |
| 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 |
| pre-execution: | master node, primary and secondary nodes |
| post-execution: | master node, primary and secondary nodes |
OP_INSTANCE_MODIFY
Modifies the instance parameters.
| directory: | instance-modify |
|---|---|
| env. vars: | INSTANCE_NAME, MEM_SIZE, VCPUS, INSTANCE_IP |
| pre-execution: | master node, primary and secondary nodes |
| post-execution: | master node, primary and secondary nodes |
OP_INSTANCE_FAILOVER
Failovers an instance.
| directory: | instance-failover |
|---|---|
| env. vars: | IGNORE_CONSISTENCY |
| pre-execution: | master node, secondary node |
| post-execution: | master node, secondary node |
OP_INSTANCE_MIGRATE
Migrates an instance.
| directory: | instance-migrate |
|---|---|
| env. vars: | INSTANCE_MIGRATE_LIVE, INSTANCE_MIGRATE_CLEANUP |
| pre-execution: | master node, secondary node |
| post-execution: | master node, secondary node |
OP_INSTANCE_REMOVE
Remove an instance.
| directory: | instance-remove |
|---|---|
| env. vars: | INSTANCE_NAME, INSTANCE_PRIMARY, INSTANCE_SECONDARIES |
| pre-execution: | master node |
| post-execution: | master node |
OP_INSTANCE_REPLACE_DISKS
Replace an instance's disks.
| directory: | mirror-replace |
|---|---|
| env. vars: | MODE, NEW_SECONDARY, OLD_SECONDARY |
| pre-execution: | master node, primary and secondary nodes |
| 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 node |
| post-execution: | master node, primary node |
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 |
| 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 |
Cluster operations
OP_POST_INIT_CLUSTER
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_DESTROY_CLUSTER
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
Verifies the cluster status. 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 |
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 |
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.
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.
- INSTANCE_NAME
- The name of the instance which is the target of the operation.
- INSTANCE_DISK_TEMPLATE
- The 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_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_OS_TYPE
- The name of the instance OS.
- INSTANCE_PRIMARY
- The name of the node which is the primary for the instance.
- INSTANCE_SECONDARIES
- Space-separated list of secondary nodes for the instance.
- 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.
- 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. This can be the name of the current secondary, if the new mirror is on the same secondary.
- 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.
- 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.
- 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_SECONDARIES=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