Ganeti customisation using hooks ================================ Documents ganeti version 2.0 .. contents:: 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