1 HAIL(1) Ganeti | Version @GANETI_VERSION@
2 =========================================
7 hail - Ganeti IAllocator plugin
12 **hail** [ **-t** *file* | **\--simulate** *spec* ] [options...] *input-file*
19 hail is a Ganeti IAllocator plugin that implements the instance
20 placement and movement using the same algorithm as **hbal**\(1).
22 The program takes input via a JSON-file containing current cluster
23 state and the request details, and output (on stdout) a JSON-formatted
24 response. In case of critical failures, the error message is printed
25 on stderr and the exit code is changed to show failure.
27 If the input file name is ``-`` (a single minus sign), then the request
28 data will be read from *stdin*.
33 The program uses a simplified version of the hbal algorithm.
35 For single-node allocations (non-mirrored instances), again we
36 select the node which, when chosen as the primary node, gives the best
39 For dual-node allocations (mirrored instances), we chose the best
40 pair; this is the only choice where the algorithm is non-trivial
41 with regard to cluster size.
43 For relocations, we try to change the secondary node of the instance to
44 all the valid other nodes; the node which results in the best cluster
47 For node changes (*change-node* mode), we currently support DRBD
48 instances only, and all three modes (primary changes, secondary changes
49 and all node changes).
51 For group moves (*change-group* mode), again only DRBD is supported, and
52 we compute the correct sequence that will result in a group change; job
53 failure mid-way will result in a split instance. The choice of node(s)
54 on the target group is based on the group score, and the choice of group
55 is based on the same algorithm as allocations (group with lowest score
58 The deprecated *multi-evacuate* modes is no longer supported.
60 In all cases, the cluster (or group) scoring is identical to the hbal
66 The options that can be passed to the program are as follows:
69 Prints the before and after node status, in a format designed to allow
70 the user to understand the node's most important parameters. See the
71 man page **htools**\(1) for more details about this option.
73 -t *datafile*, \--text-data=*datafile*
74 The name of the file holding cluster information, to override the data
75 in the JSON request itself. This is mostly used for debugging. The
76 format of the file is described in the man page **htools**\(1).
78 \--simulate *description*
79 Backend specification: similar to the **-t** option, this allows
80 overriding the cluster data with a simulated cluster. For details
81 about the description, see the man page **htools**\(1).
83 -S *filename*, \--save-cluster=*filename*
84 If given, the state of the cluster before and the iallocator run is
85 saved to a file named *filename.pre-ialloc*, respectively
86 *filename.post-ialloc*. This allows re-feeding the cluster state to
87 any of the htools utilities via the ``-t`` option.
90 This option increases verbosity and can be used for debugging in order
91 to understand how the IAllocator request is parsed; it can be passed
92 multiple times for successively more information.
98 For the tag-exclusion configuration (see the manpage of hbal for more
99 details), the list of which instance tags to consider as exclusion
100 tags will be read from the cluster tags, configured as follows:
102 - get all cluster tags starting with **htools:iextags:**
103 - use their suffix as the prefix for exclusion tags
105 For example, given a cluster tag like **htools:iextags:service**,
106 all instance tags of the form **service:X** will be considered as
107 exclusion tags, meaning that (e.g.) two instances which both have a
108 tag **service:foo** will not be placed on the same primary node.
113 The options that can be passed to the program are as follows:
118 The exist status of the command will be zero, unless for some reason
119 the algorithm fatally failed (e.g. wrong node or instance data).
124 Networks (as configured by **gnt-network**\(8)) are not taken into
125 account in Ganeti 2.7. The only way to guarantee that they work
126 correctly is having your networks connected to all nodegroups. This will
127 be fixed in a future version.
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