hspace - Online in the Cloud

PROGRAM:

NAME

hspace - Cluster space analyzer for Ganeti

SYNOPSIS

hspace {backend options...} [algorithm options...] [request options...] [output
options...] [-v... | -q]

hspace --version

Backend options:

{ -m cluster | -L[ path ] | -t data-file | --simulate spec | -I path }

Algorithm options:

[ --max-cpu cpu-ratio ] [ --min-disk disk-ratio ] [ -O name... ] [ --independent-groups ]

Request options:

[--disk-template template ]

[--standard-alloc disk,ram,cpu ]

[--tiered-alloc disk,ram,cpu ]

Output options:

[--machine-readable[=*CHOICE*] ] [-p[fields]]

DESCRIPTION

hspace computes how many additional instances can be fit on a cluster, while maintaining
N+1 status.

The program will try to place instances, all of the same size, on the cluster, until the
point where we don't have any N+1 possible allocation. It uses the exact same allocation
algorithm as the hail iallocator plugin in allocate mode.

The output of the program is designed either for human consumption (the default) or, when
enabled with the --machine-readable option (described further below), for machine
consumption. In the latter case, it is intended to interpreted as a shell fragment (or
parsed as a key=value file). Options which extend the output (e.g. -p, -v) will output
the additional information on stderr (such that the stdout is still parseable).

By default, the instance specifications will be read from the cluster; the options
--standard-alloc and --tiered-alloc can be used to override them.

The following keys are available in the machine-readable output of the script (all
prefixed with HTS_):

SPEC_MEM, SPEC_DSK, SPEC_CPU, SPEC_RQN, SPEC_DISK_TEMPLATE, SPEC_SPN
These represent the specifications of the instance model used for allocation (the
memory, disk, cpu, requested nodes, disk template, spindles).

TSPEC_INI_MEM, TSPEC_INI_DSK, TSPEC_INI_CPU, ...
Only defined when the tiered mode allocation is enabled, these are similar to the
above specifications but show the initial starting spec for tiered allocation.

CLUSTER_MEM, CLUSTER_DSK, CLUSTER_CPU, CLUSTER_NODES, CLUSTER_SPN
These represent the total memory, disk, CPU count, total nodes, and total spindles
in the cluster.

INI_SCORE, FIN_SCORE
These are the initial (current) and final cluster score (see the hbal man page for
details about the scoring algorithm).

INI_INST_CNT, FIN_INST_CNT
The initial and final instance count.

INI_MEM_FREE, FIN_MEM_FREE
The initial and final total free memory in the cluster (but this doesn't
necessarily mean available for use).

INI_MEM_AVAIL, FIN_MEM_AVAIL
The initial and final total available memory for allocation in the cluster. If
allocating redundant instances, new instances could increase the reserved memory so
it doesn't necessarily mean the entirety of this memory can be used for new
instance allocations.

INI_MEM_RESVD, FIN_MEM_RESVD
The initial and final reserved memory (for redundancy/N+1 purposes).

INI_MEM_INST, FIN_MEM_INST
The initial and final memory used for instances (actual runtime used RAM).

INI_MEM_OVERHEAD, FIN_MEM_OVERHEAD
The initial and final memory overhead, i.e. memory used for the node itself and
unaccounted memory (e.g. due to hypervisor overhead).

INI_MEM_EFF, HTS_INI_MEM_EFF
The initial and final memory efficiency, represented as instance memory divided by
total memory.

INI_DSK_FREE, INI_DSK_AVAIL, INI_DSK_RESVD, INI_DSK_INST, INI_DSK_EFF
Initial disk stats, similar to the memory ones.

FIN_DSK_FREE, FIN_DSK_AVAIL, FIN_DSK_RESVD, FIN_DSK_INST, FIN_DSK_EFF
Final disk stats, similar to the memory ones.

INI_SPN_FREE, ..., FIN_SPN_FREE, ..
Initial and final spindles stats, similar to memory ones.

INI_CPU_INST, FIN_CPU_INST
Initial and final number of virtual CPUs used by instances.

INI_CPU_EFF, FIN_CPU_EFF
The initial and final CPU efficiency, represented as the count of virtual instance
CPUs divided by the total physical CPU count.

INI_MNODE_MEM_AVAIL, FIN_MNODE_MEM_AVAIL
The initial and final maximum per-node available memory. This is not very useful
as a metric but can give an impression of the status of the nodes; as an example,
this value restricts the maximum instance size that can be still created on the
cluster.

INI_MNODE_DSK_AVAIL, FIN_MNODE_DSK_AVAIL
Like the above but for disk.

TSPEC This parameter holds the pairs of specifications and counts of instances that can
be created in the tiered allocation mode. The value of the key is a
space-separated list of values; each value is of the form
memory,disk,vcpu,spindles=count where the memory, disk and vcpu are the values for
the current spec, and count is how many instances of this spec can be created. A
complete value for this variable could be: 4096,102400,2,1=225 2560,102400,2,1=20
512,102400,2,1=21.

KM_USED_CPU, KM_USED_NPU, KM_USED_MEM, KM_USED_DSK
These represents the metrics of used resources at the start of the computation
(only for tiered allocation mode). The NPU value is "normalized" CPU count, i.e.
the number of virtual CPUs divided by the maximum ratio of the virtual to physical
CPUs.

KM_POOL_CPU, KM_POOL_NPU, KM_POOL_MEM, KM_POOL_DSK
These represents the total resources allocated during the tiered allocation
process. In effect, they represent how much is readily available for allocation.

KM_UNAV_CPU, KM_POOL_NPU, KM_UNAV_MEM, KM_UNAV_DSK
These represents the resources left over (either free as in unallocable or
allocable on their own) after the tiered allocation has been completed. They
represent better the actual unallocable resources, because some other resource has
been exhausted. For example, the cluster might still have 100GiB disk free, but
with no memory left for instances, we cannot allocate another instance, so in
effect the disk space is unallocable. Note that the CPUs here represent instance
virtual CPUs, and in case the --max-cpu option hasn't been specified this will be
-1.

ALLOC_USAGE
The current usage represented as initial number of instances divided per final
number of instances.

ALLOC_COUNT
The number of instances allocated (delta between FIN_INST_CNT and INI_INST_CNT).

ALLOC_FAIL*_CNT
For the last attemp at allocations (which would have increased FIN_INST_CNT with
one, if it had succeeded), this is the count of the failure reasons per failure
type; currently defined are FAILMEM, FAILDISK and FAILCPU which represent errors
due to not enough memory, disk and CPUs, and FAILN1 which represents a non N+1
compliant cluster on which we can't allocate instances at all.

ALLOC_FAIL_REASON
The reason for most of the failures, being one of the above FAIL* strings.

OK A marker representing the successful end of the computation, and having value "1".
If this key is not present in the output it means that the computation failed and
any values present should not be relied upon.

Many of the INI_/FIN_ metrics will be also displayed with a TRL_ prefix, and denote the
cluster status at the end of the tiered allocation run.

The human output format should be self-explanatory, so it is not described further.

OPTIONS

The options that can be passed to the program are as follows:

--disk-template template
Overrides the disk template for the instance read from the cluster; one of the
Ganeti disk templates (e.g. plain, drbd, so on) should be passed in.

--spindle-use spindles
Override the spindle use for the instance read from the cluster. The value can be
0 (for example for instances that use very low I/O), but not negative. For shared
storage the value is ignored.

--max-cpu=*cpu-ratio*
The maximum virtual to physical cpu ratio, as a floating point number greater than
or equal to one. For example, specifying cpu-ratio as 2.5 means that, for a 4-cpu
machine, a maximum of 10 virtual cpus should be allowed to be in use for primary
instances. A value of exactly one means there will be no over-subscription of CPU
(except for the CPU time used by the node itself), and values below one do not make
sense, as that means other resources (e.g. disk) won't be fully utilised due to
CPU restrictions.

--min-disk=*disk-ratio*
The minimum amount of free disk space remaining, as a floating point number. For
example, specifying disk-ratio as 0.25 means that at least one quarter of disk
space should be left free on nodes.

--independent-groups
Consider all groups independent. That is, if a node that is not N+1 happy is
found, ignore its group, but still do allocation in the other groups. The default
is to not try allocation at all, if some not N+1 happy node is found.

--accept-existing-errors
This is a strengthened form of --independent-groups. It tells hspace to ignore the
presence of not N+1 happy nodes and just allocate on all other nodes without
introducing new N+1 violations. Note that this tends to overestimate the capacity,
as instances still have to be moved away from the existing not N+1 happy nodes.

-l rounds, --max-length=*rounds*
Restrict the number of instance allocations to this length. This is not very
useful in practice, but can be used for testing hspace itself, or to limit the
runtime for very big clusters.

-p, --print-nodes
Prints the before and after node status, in a format designed to allow the user to
understand the node's most important parameters. See the man page htools(1) for
more details about this option.

-O name
This option (which can be given multiple times) will mark nodes as being offline.
This means a couple of things:

· instances won't be placed on these nodes, not even temporarily; e.g. the replace
primary move is not available if the secondary node is offline, since this move
requires a failover.

· these nodes will not be included in the score calculation (except for the
percentage of instances on offline nodes)

Note that the algorithm will also mark as offline any nodes which are reported by
RAPI as such, or that have "?" in file-based input in any numeric fields.

-S filename, --save-cluster=*filename*
If given, the state of the cluster at the end of the allocation is saved to a file
named filename.alloc, and if tiered allocation is enabled, the state after tiered
allocation will be saved to filename.tiered. This allows re-feeding the cluster
state to either hspace itself (with different parameters) or for example hbal, via
the -t option.

-t datafile, --text-data=*datafile*
Backend specification: the name of the file holding node and instance information
(if not collecting via RAPI or LUXI). This or one of the other backends must be
selected. The option is described in the man page htools(1).

-m cluster
Backend specification: collect data directly from the cluster given as an argument
via RAPI. The option is described in the man page htools(1).

-L [path]
Backend specification: collect data directly from the master daemon, which is to be
contacted via LUXI (an internal Ganeti protocol). The option is described in the
man page htools(1).

--simulate description
Backend specification: similar to the -t option, this allows overriding the cluster
data with a simulated cluster. For details about the description, see the man page
htools(1).

--standard-alloc disk,ram,cpu
This option overrides the instance size read from the cluster for the standard
allocation mode, where we simply allocate instances of the same, fixed size until
the cluster runs out of space.

The specification given is similar to the --simulate option and it holds:

· the disk size of the instance (units can be used)

· the memory size of the instance (units can be used)

· the vcpu count for the insance

An example description would be 100G,4g,2 describing an instance specification of
100GB of disk space, 4GiB of memory and 2 VCPUs.

--tiered-alloc disk,ram,cpu
This option overrides the instance size for the tiered allocation mode. In this
mode, the algorithm starts from the given specification and allocates until there
is no more space; then it decreases the specification and tries the allocation
again. The decrease is done on the metric that last failed during allocation. The
argument should have the same format as for --standard-alloc.

Also note that the normal allocation and the tiered allocation are independent, and
both start from the initial cluster state; as such, the instance count for these
two modes are not related one to another.

--machine-readable[=*choice*]
By default, the output of the program is in "human-readable" format, i.e. text
descriptions. By passing this flag you can either enable (--machine-readable or
--machine-readable=yes) or explicitly disable (--machine-readable=no) the machine
readable format described above.

-v, --verbose
Increase the output verbosity. Each usage of this option will increase the
verbosity (currently more than 2 doesn't make sense) from the default of one.

-q, --quiet
Decrease the output verbosity. Each usage of this option will decrease the
verbosity (less than zero doesn't make sense) from the default of one.

-V, --version
Just show the program version and exit.

UNITS
By default, all unit-accepting options use mebibytes. Using the lower-case letters of m,
g and t (or their longer equivalents of mib, gib, tib, for which case doesn't matter)
explicit binary units can be selected. Units in the SI system can be selected using the
upper-case letters of M, G and T (or their longer equivalents of MB, GB, TB, for which
case doesn't matter).

More details about the difference between the SI and binary systems can be read in the
units(7) man page.

EXIT STATUS

The exist status of the command will be zero, unless for some reason the algorithm fatally
failed (e.g. wrong node or instance data).

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