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NAME

hspace - Cluster space analyzer for Ganeti

SYNOPSIS

hspace [backend options...] [algorithm options...] [request options...] [ -p[fields] ] [-v... | -q]

hspace --version

Backend options:

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

Algorithm options:

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

Request options:

[--memory mem] [--disk disk] [--req-nodes req-nodes] [--vcpus vcpus] [--tiered-alloc spec]

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.

The output of the program is designed 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).

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

SPEC_MEM, SPEC_DSK, SPEC_CPU, SPEC_RQN

These represent the specifications of the instance model used for allocation (the memory, disk, cpu, requested nodes).

CLUSTER_MEM, CLUSTER_DSK, CLUSTER_CPU, CLUSTER_NODES

These represent the total memory, disk, CPU count and total nodes 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 --- memory used for the node itself and unacounted 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_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

If the tiered allocation mode has been enabled, this parameter holds the pairs of specifications and counts of instances that can be created in this mode. The value of the key is a space-separated list of values; each value is of the form memory,disk,vcpu=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=225 2560,102400,2=20 512,102400,2=21.

KM_USED_CPU, KM_USED_MEM, KM_USED_DSK

These represents the metrics of used resources at the start of the computation (only for tiered allocation mode).

KM_POOL_CPU, 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_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.

If the tiered allocation mode is enabled, then 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.

OPTIONS

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

--memory mem

The memory size of the instances to be placed (defaults to 4GiB).

--disk disk

The disk size of the instances to be placed (defaults to 100GiB).

--req-nodes num-nodes

The number of nodes for the instances; the default of two means mirrored instances, while passing one means plain type instances.

--vcpus vcpus

The number of VCPUs of the instances to be placed (defaults to 1).

--max-cpu cpu-ratio

The maximum virtual-to-physical cpu ratio, as a floating point number between zero and 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 one doesn't make sense though, as that means no disk space can be used on it.

--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.

-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.

It is possible to customise the listed information by passing a comma-separated list of field names to this option (the field list is currently undocumented). By default, the node list will contain these informations:

F

a character denoting the status of the node, with '-' meaning an offline node, '*' meaning N+1 failure and blank meaning a good node

Name

the node name

t_mem

the total node memory

n_mem

the memory used by the node itself

i_mem

the memory used by instances

x_mem

amount memory which seems to be in use but cannot be determined why or by which instance; usually this means that the hypervisor has some overhead or that there are other reporting errors

f_mem

the free node memory

r_mem

the reserved node memory, which is the amount of free memory needed for N+1 compliance

t_dsk

total disk

f_dsk

free disk

pcpu

the number of physical cpus on the node

vcpu

the number of virtual cpus allocated to primary instances

pri

number of primary instances

sec

number of secondary instances

p_fmem

percent of free memory

p_fdsk

percent of free disk

r_cpu

ratio of virtual to physical cpus

lCpu

the dynamic CPU load (if the information is available)

lMem

the dynamic memory load (if the information is available)

lDsk

the dynamic disk load (if the information is available)

lNet

the dynamic net load (if the information is available)

-O name

This option (which can be given multiple times) will mark nodes as being offline, and instances won't be placed on these nodes.

Note that hspace 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.

-tdatafile, --text-data=datafile

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.

-mcluster

Collect data directly from the cluster given as an argument via RAPI. If the argument doesn't contain a colon (:), then it is converted into a fully-built URL via prepending https:// and appending the default RAPI port, otherwise it's considered a fully-specified URL and is used as-is.

-L[path]

Collect data directly from the master daemon, which is to be contacted via the luxi (an internal Ganeti protocol). An optional path argument is interpreted as the path to the unix socket on which the master daemon listens; otherwise, the default path used by ganeti when installed with --localstatedir=/var is used.

--simulate description

Instead of using actual data, build an empty cluster given a node description. The description parameter must be a comma-separated list of four elements, describing in order:

the number of nodes in the cluster

the disk size of the nodes, in mebibytes

the memory size of the nodes, in mebibytes

the cpu core count for the nodes

An example description would be 20,102400,16384,4 describing a 20-node cluster where each node has 100GiB of disk space, 16GiB of memory and 4 CPU cores. Note that all nodes must have the same specs currently.

--tiered-alloc spec

Beside the standard, fixed-size allocation, also do a tiered allocation scheme where 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 matric that last failed during allocation. The specification given is similar to the --simulate option and it holds:

the disk size of the instance

the memory size of the instance

the vcpu count for the insance

An example description would be 10240,8192,2 describing an initial starting specification of 10GiB of disk space, 4GiB of memory and 2 VCPUs.

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.

-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. At verbosity 2 the location of the new instances is shown in the standard error.

-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.

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).

BUGS

The algorithm is highly dependent on the number of nodes; its runtime grows exponentially with this number, and as such is impractical for really big clusters.

The algorithm doesn't rebalance the cluster or try to get the optimal fit; it just allocates in the best place for the current step, without taking into consideration the impact on future placements.

ENVIRONMENT

If the variables HTOOLS_NODES and HTOOLS_INSTANCES are present in the environment, they will override the default names for the nodes and instances files. These will have of course no effect when the RAPI or Luxi backends are used.

SEE ALSO

hbal(1), hscan(1), ganeti(7), gnt-instance(8), gnt-node(8)

COPYRIGHT

Copyright (C) 2009 Google Inc. Permission is granted to copy, distribute and/or modify under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL.