various improvements

2023-11-09 01:17:50 +03:00
parent 8e7f185fc6
commit 1dd3e9a720
28 changed files with 557 additions and 219 deletions
--- a/4
+++ b/4
@@ -11,7 +11,7 @@ build: format lint
 	poetry build

 format:
-	poetry run isort --lai 2 $(SRC)
+	poetry run isort $(SRC)
 	poetry run ruff format $(SRC)

 lint:
@@ -23,7 +23,7 @@ docs:
 docs-versions:
 	poetry run sphinx-multiversion $(DOCS_SRC) $(DOCS_BUILD)

-serve-docs: docs-versions
+serve-docs:
 	poetry run sphinx-autobuild $(DOCS_SRC) $(DOCS_BUILD)

 clean:
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ Currently supports only QEMU/KVM based virtual machines.

 ## Docs

-Run `make serve-docs`.
+Run `make serve-docs`. See [Development](#development) below.

 ## Roadmap

@@ -39,3 +39,11 @@ Run `make serve-docs`.
 - [ ] Instance migrations
 - [ ] HTTP API
 - [ ] Full functional CLI [in progress]
+
+## Development
+
+Install [poetry](https://python-poetry.org/), clone this repository and run:
+
+```
+poetry install --with dev --with docs
+```
--- a/compute/init.py
+++ b/compute/init.py
@@ -1,4 +1,4 @@
-"""Compute Service library."""
+"""Compute instances management library."""

 __version__ = '0.1.0'

--- a/compute/cli/_create.py
+++ b/compute/cli/_create.py
@@ -1,26 +0,0 @@
-import argparse
-
-from compute import Session
-from compute.utils import identifiers
-
-
-def _create_instance(session: Session, args: argparse.Namespace) -> None:
-    """
-    Умолчания (достать информацию из либвирта):
-    - arch
-    - machine
-    - emulator
-    - CPU
-        - cpu_vendor
-        - cpu_model
-        - фичи
-    - max_memory
-    - max_vcpus
-
-    (сегнерировать):
-    - MAC адрес
-    - boot_order = ('cdrom', 'hd')
-    - title = ''
-    - name = uuid.uuid4().hex
-    """
-    print(args)
--- a/compute/cli/control.py
+++ b/compute/cli/control.py
@@ -1,12 +1,18 @@
 """Command line interface."""

 import argparse
+import io
 import logging
 import os
 import shlex
 import sys
+from collections import UserDict
+from typing import Any
+from uuid import uuid4

 import libvirt
+import yaml
+from pydantic import ValidationError

 from compute import __version__
 from compute.exceptions import (
@@ -15,8 +21,7 @@ from compute.exceptions import (
 )
 from compute.instance import GuestAgent
 from compute.session import Session
-
-from ._create import _create_instance
+from compute.utils import ids


 log = logging.getLogger(__name__)
@@ -37,41 +42,41 @@ class Table:
        """Initialise Table."""
        self.whitespace = whitespace or '\t'
        self.header = []
-        self._rows = []
-        self._table = ''
+        self.rows = []
+        self.table = ''

-    def row(self, row: list) -> None:
+    def add_row(self, row: list) -> None:
        """Add table row."""
-        self._rows.append([str(col) for col in row])
+        self.rows.append([str(col) for col in row])

-    def rows(self, rows: list[list]) -> None:
+    def add_rows(self, rows: list[list]) -> None:
        """Add multiple rows."""
        for row in rows:
-            self.row(row)
+            self.add_row(row)

    def __str__(self) -> str:
        """Build table and return."""
-        widths = [max(map(len, col)) for col in zip(*self._rows, strict=True)]
-        self._rows.insert(0, [str(h).upper() for h in self.header])
-        for row in self._rows:
-            self._table += self.whitespace.join(
+        widths = [max(map(len, col)) for col in zip(*self.rows, strict=True)]
+        self.rows.insert(0, [str(h).upper() for h in self.header])
+        for row in self.rows:
+            self.table += self.whitespace.join(
                (
                    val.ljust(width)
                    for val, width in zip(row, widths, strict=True)
                )
            )
-            self._table += '\n'
-        return self._table.strip()
+            self.table += '\n'
+        return self.table.strip()


 def _list_instances(session: Session) -> None:
    table = Table()
    table.header = ['NAME', 'STATE']
    for instance in session.list_instances():
-        table.row(
+        table.add_row(
            [
                instance.name,
-                instance.status,
+                instance.get_status(),
            ]
        )
    print(table)
@@ -113,11 +118,93 @@ def _exec_guest_agent_command(
    sys.exit(output.exitcode)


+class _NotPresent:
+    """
+    Type for representing non-existent dictionary keys.
+
+    See :class:`_FillableDict`.
+    """
+
+
+class _FillableDict(UserDict):
+    """Use :method:`fill` to add key if not present."""
+
+    def __init__(self, data: dict):
+        self.data = data
+
+    def fill(self, key: str, value: Any) -> None:  # noqa: ANN401
+        if self.data.get(key, _NotPresent) is _NotPresent:
+            self.data[key] = value
+
+
+def _merge_dicts(a: dict, b: dict, path: list[str] | None = None) -> dict:
+    """Merge `b` into `a`. Return modified `a`."""
+    if path is None:
+        path = []
+    for key in b:
+        if key in a:
+            if isinstance(a[key], dict) and isinstance(b[key], dict):
+                _merge_dicts(a[key], b[key], [path + str(key)])
+            elif a[key] == b[key]:
+                pass  # same leaf value
+            else:
+                a[key] = b[key]  # replace existing key's values
+        else:
+            a[key] = b[key]
+    return a
+
+
+def _create_instance(session: Session, file: io.TextIOWrapper) -> None:
+    try:
+        data = _FillableDict(yaml.load(file.read(), Loader=yaml.SafeLoader))
+        log.debug('Read from file: %s', data)
+    except yaml.YAMLError as e:
+        sys.exit(f'error: cannot parse YAML: {e}')
+
+    capabilities = session.get_capabilities()
+    node_info = session.get_node_info()
+
+    data.fill('name', uuid4().hex)
+    data.fill('title', None)
+    data.fill('description', None)
+    data.fill('arch', capabilities.arch)
+    data.fill('machine', capabilities.machine)
+    data.fill('emulator', capabilities.emulator)
+    data.fill('max_vcpus', node_info.cpus)
+    data.fill('max_memory', node_info.memory)
+    data.fill('cpu', {})
+    cpu = {
+        'emulation_mode': 'host-passthrough',
+        'model': None,
+        'vendor': None,
+        'topology': None,
+        'features': None,
+    }
+    data['cpu'] = _merge_dicts(data['cpu'], cpu)
+    data.fill(
+        'network_interfaces',
+        [{'source': 'default', 'mac': ids.random_mac()}],
+    )
+    data.fill('boot', {'order': ['cdrom', 'hd']})
+
+    try:
+        log.debug('Input data: %s', data)
+        session.create_instance(**data)
+    except ValidationError as e:
+        for error in e.errors():
+            fields = '.'.join([str(lc) for lc in error['loc']])
+            print(
+                f"validation error: {fields}: {error['msg']}",
+                file=sys.stderr,
+            )
+        sys.exit()
+
+
 def main(session: Session, args: argparse.Namespace) -> None:
    """Perform actions."""
    match args.command:
        case 'create':
-            _create_instance(session, args)
+            _create_instance(session, args.file)
        case 'exec':
            _exec_guest_agent_command(session, args)
        case 'ls':
@@ -179,30 +266,13 @@ def cli() -> None:  # noqa: PLR0915
    subparsers = root.add_subparsers(dest='command', metavar='COMMAND')

    # create command
-    create = subparsers.add_parser('create', help='create compute instance')
-    create.add_argument('image', nargs='?')
-    create.add_argument('--name', help='instance name, used as ID')
-    create.add_argument('--title', help='human-understandable instance title')
-    create.add_argument('--desc', default='', help='instance description')
-    create.add_argument('--memory', type=int, help='memory in MiB')
-    create.add_argument('--max-memory', type=int, help='max memory in MiB')
-    create.add_argument('--vcpus', type=int)
-    create.add_argument('--max-vcpus', type=int)
-    create.add_argument('--cpu-vendor')
-    create.add_argument('--cpu-model')
-    create.add_argument(
-        '--cpu-emulation-mode',
-        choices=['host-passthrough', 'host-model', 'custom'],
-        default='host-passthrough',
+    create = subparsers.add_parser(
+        'create', help='create new instance from YAML config file'
+    )
+    create.add_argument(
+        'file',
+        type=argparse.FileType('r', encoding='UTF-8'),
    )
-    create.add_argument('--cpu-features')
-    create.add_argument('--cpu-topology')
-    create.add_argument('--mahine')
-    create.add_argument('--emulator')
-    create.add_argument('--arch')
-    create.add_argument('--boot-order')
-    create.add_argument('--volume')
-    create.add_argument('-f', '--file', help='create instance from YAML')

    # exec subcommand
    execute = subparsers.add_parser(
@@ -303,14 +373,17 @@ def cli() -> None:  # noqa: PLR0915
    if log_level in log_levels:
        logging.basicConfig(level=log_levels[log_level])

+    log.debug('CLI started with args: %s', args)
    # Perform actions
    try:
        with Session(args.connect) as session:
            main(session, args)
    except ComputeServiceError as e:
        sys.exit(f'error: {e}')
-    except (KeyboardInterrupt, SystemExit):
+    except KeyboardInterrupt:
        sys.exit()
+    except SystemExit as e:
+        sys.exit(e)
    except Exception as e:  # noqa: BLE001
        sys.exit(f'unexpected error {type(e)}: {e}')

--- a/compute/exceptions.py
+++ b/compute/exceptions.py
@@ -1,4 +1,4 @@
-"""Compute Service exceptions."""
+"""Exceptions."""


 class ComputeServiceError(Exception):
--- a/compute/instance/guest_agent.py
+++ b/compute/instance/guest_agent.py
@@ -1,4 +1,4 @@
-"""Manage QEMU guest agent."""
+"""Interacting with the QEMU Guest Agent."""

 import json
 import logging
@@ -19,9 +19,6 @@ from compute.exceptions import (

 log = logging.getLogger(__name__)

-QEMU_TIMEOUT = 60
-POLL_INTERVAL = 0.3
-

 class GuestExecOutput(NamedTuple):
    """QEMU guest-exec command output."""
@@ -35,7 +32,7 @@ class GuestExecOutput(NamedTuple):
 class GuestAgent:
    """Class for interacting with QEMU guest agent."""

-    def __init__(self, domain: libvirt.virDomain, timeout: int | None = None):
+    def __init__(self, domain: libvirt.virDomain, timeout: int = 60):
        """
        Initialise GuestAgent.

@@ -43,7 +40,7 @@ class GuestAgent:
        :param timeout: QEMU timeout
        """
        self.domain = domain
-        self.timeout = timeout or QEMU_TIMEOUT
+        self.timeout = timeout
        self.flags = libvirt_qemu.VIR_DOMAIN_QEMU_MONITOR_COMMAND_DEFAULT
        self.last_pid = None

@@ -65,9 +62,6 @@ class GuestAgent:
            return json.loads(output)
        except libvirt.libvirtError as e:
            if e.get_error_code() == libvirt.VIR_ERR_AGENT_UNRESPONSIVE:
-                log.exception(
-                    'Guest agent is unavailable on instanse=%s', self.name
-                )
                raise GuestAgentUnavailableError(e) from e
            raise GuestAgentError(e) from e

@@ -95,9 +89,7 @@ class GuestAgent:

    def raise_for_commands(self, commands: list[str]) -> None:
        """
-        Check QEMU guest agent command availability.
-
-        Raise exception if command is not available.
+        Raise exception if QEMU GA command is not available.

        :param commands: List of required commands
        :raise: GuestAgentCommandNotSupportedError
@@ -164,12 +156,15 @@ class GuestAgent:
            stderr = b64decode(stderr or '').decode('utf-8')
        return GuestExecOutput(exited, exitcode, stdout, stderr)

-    def guest_exec_status(self, pid: int, *, poll: bool = False) -> dict:
+    def guest_exec_status(
+        self, pid: int, *, poll: bool = False, poll_interval: float = 0.3
+    ) -> dict:
        """
        Execute guest-exec-status and return output.

-        :param pid: PID in guest
-        :param poll: If True poll command status with POLL_INTERVAL
+        :param pid: PID in guest.
+        :param poll: If True poll command status.
+        :param poll_interval: Time between attempts to obtain command status.
        :return: Command output
        :rtype: dict
        """
@@ -185,7 +180,7 @@ class GuestAgent:
            command_status = self.execute(command)
            if command_status['return']['exited']:
                break
-            sleep(POLL_INTERVAL)
+            sleep(poll_interval)
            now = time()
            if now - start_time > self.timeout:
                raise GuestAgentTimeoutExceededError(self.timeout)
--- a/compute/instance/instance.py
+++ b/compute/instance/instance.py
@@ -1,9 +1,9 @@
 """Manage compute instances."""

-__all__ = ['Instance', 'InstanceConfig']
+__all__ = ['Instance', 'InstanceConfig', 'InstanceInfo']

 import logging
-from dataclasses import dataclass
+from typing import NamedTuple

 import libvirt
 from lxml import etree
@@ -16,14 +16,19 @@ from compute.exceptions import (
 from compute.utils import units

 from .guest_agent import GuestAgent
-from .schemas import CPUSchema, InstanceSchema, NetworkInterfaceSchema
+from .schemas import (
+    CPUEmulationMode,
+    CPUSchema,
+    InstanceSchema,
+    NetworkInterfaceSchema,
+)


 log = logging.getLogger(__name__)


 class InstanceConfig:
-    """Compute instance description for libvirt."""
+    """Compute instance config builder."""

    def __init__(self, schema: InstanceSchema):
        """
@@ -46,21 +51,33 @@ class InstanceConfig:
        self.network_interfaces = schema.network_interfaces

    def _gen_cpu_xml(self, cpu: CPUSchema) -> etree.Element:
-        xml = E.cpu(match='exact', mode=cpu.emulation_mode)
-        xml.append(E.model(cpu.model, fallback='forbid'))
-        xml.append(E.vendor(cpu.vendor))
-        xml.append(
-            E.topology(
-                sockets=str(cpu.topology.sockets),
-                dies=str(cpu.topology.dies),
-                cores=str(cpu.topology.cores),
-                threads=str(cpu.topology.threads),
+        options = {
+            'mode': cpu.emulation_mode,
+            'match': 'exact',
+            'check': 'partial',
+        }
+        if cpu.emulation_mode == CPUEmulationMode.HOST_PASSTHROUGH:
+            options['check'] = 'none'
+            options['migratable'] = 'on'
+        xml = E.cpu(**options)
+        if cpu.model:
+            xml.append(E.model(cpu.model, fallback='forbid'))
+        if cpu.vendor:
+            xml.append(E.vendor(cpu.vendor))
+        if cpu.topology:
+            xml.append(
+                E.topology(
+                    sockets=str(cpu.topology.sockets),
+                    dies=str(cpu.topology.dies),
+                    cores=str(cpu.topology.cores),
+                    threads=str(cpu.topology.threads),
+                )
            )
-        )
-        for feature in cpu.features.require:
-            xml.append(E.feature(policy='require', name=feature))
-        for feature in cpu.features.disable:
-            xml.append(E.feature(policy='disable', name=feature))
+        if cpu.features:
+            for feature in cpu.features.require:
+                xml.append(E.feature(policy='require', name=feature))
+            for feature in cpu.features.disable:
+                xml.append(E.feature(policy='disable', name=feature))
        return xml

    def _gen_vcpus_xml(self, vcpus: int, max_vcpus: int) -> etree.Element:
@@ -89,15 +106,15 @@ class InstanceConfig:

    def to_xml(self) -> str:
        """Return XML config for libvirt."""
-        xml = E.domain(
-            E.name(self.name),
-            E.title(self.title),
-            E.description(self.description),
-            E.metadata(),
-            E.memory(str(self.memory * 1024), unit='KiB'),
-            E.currentMemory(str(self.memory * 1024), unit='KiB'),
-            type='kvm',
-        )
+        xml = E.domain(type='kvm')
+        xml.append(E.name(self.name))
+        if self.title:
+            xml.append(E.title(self.title))
+        if self.description:
+            xml.append(E.description(self.description))
+        xml.append(E.metadata())
+        xml.append(E.memory(str(self.max_memory * 1024), unit='KiB'))
+        xml.append(E.currentMemory(str(self.memory * 1024), unit='KiB'))
        xml.append(
            E.vcpu(
                str(self.max_vcpus),
@@ -148,8 +165,14 @@ class InstanceConfig:
        return etree.tostring(xml, encoding='unicode', pretty_print=True)


-@dataclass
-class InstanceInfo:
+class InstanceInfo(NamedTuple):
+    """
+    Store compute instance info.
+
+    Reference:
+    https://libvirt.org/html/libvirt-libvirt-domain.html#virDomainInfo
+    """
+
    state: str
    max_memory: int
    memory: int
@@ -193,13 +216,8 @@ class Instance:
        }
        return states[state]

-    @property
-    def info(self) -> InstanceInfo:
-        """
-        Return instance info.
-
-        https://libvirt.org/html/libvirt-libvirt-domain.html#virDomainInfo
-        """
+    def get_info(self) -> InstanceInfo:
+        """Return instance info."""
        _info = self.domain.info()
        return InstanceInfo(
            state=self._expand_instance_state(_info[0]),
@@ -209,8 +227,7 @@ class Instance:
            cputime=_info[4],
        )

-    @property
-    def status(self) -> str:
+    def get_status(self) -> str:
        """
        Return instance state: 'running', 'shutoff', etc.

@@ -225,7 +242,6 @@ class Instance:
            ) from e
        return self._expand_instance_state(state)

-    @property
    def is_running(self) -> bool:
        """Return True if instance is running, else return False."""
        if self.domain.isActive() != 1:
@@ -233,7 +249,6 @@ class Instance:
            return False
        return True

-    @property
    def is_autostart(self) -> bool:
        """Return True if instance autostart is enabled, else return False."""
        try:
@@ -244,10 +259,18 @@ class Instance:
                f'instance={self.name}: {e}'
            ) from e

+    def get_max_memory(self) -> int:
+        """Maximum memory value for domain in KiB."""
+        return self.domain.maxMemory()
+
+    def get_max_vcpus(self) -> int:
+        """Maximum vCPUs number for domain."""
+        return self.domain.maxVcpus()
+
    def start(self) -> None:
        """Start defined instance."""
        log.info('Starting instnce=%s', self.name)
-        if self.is_running:
+        if self.is_running():
            log.warning(
                'Already started, nothing to do instance=%s', self.name
            )
@@ -311,6 +334,15 @@ class Instance:
                f'Cannot shutdown instance={self.name} ' f'{method=}: {e}'
            ) from e

+    def reboot(self) -> None:
+        """Send ACPI signal to guest OS to reboot. OS may ignore this."""
+        try:
+            self.domain.reboot()
+        except libvirt.libvirtError as e:
+            raise InstanceError(
+                f'Cannot reboot instance={self.name}: {e}'
+            ) from e
+
    def reset(self) -> None:
        """
        Reset instance.
@@ -331,14 +363,19 @@ class Instance:
                f'Cannot reset instance={self.name}: {e}'
            ) from e

-    def reboot(self) -> None:
-        """Send ACPI signal to guest OS to reboot. OS may ignore this."""
-        try:
-            self.domain.reboot()
-        except libvirt.libvirtError as e:
-            raise InstanceError(
-                f'Cannot reboot instance={self.name}: {e}'
-            ) from e
+    def power_reset(self) -> None:
+        """
+        Shutdown instance and start.
+
+        By analogy with real hardware, this is a normal server shutdown,
+        and then turning off from the power supply and turning it on again.
+
+        This method is applicable in cases where there has been a
+        configuration change in libvirt and you need to restart the
+        instance to apply the new configuration.
+        """
+        self.shutdown(method='NORMAL')
+        self.start()

    def set_autostart(self, *, enabled: bool) -> None:
        """
@@ -383,7 +420,7 @@ class Instance:
            flags = libvirt.VIR_DOMAIN_AFFECT_CONFIG
            self.domain.setVcpusFlags(nvcpus, flags=flags)
            if live is True:
-                if not self.is_running:
+                if not self.is_running():
                    log.warning(
                        'Instance is not running, changes applied in '
                        'instance config.'
@@ -453,7 +490,7 @@ class Instance:
        :param device: Object with device description e.g. DiskConfig
        :param live: Affect a running instance
        """
-        if live and self.is_running:
+        if live and self.is_running():
            flags = (
                libvirt.VIR_DOMAIN_AFFECT_LIVE
                | libvirt.VIR_DOMAIN_AFFECT_CONFIG
@@ -471,7 +508,7 @@ class Instance:
        :param device: Object with device description e.g. DiskConfig
        :param live: Affect a running instance
        """
-        if live and self.is_running:
+        if live and self.is_running():
            flags = (
                libvirt.VIR_DOMAIN_AFFECT_LIVE
                | libvirt.VIR_DOMAIN_AFFECT_CONFIG
--- a/compute/instance/schemas.py
+++ b/compute/instance/schemas.py
@@ -4,11 +4,20 @@ import re
 from enum import StrEnum
 from pathlib import Path

-from pydantic import BaseModel, validator
+from pydantic import BaseModel, Extra, validator

 from compute.utils.units import DataUnit


+class EntityModel(BaseModel):
+    """Basic entity model."""
+
+    class Config:
+        """Do not allow extra fields."""
+
+        extra = Extra.forbid
+
+
 class CPUEmulationMode(StrEnum):
    """CPU emulation mode enumerated."""

@@ -18,7 +27,7 @@ class CPUEmulationMode(StrEnum):
    MAXIMUM = 'maximum'


-class CPUTopologySchema(BaseModel):
+class CPUTopologySchema(EntityModel):
    """CPU topology model."""

    sockets: int
@@ -27,67 +36,66 @@ class CPUTopologySchema(BaseModel):
    dies: int = 1


-class CPUFeaturesSchema(BaseModel):
+class CPUFeaturesSchema(EntityModel):
    """CPU features model."""

    require: list[str]
    disable: list[str]


-class CPUSchema(BaseModel):
+class CPUSchema(EntityModel):
    """CPU model."""

    emulation_mode: CPUEmulationMode
-    model: str
-    vendor: str
-    topology: CPUTopologySchema
-    features: CPUFeaturesSchema
+    model: str | None
+    vendor: str | None
+    topology: CPUTopologySchema | None
+    features: CPUFeaturesSchema | None


 class VolumeType(StrEnum):
    """Storage volume types enumeration."""

    FILE = 'file'
-    NETWORK = 'network'


-class VolumeCapacitySchema(BaseModel):
+class VolumeCapacitySchema(EntityModel):
    """Storage volume capacity field model."""

    value: int
    unit: DataUnit


-class VolumeSchema(BaseModel):
+class VolumeSchema(EntityModel):
    """Storage volume model."""

    type: VolumeType  # noqa: A003
-    source: Path
    target: str
    capacity: VolumeCapacitySchema
-    readonly: bool = False
+    source: str | None = None
+    is_readonly: bool = False
    is_system: bool = False


-class NetworkInterfaceSchema(BaseModel):
+class NetworkInterfaceSchema(EntityModel):
    """Network inerface model."""

    source: str
    mac: str


-class BootOptionsSchema(BaseModel):
+class BootOptionsSchema(EntityModel):
    """Instance boot settings."""

    order: tuple


-class InstanceSchema(BaseModel):
+class InstanceSchema(EntityModel):
    """Compute instance model."""

    name: str
-    title: str
-    description: str
+    title: str | None
+    description: str | None
    memory: int
    max_memory: int
    vcpus: int
@@ -96,10 +104,10 @@ class InstanceSchema(BaseModel):
    machine: str
    emulator: Path
    arch: str
-    image: str
    boot: BootOptionsSchema
    volumes: list[VolumeSchema]
    network_interfaces: list[NetworkInterfaceSchema]
+    image: str | None = None

    @validator('name')
    def _check_name(cls, value: str) -> str:  # noqa: N805
@@ -111,12 +119,28 @@ class InstanceSchema(BaseModel):
            raise ValueError(msg)
        return value

-    @validator('volumes')
-    def _check_volumes(cls, value: list) -> list:  # noqa: N805
-        if len([v for v in value if v.is_system is True]) != 1:
-            msg = 'Volumes list must contain one system volume'
+    @validator('cpu')
+    def _check_topology(cls, cpu: int, values: dict) -> CPUSchema:  # noqa: N805
+        topo = cpu.topology
+        max_vcpus = values['max_vcpus']
+        if topo and topo.sockets * topo.cores * topo.threads != max_vcpus:
+            msg = f'CPU topology does not match with {max_vcpus=}'
            raise ValueError(msg)
-        return value
+        return cpu
+
+    @validator('volumes')
+    def _check_volumes(cls, volumes: list) -> list:  # noqa: N805
+        if len([v for v in volumes if v.is_system is True]) != 1:
+            msg = 'volumes list must contain one system volume'
+            raise ValueError(msg)
+        vol_with_source = 0
+        for vol in volumes:
+            if vol.is_system is True and vol.is_readonly is True:
+                msg = 'volume marked as system cannot be readonly'
+                raise ValueError(msg)
+            if vol.source is not None:
+                vol_with_source += 1
+        return volumes

    @validator('network_interfaces')
    def _check_network_interfaces(cls, value: list) -> list:  # noqa: N805
--- a/compute/session.py
+++ b/compute/session.py
@@ -26,6 +26,25 @@ class Capabilities(NamedTuple):
    virt: str
    emulator: str
    machine: str
+    max_vcpus: int
+
+
+class NodeInfo(NamedTuple):
+    """
+    Store compute node info.
+
+    See https://libvirt.org/html/libvirt-libvirt-host.html#virNodeInfo
+    NOTE: memory unit in libvirt docs is wrong! Actual unit is MiB.
+    """
+
+    arch: str
+    memory: int
+    cpus: int
+    mhz: int
+    nodes: int
+    sockets: int
+    cores: int
+    threads: int


 class Session(AbstractContextManager):
@@ -68,7 +87,21 @@ class Session(AbstractContextManager):
        """Close connection to libvirt daemon."""
        self.connection.close()

-    def capabilities(self) -> Capabilities:
+    def get_node_info(self) -> NodeInfo:
+        """Return information about compute node."""
+        info = self.connection.getInfo()
+        return NodeInfo(
+            arch=info[0],
+            memory=info[1],
+            cpus=info[2],
+            mhz=info[3],
+            nodes=info[4],
+            sockets=info[5],
+            cores=info[6],
+            threads=info[7],
+        )
+
+    def get_capabilities(self) -> Capabilities:
        """Return capabilities e.g. arch, virt, emulator, etc."""
        prefix = '/domainCapabilities'
        caps = etree.fromstring(self.connection.getDomainCapabilities())  # noqa: S320
@@ -77,6 +110,7 @@ class Session(AbstractContextManager):
            virt=caps.xpath(f'{prefix}/domain/text()')[0],
            emulator=caps.xpath(f'{prefix}/path/text()')[0],
            machine=caps.xpath(f'{prefix}/machine/text()')[0],
+            max_vcpus=int(caps.xpath(f'{prefix}/vcpu/@max')[0]),
        )

    def create_instance(self, **kwargs: Any) -> Instance:
@@ -87,14 +121,35 @@ class Session(AbstractContextManager):
        :type name: str
        :param title: Instance title for humans.
        :type title: str
-        :param description: Some information about instance
+        :param description: Some information about instance.
        :type description: str
        :param memory: Memory in MiB.
        :type memory: int
        :param max_memory: Maximum memory in MiB.
        :type max_memory: int
+        :param vcpus: Number of vCPUs.
+        :type vcpus: int
+        :param max_vcpus: Maximum vCPUs.
+        :type max_vcpus: int
+        :param cpu: CPU configuration. See :class:`CPUSchema` for info.
+        :type cpu: dict
+        :param machine: QEMU emulated machine.
+        :type machine: str
+        :param emulator: Path to emulator.
+        :type emulator: str
+        :param arch: CPU architecture to virtualization.
+        :type arch: str
+        :param boot: Boot settings. See :class:`BootOptionsSchema`.
+        :type boot: dict
+        :param image: Source disk image name for system disk.
+        :type image: str
+        :param volumes: List of storage volume configs. For more info
+            see :class:`VolumeSchema`.
+        :type volumes: list[dict]
+        :param network_interfaces: List of virtual network interfaces
+            configs. See :class:`NetworkInterfaceSchema` for more info.
+        :type network_interfaces: list[dict]
        """
-        # TODO @ge: create instances in transaction
        data = InstanceSchema(**kwargs)
        config = InstanceConfig(data)
        log.info('Define XML...')
@@ -113,19 +168,17 @@ class Session(AbstractContextManager):
            log.info('Connecting to volumes pool...')
            volumes_pool = self.get_storage_pool(self.VOLUMES_POOL)
            log.info('Building volume configuration...')
-            # if not volume.source:
-            # В случае если пользователь передаёт source для волюма, следует
-            # в либвирте делать поиск волюма по пути, а не по имени
-            #    gen_vol_name
-            # TODO @ge: come up with something else
-            vol_name = f'{config.name}-{volume.target}-{uuid4()}.qcow2'
+            if not volume.source:
+                vol_name = f'{config.name}-{volume.target}-{uuid4()}.qcow2'
+            else:
+                vol_name = volume.source
            vol_conf = VolumeConfig(
                name=vol_name,
                path=str(volumes_pool.path.joinpath(vol_name)),
                capacity=capacity,
            )
            log.info('Volume configuration is:\n %s', vol_conf.to_xml())
-            if volume.is_system is True:
+            if volume.is_system is True and data.image:
                log.info(
                    "Volume is marked as 'system', start cloning image..."
                )
--- a/compute/storage/pool.py
+++ b/compute/storage/pool.py
@@ -15,8 +15,8 @@ from .volume import Volume, VolumeConfig
 log = logging.getLogger(__name__)


-class StoragePoolUsage(NamedTuple):
-    """Storage pool usage info schema."""
+class StoragePoolUsageInfo(NamedTuple):
+    """Storage pool usage info."""

    capacity: int
    allocation: int
@@ -30,17 +30,17 @@ class StoragePool:
        """Initislise StoragePool."""
        self.pool = pool
        self.name = pool.name()
+        self.path = self._get_path()

-    @property
-    def path(self) -> Path:
+    def _get_path(self) -> Path:
        """Return storage pool path."""
        xml = etree.fromstring(self.pool.XMLDesc())  # noqa: S320
        return Path(xml.xpath('/pool/target/path/text()')[0])

-    def usage(self) -> StoragePoolUsage:
+    def get_usage_info(self) -> StoragePoolUsageInfo:
        """Return info about storage pool usage."""
        xml = etree.fromstring(self.pool.XMLDesc())  # noqa: S320
-        return StoragePoolUsage(
+        return StoragePoolUsageInfo(
            capacity=int(xml.xpath('/pool/capacity/text()')[0]),
            allocation=int(xml.xpath('/pool/allocation/text()')[0]),
            available=int(xml.xpath('/pool/available/text()')[0]),
@@ -58,7 +58,7 @@ class StoragePool:
    def create_volume(self, vol_conf: VolumeConfig) -> Volume:
        """Create storage volume and return Volume instance."""
        log.info(
-            'Create storage volume vol=%s in pool=%s', vol_conf.name, self.pool
+            'Create storage volume vol=%s in pool=%s', vol_conf.name, self.name
        )
        vol = self.pool.createXML(
            vol_conf.to_xml(),
--- a/compute/storage/volume.py
+++ b/compute/storage/volume.py
@@ -87,11 +87,7 @@ class Volume:
        self.pool_name = pool.name()
        self.vol = vol
        self.name = vol.name()
-
-    @property
-    def path(self) -> Path:
-        """Return path to volume."""
-        return Path(self.vol.path())
+        self.path = Path(vol.path())

    def dump_xml(self) -> str:
        """Return volume XML description as string."""
--- a/compute/utils/identifiers.py
+++ b/compute/utils/identifiers.py
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -1,3 +1,4 @@
+# Add ../../compute to path for autodoc
 import os
 import sys
 sys.path.insert(0, os.path.abspath('../../compute'))
--- a/docs/source/python-api/exceptions.rst
+++ b/docs/source/python-api/exceptions.rst
@@ -0,0 +1,5 @@
+``exceptions``
+==============
+
+.. automodule:: compute.exceptions
+   :members:
--- a/docs/source/python-api/index.rst
+++ b/docs/source/python-api/index.rst
@@ -45,3 +45,5 @@ Modules documentation
    session
    instance/index
    storage/index
+    utils
+    exceptions
--- a/docs/source/python-api/instance/guest_agent.rst
+++ b/docs/source/python-api/instance/guest_agent.rst
@@ -3,3 +3,4 @@

 .. automodule:: compute.instance.guest_agent
   :members:
+   :special-members: __init__
--- a/docs/source/python-api/instance/instance.rst
+++ b/docs/source/python-api/instance/instance.rst
@@ -3,4 +3,4 @@

 .. automodule:: compute.instance.instance
   :members:
-   :special-members:
+   :special-members: __init__
--- a/docs/source/python-api/session.rst
+++ b/docs/source/python-api/session.rst
@@ -1,9 +1,6 @@
 ``session``
 ===========

-.. autoclass:: compute.Session
-   :members:
-   :special-members:
-
-.. autoclass:: compute.session.Capabilities
+.. automodule:: compute.session
   :members:
+   :special-members: __init__
--- a/docs/source/python-api/storage/pool.rst
+++ b/docs/source/python-api/storage/pool.rst
@@ -3,3 +3,4 @@

 .. automodule:: compute.storage.pool
   :members:
+   :special-members: __init__
--- a/docs/source/python-api/storage/volume.rst
+++ b/docs/source/python-api/storage/volume.rst
@@ -3,3 +3,4 @@

 .. automodule:: compute.storage.volume
   :members:
+   :special-members: __init__
--- a/docs/source/python-api/utils.rst
+++ b/docs/source/python-api/utils.rst
@@ -0,0 +1,14 @@
+``utils``
+=========
+
+``utils.units``
+---------------
+
+.. automodule:: compute.utils.units
+   :members:
+
+``utils.ids``
+-------------
+
+.. automodule:: compute.utils.ids
+   :members:
--- a/fdict.py
+++ b/fdict.py
@@ -0,0 +1,25 @@
+from collections import UserDict
+from typing import Any
+
+class _NotPresent:
+    """
+    Type for representing non-existent dictionary keys.
+
+    See :class:`_FillableDict`
+    """
+
+class _FillableDict(UserDict):
+    """Use :method:`fill` to add key if not present."""
+
+    def __init__(self, data: dict):
+        self.data = data
+
+    def fill(self, key: str, value: Any) -> None:
+        if self.data.get(key, _NotPresent) is _NotPresent:
+            self.data[key] = value
+
+d = _FillableDict({'a': None, 'b': 'BBBB'})
+d.fill('c', 'CCCCCCCCC')
+d.fill('a', 'CCCCCCCCC')
+d['a'].fill('gg', 'AAAAAAAA')
+print(d)
--- a/instance.yaml
+++ b/instance.yaml
@@ -0,0 +1,10 @@
+title: dev-1
+vcpus: 4
+memory: 4096
+volumes:
+  - is_system: true
+    type: file
+    target: vda
+    capacity:
+      value: 5
+      unit: GiB
--- a/pars.py
+++ b/pars.py
@@ -0,0 +1,34 @@
+import re
+
+
+def _split_unit(val: str) -> dict | None:
+    match = re.match(r'([0-9]+)([a-z]+)', val, re.I)
+    if match:
+        return {
+            'value': match.groups()[0],
+            'unit': match.groups()[1],
+        }
+    return None
+
+
+def _parse_complex_arg(arg: str) -> dict:
+    # key=value --> {'key': 'value'}
+    if re.match(r'.+=.+', arg):
+        key, val = arg.split('=')
+    # system --> {'is_system': True}
+    # ro --> {'is_readonly': True}
+    elif re.match(r'^[a-z0-9_\.\-]+$', arg, re.I):
+        key = 'is_' + arg.replace('ro', 'readonly')
+        val = True
+    else:
+        raise ValueError('Invalid argument pattern')
+    # key=15GiB --> {'key': {'value': 15, 'unit': 'GiB'}}
+    if not isinstance(val, bool):
+        val = _split_unit(val) or val
+    return {key: val}
+
+
+print(_parse_complex_arg('source=/volumes/50c4410b-2ef0-4ffd-a2e5-04f0212772d4.qcow2'))
+print(_parse_complex_arg('capacity=15GiB'))
+print(_parse_complex_arg('system'))
+print(_parse_complex_arg('cpu.cores=8'))
--- a/pd.py
+++ b/pd.py
@@ -0,0 +1,20 @@
+from pydantic import BaseModel, Extra
+
+
+class EntityModel(BaseModel):
+    """Basic entity model."""
+
+    aaa: int
+    bbb: int
+
+    class Config:
+        extra = Extra.forbid
+
+
+class Some(EntityModel):
+    ooo: str
+    www: str
+
+a = Some(ooo='dsda', www='wcd', sds=1)
+
+print(a)
--- a/poetry.lock
+++ b/poetry.lock
@@ -511,6 +511,66 @@ files = [
 [package.extras]
 plugins = ["importlib-metadata"]

+[[package]]
+name = "pyyaml"
+version = "6.0.1"
+description = "YAML parser and emitter for Python"
+category = "main"
+optional = false
+python-versions = ">=3.6"
+files = [
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+    {file = "PyYAML-6.0.1-cp38-cp38-win32.whl", hash = "sha256:184c5108a2aca3c5b3d3bf9395d50893a7ab82a38004c8f61c258d4428e80206"},
+    {file = "PyYAML-6.0.1-cp38-cp38-win_amd64.whl", hash = "sha256:1e2722cc9fbb45d9b87631ac70924c11d3a401b2d7f410cc0e3bbf249f2dca62"},
+    {file = "PyYAML-6.0.1-cp39-cp39-macosx_10_9_x86_64.whl", hash = "sha256:9eb6caa9a297fc2c2fb8862bc5370d0303ddba53ba97e71f08023b6cd73d16a8"},
+    {file = "PyYAML-6.0.1-cp39-cp39-macosx_11_0_arm64.whl", hash = "sha256:c8098ddcc2a85b61647b2590f825f3db38891662cfc2fc776415143f599bb859"},
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+    {file = "PyYAML-6.0.1-cp39-cp39-manylinux_2_17_s390x.manylinux2014_s390x.whl", hash = "sha256:b786eecbdf8499b9ca1d697215862083bd6d2a99965554781d0d8d1ad31e13a0"},
+    {file = "PyYAML-6.0.1-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:bc1bf2925a1ecd43da378f4db9e4f799775d6367bdb94671027b73b393a7c42c"},
+    {file = "PyYAML-6.0.1-cp39-cp39-musllinux_1_1_x86_64.whl", hash = "sha256:04ac92ad1925b2cff1db0cfebffb6ffc43457495c9b3c39d3fcae417d7125dc5"},
+    {file = "PyYAML-6.0.1-cp39-cp39-win32.whl", hash = "sha256:faca3bdcf85b2fc05d06ff3fbc1f83e1391b3e724afa3feba7d13eeab355484c"},
+    {file = "PyYAML-6.0.1-cp39-cp39-win_amd64.whl", hash = "sha256:510c9deebc5c0225e8c96813043e62b680ba2f9c50a08d3724c7f28a747d1486"},
+    {file = "PyYAML-6.0.1.tar.gz", hash = "sha256:bfdf460b1736c775f2ba9f6a92bca30bc2095067b8a9d77876d1fad6cc3b4a43"},
+]
+
 [[package]]
 name = "requests"
 version = "2.31.0"
@@ -834,5 +894,5 @@ zstd = ["zstandard (>=0.18.0)"]

 [metadata]
 lock-version = "2.0"
-python-versions = "^3.11"
-content-hash = "413ca8b2e0d37bf9e2835dd9050a3cc98e4a37186c78b780a65d62d05adce8c1"
+python-versions = '^3.11'
+content-hash = "e5c07eebe683b92360ec12cada14fc5ccbe4e4add52549bf978f580e551abfb0"
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,53 +1,60 @@
 [tool.poetry]
-name = "compute"
-version = "0.1.0"
-description = "Library built on top of libvirt for Compute Service"
-authors = ["ge <ge@nixhacks.net>"]
-readme = "README.md"
+name = 'compute'
+version = '0.1.0'
+description = 'Compute instances management library'
+authors = ['ge <ge@nixhacks.net>']
+readme = 'README.md'

 [tool.poetry.dependencies]
-python = "^3.11"
-libvirt-python = "9.0.0"
-lxml = "^4.9.2"
-pydantic = "1.10.4"
+python = '^3.11'
+libvirt-python = '9.0.0'
+lxml = '^4.9.2'
+pydantic = '1.10.4'
+pyyaml = "^6.0.1"

 [tool.poetry.scripts]
-compute = "compute.cli.control:cli"
+compute = 'compute.cli.control:cli'

 [tool.poetry.group.dev.dependencies]
-ruff = "^0.1.3"
-isort = "^5.12.0"
+ruff = '^0.1.3'
+isort = '^5.12.0'

 [tool.poetry.group.docs.dependencies]
-sphinx = "^7.2.6"
-sphinx-autobuild = "^2021.3.14"
-sphinx-multiversion = "^0.2.4"
+sphinx = '^7.2.6'
+sphinx-autobuild = '^2021.3.14'
+sphinx-multiversion = '^0.2.4'

 [build-system]
-requires = ["poetry-core"]
-build-backend = "poetry.core.masonry.api"
+requires = ['poetry-core']
+build-backend = 'poetry.core.masonry.api'
+
+[tool.isort]
+skip = ['.gitignore']
+lines_after_imports = 2
+include_trailing_comma = true
+split_on_trailing_comma = true

 [tool.ruff]
 line-length = 79
 indent-width = 4
-target-version = "py311"
+target-version = 'py311'

 [tool.ruff.lint]
-select = ["ALL"]
+select = ['ALL']
 ignore = [
-    "Q000", "Q003", "D211", "D212", "ANN101", "ISC001", "COM812",
-    "D203", "ANN204", "T201",
-    "EM102", "TRY003", # maybe not ignore?
-    "TD003", "TD006", "FIX002",  # todo strings linting
+    'Q000', 'Q003', 'D211', 'D212', 'ANN101', 'ISC001', 'COM812',
+    'D203', 'ANN204', 'T201',
+    'EM102', 'TRY003',  # maybe not ignore?
+    'TD003', 'TD006', 'FIX002',  # todo strings linting
 ]
-exclude = ["__init__.py"]
+exclude = ['__init__.py']

 [tool.ruff.lint.flake8-annotations]
 mypy-init-return = true
 allow-star-arg-any = true

 [tool.ruff.format]
-quote-style = "single"
+quote-style = 'single'

 [tool.ruff.isort]
 lines-after-imports = 2