一个Openstack 系统中通常包括多个计算节点
root@controller:/etc/nova# nova hypervisor-list +----+---------------------+ | ID | Hypervisor hostname | +----+---------------------+ | 1 | compute | | 2 | network | | 3 | compute2 | +----+---------------------+这就产生了一个问题，当发出创建虚拟机请求时，应该把虚拟机创建到哪个计算节点上呢？ nova-scheduler 服务即是实现这个调度工作的，调度算法通过filter 和weight 来实现。filter 用于选择可用的计算节点。weight 用于在可用的计算节点中选择一个最佳的节点。
filter
filter 在nova.conf 中配置，改动须要重新启动nova-scheduler 服务
默认的filter 为（截取icehouse版）
scheduler_default_filters = RetryFilter, AvailabilityZoneFilter, RamFilter,ComputeFilter, ComputeCapabilitiesFilter, ImagePropertiesFilter
以下列出各个filter 的功能
RetryFilter: 剔除上传已经被尝试调度过的计算节点AvailabilityZoneFilter:剔除那些AvailabilityZone 不满足要求的计算节点
ComputeFilter 剔除那些非活动的计算节点
ComputeCapabilitiesFilter 检查计算节点的其它属性
ImagePropertiesFilter 剔除那些硬件架构，Hypervisor，虚拟机模式等属性不满足磁盘镜像要求的节点
filter 类存放在nova/scheduler/filter 文件夹下全部的
root@controller:/usr/lib/python2.7/dist-packages/nova/scheduler/filters# ll *.pyc -rw-r--r-- 1 root root 7207 Jul 15 09:33 affinity_filter.pyc -rw-r--r-- 1 root root 2400 Jul 15 09:33 aggregate_image_properties_isolation.pyc -rw-r--r-- 1 root root 2399 Jul 15 09:33 aggregate_instance_extra_specs.pyc -rw-r--r-- 1 root root 1896 Jul 15 09:33 aggregate_multitenancy_isolation.pyc -rw-r--r-- 1 root root 807 Jul 15 09:33 all_hosts_filter.pyc -rw-r--r-- 1 root root 1588 Jul 15 09:33 availability_zone_filter.pyc -rw-r--r-- 1 root root 2514 Jul 15 09:33 compute_capabilities_filter.pyc -rw-r--r-- 1 root root 1763 Jul 15 09:33 compute_filter.pyc -rw-r--r-- 1 root root 3671 Jul 15 09:33 core_filter.pyc -rw-r--r-- 1 root root 1900 Jul 15 09:33 disk_filter.pyc -rw-r--r-- 1 root root 2107 Jul 15 09:33 extra_specs_ops.pyc -rw-r--r-- 1 root root 4003 Jul 15 09:33 image_props_filter.pyc -rw-r--r-- 1 root root 2007 Jul 15 09:33 __init__.pyc -rw-r--r-- 1 root root 1641 Jul 15 09:33 io_ops_filter.pyc -rw-r--r-- 1 root root 2300 Jul 15 09:33 isolated_hosts_filter.pyc -rw-r--r-- 1 root root 5435 Jul 15 09:33 json_filter.pyc -rw-r--r-- 1 root root 2021 Jul 15 09:33 metrics_filter.pyc -rw-r--r-- 1 root root 1521 Jul 15 09:33 num_instances_filter.pyc -rw-r--r-- 1 root root 1497 Jul 15 09:33 pci_passthrough_filter.pyc -rw-r--r-- 1 root root 3824 Jul 15 09:33 ram_filter.pyc -rw-r--r-- 1 root root 1448 Jul 15 09:33 retry_filter.pyc -rw-r--r-- 1 root root 9769 Jul 15 09:33 trusted_filter.pyc -rw-r--r-- 1 root root 2237 Jul 15 09:33 type_filter.pyc
affinity_filter.py
这里文件中事实上有四个可用filter，都是关于亲和性的调度策略。分别例如以下：
DifferentHostFilter
创建虚拟机的同一时候能够指定一些虚拟机，要求新的虚拟机不能在这些虚拟机所在主机上创建。
说的简单一点，在host1上执行着vm1，要创建vm2。创建时指定了scheduler_hints->different_host=[vm1]。那么vm2就不会在host1上创建。
SameHostFilter
与上面的filter功能相反，假设创建时指定了scheduler_hints-> same_host=[vm1]，那么vm2就能够创建在host1上。
SimpleCIDRAffinityFilter
假设指定了scheduler_hints-> build_near_host_ip，那么仅仅能在host1的管理IP网段内选择主机。
GroupAntiAffinityFilter
功能：指定scheduler_hints-> group_hosts=[host1, host2]，那么虚拟机不能创建在这些host上。
core_filter.py
CoreFilter
功能：看host上的vcpu个数是否能满足创建虚拟机的instance_type中的vcpu个数。
依据CONF.cpu_allocation_ratio（默认是16）确定host上当前的vcpus_total。
disk_filter.py
DiskFilter
功能：看host上的disk大小是否能满足创建虚拟机的instance_type中的(root_gb + ephemeral_gb)。
计算disk总量时，会依据CONF.disk_allocation_ratio计算
ram_filter.py
RamFilter
AggregateRamFilter
同CoreFilter同样。
CONF.ram_allocation_ratio=1.5
image_props_filter.py
ImagePropertiesFilter
功能：看虚拟机image->properties中某些属性是否在host的capabilities->supported_instances内。
属性包含：architecture、hypervisor_type、vm_mode。假设image->properties中没有这些属性，则通过过滤；假设有这些属性，而host->capabilities->supported_instances没有，返回False。
io_ops_filter.py
IoOpsFilter
功能：依据主机的IO负载过滤。
IO负载由host->num_io_ops表示，与CONF.max_io_ops_per_host（默认是8）比較。
isolated_hosts_filter.py
IsolatedHostsFilter
功能：假设没有配置CONF.isolated_images，当前host不在CONF.isolated_hosts中，返回True。假设虚拟机image_ref在CONF.isolated_images中，且host在CONF.isolated_hosts中，返回True。其它情况返回False。
測试filter
我的环境眼下启动两个计算节点，horizon中的虚拟机管理器能够看到，compue 上可用资源最多。理论应该创建到compue 上
虚拟机在同样计算节点
改动scheduler_default_filters=SameHostFilter
root@controller:/etc/nova# cat nova.conf [DEFAULT] scheduler_default_filters=SameHostFilter
或者在原有filter 前面加入 （规则从前到后优先）
scheduler_default_filters = SameHostFilter,RetryFilter, AvailabilityZoneFilter, RamFilter,ComputeFilter, ComputeCapabilitiesFilter, ImagePropertiesFilter
运行创建虚拟机，加入參数same_host=想要指定的虚拟机，6c16999c-e94a-4947-8489-1333d28862f8 为
在network 节点。
root@controller:/etc/nova# nova show 6c16999c-e94a-4947-8489-1333d28862f8
+--------------------------------------+------------------------------------------------------------+
| Property | Value |
+--------------------------------------+------------------------------------------------------------+
| OS-DCF:diskConfig | MANUAL |
| OS-EXT-AZ:availability_zone | nova |
| OS-EXT-SRV-ATTR:host | network |
| OS-EXT-SRV-ATTR:hypervisor_hostname | network |
| OS-EXT-SRV-ATTR:instance_name | instance-00000135 |
| OS-EXT-STS:power_state | 1 |
| OS-EXT-STS:task_state | - |
| OS-EXT-STS:vm_state | active |
| OS-SRV-USG:launched_at | 2015-12-25T03:30:35.000000 |
| OS-SRV-USG:terminated_at | - |
| accessIPv4 | |
| accessIPv6 | |
| config_drive | |
| created | 2015-12-25T03:30:29Z |
| flavor | m1 (bbf0b691-2f6a-4781-885c-26511f3f9318) |
| hostId | 98b5cba71c2e72f61d0acb210bf7cc01a6ed8a3facabd5b6f4560f2a |
| id | 6c16999c-e94a-4947-8489-1333d28862f8 |
| image | cirros-0.3.2-x86_64 (d5aab3ac-74b5-4d53-91ee-92a22b48bb61) |
| key_name | admin-key |
| metadata | {} |
| name | vm2 |
| os-extended-volumes:volumes_attached | [] |
| progress | 0 |
| security_groups | default |
| sharednet1 network | 192.168.12.116 |
| status | ACTIVE |
| tenant_id | 2996e46c2519415d8de2b141d6c607ba |
| updated | 2015-12-25T03:30:35Z |
| user_id | 84ad09b97a7f41d08afdf20afee08daf |
+--------------------------------------+------------------------------------------------------------+nova boot --flavor m1 --image cirros-0.3.2-x86_64 --nic net-id=d691ca44-6ec4-4118-b8dd-76f363a2b53f --security-group default --key-name admin-key vm5 --hint same_host=6c16999c-e94a-4947-8489-1333d28862f8
root@controller:~# source admin-openrc.sh
root@controller:~# nova boot --flavor m1 --image cirros-0.3.2-x86_64 --nic net-id=d691ca44-6ec4-4118-b8dd-76f363a2b53f --security-group default --key-name admin-key vm5 --hint same_host=6c16999c-e94a-4947-8489-1333d28862f8
+--------------------------------------+------------------------------------------------------------+
| Property | Value |
+--------------------------------------+------------------------------------------------------------+
| OS-DCF:diskConfig | MANUAL |
| OS-EXT-AZ:availability_zone | nova |
| OS-EXT-SRV-ATTR:host | - |
| OS-EXT-SRV-ATTR:hypervisor_hostname | - |
| OS-EXT-SRV-ATTR:instance_name | instance-0000013c |
| OS-EXT-STS:power_state | 0 |
| OS-EXT-STS:task_state | scheduling |
| OS-EXT-STS:vm_state | building |
| OS-SRV-USG:launched_at | - |
| OS-SRV-USG:terminated_at | - |
| accessIPv4 | |
| accessIPv6 | |
| adminPass | LHdQ245ZKktd |
| config_drive | |
| created | 2015-12-25T07:27:38Z |
| flavor | m1 (bbf0b691-2f6a-4781-885c-26511f3f9318) |
| hostId | |
| id | e9863fe9-effc-475a-b1c1-5925080c8399 |
| image | cirros-0.3.2-x86_64 (d5aab3ac-74b5-4d53-91ee-92a22b48bb61) |
| key_name | admin-key |
| metadata | {} |
| name | vm5 |
| os-extended-volumes:volumes_attached | [] |
| progress | 0 |
| security_groups | default |
| status | BUILD |
| tenant_id | 2996e46c2519415d8de2b141d6c607ba |
| updated | 2015-12-25T07:27:39Z |
| user_id | 84ad09b97a7f41d08afdf20afee08daf |
+--------------------------------------+------------------------------------------------------------+
root@controller:~# nova show e9863fe9-effc-475a-b1c1-5925080c8399
+--------------------------------------+------------------------------------------------------------+
| Property | Value |
+--------------------------------------+------------------------------------------------------------+
| OS-DCF:diskConfig | MANUAL |
| OS-EXT-AZ:availability_zone | nova |
| OS-EXT-SRV-ATTR:host | network |
| OS-EXT-SRV-ATTR:hypervisor_hostname | network |
| OS-EXT-SRV-ATTR:instance_name | instance-0000013c |
| OS-EXT-STS:power_state | 1 |
| OS-EXT-STS:task_state | - |
| OS-EXT-STS:vm_state | active |
| OS-SRV-USG:launched_at | 2015-12-25T07:27:46.000000 |
| OS-SRV-USG:terminated_at | - |
| accessIPv4 | |
| accessIPv6 | |
| config_drive | |
| created | 2015-12-25T07:27:38Z |
| flavor | m1 (bbf0b691-2f6a-4781-885c-26511f3f9318) |
| hostId | 98b5cba71c2e72f61d0acb210bf7cc01a6ed8a3facabd5b6f4560f2a |
| id | e9863fe9-effc-475a-b1c1-5925080c8399 |
| image | cirros-0.3.2-x86_64 (d5aab3ac-74b5-4d53-91ee-92a22b48bb61) |
| key_name | admin-key |
| metadata | {} |
| name | vm5 |
| os-extended-volumes:volumes_attached | [] |
| progress | 0 |
| security_groups | default |
| sharednet1 network | 192.168.12.122 |
| status | ACTIVE |
| tenant_id | 2996e46c2519415d8de2b141d6c607ba |
| updated | 2015-12-25T07:27:46Z |
| user_id | 84ad09b97a7f41d08afdf20afee08daf |
+--------------------------------------+------------------------------------------------------------+
root@controller:~#查看，新虚拟机又创建到了network 上面
