别以为真懂Openstack: 虚拟机创建的50个步骤和100个知识点(2)

二、nova-api

步骤3：nova-api接收请求

nova-api接收请求，也不是随便怎么来都接收的，而是需要设定rate limits，默认的实现是在ratelimit的middleware里面实现的。

然而有时候，我们希望实现distributed rate-limiting，从而Turnstile是一个不错的选择。

https://github.com/klmitch/turnstile
http://pypi.python.org/pypi/turnstile

步骤4：对Token的验证

步骤5：查看Policy

这两步已经在keystone的时候研究过

步骤6：检查quota

nova, neutron, Cinder各有各的quota，并且可以从命令行进行管理

# nova -h | grep quota
    quota-class-show    List the quotas for a quota class.
    quota-class-update  Update the quotas for a quota class.
    quota-defaults      List the default quotas for a tenant.
    quota-delete        Delete quota for a tenant/user so their quota will
    quota-show          List the quotas for a tenant/user.
    quota-update        Update the quotas for a tenant/user.

# nova quota-show
+-----------------------------+-------+
| Quota                       | Limit |
+-----------------------------+-------+
| instances                   | 10    |
| cores                       | 20    |
| ram                         | 51200 |
| floating_ips                | 10    |
| fixed_ips                   | -1    |
| metadata_items              | 128   |
| injected_files              | 5     |
| injected_file_content_bytes | 10240 |
| injected_file_path_bytes    | 255   |
| key_pairs                   | 100   |
| security_groups             | 10    |
| security_group_rules        | 20    |
+-----------------------------+-------+

# cinder -h | grep quota
    quota-class-show    List the quotas for a quota class.
    quota-class-update  Update the quotas for a quota class.
    quota-defaults      List the default quotas for a tenant.
    quota-show          List the quotas for a tenant.
    quota-update        Update the quotas for a tenant.
    quota-usage         List the quota usage for a tenant.

# cinder quota-show 1779b3bc725b44b98726fb0cbdc617b1
+-----------+-------+
|  Property | Value |
+-----------+-------+
| gigabytes |  1000 |
| snapshots |   10  |
|  volumes  |   10  |
+-----------+-------+

# neutron -h | grep quota
  quota-delete                   Delete defined quotas of a given tenant.
  quota-list                     List quotas of all tenants who have non-default quota values.
  quota-show                     Show quotas of a given tenant
  quota-update                   Define tenant's quotas not to use defaults.

# neutron quota-show 1779b3bc725b44b98726fb0cbdc617b1
+---------------------+-------+
| Field               | Value |
+---------------------+-------+
| floatingip          | 50    |
| network             | 10    |
| port                | 50    |
| router              | 10    |
| security_group      | 10    |
| security_group_rule | 100   |
| subnet              | 10    |
+---------------------+-------+

推荐下面的文章

openstack nova 基础知识——Quota（配额管理）

http://www.sebastien-han.fr/blog/2012/09/19/openstack-play-with-quota/

步骤7：在数据库中创建Instance实例

有关nova的database schema参考下面的文章

http://www.prestonlee.com/2012/05/03/openstack-nova-essex-mysql-database-schema-diagram-and-sql/

MySQL是Openstack中最重要的组件之一，所以在生产环境中High Availability是必须的。

MySQL的HA有下面几种方式：

http://dev.mysql.com/doc/mysql-ha-scalability/en/index.html

Requirement	MySQL Replication	MySQL with DRBD with Corosync and Pacemaker	MySQL Cluster
Availability
Platform Support	All Supported by MySQL Server	Linux	All Supported by MySQL Cluster
Automated IP Failover	No	Yes	Depends on Connector and Configuration
Automated Database Failover	No	Yes	Yes
Automatic Data Resynchronization	No	Yes	Yes
Typical Failover Time	User / Script Dependent	Configuration Dependent, 60 seconds and Above	1 Second and Less
Synchronous Replication	No, Asynchronous and Semisynchronous	Yes	Yes
Shared Storage	No, Distributed	No, Distributed	No, Distributed
Geographic redundancy support	Yes	Yes, via MySQL Replication	Yes, via MySQL Replication
Update Schema On-Line	No	No	Yes
Scalability
Number of Nodes	One Master, Multiple Slaves	One Active (primary), one Passive (secondary) Node	255
Built-in Load Balancing	Reads, via MySQL Replication	Reads, via MySQL Replication	Yes, Reads and Writes
Supports Read-Intensive Workloads	Yes	Yes	Yes
Supports Write-Intensive Workloads	Yes, via Application-Level Sharding	Yes, via Application-Level Sharding to Multiple Active/Passive Pairs	Yes, via Auto-Sharding
Scale On-Line (add nodes, repartition, etc.)	No	No	Yes

要想系统的学习Mysql replication，推荐下面的这本书

《MySQL High Availability Tools for Building Robust Data Centers》

还有一种方式是Mysql + galera，可以搭建Active + Active的Mysql应用

参考下面的两篇文章

http://www.sebastien-han.fr/blog/2012/04/08/mysql-galera-cluster-with-haproxy/

http://www.sebastien-han.fr/blog/2012/04/01/mysql-multi-master-replication-with-galera/

还有一种常见的HA的技术，就是pacemaker

最底层是通信层corosync/openais

负责cluster中node之间的通信

上一层是Resource Allocation Layer，包含下面的组件：

CRM Cluster Resouce Manager

是总管，对于resource做的任何操作都是通过它。每个机器上都有一个CRM。

CIB Cluster Information Base

CIB由CRM管理，是在内存中的XML数据库，保存了cluster的配置和状态。我们查询出来的configuration都是保存在CIB里面的。nodes, resources, constraints, relationship.

DC Designated Coordinator

每个node都有CRM，会有一个被选为DC，是整个Cluster的大脑，这个DC控制的CIB是master CIB，其他的CIB都是副本。

PE Policy Engine

当DC需要进行一些全局配置的时候，首先由PE根据当前的状态和配置，计算出将来的状态，并生成一系列的action，使得cluster从初始状态变为结果状态。PE仅仅在DC上运行。

LRM Local Resource Manager

本地的resource管理，调用resource agent完成操作，启停resource，将结果返回给CRM

再上一层是Resource Layer

包含多个resource agent。resource agent往往是一些shell script，用来启动，停止，监控resource的状态。

要弄懂Pacemaker，推荐读《SUSE high availability guide》

https://www.suse.com/documentation/sle_ha/singlehtml/book_sleha/book_sleha.html

本人做了一些笔记和实验，请参考

High Availability手册(1): 环境

High Availability手册(2): 架构

High Availability手册(3): 配置

步骤8：创建filter_properties，用于nova scheduler

步骤9：发送RPC给nova-conductor

有关nova-conductor的文章

http://cloudystuffhappens.blogspot.com/2013/04/understanding-nova-conductor-in.html

在Openstack中，RPC的发送是通过RabbitMQ

RabbitMQ可以通过Pacemaker进行HA，当然也可以搭建自己的RabbitMQ Cluster

学习RabbitMQ当然首推《RabbitMQ in Action》

本人也做了一些笔记

RabbitMQ in Action (1): Understanding messaging

RabbitMQ in Action (2): Running and administering Rabbit

RabbitMQ in Action(5): Clustering and dealing with failure

还没完全读完，敬请谅解

当然Openstack中对于RabbitMQ的使用，一篇很好的文章是

NOVA源码分析——NOVA中的RabbitMQ解析

本人也对RPC的调用过程进行了代码分析

Openstack中RabbitMQ RPC代码分析

步骤10：nova-condutor创建request_spec，用于scheduler

步骤11：nova-conductor发送RPC给nova-scheduler

三、nova-scheduler

选择一个物理机来创建虚拟机，我们称为schedule的过程

nova scheduler的一个经典的图如下

就是先Filter再Weighting，其实scheduler的过程在很早就参与了。

步骤13：对Host进行Filtering

Filtering主要通过两个变量进行，request_spec和filter_properties，而这些变量在前面的步骤，都已经准备好了。

而不同的Filter只是利用这些信息，然后再根据从HostManager统计上来的HostState信息，选出匹配的Host。

request_spec中的第一个信息就是image的properties信息，尤其是当你想支持多种Hypervisor的时候，Xen的image, KVM的image, Hyper-V的image各不相同，如何保证image跑在正确的Hypervisor上？在image里面这种hypervisor_type property就很必要。

请阅读下面的文章

http://www.cloudbase.it/filtering-glance-images-for-hyper-v/

image properties还会有min_ram, min_disk，只有内存和硬盘够大才可以。

Flavor里面可以设置extra_specs，这是一系列key-value值，在数据结构中，以instance_type变量实现，可以在里面输入这个Flavor除了资源需求的其他参数，从而在Filter的时候，可以使用。

host aggregates将所有的Host分成多个Group，当然不同的Group可以根据不同的属性Metadata划分，一种是高性能和低性能。

在Openstack文档中，这个例子很好的展示了host aggregates和Flavor extra_specs的配合使用

http://docs.openstack.org/trunk/config-reference/content/section_compute-scheduler.html

Example: Specify compute hosts with SSDs

This example configures the Compute service to enable users to request nodes that have solid-state drives (SSDs). You create a fast-io host aggregate in the nova availability zone and you add the ssd=true key-value pair to the aggregate. Then, you add the node1, and node2 compute nodes to it.

$ nova aggregate-create fast-io nova
+----+---------+-------------------+-------+----------+
| Id | Name    | Availability Zone | Hosts | Metadata |
+----+---------+-------------------+-------+----------+
| 1  | fast-io | nova              |       |          |
+----+---------+-------------------+-------+----------+

$ nova aggregate-set-metadata 1 ssd=true
+----+---------+-------------------+-------+-------------------+
| Id | Name    | Availability Zone | Hosts | Metadata          |
+----+---------+-------------------+-------+-------------------+
| 1  | fast-io | nova              | []    | {u'ssd': u'true'} |
+----+---------+-------------------+-------+-------------------+

$ nova aggregate-add-host 1 node1
+----+---------+-------------------+-----------+-------------------+
| Id | Name    | Availability Zone | Hosts      | Metadata          |
+----+---------+-------------------+------------+-------------------+
| 1  | fast-io | nova              | [u'node1'] | {u'ssd': u'true'} |
+----+---------+-------------------+------------+-------------------+

$ nova aggregate-add-host 1 node2
+----+---------+-------------------+---------------------+-------------------+
| Id | Name    | Availability Zone | Hosts                | Metadata          |
+----+---------+-------------------+----------------------+-------------------+
| 1  | fast-io | nova              | [u'node1', u'node2'] | {u'ssd': u'true'} |
+----+---------+-------------------+----------------------+-------------------+

Use the nova flavor-create command to create the ssd.large flavor called with an ID of 6, 8 GB of RAM, 80 GB root disk, and four vCPUs.

$ nova flavor-create ssd.large 6 8192 80 4
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+-------------+
| ID | Name      | Memory_MB | Disk | Ephemeral | Swap | VCPUs | RXTX_Factor | Is_Public | extra_specs |
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+-------------+
| 6  | ssd.large | 8192      | 80   | 0         |      | 4     | 1           | True      | {}          |
+----+-----------+-----------+------+-----------+------+-------+-------------+-----------+-------------+

Once the flavor is created, specify one or more key-value pairs that match the key-value pairs on the host aggregates. In this case, that is the ssd=true key-value pair. Setting a key-value pair on a flavor is done using the nova flavor-key command.

$ nova flavor-key ssd.large set ssd=true

Once it is set, you should see the extra_specs property of the ssd.large flavor populated with a key of ssd and a corresponding value of true.

$ nova flavor-show ssd.large
+----------------------------+-------------------+
| Property                   | Value             |
+----------------------------+-------------------+
| OS-FLV-DISABLED:disabled   | False             |
| OS-FLV-EXT-DATA:ephemeral  | 0                 |
| disk                       | 80                |
| extra_specs                | {u'ssd': u'true'} |
| id                         | 6                 |
| name                       | ssd.large         |
| os-flavor-access:is_public | True              |
| ram                        | 8192              |
| rxtx_factor                | 1.0               |
| swap                       |                   |
| vcpus                      | 4                 |
+----------------------------+-------------------+

Now, when a user requests an instance with the ssd.large flavor, the scheduler only considers hosts with the ssd=true key-value pair. In this example, these are node1 and node2.

另一个作用是Xen和KVM的POOL分开，有利于XEN进行Live Migration

另一个作用是Windows和Linux的POOL分开，因为Windows是需要收费的，而Linux大多不需要，Windows的收费是按照物理机，而非虚拟机来收费的，所有需要尽量的将windows的虚拟机放到一个物理机上。

Filter_properties的里面scheduler_hints是一个json，里面可以设置任何值，用于Filter的时候使用。

例如JsonFilter

The JsonFilter allows a user to construct a custom filter by passing a scheduler hint in JSON format. The following operators are supported:

• =
• <
• >
• in
• <=
• >=
• not
• or
• and

The filter supports the following variables:

• $free_ram_mb
• $free_disk_mb
• $total_usable_ram_mb
• $vcpus_total
• $vcpus_used

Using the nova command-line tool, use the --hint flag:

$ nova boot --image 827d564a-e636-4fc4-a376-d36f7ebe1747 --flavor 1 --hint query='[">=","$free_ram_mb",1024]' server1

With the API, use the os:scheduler_hints key:

{

"server": {

"name": "server-1",

"imageRef": "cedef40a-ed67-4d10-800e-17455edce175",

"flavorRef": "1"

},

"os:scheduler_hints": {

"query": "[>=,$free_ram_mb,1024]"

}

}

我们可以指定某个物理机，用下面的命令--availability-zone <zone-name>:<host-name>

步骤14：对合适的Hosts进行weighting并且排序

选出了Hosts，接下来就是进行Weighting的操作

Weighting可以根据很多变量来，一般来说Memory和disk是最先需要满足的，CPU和network io则需要次要考虑，一般来说，对于付钱较少的Flavor，能满足memory和disk就可以了，对于付钱较多的Flavor，则需要保证其CPU和network io.

步骤15：nova-scheduler想选出的Host发送RPC