kong简介
Kong 是一个开源的API网关，集成了服务注册和发现、负载均衡、健康检查等功能，还可以通过插件来提供限流、熔断、监控、日志等能力，
在kong的微服务架构中，kong担当了注册中心的角色，服务提供者(Provider)首先将服务信息注册到 kong，服务消费者(Consumer)调用服务的过程是调用端先将请求发到 kong，再通过 kong 把请求转发到服务提供者而实现间接调用。
本文通过梳理kong数据库中的字段关联关系，从而了解请求的转发流程。
kong服务定义
一个完整的kong服务由四部分实体构成：route，service，upstream和target。各自作用介绍如下：
route：记录了请求规则和服务service的对应关系；services：服务实体，是上游服务upstream的抽象；upstream：一个或多个target的集合，负责流量的转发；target：提供服务的最小单位，也是负载均衡的终端。
kong转发请求的整体流程可以概述为：当客户端发起一个请求时，routes通过提前注册的信息匹配出对应的service服务，根据service对应的upstream信息就可以找到最终处理请求的目标tartget，从而完成请求的处理。调用流程图示如下：
以下就客户端请求/api/tembin/atsani为例，结合kong数据库中的关联关系来具体说明请求的转发流程。
转发流程梳理
从 Route 到 Service
routes
routes路由匹配客户端的请求规则，匹配成功后分配到service层，以请求的方法、host、路径等作为转发依据。route与service是多对一的关系，所以可根据请求的路径可匹配出对应的service。
表结构
以下字段需要特殊注意：
| 字段 | 值 |
|---|---|
| protocols | 允许访问该路由的协议（默认https\http都允许） |
| paths | 匹配路由访问的路径 |
| service_id | 指向服务的id |
kong=# \d routes;
Table "public.routes"
Column | Type | Modifiers
----------------------------+--------------------------+--------------------
id | uuid | not null
created_at | timestamp with time zone |
updated_at | timestamp with time zone |
name | text |
service_id | uuid |
protocols | text[] |
methods | text[] |
hosts | text[] |
paths | text[] |
snis | text[] |
sources | jsonb[] |
destinations | jsonb[] |
regex_priority | bigint |
strip_path | boolean |
preserve_host | boolean |
tags | text[] |
https_redirect_status_code | integer |
headers | jsonb |
path_handling | text | default 'v0'::text
Indexes:
"routes_pkey" PRIMARY KEY, btree (id)
"routes_name_key" UNIQUE CONSTRAINT, btree (name)
"routes_service_id_idx" btree (service_id)
"routes_tags_idx" gin (tags)
Foreign-key constraints:
"routes_service_id_fkey" FOREIGN KEY (service_id) REFERENCES services(id)
Referenced by:
TABLE "plugins" CONSTRAINT "plugins_route_id_fkey" FOREIGN KEY (route_id) REFERENCES routes(id) ON DELETE CASCADE
Triggers:
routes_sync_tags_trigger AFTER INSERT OR DELETE OR UPDATE OF tags ON routes FOR EACH ROW EXECUTE PROCEDURE sync_tags()
可看出routes和service表通过service_id进行关联
示例
在routes表中可根据指定路径筛选出对应的service_id为27f7d1f2-67f3-430f-b5a1-417c6dcb1198
kong=# select * from routes where paths='{/api/tembin/atsani}';
-[ RECORD 1 ]--------------+-------------------------------------
id | 00dd061d-438c-4e76-92a2-92984c6c55dc
created_at | 2022-10-30 11:53:15+00
updated_at | 2022-10-30 11:53:15+00
name | nscloud.kong-tembin.029
service_id | 27f7d1f2-67f3-430f-b5a1-417c6dcb1198
protocols | {http,https}
methods |
hosts |
paths | {/api/tembin/atsani}
snis |
sources |
destinations |
regex_priority | 0
strip_path | f
preserve_host | t
tags | {managed-by-ingress-controller}
https_redirect_status_code | 426
headers |
path_handling | v0
```
services
service服务是一个抽象服务层，可以用于指向具体物理服务(target)，也可以指向upstream用于实现物理服务的负载效果，其中service和upstream是一对一的关系。
注：service中的host可以是upstream的name，也可以配置为外部的域名，这样请求会直接转发给外部
表结构
以下字段需要特殊注意：
| 字段 | 值 |
|---|---|
| protocol | 请求upstream的协议（http、https）默认http |
| host | upstream name（一定要和upstream名称保持一致） |
| port | 请求upstream的端口（虚拟端口，可自定义）默认80 |
| path | 请求upstream的路径 |
kong=# \d services;
Table "public.services"
Column | Type | Modifiers
-----------------------+--------------------------+-----------
id | uuid | not null
created_at | timestamp with time zone |
updated_at | timestamp with time zone |
name | text |
retries | bigint |
protocol | text |
host | text |
port | bigint |
path | text |
connect_timeout | bigint |
write_timeout | bigint |
read_timeout | bigint |
tags | text[] |
client_certificate_id | uuid |
Indexes:
"services_pkey" PRIMARY KEY, btree (id)
"services_name_key" UNIQUE CONSTRAINT, btree (name)
"services_fkey_client_certificate" btree (client_certificate_id)
"services_tags_idx" gin (tags)
Foreign-key constraints:
"services_client_certificate_id_fkey" FOREIGN KEY (client_certificate_id) REFERENCES certificates(id)
Referenced by:
TABLE "oauth2_authorization_codes" CONSTRAINT "oauth2_authorization_codes_service_id_fkey" FOREIGN KEY (service_id) REFERENCES services(id) ON DELETE CASCADE
TABLE "oauth2_tokens" CONSTRAINT "oauth2_tokens_service_id_fkey" FOREIGN KEY (service_id) REFERENCES services(id) ON DELETE CASCADE
TABLE "plugins" CONSTRAINT "plugins_service_id_fkey" FOREIGN KEY (service_id) REFERENCES services(id) ON DELETE CASCADE
TABLE "routes" CONSTRAINT "routes_service_id_fkey" FOREIGN KEY (service_id) REFERENCES services(id)
Triggers:
services_sync_tags_trigger AFTER INSERT OR DELETE OR UPDATE OF tags ON services FOR EACH ROW EXECUTE PROCEDURE sync_tags()
示例
通过上一步查找的service_id，可在service表中匹配出对应记录
kong=# select * from services where id='27f7d1f2-67f3-430f-b5a1-417c6dcb1198';
-[ RECORD 1 ]---------+-------------------------------------
id | 27f7d1f2-67f3-430f-b5a1-417c6dcb1198
created_at | 2022-10-30 11:53:15+00
updated_at | 2022-10-30 11:53:15+00
name | nscloud.atsani.80
retries | 5
protocol | http
host | atsani.nscloud.80.svc
port | 80
path | /
connect_timeout | 60000
write_timeout | 60000
read_timeout | 60000
tags | {managed-by-ingress-controller}
client_certificate_id |
从 Service到Upstream
upstreams
upstream主要用于实现kong的负载功能，一个service匹配到一个upstream后，upstream可以指向多个target服务以此来实现负载的效果。
表结构
以下字段需要特殊注意：
| 字段 | 值 |
|---|---|
| name | service指向时使用 |
| algorithm | 默认round-robin。目前支持round-robin, consistent-hashing, least-connections |
| healthchecks.active.type | 检查目标服务器target的健康方式。一共三类tcp、http、https |
| healthchecks.active.http_path | 使用http协议检查target服务是否健康时绑定的路径 |
kong=# \d upstreams
Table "public.upstreams"
Column | Type | Modifiers
----------------------+--------------------------+---------------------------------------------------------------------------
id | uuid | not null
created_at | timestamp with time zone | default timezone('UTC'::text, ('now'::text)::timestamp(3) with time zone)
name | text |
hash_on | text |
hash_fallback | text |
hash_on_header | text |
hash_fallback_header | text |
hash_on_cookie | text |
hash_on_cookie_path | text |
slots | integer | not null
healthchecks | jsonb |
tags | text[] |
algorithm | text |
host_header | text |
Indexes:
"upstreams_pkey" PRIMARY KEY, btree (id)
"upstreams_name_key" UNIQUE CONSTRAINT, btree (name)
"upstreams_tags_idx" gin (tags)
Referenced by:
TABLE "targets" CONSTRAINT "targets_upstream_id_fkey" FOREIGN KEY (upstream_id) REFERENCES upstreams(id) ON DELETE CASCADE
Triggers:
upstreams_sync_tags_trigger AFTER INSERT OR DELETE OR UPDATE OF tags ON upstreams FOR EACH ROW EXECUTE PROCEDURE sync_tags()
从表索引中可看出对于target表和upstreams表针对upstreams.id和targets.upstream_id做了外键约束
示例
通过上一步查找出的host字段匹配出对应的upstream
kong=# select * from upstreams where name='atsani.nscloud.80.svc';
-[ RECORD 1 ]---------------------------------------------------
id | b85dd291-d561-4605-8771-2895c1decaa3
created_at | 2022-10-31 02:52:43+00
name | atsani.nscloud.80.svc
hash_on | none
hash_fallback | none
hash_on_header |
hash_fallback_header |
hash_on_cookie |
hash_on_cookie_path | /
slots | 10000
healthchecks | {"active": {"type": "http", "healthy": {"interval": 0, "successes": 0, "http_statuses": [200, 302]}, "timeout": 1, "http_path": "/", "https_sni": null, "unhealthy": {"interval": 0, "timeouts": 0, "tcp_failures": 0, "http_failures": 0, "http_statuses": [429, 404, 500, 501, 502, 503, 504, 505]}, "concurrency": 10, "https_verify_certificate": true}, "passive": {"type": "http", "healthy": {"successes": 0, "http_statuses": [200, 201, 202, 203, 204, 205, 206, 207, 208, 226, 300, 301, 302, 303, 304, 305, 306, 307, 308]}, "unhealthy": {"timeouts": 0, "tcp_failures": 0, "http_failures": 0, "http_statuses": [429, 500, 503]}}, "threshold": 0}
tags | {managed-by-ingress-controller}
algorithm | round-robin
host_header |
从Upstream到Target
对请求进行处理的时候，主要有两项处理，一是进行负载均衡，二是调用插件进行处理。
一个Upstream可以包含多个Target，负载均衡的过程，就是为当前的请求选择一个Target的过程
target
target是IP或者host加port，是提供服务的最小单位。每个tartget还可设置不同的权重。
表结构
以下字段需要特殊注意：
| 字段 | 值 |
|---|---|
| upstream_id | tag对应的upstream表的主键 |
| target | 转发目的的ip和port |
| weight | 该target在整个upstream中所占的权重 |
kong=# \d targets
Table "public.targets"
Column | Type | Modifiers
-------------+--------------------------+---------------------------------------------------------------------------
id | uuid | not null
created_at | timestamp with time zone | default timezone('UTC'::text, ('now'::text)::timestamp(3) with time zone)
upstream_id | uuid |
target | text | not null
weight | integer | not null
tags | text[] |
Indexes:
"targets_pkey" PRIMARY KEY, btree (id)
"targets_tags_idx" gin (tags)
"targets_target_idx" btree (target)
"targets_upstream_id_idx" btree (upstream_id)
Foreign-key constraints:
"targets_upstream_id_fkey" FOREIGN KEY (upstream_id) REFERENCES upstreams(id) ON DELETE CASCADE
Triggers:
targets_sync_tags_trigger AFTER INSERT OR DELETE OR UPDATE OF tags ON targets FOR EACH ROW EXECUTE PROCEDURE sync_tags()
从表结构中可看出通过upstream_id和upstreams表进行关联。
示例
kong=# select * from targets where upstream_id='b85dd291-d561-4605-8771-2895c1decaa3';
-[ RECORD 1 ]-------------------------------------
id | f88f7a83-e973-4414-ae64-fd1b34e96a2a
created_at | 2022-10-30 11:53:16.174+00
upstream_id | b85dd291-d561-4605-8771-2895c1decaa3
target | 10.244.0.215:80
weight | 100
tags | {managed-by-ingress-controller}
由于本地环境中将kong与k8s进行结合，所以最终在环境上可通过target获取出对应提供服务的Pod
[root@master-1 ~]# kubectl get pods -A -o wide | grep 10.244.0.215
nscloud /api/tembin/atsani 1/1 Running 1 23h 10.244.0.215 master-1 <none> <none>
至此就可以将对于/api/tembin/atsani路径的请求转发至本机10.244.0.215所对应的pod，完成请求的处理了。
