如何連接k8s、redis哨兵、flask_caching？

Question

我使用 Helm 圖表部署了一個 k8s redis 哨兵： https://github.com/bitnami/charts/tree/master/bitnami/redis

我確實只更改了這些值（ https://github.com/bitnami/charts/blob/master/bitnami/redis/values.yaml ）：

auth:
  enabled: false
  sentinel: false
sentinel:
  enabled: true
  masterSet: mymaster

部署后，我收到以下消息：

Redis™ can be accessed via port 6379 on the following DNS name from within your cluster:          
                                                                                                        
    redis.default.svc.cluster.local for read only operations                                            
                                                                                                        
For read/write operations, first access the Redis™ Sentinel cluster, which is available in port 26379 using the same domain name above.



To connect to your Redis™ server:

1. Run a Redis™ pod that you can use as a client:

   kubectl run --namespace default redis-client --restart='Never'  --image docker.io/bitnami/redis:6.2.6-debian-10-r103 --command -- sleep infinity

   Use the following command to attach to the pod:

   kubectl exec --tty -i redis-client \
   --namespace default -- bash

2. Connect using the Redis™ CLI:
   redis-cli -h redis -p 6379 # Read only operations
   redis-cli -h redis -p 26379 # Sentinel access

To connect to your database from outside the cluster execute the following commands:

    kubectl port-forward --namespace default svc/redis 6379:6379 &
    redis-cli -h 127.0.0.1 -p 6379

這很好用：

 kubectl get pods
NAME           READY   STATUS    RESTARTS   AGE
redis-node-0   2/2     Running   0          2m23s
redis-node-1   2/2     Running   0          71s
redis-node-2   2/2     Running   0          43s

但是關於訪問 - 總結一下 - 我有兩個選項可以訪問 redis：

1. redis.default.svc.cluster.local:6379 的只讀訪問
2. redis.default.svc.cluster.local:26379 的讀寫訪問（某種哨兵訪問，在文檔中：

Master-Replicas with Sentinel
When installing the chart with architecture=replication and sentinel.enabled=true, it will deploy a Redis™ master StatefulSet (only one master allowed) and a Redis™ replicas StatefulSet. In this case, the pods will contain an extra container with Redis™ Sentinel. This container will form a cluster of Redis™ Sentinel nodes, which will promote a new master in case the actual one fails. In addition to this, only one service is exposed:

Redis™ service: Exposes port 6379 for Redis™ read-only operations and port 26379 for accessing Redis™ Sentinel.
For read-only operations, access the service using port 6379. For write operations, it's necessary to access the Redis™ Sentinel cluster and query the current master using the command below (using redis-cli or similar):

SENTINEL get-master-addr-by-name <name of your MasterSet. e.g: mymaster>
This command will return the address of the current master, which can be accessed from inside the cluster.

In case the current master crashes, the Sentinel containers will elect a new master node.

現在我想將我的 Flask 緩存模塊連接到它： https://flask-caching.readthedocs.io/en/latest/

如您所見，有一個連接到 redis 哨兵的選項，但我不知道如何。 這是我的代碼：

from flask_caching import Cache
cache = Cache(app, config={
  'CACHE_TYPE': 'RedisSentinelCache', 
  'CACHE_REDIS_SENTINELS': ['redis.default.svc.cluster.local'], 
  'CACHE_REDIS_SENTINEL_MASTER': 'mymaster'}
)

我的問題是：

1. 參數 CACHE_REDIS_SENTINELS 中應該包含什么？ 我是否應該以某種方式獲取每個節點的 IP 地址並在那里獲取這些地址？

2. 參數 CACHE_REDIS_SENTINEL_MASTER 應該是什么？ 是“mymaster”（哨兵-> masterSet？）

3. 我是否應該始終連接到讀寫服務器（在這種情況下，是否會使用其他副本）？ 或者我是否需要以這種方式調整我的應用程序：如果我寫我總是使用端口 26379 的哨兵訪問，如果我讀我總是連接到只讀的 6379 端口？ 我需要保持 2 個連接嗎？

謝謝

編輯：我正在研究 flask_caching 的代碼，看來這可以正常工作（但我不確定是否使用了副本）：

import time
from flask import Flask
from flask_caching import Cache

config = {
    "DEBUG": True,          # some Flask specific configs
    'CACHE_TYPE': 'RedisSentinelCache',
    'CACHE_REDIS_SENTINELS': [
        ['redis.default.svc.cluster.local', 26379]
    ],
    'CACHE_REDIS_SENTINEL_MASTER': 'mymaster'
}
app = Flask(__name__)
# tell Flask to use the above defined config
app.config.from_mapping(config)
cache = Cache(app)

@app.route("/")
@cache.cached(timeout=5)
def index():
    return "%d\n" % time.time()

app.run()

編輯2：

確實，有點深入flask_caching，它也使用副本：

在文件flask_caching/backends/rediscache.py

該代碼正在獲取主機以進行寫入和讀取訪問：

        self._write_client = sentinel.master_for(master)
        self._read_clients = sentinel.slave_for(master)

干杯!

編輯3：

redis 驅動程序示例：

from redis.sentinel import Sentinel
sentinel = Sentinel([('redis.default.svc.cluster.local', 26379)])
redis_conn = sentinel.master_for('mymaster')
redis_conn_read = sentinel.slave_for('mymaster')

redis_conn.set('test', 'Hola!')
print(redis_conn_read.get('test'))

Answer 1

TLDR：

import time
from flask import Flask
from flask_caching import Cache

config = {
    "DEBUG": True,          # some Flask specific configs
    'CACHE_TYPE': 'RedisSentinelCache',
    'CACHE_REDIS_SENTINELS': [
        ['redis.default.svc.cluster.local', 26379]
    ],
    'CACHE_REDIS_SENTINEL_MASTER': 'mymaster'
}
app = Flask(__name__)
# tell Flask to use the above defined config
app.config.from_mapping(config)
cache = Cache(app)

@app.route("/")
@cache.cached(timeout=5)
def index():
    return "%d\n" % time.time()

app.run()

有關更多詳細信息，請參閱我的原始問題（EDIT 和 EDIT2）。