如何在flask redis緩存中設置連接超時

Question

我正在嘗試將 redis 緩存與我的 python 代碼一起使用，下面的代碼工作正常並且它完美地設置了鍵。 我想在無法連接到 redis 或端口未打開時設置超時。 不幸的是，我找不到任何關於如何將超時傳遞給連接參數的文檔。

以下是我的代碼。

from flask import Flask, render_template
from flask_caching import Cache

app = Flask(__name__, static_url_path='/static')

config = {
    "DEBUG": True,          
    "CACHE_TYPE": "redis",
    "CACHE_DEFAULT_TIMEOUT": 300,
    "CACHE_KEY_PREFIX": "inventory",
    "CACHE_REDIS_HOST": "localhost",
    "CACHE_REDIS_PORT": "6379",
    "CACHE_REDIS_URL": 'redis://localhost:6379'
}

cache = Cache(app, config=config)
socket_timeout = 5


@app.route('/')
@cache.memoize()
def dev():
  # some code
  return render_template("index.html", data=json_data, columns=columns)

當它無法連接時，它會等待很長時間並引發以下錯誤：

Traceback (most recent call last):
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/flask_caching/__init__.py", line 771, in decorated_function
    f, *args, **kwargs
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/flask_caching/__init__.py", line 565, in make_cache_key
    f, args=args, timeout=_timeout, forced_update=forced_update
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/flask_caching/__init__.py", line 524, in _memoize_version
    version_data_list = list(self.cache.get_many(*fetch_keys))
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/flask_caching/backends/rediscache.py", line 101, in get_many
    return [self.load_object(x) for x in self._read_clients.mget(keys)]
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/redis/client.py", line 1329, in mget
    return self.execute_command('MGET', *args, **options)
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/redis/client.py", line 772, in execute_command
    connection = pool.get_connection(command_name, **options)
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/redis/connection.py", line 994, in get_connection
    connection.connect()
  File "/Users/amjad/.virtualenvs/inventory/lib/python3.7/site-packages/redis/connection.py", line 497, in connect
    raise ConnectionError(self._error_message(e))
redis.exceptions.ConnectionError: Error 60 connecting to localhost:6379. Operation timed out.

提前致謝。

Answer 1

這個問題已經很老了，但剛剛遇到了這個確切的問題，我找到了解決方案。 留在這里為未來的讀者留作后代。

根據https://flask-caching.readthedocs.io/en/latest/index.html上的文檔， CACHE_TYPE參數：

指定要使用的緩存對象類型。 這是將被導入和實例化的導入字符串。 假設導入對象是一個函數，它將返回一個符合緩存 API 的緩存對象。

因此，在flask_caching.backends.cache找到redis函數的修改版本，如下所示：

def redis_with_timeout(app, config, args, kwargs):

    try:
        from redis import from_url as redis_from_url
    except ImportError:
        raise RuntimeError("no redis module found")

    # [... extra lines skipped for brevity ...]

    # kwargs set here are passed through to the underlying Redis client
    kwargs["socket_connect_timeout"] = 0.5
    kwargs["socket_timeout"] = 0.5

    return RedisCache(*args, **kwargs)

並使用它代替默認的redis如下所示：

CACHE_TYPE = 'path.to.redis_with_timeout'

該庫將使用該庫，並將自定義 kwargs 傳遞到底層 Redis 客戶端。 希望有幫助。

Answer 2

從最新文檔中，有一個CACHE_OPTIONS配置作為關鍵字參數傳遞給幾乎所有類型的緩存后端：

CACHE_OPTIONS 中的條目作為 **kwargs 傳遞給 redis 客戶端

我們可以簡單地傳遞這樣的附加設置：

from flask import Flask
from flask_caching import Cache

app = Flask(__name__)

config = {
    "CACHE_TYPE": "redis",
    ...
    "CACHE_REDIS_HOST": "localhost",
    "CACHE_REDIS_PORT": "6379",
    "CACHE_REDIS_URL": 'redis://localhost:6379',
    "CACHE_OPTIONS": {
        "socket_connect_timeout": 5,    # connection timeout in seconds
        "socket_timeout": 5,            # send/recv timeout in seconds
    }
}

cache = Cache(app, config=config)