Python之路第十篇Python操作MemcacheRedisRabbitMQSQLAlchemy
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Memcached
Memcached 是一个高性能的分布式内存对象缓存系统，用于动态Web应用以减轻数据库负载。它通过在内存中缓存数据和对象来减少读取数据库的次数，从而提高动态、数据库驱动网站的速度。Memcached基于一个存储键/值对的hashmap。其守护进程（daemon ）是用C写的，但是客户端可以用任何语言来编写，并通过memcached协议与守护进程通信。
1、Memcached安装配置
#安装倚赖包 yum install libevent-devel #安装软件 yum -y install memcached #启动服务 /usr/bin/memcached -d -u root -l 192.168.7.102 -m 1024 -p 11211 #命令解释 ‘‘‘ 启动Memcache 常用参数 -p <num> 设置TCP端口号(默认不设置为: 11211) -U <num> UDP监听端口(默认: 11211, 0 时关闭) -l <ip_addr> 绑定地址(默认:所有都允许,无论内外网或者本机更换IP，有安全隐患，若设置为127.0.0.1就只能本机访问) -d 以daemon方式运行 -u <username> 绑定使用指定用于运行进程<username> -m <num> 允许最大内存用量，单位M (默认: 64 MB) -P <file> 将PID写入文件<file>，这样可以使得后边进行快速进程终止, 需要与-d 一起使用 ‘‘‘
2、Memcached命令
#测试连接Memcached telnet hostip port telnet 192.168.7.102 11211 #例子 ‘‘‘ telnet 192.168.7.102 11211 Trying 192.168.7.102... Connected to 192.168.7.102. Escape character is ‘^]‘. #连接成功之后输入命令即可 ‘‘‘ 存储命令: set/add/replace/append/prepend/cas 获取命令: get/gets 其他命令: delete/stats..
3、python操作Memcached
#linxu下安装pip yum -y install pip #安装python操作Memcached模块 pip install python-memcached
4、Memcached常用操作
import memcache #导入模块 mc = memcache.Client([‘10.211.55.4:12000‘], debug=True) #连接memcached mc.set("foo", "bar")#插入一条数据 ret = mc.get(‘foo‘)#获取一条数据的值 print ret
5、Memcached源码
class Client(threading.local): """Object representing a pool of memcache servers. See L{memcache} for an overview. In all cases where a key is used, the key can be either: 1. A simple hashable type (string, integer, etc.). 2. A tuple of C{(hashvalue, key)}. This is useful if you want to avoid making this module calculate a hash value. You may prefer, for example, to keep all of a given user‘s objects on the same memcache server, so you could use the user‘s unique id as the hash value. @group Setup: __init__, set_servers, forget_dead_hosts, disconnect_all, debuglog @group Insertion: set, add, replace, set_multi @group Retrieval: get, get_multi @group Integers: incr, decr @group Removal: delete, delete_multi @sort: __init__, set_servers, forget_dead_hosts, disconnect_all, debuglog, set, set_multi, add, replace, get, get_multi, incr, decr, delete, delete_multi """ _FLAG_PICKLE = 1 << 0 _FLAG_INTEGER = 1 << 1 _FLAG_LONG = 1 << 2 _FLAG_COMPRESSED = 1 << 3 _SERVER_RETRIES = 10 # how many times to try finding a free server. # exceptions for Client class MemcachedKeyError(Exception): pass class MemcachedKeyLengthError(MemcachedKeyError): pass class MemcachedKeyCharacterError(MemcachedKeyError): pass class MemcachedKeyNoneError(MemcachedKeyError): pass class MemcachedKeyTypeError(MemcachedKeyError): pass class MemcachedStringEncodingError(Exception): pass def __init__(self, servers, debug=0, pickleProtocol=0, pickler=pickle.Pickler, unpickler=pickle.Unpickler, compressor=zlib.compress, decompressor=zlib.decompress, pload=None, pid=None, server_max_key_length=None, server_max_value_length=None, dead_retry=_DEAD_RETRY, socket_timeout=_SOCKET_TIMEOUT, cache_cas=False, flush_on_reconnect=0, check_keys=True): """Create a new Client object with the given list of servers. @param servers: C{servers} is passed to L{set_servers}. @param debug: whether to display error messages when a server can‘t be contacted. @param pickleProtocol: number to mandate protocol used by (c)Pickle. @param pickler: optional override of default Pickler to allow subclassing. @param unpickler: optional override of default Unpickler to allow subclassing. @param pload: optional persistent_load function to call on pickle loading. Useful for cPickle since subclassing isn‘t allowed. @param pid: optional persistent_id function to call on pickle storing. Useful for cPickle since subclassing isn‘t allowed. @param dead_retry: number of seconds before retrying a blacklisted server. Default to 30 s. @param socket_timeout: timeout in seconds for all calls to a server. Defaults to 3 seconds. @param cache_cas: (default False) If true, cas operations will be cached. WARNING: This cache is not expired internally, if you have a long-running process you will need to expire it manually via client.reset_cas(), or the cache can grow unlimited. @param server_max_key_length: (default SERVER_MAX_KEY_LENGTH) Data that is larger than this will not be sent to the server. @param server_max_value_length: (default SERVER_MAX_VALUE_LENGTH) Data that is larger than this will not be sent to the server. @param flush_on_reconnect: optional flag which prevents a scenario that can cause stale data to be read: If there‘s more than one memcached server and the connection to one is interrupted, keys that mapped to that server will get reassigned to another. If the first server comes back, those keys will map to it again. If it still has its data, get()s can read stale data that was overwritten on another server. This flag is off by default for backwards compatibility. @param check_keys: (default True) If True, the key is checked to ensure it is the correct length and composed of the right characters. """ super(Client, self).__init__() self.debug = debug self.dead_retry = dead_retry self.socket_timeout = socket_timeout self.flush_on_reconnect = flush_on_reconnect self.set_servers(servers) self.stats = {} self.cache_cas = cache_cas self.reset_cas() self.do_check_key = check_keys # Allow users to modify pickling/unpickling behavior self.pickleProtocol = pickleProtocol self.pickler = pickler self.unpickler = unpickler self.compressor = compressor self.decompressor = decompressor self.persistent_load = pload self.persistent_id = pid self.server_max_key_length = server_max_key_length if self.server_max_key_length is None: self.server_max_key_length = SERVER_MAX_KEY_LENGTH self.server_max_value_length = server_max_value_length if self.server_max_value_length is None: self.server_max_value_length = SERVER_MAX_VALUE_LENGTH # figure out the pickler style file = BytesIO() try: pickler = self.pickler(file, protocol=self.pickleProtocol) self.picklerIsKeyword = True except TypeError: self.picklerIsKeyword = False def _encode_key(self, key): if isinstance(key, tuple): if isinstance(key[1], six.text_type): return (key[0], key[1].encode(‘utf8‘)) elif isinstance(key, six.text_type): return key.encode(‘utf8‘) return key def _encode_cmd(self, cmd, key, headers, noreply, *args): cmd_bytes = cmd.encode() if six.PY3 else cmd fullcmd = [cmd_bytes, b‘ ‘, key] if headers: if six.PY3: headers = headers.encode() fullcmd.append(b‘ ‘) fullcmd.append(headers) if noreply: fullcmd.append(b‘ noreply‘) if args: fullcmd.append(b‘ ‘) fullcmd.extend(args) return b‘‘.join(fullcmd) def reset_cas(self): """Reset the cas cache. This is only used if the Client() object was created with "cache_cas=True". If used, this cache does not expire internally, so it can grow unbounded if you do not clear it yourself. """ self.cas_ids = {} def set_servers(self, servers): """Set the pool of servers used by this client. @param servers: an array of servers. Servers can be passed in two forms: 1. Strings of the form C{"host:port"}, which implies a default weight of 1. 2. Tuples of the form C{("host:port", weight)}, where C{weight} is an integer weight value. """ self.servers = [_Host(s, self.debug, dead_retry=self.dead_retry, socket_timeout=self.socket_timeout, flush_on_reconnect=self.flush_on_reconnect) for s in servers] self._init_buckets() def get_stats(self, stat_args=None): """Get statistics from each of the servers. @param stat_args: Additional arguments to pass to the memcache "stats" command. @return: A list of tuples ( server_identifier, stats_dictionary ). The dictionary contains a number of name/value pairs specifying the name of the status field and the string value associated with it. The values are not converted from strings. """ data = [] for s in self.servers: if not s.connect(): continue if s.family == socket.AF_INET: name = ‘%s:%s (%s)‘ % (s.ip, s.port, s.weight) elif s.family == socket.AF_INET6: name = ‘[%s]:%s (%s)‘ % (s.ip, s.port, s.weight) else: name = ‘unix:%s (%s)‘ % (s.address, s.weight) if not stat_args: s.send_cmd(‘stats‘) else: s.send_cmd(‘stats ‘ + stat_args) serverData = {} data.append((name, serverData)) readline = s.readline while 1: line = readline() if not line or line.strip() == ‘END‘: break stats = line.split(‘ ‘, 2) serverData[stats[1]] = stats[2] return(data) def get_slabs(self): data = [] for s in self.servers: if not s.connect(): continue if s.family == socket.AF_INET: name = ‘%s:%s (%s)‘ % (s.ip, s.port, s.weight) elif s.family == socket.AF_INET6: name = ‘[%s]:%s (%s)‘ % (s.ip, s.port, s.weight) else: name = ‘unix:%s (%s)‘ % (s.address, s.weight) serverData = {} data.append((name, serverData)) s.send_cmd(‘stats items‘) readline = s.readline while 1: line = readline() if not line or line.strip() == ‘END‘: break item = line.split(‘ ‘, 2) # 0 = STAT, 1 = ITEM, 2 = Value slab = item[1].split(‘:‘, 2) # 0 = items, 1 = Slab #, 2 = Name if slab[1] not in serverData: serverData[slab[1]] = {} serverData[slab[1]][slab[2]] = item[2] return data def flush_all(self): """Expire all data in memcache servers that are reachable.""" for s in self.servers: if not s.connect(): continue s.flush() def debuglog(self, str): if self.debug: sys.stderr.write("MemCached: %s " % str) def _statlog(self, func): if func not in self.stats: self.stats[func] = 1 else: self.stats[func] += 1 def forget_dead_hosts(self): """Reset every host in the pool to an "alive" state.""" for s in self.servers: s.deaduntil = 0 def _init_buckets(self): self.buckets = [] for server in self.servers: for i in range(server.weight): self.buckets.append(server) def _get_server(self, key): if isinstance(key, tuple): serverhash, key = key else: serverhash = serverHashFunction(key) if not self.buckets: return None, None for i in range(Client._SERVER_RETRIES): server = self.buckets[serverhash % len(self.buckets)] if server.connect(): # print("(using server %s)" % server,) return server, key serverhash = serverHashFunction(str(serverhash) + str(i)) return None, None def disconnect_all(self): for s in self.servers: s.close_socket() def delete_multi(self, keys, time=0, key_prefix=‘‘, noreply=False): """Delete multiple keys in the memcache doing just one query. >>> notset_keys = mc.set_multi({‘a1‘ : ‘val1‘, ‘a2‘ : ‘val2‘}) >>> mc.get_multi([‘a1‘, ‘a2‘]) == {‘a1‘ : ‘val1‘,‘a2‘ : ‘val2‘} >>> mc.delete_multi([‘key1‘, ‘key2‘]) >>> mc.get_multi([‘key1‘, ‘key2‘]) == {} This method is recommended over iterated regular L{delete}s as it reduces total latency, since your app doesn‘t have to wait for each round-trip of L{delete} before sending the next one. @param keys: An iterable of keys to clear @param time: number of seconds any subsequent set / update commands should fail. Defaults to 0 for no delay. @param key_prefix: Optional string to prepend to each key when sending to memcache. See docs for L{get_multi} and L{set_multi}. @param noreply: optional parameter instructs the server to not send the reply. @return: 1 if no failure in communication with any memcacheds. @rtype: int """ self._statlog(‘delete_multi‘) server_keys, prefixed_to_orig_key = self._map_and_prefix_keys( keys, key_prefix) # send out all requests on each server before reading anything dead_servers = [] rc = 1 for server in six.iterkeys(server_keys): bigcmd = [] write = bigcmd.append extra = ‘ noreply‘ if noreply else ‘‘ if time is not None: for key in server_keys[server]: # These are mangled keys write("delete %s %d%s " % (key, time, extra)) else: for key in server_keys[server]: # These are mangled keys write("delete %s%s " % (key, extra)) try: server.send_cmds(‘‘.join(bigcmd)) except socket.error as msg: rc = 0 if isinstance(msg, tuple): msg = msg[1] server.mark_dead(msg) dead_servers.append(server) # if noreply, just return if noreply: return rc # if any servers died on the way, don‘t expect them to respond. for server in dead_servers: del server_keys[server] for server, keys in six.iteritems(server_keys): try: for key in keys: server.expect("DELETED") except socket.error as msg: if isinstance(msg, tuple): msg = msg[1] server.mark_dead(msg) rc = 0 return rc def delete(self, key, time=0, noreply=False): ‘‘‘Deletes a key from the memcache. @return: Nonzero on success. @param time: number of seconds any subsequent set / update commands should fail. Defaults to None for no delay. @param noreply: optional parameter instructs the server to not send the reply. @rtype: int ‘‘‘ return self._deletetouch([b‘DELETED‘, b‘NOT_FOUND‘], "delete", key, time, noreply) def touch(self, key, time=0, noreply=False): ‘‘‘Updates the expiration time of a key in memcache. @return: Nonzero on success. @param time: Tells memcached the time which this value should expire, either as a delta number of seconds, or an absolute unix time-since-the-epoch value. See the memcached protocol docs section "Storage Commands" for more info on <exptime>. We default to 0 == cache forever. @param noreply: optional parameter instructs the server to not send the reply. @rtype: int ‘‘‘ return self._deletetouch([b‘TOUCHED‘], "touch", key, time, noreply) def _deletetouch(self, expected, cmd, key, time=0, noreply=False): key = self._encode_key(key) if self.do_check_key: self.check_key(key) server, key = self._get_server(key) if not server: return 0 self._statlog(cmd) if time is not None and time != 0: fullcmd = self._encode_cmd(cmd, key, str(time), noreply) else: fullcmd = self._encode_cmd(cmd, key, None, noreply) try: server.send_cmd(fullcmd) if noreply: return 1 line = server.readline() if line and line.strip() in expected: return 1 self.debuglog(‘%s expected %s, got: %r‘ % (cmd, ‘ or ‘.join(expected), line)) except socket.error as msg: if isinstance(msg, tuple): msg = msg[1] server.mark_dead(msg) return 0 def incr(self, key, delta=1, noreply=False): """Increment value for C{key} by C{delta} Sends a command to the server to atomically increment the value for C{key} by C{delta}, or by 1 if C{delta} is unspecified. Returns None if C{key} doesn‘t exist on server, otherwise it returns the new value after incrementing. Note that the value for C{key} must already exist in the memcache, and it must be the string representation of an integer. >>> mc.set("counter", "20") # returns 1, indicating success >>> mc.incr("counter") >>> mc.incr("counter") Overflow on server is not checked. Be aware of values approaching 2**32. See L{decr}. @param delta: Integer amount to increment by (should be zero or greater). @param noreply: optional parameter instructs the server to not send the reply. @return: New value after incrementing, no None for noreply or error. @rtype: int """ return self._incrdecr("incr", key, delta, noreply) def decr(self, key, delta=1, noreply=False): """Decrement value for C{key} by C{delta} Like L{incr}, but decrements. Unlike L{incr}, underflow is checked and new values are capped at 0. If server value is 1, a decrement of 2 returns 0, not -1. @param delta: Integer amount to decrement by (should be zero or greater). @param noreply: optional parameter instructs the server to not send the reply. @return: New value after decrementing, or None for noreply or error. @rtype: int """ return self._incrdecr("decr", key, delta, noreply) def _incrdecr(self, cmd, key, delta, noreply=False): key = self._encode_key(key) if self.do_check_key: self.check_key(key) server, key = self._get_server(key) if not server: return None self._statlog(cmd) fullcmd = self._encode_cmd(cmd, key, str(delta), noreply) try: server.send_cmd(fullcmd) if noreply: return line = server.readline() if line is None or line.strip() == b‘NOT_FOUND‘: return None return int(line) except socket.error as msg: if isinstance(msg, tuple): msg = msg[1] server.mark_dead(msg) return None def add(self, key, val, time=0, min_compress_len=0, noreply=False): ‘‘‘Add new key with value. Like L{set}, but only stores in memcache if the key doesn‘t already exist. @return: Nonzero on success. @rtype: int ‘‘‘ return self._set("add", key, val, time, min_compress_len, noreply) def append(self, key, val, time=0, min_compress_len=0, noreply=False): ‘‘‘Append the value to the end of the existing key‘s value. Only stores in memcache if key already exists. Also see L{prepend}. @return: Nonzero on success. @rtype: int ‘‘‘ return self._set("append", key, val, time, min_compress_len, noreply) def prepend(self, key, val, time=0, min_compress_len=0, noreply=False): ‘‘‘Prepend the value to the beginning of the existing key‘s value. Only stores in memcache if key already exists. Also see L{append}. @return: Nonzero on success. @rtype: int ‘‘‘ return self._set("prepend", key, val, time, min_compress_len, noreply) def replace(self, key, val, time=0, min_compress_len=0, noreply=False): ‘‘‘Replace existing key with value. Like L{set}, but only stores in memcache if the key already exists. The opposite of L{add}. @return: Nonzero on success. @rtype: int ‘‘‘ return self._set("replace", key, val, time, min_compress_len, noreply) def set(self, key, val, time=0, min_compress_len=0, noreply=False): ‘‘‘Unconditionally sets a key to a given value in the memcache. The C{key} can optionally be an tuple, with the first element being the server hash value and the second being the key. If you want to avoid making this module calculate a hash value. You may prefer, for example, to keep all of a given user‘s objects on the same memcache server, so you could use the user‘s unique id as the hash value. @return: Nonzero on success. @rtype: int @param time: Tells memcached the time which this value should expire, either as a delta number of seconds, or an absolute unix time-since-the-epoch value. See the memcached protocol docs section "Storage Commands" for more info on <exptime>. We default to 0 == cache forever. @param min_compress_len: The threshold length to kick in auto-compression of the value using the compressor routine. If the value being cached is a string, then the length of the string is measured, else if the value is an object, then the length of the pickle result is measured. If the resulting attempt at compression yeilds a larger string than the input, then it is discarded. For backwards compatability, this parameter defaults to 0, indicating don‘t ever try to compress. @param noreply: optional parameter instructs the server to not send the reply. ‘‘‘ return self._set("set", key, val, time, min_compress_len, noreply) def cas(self, key, val, time=0, min_compress_len=0, noreply=False): ‘‘‘Check and set (CAS) Sets a key to a given value in the memcache if it hasn‘t been altered since last fetched. (See L{gets}). The C{key} can optionally be an tuple, with the first element being the server hash value and the second being the key. If you want to avoid making this module calculate a hash value. You may prefer, for example, to keep all of a given user‘s objects on the same memcache server, so you could use the user‘s unique id as the hash value. @return: Nonzero on success. @rtype: int @param time: Tells memcached the time which this value should expire, either as a delta number of seconds, or an absolute unix time-since-the-epoch value. See the memcached protocol docs section "Storage Commands" for more info on <exptime>. We default to 0 == cache forever. @param min_compress_len: The threshold length to kick in auto-compression of the value using the compressor routine. If the value being cached is a string, then the length of the string is measured, else if the value is an object, then the length of the pickle result is measured. If the resulting attempt at compression yeilds a larger string than the input, then it is discarded. For backwards compatability, this parameter defaults to 0, indicating don‘t ever try to compress. @param noreply: optional parameter instructs the server to not send the reply. ‘‘‘ return self._set("cas", key, val, time, min_compress_len, noreply) def _map_and_prefix_keys(self, key_iterable, key_prefix): """Compute the mapping of server (_Host instance) -> list of keys to stuff onto that server, as well as the mapping of prefixed key -> original key. """ key_prefix = self._encode_key(key_prefix) # Check it just once ... key_extra_len = len(key_prefix) if key_prefix and self.do_check_key: self.check_key(key_prefix) # server (_Host) -> list of unprefixed server keys in mapping server_keys = {} prefixed_to_orig_key = {} # build up a list for each server of all the keys we want. for orig_key in key_iterable: if isinstance(orig_key, tuple): # Tuple of hashvalue, key ala _get_server(). Caller is # essentially telling us what server to stuff this on. # Ensure call to _get_server gets a Tuple as well. serverhash, key = orig_key key = self._encode_key(key) if not isinstance(key, six.binary_type): # set_multi supports int / long keys. key = str(key) if six.PY3: key = key.encode(‘utf8‘) bytes_orig_key = key # Gotta pre-mangle key before hashing to a # server. Returns the mangled key. server, key = self._get_server( (serverhash, key_prefix + key)) orig_key = orig_key[1] else: key = self._encode_key(orig_key) if not isinstance(key, six.binary_type): # set_multi supports int / long keys. key = str(key) if six.PY3: key = key.encode(‘utf8‘) bytes_orig_key = key server, key = self._get_server(key_prefix + key) # alert when passed in key is None if orig_key is None: self.check_key(orig_key, key_extra_len=key_extra_len) # Now check to make sure key length is proper ... if self.do_check_key: self.check_key(bytes_orig_key, key_extra_len=key_extra_len) if not server: continue if server not in server_keys: server_keys[server] = [] server_keys[server].append(key) prefixed_to_orig_key[key] = orig_key return (server_keys, prefixed_to_orig_key) def set_multi(self, mapping, time=0, key_prefix=‘‘, min_compress_len=0, noreply=False): ‘‘‘Sets multiple keys in the memcache doing just one query. >>> notset_keys = mc.set_multi({‘key1‘ : ‘val1‘, ‘key2‘ : ‘val2‘}) >>> mc.get_multi([‘key1‘, ‘key2‘]) == {‘key1‘ : ‘val1‘, ... ‘key2‘ : ‘val2‘} This method is recommended over regular L{set} as it lowers the number of total packets flying around your network, reducing total latency, since your app doesn‘t have to wait for each round-trip of L{set} before sending the next one. @param mapping: A dict of key/value pairs to set. @param time: Tells memcached the time which this value should expire, either as a delta number of seconds, or an absolute unix time-since-the-epoch value. See the memcached protocol docs section "Storage Commands" for more info on <exptime>. We default to 0 == cache forever. @param key_prefix: Optional string to prepend to each key when sending to memcache. Allows you to efficiently stuff these keys into a pseudo-namespace in memcache: >>> notset_keys = mc.set_multi( ... {‘key1‘ : ‘val1‘, ‘key2‘ : ‘val2‘}, ... key_prefix=‘subspace_‘) >>> len(notset_keys) == 0 True >>> mc.get_multi([‘subspace_key1‘, ... ‘subspace_key2‘]) == {‘subspace_key1‘: ‘val1‘, ... ‘subspace_key2‘ : ‘val2‘} True Causes key ‘subspace_key1‘ and ‘subspace_key2‘ to be set. Useful in conjunction with a higher-level layer which applies namespaces to data in memcache. In this case, the return result would be the list of notset original keys, prefix not applied. @param min_compress_len: The threshold length to kick in auto-compression of the value using the compressor routine. If the value being cached is a string, then the length of the string is measured, else if the value is an object, then the length of the pickle result is measured. If the resulting attempt at compression yeilds a larger string than the input, then it is discarded. For backwards compatability, this parameter defaults to 0, indicating don‘t ever try to compress. @param noreply: optional parameter instructs the server to not send the reply. @return: List of keys which failed to be stored [ memcache out of memory, etc. ]. @rtype: list ‘‘‘ self._statlog(‘set_multi‘) server_keys, prefixed_to_orig_key = self._map_and_prefix_keys( six.iterkeys(mapping), key_prefix) # send out all requests on each server before reading anything dead_servers = [] notstored = [] # original keys. for server in six.iterkeys(server_keys): bigcmd = [] write = bigcmd.append try: for key in server_keys[server]: # These are mangled keys store_info = self._val_to_store_info( mapping[prefixed_to_orig_key[key]], min_compress_len) if store_info: flags, len_val, val = store_info headers = "%d %d %d" % (flags, time, len_val) fullcmd = self._encode_cmd(‘set‘, key, headers, noreply, b‘ ‘, val, b‘ ‘) write(fullcmd) else: notstored.append(prefixed_to_orig_key[key]) server.send_cmds(b‘‘.join(bigcmd)) except socket.error as msg: if isinstance(msg, tuple): msg = msg[1以上是关于Python之路第十篇Python操作MemcacheRedisRabbitMQSQLAlchemy的主要内容，如果未能解决你的问题，请参考以下文章