Features of Redis and Mecache and Ehcache

The recent project team has been useful to these three caches, go to their respective official look under, feel really different! Today deliberately summed up the advantages and disadvantages of each cache, for reference only!

Ehcache

Widely used in Java projects. It is an open source, designed to increase the high cost of data removed from the RDBMS, high latency to take a caching scheme. Because Ehcache is robust (Java-based development), certified (with Apache 2.0 license), full of features (described later), it is used in various nodes of large, complex distributed Web application.

What features?

1. Fast enough

Ehcache's release has been a long time, after several years of effort and countless performance tests, Ehcache was eventually designed in large, high concurrency systems.

2. Simple enough

The interface provided by the developer is very simple and straightforward, and it only takes a few minutes of your time to build from Ehcache to use. In fact, many developers do not know that they use Ehcache,ehcache is widely used in other open source projects

For example: Hibernate

3. Compact Enough

On this feature, the official gave a very cute name small foot print, the general Ehcache release version will not go to 2m,v 2.2.3 668KB.

4. Enough light weight

The core program relies only on SLF4J this one package, not one!

5. Good expansion

Ehcache provides memory and hard disk storage for big data, recent versions allow multiple instances, save objects with high flexibility, LRU, LFU, FIFO culling algorithms, base properties to support hot provisioning, multiple plugins supported

6. Listener

Cache Manager Listener (Cachemanagerlistener) and Cache Listener (Cacheevenlistener), do some statistics or data consistency broadcast very useful

How do I use it?

Simple enough is a major feature of Ehcache, naturally used up just so easy!

Post a basic code of use

CacheManager manager = cachemanager.newinstance ("Src/config/ehcache.xml"); Ehcache cache = new Cache ("Testcache", Cachemanager.addcache, False, False, 5, 2);

There is a ehcache.xml file in the code, now let's introduce some of the properties in this file.

2. Name: Cache names.
4. Maxelementsinmemory: Maximum number of caches.
6. Eternal: The object is permanently valid, but if set, timeout will not work.
8. Timetoidleseconds: Sets the allowable idle time (in seconds) for an object before it expires. An optional property is used only if the Eternal=false object is not permanently valid, and the default value is 0, which means that the idle time is infinite.
10. Timetoliveseconds: Sets the time that an object is allowed to survive before it expires, with a maximum time between creation time and expiration time. Used only when the Eternal=false object is not permanently valid, the default is 0, which means that the object survives indefinitely.
12. Overflowtodisk: When the number of objects in memory reaches Maxelementsinmemory, Ehcache writes the object to disk.
14. DISKSPOOLBUFFERSIZEMB: This parameter sets the buffer size of the Diskstore (disk cache). The default is 30MB. Each cache should have its own buffer.
16. Maxelementsondisk: Maximum number of hard disk caches.
18. Diskpersistent: Whether to cache VM Restart period data Whether The disk store persists between restarts of the virtual machine. The default value is False.
20. Diskexpirythreadintervalseconds: Disk failed thread run time interval, default is 120 seconds.
22. Memorystoreevictionpolicy: When the maxelementsinmemory limit is reached, Ehcache will clean up the memory according to the specified policy. The default policy is LRU. You can set it to FIFO or LFU.
24. Clearonflush: If the maximum amount of memory is cleared.

Memcache

Memcache is a high-performance, distributed object caching system, originally designed to mitigate the latency of Dynamic Web database loading data, you can think of it as a large memory hashtable, is a Key-value key-value cache. Danga Interactive in order to LiveJournal the development of the BSD license released a set of open-source software.

1. Reliance

Written in the Memcache C language, relies on the most recent version of GCC and libevent. GCC is its compiler, and colleagues do socket IO based on libevent. Ensure that your system colleague has both environments when installing memcache.

2. Multithreading support

Memcache supports multiple CPUs at the same time, under the Memcache installation file There is a named Threads.txt in the special instructions, by default, Memcached is compiled as a single-threaded Application. The default is a single-threaded compilation installation, which needs to be modified if you need multi-threading./configure--enable-threads, in order to support multicore systems, the premise is that your system must have multithreaded working mode. The number of threads that turn on multithreaded work is 4 by default, and if the number of threads exceeds the number of CPUs, the probability of an operation deadlock occurs. Combine your business model selection to make the most of what you do.

3. High Performance

Through libevent to complete the socket communication, theoretically the bottleneck of performance falls on the NIC.

Simple installation:

1. Download the memcached and libevent separately and put them in the/tmp directory:

# cd/tmp

# wget http://www.danga.com/memcached/dist/memcached-1.2.0.tar.gz

# wget http://www.monkey.org/~provos/libevent-1.2.tar.gz

2. Install Libevent First:

# tar ZXVF libevent-1.2.tar.gz

# CD libevent-1.2

#./CONFIGURE-PREFIX=/USR

# make (GCC is installed first if you encounter a hint that GCC is not installed)

# make Install

3. Test whether the Libevent is installed successfully:

# Ls-al/usr/lib | grep libevent

lrwxrwxrwx 1 root root 21 11?? 17:38 Libevent-1.2.so.1-libevent-1.2.so.1.0.3

-rwxr-xr-x 1 root root 263546 11?? 17:38 libevent-1.2.so.1.0.3

-rw-r-r-1 root root 454156 11?? 17:38 LIBEVENT.A

-rwxr-xr-x 1 root root 811 11?? 17:38 libevent.la

lrwxrwxrwx 1 root root 21 11?? 17:38 libevent.so-libevent-1.2.so.1.0.3

Good, all installed.

4. Install the memcached and require the installation location of the specified libevent in the installation:

# cd/tmp

# tar ZXVF memcached-1.2.0.tar.gz

# CD memcached-1.2.0

#./CONFIGURE-WITH-LIBEVENT=/USR

# make

# make Install

If there is an error in the middle, please carefully check the errors, follow the error message to configure or add the appropriate library or path.

When the installation is complete, the memcached will be put into/usr/local/bin/memcached,

5. Test whether the memcached is installed successfully:

# ls-al/usr/local/bin/mem*

-rwxr-xr-x 1 root root 137986 11?? 17:39/usr/local/bin/memcached

-rwxr-xr-x 1 root root 140179 11?? 17:39/usr/local/bin/memcached-debug

Start the Memcache service

To start the memcached service:

1. Start the server side of the memcache:

#/usr/local/bin/memcached-d-M 8096-u root-l 192.168.77.105-p 12000-c 256-p/tmp/memcached.pid

The-D option is to start a daemon,

-M is the amount of memory allocated to Memcache, in megabytes, I'm 8096MB,

-U is the user running memcache, I am root here,

-L is the server IP address of the listener, if there are multiple addresses, I specify the server IP address 192.168.77.105,

-P is the port that sets Memcache listening, I set here 12000, preferably more than 1024 ports,

The-c option is the maximum number of concurrent connections to run, the default is 1024, I set the 256 here, according to the load of your server to set,

-P is set to save memcache PID file, I am here to save in/tmp/memcached.pid,

2. If you want to end the memcache process, execute:

# Cat/tmp/memcached.pid or Ps-aux | grep memcache (find the corresponding process ID number)

# Kill Process ID Number

You can also start multiple daemons, but the ports cannot be duplicated.

Connection to the Memcache

Telnet IP Port

Note that before connecting, you need to memcache the server to add the Memcache firewall rules.

-A rh-firewall-1-input-m state--state new-m tcp-p TCP--dport 3306-j ACCEPT

Reload firewall rules

Service Iptables Restart

OK, now we should be able to connect to the memcache.

View memcache status information on client input stats

PID Memcache Process ID of the server

Uptime number of seconds the server has been running

Time Server Current UNIX timestamp

Version Memcache versions

Pointer_size the current operating system pointer size (32-bit system is generally 32bit)

Cumulative user time for the rusage_user process

Cumulative system time for the Rusage_system process

Curr_items the number of items currently stored by the server

Total_items The total number of items stored since the server was started

Bytes The number of bytes occupied by the current server storage items

Curr_connections the number of connections currently open

Total_connections number of connections that have been opened since the server was started

Connection_structures number of connection constructs allocated by the server

Cmd_get get Command (GET) total number of requests

Cmd_set set Command (SAVE) Total Request count

Get_hits Total Hit Count

Total number of get_misses misses

Evictions the number of items deleted for free memory (the space allocated to memcache needs to be removed when the old items are filled to get space allocated to the new items)

Bytes_read bytes read (number of requests bytes)

Bytes_written total number of bytes sent (result bytes)

Limit_maxbytes The amount of memory allocated to Memcache (bytes)

Threads Current number of threads

Redis

Redis is written after memcache, we often compare the two, if it is a key-value store, but it has a rich data type, I want to temporarily call it the cache Data Flow Center, like the current logistics center, order, package, Store, classification, distribute, end. Now the popular lamp PHP architecture does not know the performance comparison with Redis+mysql or Redis + MongoDB (listen to people in the group that MongoDB Shard is unstable).

Let's talk about the characteristics of Reidis.

1. Support Persistence

Redis's local persistence supports two ways: Rdb and aof. The RDB configures persistent triggers in the redis.conf configuration file, aof means that Redis does not add a record to the persisted file (which is the generated command to save the record), and if it is not used with Redis, it will not open aof, the data is too large, Restarting recovery is a huge project!

2. Rich data types

Redis supports String, Lists, sets, sorted sets, hashes multiple data types, Sina Weibo uses Redis to do nosql mainly it has these types, time sorting, functional sequencing, my Weibo, the list of these features sent to me and Sorted set

Powerful operational capabilities.

3. High Performance

This is very much like memcache. The level of memory operation is more natural and efficient than the second-level operation of hard disk operations, with less head seeking, data reading, and paging, and high overhead operations! That's why NoSQL comes out, it's supposed to be high performance.

is an RDBMS-based derivative, although the RDBMS also has a cache structure, but is always at the app level is not what we want to manipulate.

4.replication

Redis provides a master-slave replication scheme, like MySQL incremental replication and replication of the implementation are very similar, this copy is a bit like aof copy is a new record command, the main library new records will be sent to the new script from the library, from the library to generate records according to the script, the process is very fast, look at the network, General master and Slave are in the same LAN, so it can be said that Redis's master-slave approximation in time synchronization, colleagues it also supports a master more from, dynamically add from the library, the number of libraries is not limited. Master-Slave Library building, I think the use of network mode, if using a chain (master-slave-slave-slave-slave If the first slave a downtime restart, first receive data recovery script from master, this is blocked, if the main library data a few terabytes recovery process will take some time, in this process other slave can not synchronize with the main library.

5. Update fast

This seems to me that from my exposure to Redis so far has been issued a large version of 4, the small version has not been counted. Redis author is a very positive person, whether it is a mail question or forum post, he can promptly patiently answer for you, maintenance is very high. Someone to maintain, let us use also worry and rest assured. At present, the main development direction of Redis is the cluster direction of Redis.

Installation of Redis

Redis installation is actually quite simple, on the whole three steps: Download the tar package, unzip the tar package, install.

But recently I 2.6.7 with a CentOS 5.5 32bit when encountered an installation problem, the following I use the picture to share the installation process encountered problems, in the Redis folder to perform make when there is a following error undefined reference to ' __sync_ Add_and_fetch_4 '

Got a lot of surfing on the Internet. Finally find a solution in https://github.com/antirez/redis/issues/736, write cflags=-march=i686 on Src/makefile head!

Remember to delete the file you just failed to install, re-unzip the new installation file, modify the makefile file, and then make the installation. You won't find that mistake.

Some properties comments and basic type operations on Redis in the previous Redis appetizer, there is a detailed explanation, here will not repeat the cumbersome (in essence, want to lazy, haha!). ）

Finally, put Memcache and Redis together have to let people think of the comparison, who fast who easy to use Ah, the group has been fighting for this thing for a long time, I will see me here to share with you.

After someone has sent a memcache performance that is much better than Redis, the Redis author Antirez published a blog post on how to do stress testing for Redis and memcache, a person who says that many open source software should be thrown into the toilet, Because their stress test script is 2, the author explains it. Redis vs Memcache is definitely a apple to Apple comparison. Hehe, it is clear that the comparison between the two is not a bit of egg pick bone effect, the author in the same operating environment to do three times to test how good value, get the results such as:

What needs to be stated is that the data in the process of the single core processing of this test, Memcache is to support multi-core multithreading operations (default is not open) so by default it has reference meaning, if it is memcache faster than Redis. So why does Redis not support multithreading multi-core processing?  The author also published a bit of his own view, first of all, multi-threaded fixed bug fix, in fact, is not easy to extend the software, there is data consistency problem because all operations of Redis is atomic operation, the author uses a word nightmare nightmare, hehe! Of course, do not support multi-threaded operation, there must be his shortcomings, such as the performance must certainly be poor, the author from the 2.2 version of the focus on the development of Redis cluster to alleviate its performance shortcomings, plainly speaking is not vertical, horizontal improvement.

Features of Redis and Mecache and Ehcache