sl_cache (E)

sl_cache

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Outline

• Attention： The texture data is downloaded by HTTP(S) since SL Viewer 2.1.1. Therefore, when Viewer since SL Viewer 2.1.1 is used, sl_cache seems to be useless.

• sl_cache is a UDP Texture Cache Server for sl_relay running on Linux.
• By our measurements, the texture data accounts for about max 80% of all UDP data, though it depends on the SIM's status.
• Cache data is saved in a plain file or Berkeley DB file. (It works fast enough even with a plain file)
• sl_cache doesn't rewrite the sequence number of UDP packets. It only saves data taking it out of the data stream.

• sl_cache is part of sl_proxy.
• Current version is 1.1.0 (28 Step. '11)
   

Outline of Functions

1. Texture data caching is enabled through sl_relay.

Annoyances or Bugs.

1. Cache data is saved in a plain file or a Berkeley DB file. SQL database is not supported.
2. The speed slows in Berkeley DB. Plain file is more high-speed now.
3. The program has not been stress tested.

Explanation

1. Caching of Texture Data
2. Texture Data Base
3. When the server has two network interfaces or more
4. Expire Cache Data
5. Log and Debug Mode
6. Security

Configuration

• The default configuration file is /usr/local/etc/sl_proxy/sl_cache.conf.
• It is also possible to specify other files if -f option of sl_cache is specified.
• Because the configuration file is read before sl_cache does the switch to the effective user, exec user should be able to be read.
• The setting of each item is described in the configuration file. Empty lines or lines starting with # are not read.
   

Items

Ports for communication with Relay Server

• MinUdpPutPort
• MaxUdpPutPort
• MinUdpGetPort
• MaxUdpGetPort

Number of transfer packets

• GetPacketNum

Access Control

• Hosts_Allow_File

Etc. etc.

• Temp_File_Dir
• MaxIdleTime
   

Execute Options

sl_cache  [-p port_no] [-f config_file] [-u user_name] [-i interface_address]
          [-pid pid_file] [-l [hitrate_logfile]] [-v syslog_level]
          [-xpr [expire_days]] [-lx [expire_logfile]]
          [-fdb] [-d]
          [--version] [--help] [-h]
       
-p   : port number that Relay Server(sl_relay) connects. default is 8200.
-f   : configuration file. default is /usr/local/etc/sl_proxy/sl_cahe.conf
-u   : specify effective user.
-i   : specify sl_relay side network interface IP address.
       if your server has two or more network interfaces, you need to use this option.
       
-pid : specify pid file.
-l   : create hit rate log file. default file name is /var/sl_proxy/sl_cache_hitrate.log
-v   : level of syslog. default is LOG_INFO (7).
       
-xpr : execute the cache expire daemon. 
       The expire time can be continuously specified by day unit. default is the 30days.
       the expire demon retrieves at random and deletes data without the access during 
       the specified days.
-lx  : create cache expire log file. default file name is /var/sl_proxy/sl_expire_cache.log
       
-fdb : Berkeley DB is used for the data base. default is plane file.
       
-d   : debug mode. display debug information.
       
--version  : display Version information.
--help, -h : display this Help messages.

Processes

Data Caching

• There is a two step data save process so that a single process can control the actually data save, thus avoiding file locking problems.

• [Save Data Process] is Cache Put Server
• [Get Cache Process] is Cache Control Process