ServerKit

Server

Libserver

API

• Thread pools & delayed work management
• Thread-safe fixed-unit-size heaps
• Thread-safe queues
• Logging via either libc-syslog, or optionally more efficient direct UDP-based syslog-compatible logging
• Lightweight & efficient sequence logging
• Reader-writer locks similar to UNIX98 pthread_rwlock*
• Parse tree (ptree) implementation for fast and simple parsing of byte streams

Basic operation

1. Acquire a personality specified via the SERVER_PERSONALITY_PATH environment variable.
2. Open any modules found within ${SERVER_PERSONALITY_PATH}/modules serially, adding any per-module configuration options to the parser vocabulary under a section named after the modules name. Upon opening, the construct method of each module is invoked so any required early initialization can be performed.
3. Open and parse the configuration file found at ${SERVER_PERSONALITY_PATH}/c11n using libconfuse and a vocabulary combining both core server program configuration options and module-specific options imported in the previous step.
4. Check the process' UID, if it is root check that the configuration set executes_as_root to true. If not, abort, otherwise continue.
5. Modify the process' argv[0] to reflect the configured identity.
6. Create all database pools configured in the c11n file, making them available for lookup via their configured identifier by the loaded modules.
7. Invoke the prestart method of each loaded module serially, note that this occurs before the server program makes any attempt to switch users. If a configuration section was found whose name matched the module being prestarted, the configuration data from that section is provided to the modules prestart method in the form of a libconfuse cfg_t type.
8. If the configuration specified uid and/or gid settings, attempt to switch the uid and gid respectively, aborting on failure.
9. Create an operator thread for each loaded module serially, the thread function used is the operator function in each module.
10. Wait indefinitely for signals. Upon receipt of SIGUSR1 process-wide statistics are reported on stderr.

Note that the server program does not perform a "daemonize" step, this is due to being generally used under DJB's daemontools. A daemonize configuration option may be added in the future if there is sufficient demand.

In the final step process-wide statistics can be reported upon delivery of the SIGUSR1 signal.

Sample output upon delivery of SIGUSR1 to a personality running shttp with 30 threads during an apachebench run with 1000 concurrency:

ServerKit status report

 Thread pools
  Label                  MinThreads MaxThreads StackSize  ActiveBusy ActiveTotal
  ------------------------------------------------------------------------------
  shttp_workers          1          30         32768      30         30         
                  WaitCount   Channel
                  -------------------
                  30          recv
                  0           send
                  0           send headers
                  0           send autoidx
                  0           send constant response
                  0           sendfile
                  0           open
                  0           opendir
                  0           readdir

 Database connection pools
  Identifier             MinConns   MaxConns   ActiveBusy ActivTotal Errors
  ------------------------------------------------------------------------------

 Heaps
  Label             MaxUnits   Opts ActChnkSiz ActivUnits ActivChnks AllocUnits
  ------------------------------------------------------------------------------
  shttp_sessions    2000       ES-  640        1260       6          894        
  log_entry_heap    1000       ES-  10         0          0          0          

Utilizing the vtstats module these statistics can be displayed periodically through a virtual terminal on the system console as well.

Configuration

Core configuration options

Database section configuration options

Sample configuration of a theoretical POP3 server personality

identity = pop
bypass_libc_syslog = true
libc_syslog_bypass_address = 192.168.2.100

#Since pop binds to port 110 it needs root, binding to the port is part of
#the pop module prestart routine, so we setup a mail uid and gid for server
#to switch to post-prestart.  If you omitted the uid and gid lines, server
#would just continue running as root, a bad idea.
executes_as_root = true
uid = 30000
gid = 30000

database FOOFOO {
	name = maildatabase
	user = mailuser
	password = sekret
	host = localhost
	pool_max = 30
	pool_min = 2
}

#pop section vocabulary is added by a pop module, note FOOFOO is supplied
#to the pop module so it can lookup the database pool defined above.
pop {   
	database = FOOFOO 
	port = 110
	address = 230.120.11.4
	backlog = 32
	min_sessions = 10
	max_sessions = 2000
	max_threads = 30
	min_threads = 1
	maildrop_query_format_string = select maildrop from EMailUsers where EMailUsers.password="PASSWORD(%p)" and EMailUsers.user="%u"
}

Contributed modules

Shttp

Small and fast web server by Yingyuan Cheng