1. 1
DAEMONS IN PHP
Zoltán Németh
Core Systems Manager @ Ustream
We. Are.
NOW PLAYING
DAEMONS IN PHP
1
Mar 26, 2013
.

2. CONTENTS







NOW PLAYING
WHY????
The core: daemonizing
Signal handling
Init scripts
Easy building of daemons
The current package
Open sourcing
DAEMONS IN PHP
2
Mar 26, 2013

3. WHY????
 The need for daemons
– Frequently running scheduled tasks
– Async processing
– Cron drawbacks:
 Can do only minute level
 Does not guarantee exact timing
 Cron jobs cannot be monitored
NOW PLAYING
DAEMONS IN PHP
3
Mar 26, 2013

4. WHY????
 PHP had some problems in the early days
– Hard to manage long running scripts
– Memory leaks
– Problems with forking
– Handling code changes
NOW PLAYING
DAEMONS IN PHP
4
Mar 26, 2013

5. WHY????
 Why daemons in PHP?
– Mostly PHP codebase
– Duplication of business logic leads to hell
 Lot of the logic codes used in daemons were
already used on the site
– PHP experience
– Quick and easy development
NOW PLAYING
DAEMONS IN PHP
5
Mar 26, 2013

6. DAEMONIZING – THE CONCEPT
 At startup, fork a child and exit from the
parent
– Start a new background session for the child
 In the child, have a loop which does the task
 Calculate timing after each loop and use
usleep for precision
 Have a pidfile (for monit etc)
NOW PLAYING
DAEMONS IN PHP
6
Mar 26, 2013

7. DAEMONIZING – THE CODE
NOW PLAYING
DAEMONS IN PHP
7
Mar 26, 2013

8. DAEMONIZING – THE CODE
NOW PLAYING
DAEMONS IN PHP
8
Mar 26, 2013

9. DAEMONIZING – THE CODE
NOW PLAYING
DAEMONS IN PHP
9
Mar 26, 2013

10. THE MAIN LOOP
NOW PLAYING
DAEMONS IN PHP
10
Mar 26, 2013

11. TIMING
NOW PLAYING
DAEMONS IN PHP
11
Mar 26, 2013

12. MEMORY LEAK CHECKING
NOW PLAYING
DAEMONS IN PHP
12
Mar 26, 2013

13. SIGNAL HANDLING
 Before PHP 5.3
– declare(ticks=1);
– Signal dispatch by php system, at every tick
– Unreliable
– Precise, fixed intervals
 Handler functions with pcntl_signal
NOW PLAYING
DAEMONS IN PHP
13
Mar 26, 2013

14. SIGNAL HANDLING
 PHP 5.3
– declare(ticks=1); is deprecated
– Signal dispatch by code:
pcntl_signal_dispatch
– More reliable
– Not precise, changing intervals (code
execution determines timing)
NOW PLAYING
DAEMONS IN PHP
14
Mar 26, 2013

15. SIGNAL HANDLING
NOW PLAYING
DAEMONS IN PHP
15
Mar 26, 2013

16. SIGNAL HANDLING
NOW PLAYING
DAEMONS IN PHP
16
Mar 26, 2013

17. INIT SCRIPTS
 Needed for monit, run daemons on startup,
etc
 In the beginning: separate init script for every
daemon
 Lot of copy-paste with minimal changing
information
 Hard to keep consistent: changes do not
propagate
NOW PLAYING
DAEMONS IN PHP
17
Mar 26, 2013

18. INIT SCRIPTS
NOW PLAYING
DAEMONS IN PHP
18
Mar 26, 2013

19. INIT SCRIPTS
 Conclusion: let’s have a common script in
the repo
 Take the name of the daemon as a
parameter
 Required: a class to run a daemon by its
name
– Daemon_Runner
NOW PLAYING
DAEMONS IN PHP
19
Mar 26, 2013

20. DAEMON RUNNER AND BUILDER
 Original setup: one php file for each daemon
 Each has its own class definition
– All variable initializations
– All configurations
 Constructing the object and all dependencies
 Starting the daemon
 Lot of boilerplate code  Daemon_Runner
NOW PLAYING
DAEMONS IN PHP
20
Mar 26, 2013

21. THE BOILERPLATE
NOW PLAYING
DAEMONS IN PHP
21
Mar 26, 2013

22. DAEMON RUNNER AND BUILDER
 Concept: a generic Runner class to run a
daemon based with a given task
 Task: the repeatedly running part of the
daemon
 Ustream_Daemon_Task interface
 Independent of the daemon configuration
NOW PLAYING
DAEMONS IN PHP
22
Mar 26, 2013

23. DAEMON RUNNER AND BUILDER
 Builder: a factory which creates the daemon
object
 All configuration options are handed over by
the builder
 Runner: call the builder and then run the
resulting class
 Configuration in .ini files
NOW PLAYING
DAEMONS IN PHP
23
Mar 26, 2013

24. INI FILE EXAMPLE
NOW PLAYING
DAEMONS IN PHP
24
Mar 26, 2013

25. BUILDER CALL, LIST OF OPTIONS
NOW PLAYING
DAEMONS IN PHP
25
Mar 26, 2013

26. BUILDER CODE
NOW PLAYING
DAEMONS IN PHP
26
Mar 26, 2013

27. AVAILABLE OPTIONS
 Sleep: period length (running time is
substracted)
 Minimum sleep: if running time is too long
 Factory: Task factory class
 Instance: for multi instance daemons
NOW PLAYING
DAEMONS IN PHP
27
Mar 26, 2013

28. THE PACKAGE




Ustream_Daemon_Daemon
Ustream_Daemon_Builder
Ustream_Daemon_Runner
Ustream_Daemon_PreconfiguredTaskDelegator: a
generic daemon class used by the builder. Runs a
task
 Ustream_Daemon_Logger: a file based logger for
the daemon package. Should be PSR3
NOW PLAYING
DAEMONS IN PHP
28
Mar 26, 2013

29. THE PACKAGE - INTERFACES
 Ustream_Daemon_Task
– doTask()
 Ustream_Daemon_TaskFactory
– createTaskFor(Ustream_Daemon_Daemon
$daemon)
 Ustream_Daemon_Starter
– start()
NOW PLAYING
DAEMONS IN PHP
29
Mar 26, 2013

30. THE DAEMON MONITOR






Centralized status monitor system
Every daemon reports status on UDP
Server in node.js
Displays info
Sends commands: e.g. Stop
Will be moved to a separate package
NOW PLAYING
DAEMONS IN PHP
30
Mar 26, 2013

31. THE DAEMON MONITOR
NOW PLAYING
DAEMONS IN PHP
31
Mar 26, 2013

32. OPEN SOURCING
 On github: https://github.com/ustream
 Some prerequisites:
– Remove remaining Ustream codebase
specific references
– Move Daemon Monitor related stuff to
separate package
 Planned ETA in April
NOW PLAYING
DAEMONS IN PHP
32
Mar 26, 2013

33. FURTHER PLANS
 Debug mode:
– remotely enabled
– collect output and dump when stopped
 Runtime setting of loglevel
– Possibly from remote daemon monitor
 Code coverage collecting
NOW PLAYING
DAEMONS IN PHP
33
Mar 26, 2013

34. 34
QUESTIONS?
We. Are.
NOW PLAYING
DAEMONS IN PHP
34
Mar 26, 2013
.