Talk @ PHP meetup Budapest, 2013.03.26.

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DAEMONS IN PHP
Zoltán Németh
Core Systems Manager @ Ustream
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2. CONTENTS
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The core: daemonizing
Signal handling
Init scripts
Easy building of daemons
The current package
Open sourcing
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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
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4. WHY????
 PHP had some problems in the early days
– Hard to manage long running scripts
– Memory leaks
– Problems with forking
– Handling code changes
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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
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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)
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7. DAEMONIZING – THE CODE
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8. DAEMONIZING – THE CODE
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9. DAEMONIZING – THE CODE
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10. THE MAIN LOOP
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11. TIMING
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12. MEMORY LEAK CHECKING
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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
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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)
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15. SIGNAL HANDLING
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16. SIGNAL HANDLING
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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
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18. INIT SCRIPTS
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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
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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
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21. THE BOILERPLATE
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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
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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
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24. INI FILE EXAMPLE
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25. BUILDER CALL, LIST OF OPTIONS
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26. BUILDER CODE
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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
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28. THE PACKAGE
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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
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29. THE PACKAGE - INTERFACES
 Ustream_Daemon_Task
– doTask()
 Ustream_Daemon_TaskFactory
– createTaskFor(Ustream_Daemon_Daemon
$daemon)
 Ustream_Daemon_Starter
– start()
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30. THE DAEMON MONITOR
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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
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31. THE DAEMON MONITOR
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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
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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
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34. 34
QUESTIONS?
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