idanoo/php-resque
1
0
Fork 0
mirror of https://github.com/idanoo/php-resque synced 2025-07-02 14:12:21 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

Created HOWITWORKS; cleanup of README

Browse source 
Addresses a request from @chrisboulton in GitHub issue #149

Slight grammar cleanup and content update in README.md
Mention of HOWITWORKS.md in README.md, referring those who want to know more that direction
Expanded and slightly cleaner version of a comment made in #149 that prompted this commit/PR
   was placed in HOWITWORKS.md

Signed-off-by: Daniel Hunsaker <danhunsaker@gmail.com>
This commit is contained in:
Daniel Hunsaker 2013-12-07 00:38:16 -07:00
parent 02809d6632
commit 3a62e47f16
2 changed files with 243 additions and 43 deletions
Download patch file Download diff file Expand all files Collapse all files

157
HOWITWORKS.md Normal file
View file

@ -0,0 +1,157 @@
*For an overview of how to __use__ php-resque, see `README.md`.*
The following is a step-by-step breakdown of how php-resque operates.
## Enqueue Job ##
What happens when you call `Resque::enqueue()`?
1. `Resque::enqueue()` calls `Resque_Job::create()` with the same arguments it
received.
2. `Resque_Job::create()` checks that your `$args` (the third argument) are
either `null` or in an array
3. `Resque_Job::create()` generates a job ID (a "token" in most of the docs)
4. `Resque_Job::create()` pushes the job to the requested queue (first
argument)
5. `Resque_Job::create()`, if status monitoring is enabled for the job (fourth
argument), calls `Resque_Job_Status::create()` with the job ID as its only
argument
6. `Resque_Job_Status::create()` creates a key in Redis with the job ID in its
name, and the current status (as well as a couple of timestamps) as its
value, then returns control to `Resque_Job::create()`
7. `Resque_Job::create()` returns control to `Resque::enqueue()`, with the job
ID as a return value
8. `Resque::enqueue()` triggers the `afterEnqueue` event, then returns control
to your application, again with the job ID as its return value
## Workers At Work ##
How do the workers process the queues?
1. `Resque_Worker::work()`, the main loop of the worker process, calls
`Resque_Worker->reserve()` to check for a job
2. `Resque_Worker->reserve()` checks whether to use blocking pops or not (from
`BLOCKING`), then acts accordingly:
* Blocking Pop
1. `Resque_Worker->reserve()` calls `Resque_Job::reserveBlocking()` with
the entire queue list and the timeout (from `INTERVAL`) as arguments
2. `Resque_Job::reserveBlocking()` calls `Resque::blpop()` (which in turn
calls Redis' `blpop`, after prepping the queue list for the call, then
processes the response for consistency with other aspects of the
library, before finally returning control [and the queue/content of the
retrieved job, if any] to `Resque_Job::reserveBlocking()`)
3. `Resque_Job::reserveBlocking()` checks whether the job content is an
array (it should contain the job's type [class], payload [args], and
ID), and aborts processing if not
4. `Resque_Job::reserveBlocking()` creates a new `Resque_Job` object with
the queue and content as constructor arguments to initialize the job
itself, and returns it, along with control of the process, to
`Resque_Worker->reserve()`
* Queue Polling
1. `Resque_Worker->reserve()` iterates through the queue list, calling
`Resque_Job::reserve()` with the current queue's name as the sole
argument on each pass
2. `Resque_Job::reserve()` passes the queue name on to `Resque::pop()`,
which in turn calls Redis' `lpop` with the same argument, then returns
control (and the job content, if any) to `Resque_Job::reserve()`
3. `Resque_Job::reserve()` checks whether the job content is an array (as
before, it should contain the job's type [class], payload [args], and
ID), and aborts processing if not
4. `Resque_Job::reserve()` creates a new `Resque_Job` object in the same
manner as above, and also returns this object (along with control of
the process) to `Resque_Worker->reserve()`
3. In either case, `Resque_Worker->reserve()` returns the new `Resque_Job`
object, along with control, up to `Resque_Worker::work()`; if no job is
found, it simply returns `FALSE`
* No Jobs
1. If blocking mode is not enabled, `Resque_Worker::work()` sleeps for
`INTERVAL` seconds; it calls `usleep()` for this, so fractional seconds
*are* supported
* Job Reserved
1. `Resque_Worker::work()` triggers a `beforeFork` event
2. `Resque_Worker::work()` calls `Resque_Worker->workingOn()` with the new
`Resque_Job` object as its argument
3. `Resque_Worker->workingOn()` does some reference assignments to help keep
track of the worker/job relationship, then updates the job status from
`WAITING` to `RUNNING`
4. `Resque_Worker->workingOn()` stores the new `Resque_Job` object's payload
in a Redis key associated to the worker itself (this is to prevent the job
from being lost indefinitely, but does rely on that PID never being
allocated on that host to a different worker process), then returns control
to `Resque_Worker::work()`
5. `Resque_Worker::work()` forks a child process to run the actual `perform()`
6. The next steps differ between the worker and the child, now running in
separate processes:
* Worker
1. The worker waits for the job process to complete
2. If the exit status is not 0, the worker calls `Resque_Job->fail()` with
a `Resque_Job_DirtyExitException` as its only argument.
3. `Resque_Job->fail()` triggers an `onFailure` event
4. `Resque_Job->fail()` updates the job status from `RUNNING` to `FAILED`
5. `Resque_Job->fail()` calls `Resque_Failure::create()` with the job
payload, the `Resque_Job_DirtyExitException`, the internal ID of the
worker, and the queue name as arguments
6. `Resque_Failure::create()` creates a new object of whatever type has
been set as the `Resque_Failure` "backend" handler; by default, this is
a `Resque_Failure_Redis` object, whose constructor simply collects the
data passed into `Resque_Failure::create()` and pushes it into Redis
in the `failed` queue
7. `Resque_Job->fail()` increments two failure counters in Redis: one for
a total count, and one for the worker
8. `Resque_Job->fail()` returns control to the worker (still in
`Resque_Worker::work()`) without a value
* Job
1. The job calls `Resque_Worker->perform()` with the `Resque_Job` as its
only argument.
2. `Resque_Worker->perform()` sets up a `try...catch` block so it can
properly handle exceptions by marking jobs as failed (by calling
`Resque_Job->fail()`, as above)
3. Inside the `try...catch`, `Resque_Worker->perform()` triggers an
`afterFork` event
4. Still inside the `try...catch`, `Resque_Worker->perform()` calls
`Resque_Job->perform()` with no arguments
5. `Resque_Job->perform()` calls `Resque_Job->getInstance()` with no
arguments
6. If `Resque_Job->getInstance()` has already been called, it returns the
existing instance; otherwise:
7. `Resque_Job->getInstance()` checks that the job's class (type) exists
and has a `perform()` method; if not, in either case, it throws an
exception which will be caught by `Resque_Worker->perform()`
8. `Resque_Job->getInstance()` creates an instance of the job's class, and
initializes it with a reference to the `Resque_Job` itself, the job's
arguments (which it gets by calling `Resque_Job->getArguments()`, which
in turn simply returns the value of `args[0]`, or an empty array if no
arguments were passed), and the queue name
9. `Resque_Job->getInstance()` returns control, along with the job class
instance, to `Resque_Job->perform()`
10. `Resque_Job->perform()` sets up its own `try...catch` block to handle
`Resque_Job_DontPerform` exceptions; any other exceptions are passed
up to `Resque_Worker->perform()`
11. `Resque_Job->perform()` triggers a `beforePerform` event
12. `Resque_Job->perform()` calls `setUp()` on the instance, if it exists
13. `Resque_Job->perform()` calls `perform()` on the instance
14. `Resque_Job->perform()` calls `tearDown()` on the instance, if it
exists
15. `Resque_Job->perform()` triggers an `afterPerform` event
16. The `try...catch` block ends, suppressing `Resque_Job_DontPerform`
exceptions by returning control, and the value `FALSE`, to
`Resque_Worker->perform()`; any other situation returns the value
`TRUE` along with control, instead
17. The `try...catch` block in `Resque_Worker->perform()` ends
18. `Resque_Worker->perform()` updates the job status from `RUNNING` to
`COMPLETE`, then returns control, with no value, to the worker (again
still in `Resque_Worker::work()`)
19. `Resque_Worker::work()` calls `exit(0)` to terminate the job process
cleanly
* SPECIAL CASE: Non-forking OS (Windows)
1. Same as the job above, except it doesn't call `exit(0)` when done
7. `Resque_Worker::work()` calls `Resque_Worker->doneWorking()` with no
arguments
8. `Resque_Worker->doneWorking()` increments two processed counters in Redis:
one for a total count, and one for the worker
9. `Resque_Worker->doneWorking()` deletes the Redis key set in
`Resque_Worker->workingOn()`, then returns control, with no value, to
`Resque_Worker::work()`
4. `Resque_Worker::work()` returns control to the beginning of the main loop,
where it will wait for the next job to become available, and start this
process all over again