Scheduler: adds optional support for redis and specifying redis clientfeature/scheduler_redis_cluster_support

- allow optional support for running the scheduler without a redis
  backend for persistent schedule storage. The default is to exit on
  startup error. The user can set `redis_startup_error_hard_kill` to
  false if they really want to run the scheduler with no backend db.
- allow users the ability to specify a redis client class. this will let
  them use redis-cluster if they wish. They can install the appropriate
  module and define `redis_client_class` (and if necessary class keyword
  arguments via `redis_client_class_kwargs`).

1 files changed, 66 insertions, 4 deletions

diff --git a/docs/settings_file.rst b/docs/settings_file.rst
index 04fe451..e9f4b04 100644
--- a/docs/settings_file.rst
+++ b/docs/settings_file.rst
@@ -19,6 +19,13 @@ Default: False
 
 Enable most verbose level of debug statements
 
+hide_heartbeat_logs
+===================
+Default: True
+
+This hides heart beat messages from the logs. Disabling this will result in very
+noisy log output.
+
 max_sockets
 ===========
 Default: 1024
@@ -91,15 +98,55 @@ Default: ''
 
 Password to use when connecting to redis
 
+redis_client_class
+==================
+Default: ``redis.StrictRedis``
+
+The class to use as the redis client. This can be overridden if you want to use
+a different module to connect to redis. For example
+``rediscluster.StrictRedisCluster``. Note: You make get errors if you don't use
+a strict mode class.
+
+redis_client_class_kwargs
+=========================
+Default: {}
+
+This is a JSON hash map of keyword arguments to pass to the Python class
+constructor. This is useful for using ``redis-cluster-py`` on AWS Elasticache.
+When using Elasticache this value should be set to
+``{"skip_full_coverage_check": true}`` to prevent startup errors.
+
+redis_startup_error_hard_kill
+=============================
+Default: True
+
+If there is an error connecting to the Redis server for persistent schedule
+storage on startup then kill the app. This is useful if you want to prevent
+accidentally accepting schedules that can't be saved to a persistent store. If
+you would like to use redis you will need to ``pip install redis`` or
+``pip install redis-py-cluster`` and define the necessary options.
+
 ***********
 Job Manager
 ***********
 
+default_queue_name
+==================
+Default: default
+
+This is the default queue a job manager will listen on if nothing is specified.
+
+default_queue_weight
+====================
+Default: 10
+
+This is the default weight for the default queue is it is not explicitly set.
+
 concurrent_jobs
 ===============
 Default: 4
 
-This is the number of concurrent jobs the indiviudal job manager should execute
+This is the number of concurrent jobs the individual job manager should execute
 at a time. If you are using the multiprocess or threading model this number
 becomes important as you will want to control the load on your server. If the
 load equals the number of cores on the server, processes will begin waiting for
@@ -115,7 +162,7 @@ queues
 ======
 Default: [[10, "default"]]
 
-Comma seperated list of queues to process jobs for with their weights. This list
+Comma separated list of queues to process jobs with their weights. This list
 must be valid JSON otherwise an error will be thrown.
 Example: ``queues=[[10, "data_process"], [15, "email"]]``.  With these
 weights and the ``CONCURRENT_JOBS`` setting, you should be able to tune managers
@@ -131,14 +178,29 @@ number until the large box is ready to accept another q1 job.
    default queue so that anything that is not explicitly assigned will still be
    run.
 
-setup_callabe/setup_path
-========================
+setup_callable/setup_path
+=========================
 Default: '' (Signifies no task will be attempted)
 
 Strings containing path and callable to be run when a worker is spawned
 if applicable to that type of worker.  Currently the only supported worker is a
 MultiProcessWorker, and is useful for pulling any global state into memory.
 
+job_entry_func
+==============
+Default: '' (Signifies no function will be executed)
+
+The function to execute before **every** job a worker thread executes. For
+example: cleaning up stale database connections. (Django's
+``django.db.connections[].close_if_unusable_or_obsolete()``)
+
+job_exit_func
+=============
+Default: '' (Signifies no function will be executed)
+
+The function to execute **after** every job a worker thread executes. For
+example: closing any database handles that were left open.
+
 max_job_count
 =============
 Default: 1024