Python task queue using Redis
This version of TaskTiger switches to using the t:task:<id>:executions_count
Redis key to determine the total number of task executions. In previous versions this was accomplished by obtaining the length of t:task:<id>:executions
. This change was required for the introduction of a parameter to enable the truncation of task execution entries. This is useful for tasks with many retries, where execution entries consume a lot of memory.
This behavior is incompatible with the previous mechanism and requires a migration to populate the task execution counters. Without the migration, the execution counters will behave as though they were reset, which may result in existing tasks retrying more times than they should.
The migration can be executed fully live without concern for data integrity.
0.16.2
if running a version lower than that.tasktiger.migrations.migrate_executions_count
with your TaskTiger
instance, e.g.:from tasktiger import TaskTiger
from tasktiger.migrations import migrate_executions_count
# Instantiate directly or import from your application module
tiger = TaskTiger(...)
# This could take a while depending on the
# number of failed/retrying tasks you have
migrate_executions_count(tiger)
0.17.0
. Done!Due to a cleanup of imports, some internal TaskTiger objects can no longer be imported from the public modules. This shouldn't cause problems for most users, but it's a good idea to double check that all imports from the TaskTiger package continue to function correctly in your application.
This new version of TaskTiger uses a new locking mechanism: the Lock
provided by redis-py. It is incompatible with the old locking mechanism we were using, and several core functions in TaskTiger depends on locking to work correctly, so this warrants a careful migration process.
You can perform this migration in two ways: via a live migration, or via a downtime migration. After the migration, there's an optional cleanup step.
Update your environment to TaskTiger 0.12 as usual.
Deploy TaskTiger as it is in the commit SHA cf600449d594ac22e6d8393dc1009a84b52be0c1
. In pip
parlance, it would be:
-e git+ssh://[email protected]/closeio/tasktiger.git@cf600449d594ac22e6d8393dc1009a84b52be0c1#egg=tasktiger
Wait at least 2-3 minutes with it running in production in all your TaskTiger workers. This is to give time for the old locks to expire, and after that the new locks will be fully in effect.
Deploy TaskTiger 0.13. Your system is migrated.
Run the script in scripts/redis_scan.py
to delete the old lock keys from your Redis instance:
./scripts/redis_scan.py --host HOST --port PORT --db DB --print --match "t:lock:*" --ttl 300
The flags:
--host
: The Redis host. Required.--port
: The port the Redis instance is listening on. Defaults to 6379
.--db
: The Redis database. Defaults to 0
.--print
: If you want the script to print which keys it is modifying, use this.--match
: What pattern to look for. If you didn't change the default prefix TaskTiger uses for keys, this will be t:lock:*
, otherwise it will be PREFIX:lock:*
. By default, scans all keys.--ttl
: A TTL to set. A TTL of 300 will give you time to undo if you want to halt the migration for whatever reason. (Just call this command again with --ttl -1
.) By default, does not change keys' TTLs.Plus, there is:
--file
: A log file that will receive the changes made. Defaults to redis-stats.log
in the current working directory.--delay
: How long, in seconds, to wait between SCAN
iterations. Defaults to 0.1
.