When the number of Sidekiq jobs increases to a certain scale, the system faces some scalability issues. One of them is that the length of the queue tends to get longer. High-urgency jobs have to wait longer until other less urgent jobs finish. This head-of-line blocking situation may eventually affect the responsiveness of the system, especially critical actions. In another scenario, the performance of some jobs is degraded due to other long running or CPU-intensive jobs (computing or rendering ones) in the same machine.
To counter the aforementioned issues, one effective solution is to split
Sidekiq jobs into different queues and assign machines handling each queue
exclusively. For example, all CPU-intensive jobs could be routed to the
cpu-bound queue and handled by a fleet of CPU optimized instances. The queue
topology differs between companies depending on the workloads and usage
patterns. Therefore, GitLab supports a flexible mechanism for the
administrator to route the jobs based on their characteristics.
As an alternative to Queue selector, which configures Sidekiq cluster to listen to a specific set of workers or queues, GitLab also supports routing a job from a worker to the desired queue when it is scheduled. Sidekiq clients try to match a job against a configured list of routing rules. Rules are evaluated from first to last, and as soon as we find a match for a given worker we stop processing for that worker (first match wins). If the worker doesn’t match any rule, it falls back to the queue name generated from the worker name.
By default, if the routing rules are not configured (or denoted with an empty array), all the jobs are routed to the queue generated from the worker name.
sidekiq['routing_rules'] = [ # Route all non-CPU-bound workers that are high urgency to `high-urgency` queue ['resource_boundary!=cpu&urgency=high', 'high-urgency'], # Route all database, gitaly and global search workers that are throttled to `throttled` queue ['feature_category=database,gitaly,global_search&urgency=throttled', 'throttled'], # Route all workers having contact with outside work to a `network-intenstive` queue ['has_external_dependencies=true|feature_category=hooks|tags=network', 'network-intensive'], # Route all import workers to the queues generated by the worker name, for # example, JiraImportWorker to `jira_import`, SVNWorker to `svn_worker` ['feature_category=import', nil], # Wildcard matching, route the rest to `default` queue ['*', 'default'] ]
The routing rules list is an order-matter array of tuples of query and corresponding queue:
- The query is following a worker matching query syntax.
<queue_name>must be a valid Sidekiq queue name. If the queue name is
nil, or an empty string, the worker is routed to the queue generated by the name of the worker instead.
The query supports wildcard matching
*, which matches all workers. As a
result, the wildcard query must stay at the end of the list or the rules after it
- Attributes that can be selected.
- Operators used to construct a query.
Introduced in GitLab 13.1 (
Queue matching query works upon the worker attributes, described in Sidekiq style guide. We support querying based on a subset of worker attributes:
feature_category- the GitLab feature category the queue belongs to. For example, the
mergequeue belongs to the
has_external_dependencies- whether or not the queue connects to external services. For example, all importers have this set to
urgency- how important it is that this queue’s jobs run quickly. Can be
throttled. For example, the
authorized_projectsqueue is used to refresh user permissions, and is high urgency.
worker_name- the worker name. The other attributes are typically more useful as they are more general, but this is available in case a particular worker needs to be selected.
name- the queue name. The other attributes are typically more useful as they are more general, but this is available in case a particular queue needs to be selected.
resource_boundary- if the queue is bound by
unknown. For example, the
ProjectExportWorkeris memory bound as it has to load data in memory before saving it for export.
tags- short-lived annotations for queues. These are expected to frequently change from release to release, and may be removed entirely.
has_external_dependencies is a boolean attribute: only the exact
true is considered true, and everything else is considered
tags is a set, which means that
= checks for intersecting sets, and
!= checks for disjoint sets. For example,
tags=a,b selects queues
that have tags
b, or both.
tags!=a,b selects queues that have
neither of those tags.
The attributes of each worker are hard-coded in the source code. For convenience, we generate a list of all available attributes in GitLab Community Edition and a list of all available attributes in GitLab Enterprise Edition.
queue_selector supports the following operators, listed from highest
to lowest precedence:
|- the logical OR operator. For example,
query_bare queries made up of the other operators here) will include queues that match either query.
&- the logical AND operator. For example,
query_bare queries made up of the other operators here) will only include queues that match both queries.
!=- the NOT IN operator. For example,
feature_category!=issue_trackingexcludes all queues from the
=- the IN operator. For example,
resource_boundary=cpuincludes all queues that are CPU bound.
,- the concatenate set operator. For example,
feature_category=continuous_integration,pagesincludes all queues from either the
continuous_integrationcategory or the
pagescategory. This example is also possible using the OR operator, but allows greater brevity, as well as being lower precedence.
The operator precedence for this syntax is fixed: it’s not possible to make AND have higher precedence than OR.
In GitLab 12.9 and
later, as with the standard queue group syntax above, a single
* as the
entire queue group selects all queues.
After the Sidekiq routing rules are changed, administrators need to take care with the migration to avoid losing jobs entirely, especially in a system with long queues of jobs. The migration can be done by following the migration steps mentioned in Sidekiq job migration