Add constants module #29493
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Add constants module #29493
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joe-redpanda
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rebase |
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Pull request overview
This PR introduces a new constants module to centralize commonly used magic numbers across the Redpanda codebase. The change replaces hardcoded concurrency limits (32) and a partition balancer constant (7) with named constants defined in new header files.
Changes:
- Created
constants::common::default_concurrencyto replace hardcoded32values used in concurrent operation limits - Created
constants::balancer::missed_statuses_until_unresponsiveto replace hardcoded7in partition balancer logic - Updated all usages across multiple modules to reference these constants
Reviewed changes
Copilot reviewed 23 out of 23 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| src/v/constants/common.h | Defines default_concurrency constant (32) for concurrent operations |
| src/v/constants/balancer_constants.h | Defines missed_statuses_until_unresponsive constant (7) for partition balancer |
| src/v/constants/BUILD | Bazel build definitions for the new constants libraries |
| src/v/redpanda/admin/partition.cc | Uses default_concurrency in max_concurrent_for_each call |
| src/v/kafka/server/handlers/describe_transactions.cc | Uses default_concurrency for transaction description concurrency |
| src/v/kafka/data/rpc/service.cc | Replaces hardcoded concurrency limit with constant |
| src/v/datalake/translation/scheduling.cc | Uses default_concurrency in translator cleanup |
| src/v/datalake/translation/tests/scheduler_fixture.h | Uses constant for test fixture configuration |
| src/v/cluster_link/replication/link_replication_mgr.h | Uses constant for semaphore initialization |
| src/v/cluster_link/group_mirroring_task.h | Uses constant for concurrent request limit |
| src/v/cluster/topics_frontend.cc | Uses default_concurrency for partition move cancellation |
| src/v/cluster/rm_stm.cc | Uses constant in multiple producer management operations |
| src/v/cluster/partition_balancer_backend.cc | Uses both concurrency and balancer constants |
| src/v/config/validators.cc | Uses balancer constant in validation logic and error messages |
| Multiple BUILD files | Add dependencies on new constants libraries |
| public: | ||
| // The partition balancer will declare a node unresponsive if it misses this | ||
| // many node statuses in a row | ||
| static constexpr uint8_t missed_statuses_until_unresponsive = 7u; |
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The type uint8_t is unnecessarily restrictive for a counter value. Consider using size_t or int for consistency with typical integer constants and to avoid potential overflow issues if the value needs to increase in the future.
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If I want more than 255 I'll just change the type : )
Adds a bazel module for capturing codebase-wide constants called common_constants. To this, adds a constant called "default_concurrency" set to 32. This value is wiely used as a magic number in the cluster. A future commit will replace usages of the magic number with this constant
Replaces all usages of the magic number 32 with the common constant 'default_concurrency'
Adds balancer constants to encapsulate the constants used in the various balancers (leader and partition). Extracts a constant to represent the number of node statuses that may be missed before the balancer considers a node unresponsive (7). Uses that constant in the partition balancer planner
Use the balancer constant rather than a magic number
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[23,557 / 23,559] 895 / 900 tests; Testing //src/v/cloud_topics/level_one/domain/tests:db_domain_manager_test; 1200s remote-cache, linux-sandbox ... (2 actions running) Probably unrelated but will take a peek |
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bazel test failure was unrelated, requesting feedback |
joe-redpanda
requested review from
bashtanov,
bharathv,
dotnwat and
mmaslankaprv
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"Why?"
This was prompted by the magic number '7' in partition balancer.
I added validation on the relative sizes of time spans in the partition balancer when updating configs.
Generally node status < node unresponsiveness < node drain < auto decommission
Problem: node unresponsiveness is defined as 7 * node status interval
This number lives (lived) hardcoded in partition_balancer_backend
Should this multiplier be a configuration?
maybe?
Is it okay to have hardcoded constants?
IMO yes, just so long as theres ONE definition.
So, to have one definition usable by config validation and partition balancer, I can
I scraped together the usages of 32 as well mostly as a demonstration that this folder can be more widely useful than just partition balancer.
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