如何防止我的 sidekiq 工作人员超过其数据库连接限制？
How do I prevent my sidekiq workers from overwhelming its database connection limit?
现在我的 DigitalOcean 托管数据库后端连接限制是 22。这是我的 sidekiq.yml 和 database.yml 配置：
# config/sidekiq.yml
development:
:concurrency: 18
production:
:concurrency: 18
.
# config/database.yml
default: &default
adapter: postgresql
encoding: unicode
pool: 18
每当我启动计划任务时，我都会有一群或一些工作人员与数据库进行交互。由于我们计划允许此计划任务同时启动多次，因此我们 运行 遇到了很多连接数据库池错误。所以现在我正在尝试找出优化此过程的最佳方法或寻找其他可能对我们更好的服务。
出于测试目的，我创建了一个如下所示的 sidekiq worker：
class MySampleWorker
include Sidekiq::Worker
sidekiq_options queue: Rails.env.to_sym
def perform
User.first
end
end
如果我同时调用这个 sidekiq worker 20 次，一切 运行 都会很顺利。但是如果我同时调用它 50 次，那么我会得到大约 3-5 个失败的 worker 最终被重试。
我的问题是 -- 我将如何缩放这样的东西？就我而言，我将不得不多次呼叫同一个工人，随着需求的增长越来越多，这显然会导致几个失败的工人。在某些情况下，这些工作人员每个可能需要 5-10 分钟 - 他们本质上是 运行 在远程系统上执行运行状况检查命令并等待输出以完成工作人员。
以这种方式扩展似乎是灾难性的。有没有什么方法可以简单地让他们排队，并在有可用 space 时 运行 而不是失败，而不是让工人失败？如果我理解它的工作方式，那么 database.yml 不应该将连接限制在 18，因此，当 postgresql 数据库有一个连接时，它实际上不应该一次尝试访问超过 18 个连接的 postgresql 数据库限制为 22？我想我应该期望看到 activerecord 数据库连接超时错误 before 我看到 postgresql 数据库连接问题的任何问题。
这是我在其中一名工作人员现在失败时收到的错误：
2020-06-18T15:05:16.536Z pid=1152049 tid=gofhou0qp WARN: PG::ConnectionBad: FATAL: remaining connection slots are reserved for non-replication superuser connections
2020-06-18T15:05:16.536Z pid=1152049 tid=gofhou0qp WARN: /usr/local/rvm/gems/ruby-2.5.8/gems/pg-1.2.3/lib/pg.rb:58:in `initialize'
/usr/local/rvm/gems/ruby-2.5.8/gems/pg-1.2.3/lib/pg.rb:58:in `new'
/usr/local/rvm/gems/ruby-2.5.8/gems/pg-1.2.3/lib/pg.rb:58:in `connect'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:692:in `connect'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:223:in `initialize'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `new'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `postgresql_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:830:in `new_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:874:in `checkout_new_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:853:in `try_to_checkout_new_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:814:in `acquire_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:538:in `checkout'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:382:in `connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:1033:in `retrieve_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_handling.rb:90:in `connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/delegation.rb:76:in `connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/query_methods.rb:934:in `build_arel'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/query_methods.rb:900:in `arel'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:560:in `block in exec_queries'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:584:in `skip_query_cache_if_necessary'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:547:in `exec_queries'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:422:in `load'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:200:in `records'
/usr/local/rvm/gems/ruby-2.5.8/gems/bullet-6.1.0/lib/bullet/active_record52.rb:46:in `records'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:195:in `to_ary'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/finder_methods.rb:532:in `find_nth_with_limit'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/finder_methods.rb:517:in `find_nth'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/finder_methods.rb:125:in `first'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/querying.rb:5:in `first'
/var/www/test-dev/app/workers/my_sample_worker.rb:12:in `perform'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:196:in `execute_job'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:164:in `block (2 levels) in process'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/middleware/chain.rb:133:in `invoke'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:163:in `block in process'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:136:in `block (6 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_retry.rb:111:in `local'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:135:in `block (5 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/rails.rb:43:in `block in call'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/execution_wrapper.rb:87:in `wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/reloader.rb:73:in `block in wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/execution_wrapper.rb:87:in `wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/reloader.rb:72:in `wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/rails.rb:42:in `call'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:131:in `block (4 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:257:in `stats'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:126:in `block (3 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_logger.rb:13:in `call'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:125:in `block (2 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_retry.rb:78:in `global'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:124:in `block in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/logger.rb:10:in `with'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_logger.rb:33:in `prepare'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:123:in `dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:162:in `process'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:78:in `process_one'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:68:in `run'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/util.rb:15:in `watchdog'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/util.rb:24:in `block in safe_thread'
这是我的 Puma 配置：
threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
threads threads_count, threads_count
port ENV.fetch("PORT") { 3000 }
environment ENV.fetch("RAILS_ENV") { "development" }
当你扩大规模时，你应该只得到一个作业队列供工作人员处理——如果你的并发设置正确的话。没有失败的工作 - 你的期望是正确的。
但是，将数据库池设置为 18 的预期可能是错误的。而且，当然只适用于每个应用程序服务器（你有多个吗？）
但这将取决于您如何配置 Puma，post 该配置。
有关设置工作线程和线程大小的最佳实践，请参阅 https://devcenter.heroku.com/articles/concurrency-and-database-connections for a good description of how the pool should be shared between workers and multiple application servers. And, https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server。
现在我的 DigitalOcean 托管数据库后端连接限制是 22。这是我的 sidekiq.yml 和 database.yml 配置：
# config/sidekiq.yml
development:
:concurrency: 18
production:
:concurrency: 18
.
# config/database.yml
default: &default
adapter: postgresql
encoding: unicode
pool: 18
每当我启动计划任务时，我都会有一群或一些工作人员与数据库进行交互。由于我们计划允许此计划任务同时启动多次，因此我们 运行 遇到了很多连接数据库池错误。所以现在我正在尝试找出优化此过程的最佳方法或寻找其他可能对我们更好的服务。
出于测试目的，我创建了一个如下所示的 sidekiq worker：
class MySampleWorker
include Sidekiq::Worker
sidekiq_options queue: Rails.env.to_sym
def perform
User.first
end
end
如果我同时调用这个 sidekiq worker 20 次，一切 运行 都会很顺利。但是如果我同时调用它 50 次，那么我会得到大约 3-5 个失败的 worker 最终被重试。
我的问题是 -- 我将如何缩放这样的东西？就我而言，我将不得不多次呼叫同一个工人，随着需求的增长越来越多，这显然会导致几个失败的工人。在某些情况下，这些工作人员每个可能需要 5-10 分钟 - 他们本质上是 运行 在远程系统上执行运行状况检查命令并等待输出以完成工作人员。
以这种方式扩展似乎是灾难性的。有没有什么方法可以简单地让他们排队，并在有可用 space 时 运行 而不是失败，而不是让工人失败？如果我理解它的工作方式，那么 database.yml 不应该将连接限制在 18，因此，当 postgresql 数据库有一个连接时，它实际上不应该一次尝试访问超过 18 个连接的 postgresql 数据库限制为 22？我想我应该期望看到 activerecord 数据库连接超时错误 before 我看到 postgresql 数据库连接问题的任何问题。
这是我在其中一名工作人员现在失败时收到的错误：
2020-06-18T15:05:16.536Z pid=1152049 tid=gofhou0qp WARN: PG::ConnectionBad: FATAL: remaining connection slots are reserved for non-replication superuser connections
2020-06-18T15:05:16.536Z pid=1152049 tid=gofhou0qp WARN: /usr/local/rvm/gems/ruby-2.5.8/gems/pg-1.2.3/lib/pg.rb:58:in `initialize'
/usr/local/rvm/gems/ruby-2.5.8/gems/pg-1.2.3/lib/pg.rb:58:in `new'
/usr/local/rvm/gems/ruby-2.5.8/gems/pg-1.2.3/lib/pg.rb:58:in `connect'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:692:in `connect'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:223:in `initialize'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `new'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/postgresql_adapter.rb:48:in `postgresql_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:830:in `new_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:874:in `checkout_new_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:853:in `try_to_checkout_new_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:814:in `acquire_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:538:in `checkout'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:382:in `connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_adapters/abstract/connection_pool.rb:1033:in `retrieve_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_handling.rb:118:in `retrieve_connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/connection_handling.rb:90:in `connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/delegation.rb:76:in `connection'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/query_methods.rb:934:in `build_arel'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/query_methods.rb:900:in `arel'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:560:in `block in exec_queries'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:584:in `skip_query_cache_if_necessary'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:547:in `exec_queries'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:422:in `load'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:200:in `records'
/usr/local/rvm/gems/ruby-2.5.8/gems/bullet-6.1.0/lib/bullet/active_record52.rb:46:in `records'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation.rb:195:in `to_ary'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/finder_methods.rb:532:in `find_nth_with_limit'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/finder_methods.rb:517:in `find_nth'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/relation/finder_methods.rb:125:in `first'
/usr/local/rvm/gems/ruby-2.5.8/gems/activerecord-5.2.4/lib/active_record/querying.rb:5:in `first'
/var/www/test-dev/app/workers/my_sample_worker.rb:12:in `perform'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:196:in `execute_job'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:164:in `block (2 levels) in process'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/middleware/chain.rb:133:in `invoke'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:163:in `block in process'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:136:in `block (6 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_retry.rb:111:in `local'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:135:in `block (5 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/rails.rb:43:in `block in call'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/execution_wrapper.rb:87:in `wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/reloader.rb:73:in `block in wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/execution_wrapper.rb:87:in `wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/activesupport-5.2.4/lib/active_support/reloader.rb:72:in `wrap'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/rails.rb:42:in `call'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:131:in `block (4 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:257:in `stats'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:126:in `block (3 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_logger.rb:13:in `call'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:125:in `block (2 levels) in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_retry.rb:78:in `global'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:124:in `block in dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/logger.rb:10:in `with'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/job_logger.rb:33:in `prepare'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:123:in `dispatch'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:162:in `process'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:78:in `process_one'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/processor.rb:68:in `run'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/util.rb:15:in `watchdog'
/usr/local/rvm/gems/ruby-2.5.8/gems/sidekiq-6.0.7/lib/sidekiq/util.rb:24:in `block in safe_thread'
这是我的 Puma 配置：
threads_count = ENV.fetch("RAILS_MAX_THREADS") { 5 }
threads threads_count, threads_count
port ENV.fetch("PORT") { 3000 }
environment ENV.fetch("RAILS_ENV") { "development" }
当你扩大规模时，你应该只得到一个作业队列供工作人员处理——如果你的并发设置正确的话。没有失败的工作 - 你的期望是正确的。
但是，将数据库池设置为 18 的预期可能是错误的。而且，当然只适用于每个应用程序服务器（你有多个吗？）
但这将取决于您如何配置 Puma，post 该配置。
有关设置工作线程和线程大小的最佳实践，请参阅 https://devcenter.heroku.com/articles/concurrency-and-database-connections for a good description of how the pool should be shared between workers and multiple application servers. And, https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server。