94 lines
2.4 KiB
Ruby
94 lines
2.4 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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# Reference Counter
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#
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# A reference counter is used as a mechanism to identify when
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# a repository is being accessed by a writable operation.
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#
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# Maintenance operations would use this as a clue to when it should
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# execute significant changes in order to avoid disrupting running traffic
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class ReferenceCounter
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REFERENCE_EXPIRE_TIME = 600
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attr_reader :gl_repository, :key
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# Reference Counter instance
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#
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# @example
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# Gitlab::ReferenceCounter.new('project-1')
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#
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# @see Gitlab::GlRepository::RepoType.identifier_for_repositorable
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# @param [String] gl_repository repository identifier
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def initialize(gl_repository)
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@gl_repository = gl_repository
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@key = "git-receive-pack-reference-counter:#{gl_repository}"
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end
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# Return the actual counter value
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#
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# @return [Integer] value
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def value
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Gitlab::Redis::SharedState.with do |redis|
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(redis.get(key) || 0).to_i
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end
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end
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# Increase the counter
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#
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# @return [Boolean] whether operation was a success
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def increase
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redis_cmd do |redis|
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redis.incr(key)
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redis.expire(key, REFERENCE_EXPIRE_TIME)
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end
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end
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# Decrease the counter
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#
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# @return [Boolean] whether operation was a success
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def decrease
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redis_cmd do |redis|
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current_value = redis.decr(key)
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if current_value < 0
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Gitlab::AppLogger.warn("Reference counter for #{gl_repository} decreased" \
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" when its value was less than 1. Resetting the counter.")
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redis.del(key)
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end
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end
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end
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# Reset the reference counter
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#
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# @private Used internally by SRE and debugging purpose
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# @return [Boolean] whether reset was a success
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def reset!
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redis_cmd do |redis|
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redis.del(key)
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end
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end
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# When the reference counter would expire
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#
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# @api private Used internally by SRE and debugging purpose
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# @return [Integer] Number in seconds until expiration or false if never
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def expires_in
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Gitlab::Redis::SharedState.with do |redis|
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redis.ttl(key)
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end
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end
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private
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def redis_cmd
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Gitlab::Redis::SharedState.with { |redis| yield(redis) }
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true
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rescue StandardError => e
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Gitlab::AppLogger.warn("GitLab: An unexpected error occurred in writing to Redis: #{e}")
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false
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end
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end
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end
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