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diff --git a/lib/gitlab/exclusive_lease.rb b/lib/gitlab/exclusive_lease.rb
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+++ b/lib/gitlab/exclusive_lease.rb
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+module Gitlab
+  # This class implements an 'exclusive lease'. We call it a 'lease'
+  # because it has a set expiry time. We call it 'exclusive' because only
+  # one caller may obtain a lease for a given key at a time. The
+  # implementation is intended to work across GitLab processes and across
+  # servers. It is a 'cheap' alternative to using SQL queries and updates:
+  # you do not need to change the SQL schema to start using
+  # ExclusiveLease.
+  #
+  # It is important to choose the timeout wisely. If the timeout is very
+  # high (1 hour) then the throughput of your operation gets very low (at
+  # most once an hour). If the timeout is lower than how long your
+  # operation may take then you cannot count on exclusivity. For example,
+  # if the timeout is 10 seconds and you do an operation which may take 20
+  # seconds then two overlapping operations may hold a lease for the same
+  # key at the same time.
+  #
+  class ExclusiveLease
+    def initialize(key, timeout:)
+      @key, @timeout = key, timeout
+    end
+
+    # Try to obtain the lease. Return true on success,
+    # false if the lease is already taken.
+    def try_obtain
+      # Performing a single SET is atomic
+      !!redis.set(redis_key, '1', nx: true, ex: @timeout)
+    end
+
+    private
+
+    def redis
+      # Maybe someday we want to use a connection pool...
+      @redis ||= Redis.new(url: Gitlab::REDIS_URL)
+    end
+
+    def redis_key
+      "gitlab:exclusive_lease:#{@key}"
+    end
+  end
+end