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-- SPDX-License-Identifier: AGPL-3.0-or-later
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--
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-- This script is not a string in scheduler.py, so editors can provide syntax highlighting.
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-- The Redis KEY is defined here and not in Python on purpose:
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-- only this LUA script can read and update this key to avoid lock and concurrency issues.
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local redis_key = 'SearXNG_checker_next_call_ts'
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local now = redis.call('TIME')[1]
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local start_after_from = ARGV[1]
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local start_after_to = ARGV[2]
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local every_from = ARGV[3]
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local every_to = ARGV[4]
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local next_call_ts = redis.call('GET', redis_key)
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if (next_call_ts == false or next_call_ts == nil) then
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-- the scheduler has never run on this Redis instance, so:
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-- 1/ the scheduler does not run now
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-- 2/ the next call is a random time between start_after_from and start_after_to
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local initial_delay = math.random(start_after_from, start_after_to)
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redis.call('SET', redis_key, now + initial_delay)
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return { false, delay }
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end
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-- next_call_ts is defined
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-- --> if now is lower than next_call_ts then we don't run the embedded checker
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-- --> if now is higher then we update next_call_ts and ask to run the embedded checker now.
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local call_now = next_call_ts <= now
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if call_now then
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-- the checker runs now, define the timestamp of the next call:
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-- this is a random delay between every_from and every_to
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local periodic_delay = math.random(every_from, every_to)
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next_call_ts = redis.call('INCRBY', redis_key, periodic_delay)
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end
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return { call_now, next_call_ts - now }
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