LUA: parse multi-line variable and cut needed string

Question

I have next nginx location with Lua code (used with nginx lua-resty-redis):

location = /healthcheck {

  content_by_lua_block {

    local red = redis:new()
    used_mem_limit = 536870912

    -- connect to redis
    ok, err = red:connect(ngx.var.redis_host, 6379)
    if not ok then
        ngx.log(ngx.ERR, "Redis connection error: ", err)
        ngx.status = 500
        return
    end

    -- setting connection timeout
    red:set_timeout(1000)

    -- getting redis used_memory_rss
    memory = red:info('memory')

    red_used_memory = ...

    -- set response code
    if (red_used_memory >= used_mem_limit) then
      http_code = 500
    elseif (red_used_memory < used_mem_limit)
      http_code = 200
    else
      http_code = 500
    end

    ngx.status = http_code

  }

}

memory variable should be like this:

# Memory
used_memory:105157968
used_memory_human:100.29M
used_memory_rss:110387200
used_memory_rss_human:105.27M
used_memory_peak:105219456
used_memory_peak_human:100.35M
used_memory_peak_perc:99.94%
used_memory_overhead:32290608
used_memory_startup:487168
used_memory_dataset:72867360
used_memory_dataset_perc:69.62%
total_system_memory:1044770816

I need to get used_memory_rss value, so then I can compare it with used_mem_limit. So, I don't know, how to complete red_used_memory = ... line.

Oleg V. Volkov · Accepted Answer · 2018-02-02 16:47:00Z

2

There seems to be only digits in possible value so use a simple regexp and then convert resulting string to number:

red_used_memory = tonumber(memory:match('used_memory_rss:(%d+)'))

Line breaks are irrelevant.

answered Feb 2, 2018 at 16:47

Oleg V. Volkov

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