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List local memcached keys using Ruby
#!/usr/bin/env ruby
# List all keys stored in memcache.
# Credit to Graham King at for the original article on how to get the data from memcache in the first place.
require 'net/telnet'
headings = %w(id expires bytes cache_key)
rows = []
localhost = Net::Telnet::new("Host" => "localhost", "Port" => 11211, "Timeout" => 3)
matches = localhost.cmd("String" => "stats items", "Match" => /^END/).scan(/STAT items:(\d+):number (\d+)/)
slabs = matches.inject([]) { |items, item| items << Hash[*['id','items'].zip(item).flatten]; items }
longest_key_len = 0
slabs.each do |slab|
localhost.cmd("String" => "stats cachedump #{slab['id']} #{slab['items']}", "Match" => /^END/) do |c|
matches = c.scan(/^ITEM (.+?) \[(\d+) b; (\d+) s\]$/).each do |key_data|
cache_key, bytes, expires_time = key_data
rows << [slab['id'],, bytes, cache_key]
longest_key_len = [longest_key_len,cache_key.length].max
row_format = %Q(|%8s | %28s | %12s | %-#{longest_key_len}s |)
puts row_format%headings
rows.each{|row| puts row_format%row}
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archan937 commented Oct 16, 2019

Hello, @bkimble. I have adjusted your Gist a bit, see:

The logic is in a method called keys and you can pass your memcached host (or a list of hosts) and an optional pattern to filter on keys.
Also, prints the slab IDs with all of its keys.

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Unfortunately it does not work when the server has several 100 thousand keys...

Same here. Does not work with 60k keys.

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The require statement at the top needs to be updated because telnet was removed from the standard library at some point and made a separate gem. Otherwise script works as expected. Thanks @bkimble 👍

- require 'net/telnet'
+ gem 'net-telnet'

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