List local memcached keys using Ruby

gistfile1.rb

#!/usr/bin/env ruby

# List all keys stored in memcache. 
# Credit to Graham King at http://www.darkcoding.net/software/memcached-list-all-keys/ 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'], Time.at(expires_time.to_i), bytes, cache_key]
      longest_key_len = [longest_key_len,cache_key.length].max
    end
  end
end

row_format = %Q(|%8s | %28s | %12s | %-#{longest_key_len}s |)
puts row_format%headings
rows.each{|row| puts row_format%row}

localhost.close

Great, very useful - thanks!

+1 extremely helpful for debugging. thank you.

No problem guys! It's super silly that there is no easy way to do this out of the box. I try to use Redis as much as I can but sometimes memcached is the right tool :)

Also because it wasn't mentioned anywhere, Graham King, whose article at http://www.darkcoding.net/software/memcached-list-all-keys/ helped out here.

very useful !!

very useful! thank you :D

Thanks for the code! Used it for a simple command line tool to list and get the value for specific keys. https://gist.github.com/3168935

Thank you!

The telnet lib for me was (inconsistently) calling the code block several times, updating the block as follows did the trick for me.

slab_ids = []
# The code block will get called for each <insert technical expl>
localhost.cmd("String" => "stats items", "Match" => /^END/) do |c|
  slab_ids = slab_ids + c.scan(/STAT items:(\d+):/).flatten.uniq
end
slab_ids = slab_ids.flatten.uniq

Very useful little snippet, but I wanted the output to be a little more verbose, as well as retrieve the exact amount of items in a slab. I added the terminal-table gem in order to tabulate the data nicely.

#!/usr/bin/env ruby
require 'net/telnet'
require 'terminal-table'

tbl       = Terminal::Table.new headings: %w(id expires cache_key bytes)
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 }

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
      tbl << [slab['id'], Time.at(expires_time.to_i), cache_key, bytes]
    end
  end
end

puts tbl
localhost.close

Nice script! Very useful indeed.

Thanks

Thanks for the updates to this old gist of mine. It's amazing how well social coding works sometimes, and how this started from a blurb from Graham King's website!

@kryptek : I like what you've done, sans the gem dependency. I see this guy as a quick and dirty thing you want to throw on a system to figure out what the heck is going on with cache, and it's a distraction to install a gem. I updated the gist with your revision and with baked-in formatting instead :)

If the code block is still getting called multiple times with the new version, please let me know and I'll dig in to it further

@bkimble Thanks for the script! I've added some very simple and inefficient content grabbing to it. For my purposes I only want to see the content when it's ASCII encoded, but I've commented that line out.

# List all keys stored in memcache.
# Credit to Graham King at http://www.darkcoding.net/software/memcached-list-all-keys/ 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 content)
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
longest_content_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
      content = localhost.cmd("String" => "get #{cache_key}", "Match" => /^END/) {|c| c}
      #content = content.ascii_only? ? content : "Not ASCII, whatever it is" #make it a little more pipeline friendly
      rows << [slab['id'], Time.at(expires_time.to_i), bytes, cache_key, content]
      longest_content_len = [longest_content_len, content.length].max
      longest_key_len = [longest_key_len,cache_key.length].max
    end
  end
end

row_format = %Q(|%8s | %28s | %12s | %-#{longest_key_len}s | %-#{longest_content_len}s |)
puts row_format%headings
rows.each{|row| puts row_format%row}

localhost.close

Thanks!

Someone had to do this in a remote server, like Memcachier?

Any help on doing this in a remote server would be great!

To do this on a remote server, you'd have a few options. Either deploy this script to your memcache servers and run it there, or just change

localhost = Net::Telnet::new("Host" => "localhost", "Port" => 11211, "Timeout" => 3)

to be the actual host/port of your memcache server. Keep in mind that firewall rules on your server could limit access to memcache in this manner and you may wind up having to put the script on the server anyway.

does it list all the keys or most of them?

As I didn't know about this snippet I created a similar one based on the same source. Please have a look if you find it useful.

require 'net/telnet'
memcached = Net::Telnet::new("Host" => "localhost", "Port" => 11211)
memcached.puts 'stats items'
slab_ids = memcached.waitfor(/./).split("\n").map { |line| x = line[/([^\:]+)\d+/, 0].to_i ; x > 0 ? x : nil }.uniq.compact
slab_ids.inject([]) do |items, slab_id|
  memcached.puts "stats cachedump #{slab_id} 100"
  items << memcached.waitfor(/./).split("\n")[0].split(' ', 3)[1]
  items
end

@gfa from the first couple of lines of the source in http://www.darkcoding.net/software/memcached-list-all-keys/:
"In the general case, there is no way to list all the keys that a memcached instance is storing. You can, however, list something like the first 1Meg of keys, which is usually enough during development."

@bkimble thanks for this!

Here's yet another fork of your original gist:
https://gist.github.com/ginjo/aaa4a4395fcdbbad3d29

This revision adds a couple of features for working with cache item rows as ruby objects.

• Isolates the cache item query and enumeration into a method that yields to an optional block (passing all elements of cache item. You can do anything with the block - print rows, return rows as an array of hashes, return a single 'matching' row, etc..
• Accepts a list of servers and runs the above enumerator for all items found on every server.

I've included a method that mimics your original formatted printing, plus a method that returns all found cache items as an array of hashes.

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

excellent, thanks a lot!

Nice 😮 . I have customized this script for dump and restore using dalli gem.
https://gist.github.com/javanux/dbd005ef50ae4b8cea213af058abf771

I'm fairly certain this does not work on memcachier.

I successfully telneted in to our production servers and tried issues the stats cachedump command and got:

CLIENT_ERROR unsupported stats command

bingo! 👍

Thank you! This help me to solve problem of infinite caching(no expiration).

Hello, @bkimble. I have adjusted your Gist a bit, see: https://gist.github.com/archan937/f441146e1aeaa9da138e337514ee4000

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.