Practical session: Building cache meshes with Squid

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Practical session Building cache meshes with
Squid
Bertold Kolics MTA-SzTAKI Bertold.Kolics_at_sztaki.hu
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Agenda

• Final goal two-level cache mesh
• Step 1.
• Create 3 different cache groups
• Step 2.
• 2 of 3 groups - 1st level cache servers each
  serving different institutions
• 3rd cache group - 2nd level cache for the other
  two groups

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Step 1. Creating cache groups...

• Rules
• Each group is a fully connected mesh
• Each cache in a group uses ICP for inter-cache
  communication
• The caches use sibling relationship type
• 1st group local domain is iif.hu
• 2nd group local domain is sztaki.hu
• 3rd group no local domain, but dont allow
  requests with destination domain hu

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...Step 1. Creating cache groups...

• Configure sibling relationship
• use cache_peer and dont forget to look at the
  cache_peer options as well!
• look at cache_peer_domain, too
• Create an ACL entry for your peers
• acl mypeers src 192.168.10.10/255.255.255.255
• Setup access rules for your peers
• siblings resolve only HIT from your server!
• Examine http_access, miss_access, icp_access

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...Step 1. Creating cache groups

• Setup domain based rules (always_direct,
  never_direct)
• local domain should be contacted directly!
• Eg. acl mydomain dstdomain .foo.bar
• Test your server group!
• Fetch some pages and use another cache in the
  group to retrieve the same URL(s)
• Watch the access.log file

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Step 2. Setting up the mesh...

• Rules
• 1st, 2nd group 1st level caches
• 3rd group - 2nd level (TL) caches
• 3rd group is the parent of the 1st and the 2nd
  group
• inter-cache communication Cache Digests
• 2nd level cache must not be used for URLs with
  hostname in the hu TLD

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...Step 2. Setting up the mesh...

• Configure parent relationship (1st, 2nd)
• use cache_peer and dont forget to look at the
  cache_peer options as well! (esp. no-query)
• look at cache_peer_domain, too (!!!)
• Create an ACL entry for your child caches (3rd
  group)
• acl mychildren src 192.168.10.10/255.255.255.255
  
• Setup access rules for your child caches (3rd
  group)
• Set http_access, miss_access, icp_access

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...Step 2. Setting up the mesh

• Test the cache mesh!
• 1st level caches
• Test whether the requests in the local domain go
  directly to the origin servers
• Test whether the requests with destination domain
  .hu domain will not be resolved through your
  parents
• 2nd level caches
• Check if 1st level caches try to use your servers
  to retrieve objects found in the local domain of
  the 1st level caches
• Check if 1st level caches try to use your servers
  to retrieve objects with destination domain .hu