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An L7 Policy is a collection of L7 rules associated with a Listener, and which may also have an association to a back-end pool. Policies describe actions that should be taken by the load balancing software if all of the rules in the policy return true.
Policy logic
Policy logic is very simple: All the rules associated with a given policy are logically ANDed together. A request must match all the policy’s rules to match the policy. If you need to express a logical OR operation between rules, then do this by creating multiple policies with the same action (or, possibly, by making a more elaborate regular expression).
Policy actions
If an L7 policy matches a given request, then that policy’s action is executed. The following are the actions an L7 Policy may take:
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- In the reference implementation (haproxy amphorae) of Octavia, haproxy enforces the following ordering regarding policy actions:
- REJECT policies take precedence over all other policies.
- REDIRECT_TO_URL policies take precedence over REDIRECT_TO_POOL policies.
- REDIRECT_TO_POOL policies are only evaluated after all of the above, and in the order specified by the position of the policy.
- L7 Policies are evaluated in a specific order (as defined by the position attribute), and the first policy that matches a given request will be the one whose action is followed.
- If no policy matches a given request, then the request is routed to the listener’s default pool, if it exists. If the listener has no default pool, then an error 503 is returned.
- Policy position numbering starts with 1.
- If a new policy is created with a position that matches that of an existing policy, then the new policy is inserted at the given position and the others will move down one position.
- If a new policy is created without specifying a position, or specifying a position that is greater than the number of policies already in the list, the new policy will just be appended to the list (i.e. its position will be equal to the number of policies in the list plus one).
- When policies are inserted, deleted, or appended to the list, the policy position values are re-ordered from 1 without skipping numbers. For example, if policy A, B, and C have position values of 1, 2 and 3 respectively, if you delete policy B from the list, policy C’s position becomes 2.