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new dab332a Clarify parent selection.
dab332a is described below
commit dab332a0eadb194d600172d3a66dd5e52971a003
Author: Miles Libbey <mlib...@apache.org>
AuthorDate: Mon Nov 7 13:44:35 2016 -0800
Clarify parent selection.
---
.../configuration/hierachical-caching.en.rst | 19 +++++++++++++++
doc/admin-guide/files/parent.config.en.rst | 28 ++++++++++++----------
2 files changed, 35 insertions(+), 12 deletions(-)
diff --git a/doc/admin-guide/configuration/hierachical-caching.en.rst
b/doc/admin-guide/configuration/hierachical-caching.en.rst
index 9d5790f..32964c9 100644
--- a/doc/admin-guide/configuration/hierachical-caching.en.rst
+++ b/doc/admin-guide/configuration/hierachical-caching.en.rst
@@ -76,6 +76,25 @@ content from the origin server (or from another cache,
depending on the parent
configuration). The parent caches the content and then sends a copy to Traffic
Server (its child), where it is cached and served to the client.
+Parent Selection Policies
+-------------------------
+
+There are several parent selection policies available to the Traffic Server
child
+node.
+
+ - Consistent Hash. The child node chooses a specific parent for each URI.
This effectively
+ makes the parent's cache size the sum total of each of the individual
parent cache
+ sizes.
+ - Round Robin. The child node cycles through the parents. The child can
select the parent
+ based on the client IP ("true"), or in a strict cycling ("strict").
+ - (Unnamed). The child node chooses the first live parent listed. There
are two variants to this
+ strategy. When the strategy is set to "false," the child will use the
first listed parent
+ (for clarity called p1) until it is marked down, when the child will
switch to the second
+ listed parent (p2). Then, when the p1 is retested and found live, the
child
+ will restart using p1. When the selection strategy is set to "latched,"
the child will use
+ p1 until it is marked down, when it will switch to p2. When p1 is
retested and found live,
+ the child will continue using p2 until it is marked down.
+
Interaction with Remap.config
-----------------------------
diff --git a/doc/admin-guide/files/parent.config.en.rst
b/doc/admin-guide/files/parent.config.en.rst
index 93238d7..9f8ff9d 100644
--- a/doc/admin-guide/files/parent.config.en.rst
+++ b/doc/admin-guide/files/parent.config.en.rst
@@ -69,7 +69,8 @@ allowed values.
The secondary specifiers are optional in the :file:`parent.config` file. The
following list shows the possible secondary specifiers and their allowed
-values.
+values. Every line in the :file:`parent.config` file must contain either a
+``parent=`` or ``go_direct=`` directive.
.. _parent-config-format-port:
@@ -195,8 +196,7 @@ The following list shows the possible actions and their
allowed values.
``round_robin``
One of the following values:
- - ``true`` - Traffic Server goes through the parent cache list in a
- round robin-based on client IP address.
+ - ``true`` - Traffic Server determines the parent based on client IP
address.
- ``strict`` - Traffic Server machines serve requests strictly in
turn. For example: machine ``proxy1`` serves the first request,
``proxy2`` serves the second request, and so on.
@@ -207,8 +207,8 @@ The following list shows the possible actions and their
allowed values.
The other traffic is unaffected. Once the downed parent becomes
available, the traffic distribution returns to the pre-down
state.
- - ``latched`` - The first parent in the list is marked as primary and is
- always chosen until connection errors cause it to be marked down. When
+ - ``latched`` - The first parent in the list is marked as primary and is
+ always chosen until connection errors cause it to be marked down. When
this occurs the next parent in the list then becomes primary. The
primary
will wrap back to the first parent in the list when it is the last parent
in the list and is marked down due to a connection error. Newly chosen
@@ -230,7 +230,9 @@ The following list shows the possible actions and their
allowed values.
One of the following values:
- ``consider`` - Use the query string when finding a parent.
- - ``ignore`` - Do not consider the query string when finding a parent.
+ - ``ignore`` - Do not consider the query string when finding a parent.
This
+ is especially useful when using the ``consistent_hash`` selection
strategy,
+ and a random query string would prevent a consistent parent selection.
Examples
========
@@ -241,16 +243,18 @@ Traffic Server (which is the child) and two parents,
``p1.x.com`` and
the parent servers ``p1.x.com`` and ``p2.x.com`` in a round-robin
fashion::
- round_robin=true
dest_domain=. method=get parent="p1.x.com:8080; p2.y.com:8080"
round_robin=true
- round_robin=consistent_hash
- dest_domain=. method=get parent="p1.x.com:8080|1.0; p2.y.com:8080|2.0"
round_robin=consistent_hash
The following rule configures Traffic Server to route all requests
containing the regular expression ``politics`` and the path
``/viewpoint`` directly to the origin server (bypassing any parent
-hierarchies): ``url_regex=politics prefix=/viewpoint go_direct=true``
+hierarchies)::
-Every line in the :file:`parent.config` file must contain either a
-``parent=`` or ``go_direct=`` directive.
+ url_regex=politics prefix=/viewpoint go_direct=true
+
+The following configures Traffic Server to route http requests for example.com
(neither
+https nor www.example.com would match) through parent servers. Each url will
be hashed
+to a specific parent. If the chosen parent has been marked down, a parent from
the
+secondary ring will be chosen for the retry.::
+ dest_host=example.com scheme=http parent="p1.x.com:80,p2.x.com:80"
secondary_parent="p3.x.com:80,p4.x.com:80" round_robin=consistent_hash
go_direct=false
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