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DOC: config: Add info about variable scopes referencing the parent stream

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It is now possible for a stream to have a parent and it is also possible to
retrieve variables defined in the parent stream context. To do so, some
extra scopes were introduced. The section 2.8. was updated accordingly.
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Christopher Faulet 2024-07-19 16:28:52 +02:00
parent b643fbb1a6
commit 2e86de0e0f
1 changed files with 29 additions and 0 deletions
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doc/configuration.txt
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@ -1240,6 +1240,35 @@ different variables. Supported scopes are:
it and are not shared with other health-checks. They can be set
using dedicated "tcp-check" or "http-check" directives.
Depending on the context, extra scopes referencing the parent of a current
stream can be used:
* psess : same as "sess" but using the session of the parent stream, if any.
* ptxn : same as "txn" but using the transaction of the parent stream, if
any.
* preq : same as "req" but using the parent stream, if any. "preq"
variables are only accessible during request processing of the
parent stream.
* pres : same as "res" but using the parent stream, if any. "pres"
variables are only accessible during response processing of the
parent stream.
Scopes referencing the parent stream are usable from the moment it is defined.
Most of time, there is no parent stream. But, if applicable, this will be
explicitly specified. For now, it is only possible to retrieve the value of
variables defined in a scope of the parent stream. It is not possible to set
nor unset such variables. Usually a child stream performs some processing for
the parent at a precise moment and prevents it from making progress until the
operation it does is completed. This means that the parent may be stopped in
the middle of a request processing or a response processing for example. As
such, certain scopes will not be available from the child stream. For example
if a request is subject to some analysis performed by a child stream, this
child stream will not find any variable in the "pres" scope since the parent is
not processing a response, hence doesn't have any variables in its "res" scope.
The content of a variable is the result of the evaluation of a sample fetch
expression and it inherits of the output type of this expression. It is
important when the variable is used because its type must be compatible with