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DOC: config: Fix description of options about HTTP connection modes

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Since the HTX, the decription of options about HTTP connection modes is
wrong. In fact, it is worst, all the documentation about HTTP connection
mode is wrong. But only options will be updated for now to be backported.

So, documentation of "option httpclose", "option "http-keep-alive", "option
http-server-close" and "option "http-pretend-keepalive" was reviewed. First,
it is specify these options only concern HTT/1.x connections. Then, the
descriptions were updated to reflect the HTX implementation.

The main changes concerns the fact that server connections are no longer
attached to client connections. The connection mode on one side does not
affect the connection mode on the other side. It is especially true for
t"option httpclose". For client connections, only the frontend option is
considered and for server ones, both frontend and backend options are
considered.

This patch should be backported as far as 2.2.
This commit is contained in:
Christopher Faulet 2023-02-20 17:09:34 +01:00
parent a62201df5a
commit 85523a0212
1 changed files with 51 additions and 65 deletions
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116
doc/configuration.txt
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@ -9410,18 +9410,18 @@ no option http-ignore-probes
option http-keep-alive
no option http-keep-alive
Enable or disable HTTP keep-alive from client to server
Enable or disable HTTP keep-alive from client to server for HTTP/1.x
connections
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and
the start of a new request. This mode may be changed by several options such
as "option http-server-close" or "option httpclose". This option allows to
set back the keep-alive mode, which can be useful when another mode was used
in a defaults section.
HTTP/1.x connections: for each connection it processes each request and
response, and leaves the connection idle on both sides. This mode may be
changed by several options such as "option http-server-close" or "option
httpclose". This option allows to set back the keep-alive mode, which can be
useful when another mode was used in a defaults section.
Setting "option http-keep-alive" enables HTTP keep-alive mode on the client-
and server- sides. This provides the lowest latency on the client side (slow
@ -9438,15 +9438,6 @@ no option http-keep-alive
compared to the cost of retrieving the associated object from the server.
This last case can happen when the server is a fast static server of cache.
In this case, the server will need to be properly tuned to support high enough
connection counts because connections will last until the client sends another
request.
If the client request has to go to another backend or another server due to
content switching or the load balancing algorithm, the idle connection will
immediately be closed and a new one re-opened. Option "prefer-last-server" is
available to try optimize server selection so that if the server currently
attached to an idle connection is usable, it will be used.
At the moment, logs will not indicate whether requests came from the same
session or not. The accept date reported in the logs corresponds to the end
@ -9456,12 +9447,10 @@ no option http-keep-alive
not set.
This option disables and replaces any previous "option httpclose" or "option
http-server-close". When backend and frontend options differ, all of these 4
options have precedence over "option http-keep-alive".
http-server-close".
See also : "option httpclose",, "option http-server-close",
"option prefer-last-server", "option http-pretend-keepalive",
and "1.1. The HTTP transaction model".
"option prefer-last-server" and "option http-pretend-keepalive".
option http-no-delay
@ -9500,19 +9489,19 @@ no option http-no-delay
option http-pretend-keepalive
no option http-pretend-keepalive
Define whether HAProxy will announce keepalive to the server or not
Define whether HAProxy will announce keepalive for HTTP/1.x connection to the
server or not
May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes
Arguments : none
When running with "option http-server-close" or "option httpclose", HAProxy
adds a "Connection: close" header to the request forwarded to the server.
Unfortunately, when some servers see this header, they automatically refrain
from using the chunked encoding for responses of unknown length, while this
is totally unrelated. The immediate effect is that this prevents HAProxy from
maintaining the client connection alive. A second effect is that a client or
a cache could receive an incomplete response without being aware of it, and
consider the response complete.
adds a "Connection: close" header to the HTTP/1.x request forwarded to the
server. Unfortunately, when some servers see this header, they automatically
refrain from using the chunked encoding for responses of unknown length,
while this is totally unrelated. The effect is that a client or a cache could
receive an incomplete response without being aware of it, and consider the
response complete.
By setting "option http-pretend-keepalive", HAProxy will make the server
believe it will keep the connection alive. The server will then not fall back
@ -9532,9 +9521,7 @@ no option http-pretend-keepalive
This option may be set in backend and listen sections. Using it in a frontend
section will be ignored and a warning will be reported during startup. It is
a backend related option, so there is no real reason to set it on a
frontend. This option may be combined with "option httpclose", which will
cause keepalive to be announced to the server and close to be announced to
the client. This practice is discouraged though.
frontend.
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
@ -9572,26 +9559,25 @@ option http-restrict-req-hdr-names { preserve | delete | reject }
option http-server-close
no option http-server-close
Enable or disable HTTP connection closing on the server side
Enable or disable HTTP/1.x connection closing on the server side
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and
the start of a new request. This mode may be changed by several options such
as "option http-server-close" or "option httpclose". Setting "option
http-server-close" enables HTTP connection-close mode on the server side
while keeping the ability to support HTTP keep-alive and pipelining on the
client side. This provides the lowest latency on the client side (slow
network) and the fastest session reuse on the server side to save server
resources, similarly to "option httpclose". It also permits non-keepalive
capable servers to be served in keep-alive mode to the clients if they
conform to the requirements of RFC7230. Please note that some servers do not
always conform to those requirements when they see "Connection: close" in the
request. The effect will be that keep-alive will never be used. A workaround
consists in enabling "option http-pretend-keepalive".
HTTP/1.x connections: for each connection it processes each request and
response, and leaves the connection idle on both sides. This mode may be
changed by several options such as "option http-server-close" or "option
httpclose". Setting "option http-server-close" enables HTTP connection-close
mode on the server side while keeping the ability to support HTTP keep-alive
and pipelining on the client side. This provides the lowest latency on the
client side (slow network) and the fastest session reuse on the server side
to save server resources, similarly to "option httpclose". It also permits
non-keepalive capable servers to be served in keep-alive mode to the clients
if they conform to the requirements of RFC7230. Please note that some servers
do not always conform to those requirements when they see "Connection: close"
in the request. The effect will be that keep-alive will never be used. A
workaround consists in enabling "option http-pretend-keepalive".
At the moment, logs will not indicate whether requests came from the same
session or not. The accept date reported in the logs corresponds to the end
@ -9609,8 +9595,8 @@ no option http-server-close
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "option httpclose", "option http-pretend-keepalive",
"option http-keep-alive", and "1.1. The HTTP transaction model".
See also : "option httpclose", "option http-pretend-keepalive" and
"option http-keep-alive".
option http-use-proxy-header
no option http-use-proxy-header
@ -9702,37 +9688,37 @@ option httpchk <method> <uri> <version>
option httpclose
no option httpclose
Enable or disable HTTP connection closing
Enable or disable HTTP/1.x connection closing
May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes
Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and
leaves the connection idle on both sides between the end of a response and
the start of a new request. This mode may be changed by several options such
as "option http-server-close" or "option httpclose".
HTTP/1.x connections: for each connection it processes each request and
response, and leaves the connection idle on both sides. This mode may be
changed by several options such as "option http-server-close" or "option
httpclose".
If "option httpclose" is set, HAProxy will close connections with the server
and the client as soon as the request and the response are received. It will
also check if a "Connection: close" header is already set in each direction,
and will add one if missing. Any "Connection" header different from "close"
will also be removed.
If "option httpclose" is set, HAProxy will close the client or the server
connection, depending where the option is set. Only the frontend is
considered for client connections while the frontend and the backend are
considered for server ones. In this case the option is enabled if at least
one of the frontend or backend holding the connection has it enabled. If the
option is set on a listener, it is applied both on client and server
connections. It will check if a "Connection: close" header is already set in
each direction, and will add one if missing.
This option may also be combined with "option http-pretend-keepalive", which
will disable sending of the "Connection: close" header, but will still cause
the connection to be closed once the whole response is received.
will disable sending of the "Connection: close" request header, but will
still cause the connection to be closed once the whole response is received.
This option may be set both in a frontend and in a backend. It is enabled if
at least one of the frontend or backend holding a connection has it enabled.
It disables and replaces any previous "option http-server-close" or "option
http-keep-alive". Please check section 4 ("Proxies") to see how this option
combines with others when frontend and backend options differ.
http-keep-alive".
If this option has been enabled in a "defaults" section, it can be disabled
in a specific instance by prepending the "no" keyword before it.
See also : "option http-server-close" and "1.1. The HTTP transaction model".
See also : "option http-server-close".
option httplog [ clf ]