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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 option http-keep-alive
no 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 May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes yes | yes | yes | yes
Arguments : none Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and HTTP/1.x connections: for each connection it processes each request and
leaves the connection idle on both sides between the end of a response and response, and leaves the connection idle on both sides. This mode may be
the start of a new request. This mode may be changed by several options such changed by several options such as "option http-server-close" or "option
as "option http-server-close" or "option httpclose". This option allows to httpclose". This option allows to set back the keep-alive mode, which can be
set back the keep-alive mode, which can be useful when another mode was used useful when another mode was used in a defaults section.
in a defaults section.
Setting "option http-keep-alive" enables HTTP keep-alive mode on the client- 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 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. 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. 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 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 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. not set.
This option disables and replaces any previous "option httpclose" or "option This option disables and replaces any previous "option httpclose" or "option
http-server-close". When backend and frontend options differ, all of these 4 http-server-close".
options have precedence over "option http-keep-alive".
See also : "option httpclose",, "option http-server-close", See also : "option httpclose",, "option http-server-close",
"option prefer-last-server", "option http-pretend-keepalive", "option prefer-last-server" and "option http-pretend-keepalive".
and "1.1. The HTTP transaction model".
option http-no-delay option http-no-delay
@ -9500,19 +9489,19 @@ no option http-no-delay
option http-pretend-keepalive option http-pretend-keepalive
no 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 May be used in sections : defaults | frontend | listen | backend
yes | no | yes | yes yes | no | yes | yes
Arguments : none Arguments : none
When running with "option http-server-close" or "option httpclose", HAProxy When running with "option http-server-close" or "option httpclose", HAProxy
adds a "Connection: close" header to the request forwarded to the server. adds a "Connection: close" header to the HTTP/1.x request forwarded to the
Unfortunately, when some servers see this header, they automatically refrain server. Unfortunately, when some servers see this header, they automatically
from using the chunked encoding for responses of unknown length, while this refrain from using the chunked encoding for responses of unknown length,
is totally unrelated. The immediate effect is that this prevents HAProxy from while this is totally unrelated. The effect is that a client or a cache could
maintaining the client connection alive. A second effect is that a client or receive an incomplete response without being aware of it, and consider the
a cache could receive an incomplete response without being aware of it, and response complete.
consider the response complete.
By setting "option http-pretend-keepalive", HAProxy will make the server 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 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 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 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 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 frontend.
cause keepalive to be announced to the server and close to be announced to
the client. This practice is discouraged though.
If this option has been enabled in a "defaults" section, it can be disabled 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. 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 option http-server-close
no 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 May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes yes | yes | yes | yes
Arguments : none Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and HTTP/1.x connections: for each connection it processes each request and
leaves the connection idle on both sides between the end of a response and response, and leaves the connection idle on both sides. This mode may be
the start of a new request. This mode may be changed by several options such changed by several options such as "option http-server-close" or "option
as "option http-server-close" or "option httpclose". Setting "option httpclose". Setting "option http-server-close" enables HTTP connection-close
http-server-close" enables HTTP connection-close mode on the server side mode on the server side while keeping the ability to support HTTP keep-alive
while keeping the ability to support HTTP keep-alive and pipelining on the and pipelining on the client side. This provides the lowest latency on the
client side. This provides the lowest latency on the client side (slow client side (slow network) and the fastest session reuse on the server side
network) and the fastest session reuse on the server side to save server to save server resources, similarly to "option httpclose". It also permits
resources, similarly to "option httpclose". It also permits non-keepalive non-keepalive capable servers to be served in keep-alive mode to the clients
capable servers to be served in keep-alive mode to the clients if they if they conform to the requirements of RFC7230. Please note that some servers
conform to the requirements of RFC7230. Please note that some servers do not do not always conform to those requirements when they see "Connection: close"
always conform to those requirements when they see "Connection: close" in the in the request. The effect will be that keep-alive will never be used. A
request. The effect will be that keep-alive will never be used. A workaround workaround consists in enabling "option http-pretend-keepalive".
consists in enabling "option http-pretend-keepalive".
At the moment, logs will not indicate whether requests came from the same 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 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 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. in a specific instance by prepending the "no" keyword before it.
See also : "option httpclose", "option http-pretend-keepalive", See also : "option httpclose", "option http-pretend-keepalive" and
"option http-keep-alive", and "1.1. The HTTP transaction model". "option http-keep-alive".
option http-use-proxy-header option http-use-proxy-header
no option http-use-proxy-header no option http-use-proxy-header
@ -9702,37 +9688,37 @@ option httpchk <method> <uri> <version>
option httpclose option httpclose
no 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 May be used in sections : defaults | frontend | listen | backend
yes | yes | yes | yes yes | yes | yes | yes
Arguments : none Arguments : none
By default HAProxy operates in keep-alive mode with regards to persistent By default HAProxy operates in keep-alive mode with regards to persistent
connections: for each connection it processes each request and response, and HTTP/1.x connections: for each connection it processes each request and
leaves the connection idle on both sides between the end of a response and response, and leaves the connection idle on both sides. This mode may be
the start of a new request. This mode may be changed by several options such changed by several options such as "option http-server-close" or "option
as "option http-server-close" or "option httpclose". httpclose".
If "option httpclose" is set, HAProxy will close connections with the server If "option httpclose" is set, HAProxy will close the client or the server
and the client as soon as the request and the response are received. It will connection, depending where the option is set. Only the frontend is
also check if a "Connection: close" header is already set in each direction, considered for client connections while the frontend and the backend are
and will add one if missing. Any "Connection" header different from "close" considered for server ones. In this case the option is enabled if at least
will also be removed. 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 This option may also be combined with "option http-pretend-keepalive", which
will disable sending of the "Connection: close" header, but will still cause will disable sending of the "Connection: close" request header, but will
the connection to be closed once the whole response is received. 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 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 http-keep-alive".
combines with others when frontend and backend options differ.
If this option has been enabled in a "defaults" section, it can be disabled 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. 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 ] option httplog [ clf ]