In server-close mode particularly, the response buffer is marked for
no-auto-close after a response passed through. This prevented a POST
request from being aborted on errors, timeouts or anything if the
response was received before the request was complete.
If we enable reading of a request immediately after completing
another one, we end up performing small reads until the request
buffer is complete. This takes time and makes it harder to realign
the buffer when needed. Just enable reading when we need to.
The rq.u field is relative to buf->data, not to msg->sol. We have
to subtract msg->som everywhere this error was made. Maybe it will
be simpler to have a pointer to the buffer in the message and find
appropriate data there.
Many times we see a lot of short responses in HTTP (typically 304 on a
reload). It is a waste of network bandwidth to send that many small packets
when we know we can merge them. When we know that another HTTP request is
following a response, we set BF_EXPECT_MORE on the response buffer, which
will turn MSG_MORE on exactly once. That way, multiple short responses can
leave pipelined if their corresponding requests were also pipelined.
We used to forward more trailers than required, causing a
desynchronization of the output. Now we schedule all for forwarding
as soon as we encounter them.
This option enables HTTP keep-alive on the client side and close mode
on the server side. This offers the best latency on the slow client
side, and still saves as many resources as possible on the server side
by actively closing connections. Pipelining is supported on both requests
and responses, though there is currently no reason to get pipelined
responses.
When too large a message lies in a buffer before parsing a new
request/response, we can now wait for previous outgoing data to
leave the buffer before attempting to parse again. After that
we can consider the opportunity to realign the buffer if needed.
The HTTP parser needed the msg structure to hold pre-initialized pointers.
This causes a trouble with keep-alive because if some data is still in the
buffer, the pointers can be anywhere after the data and later become invalid
when the buffer gets realigned.
It was not needed to rely on that since we have two valid information
in the buffer itself :
- buf->lr : last visited place
- buf->w + buf->send_max : beginning of next message
So by doing the maths only on those values, we can avoid doing tricks
on msg->som.
When we catch an error from the server, speed up the connection
abort since we don't want to remain long with pending data in the
socket, and we want to be able to reuse our source port ASAP.
The "forceclose" option used to close the output channel to the
server once it started to respond. While this happened to work with
most servers, some of them considered this as a connection abort and
immediately stopped responding.
Now that we're aware of the end of a request and response, we're able
to trivially handle this option and properly close both sides when the
server's response is complete.
During this change it appeared that forwarding could be allowed when
the BF_SHUTW_NOW flag was set on a buffer, which obviously is not
acceptable and was causing some trouble. This has been fixed too and
is the reason for the MEDIUM status on this patch.
There were still issues with the buffer alignment. Now we ensure
that we always align it before a request or response is completely
parsed if there is less than maxrewrite bytes free at the end. In
practice, it's not called that often and ensures we can always work
as expected.
In many places where we perform header insertion, an error control
is performed but due to a mistake, it cannot match any error :
if (unlikely(error) < 0)
instead of
if (unlikely(error < 0))
This prevents error 400 responses from being sent when the buffer is
full due to many header additions. This must be backported to 1.3.
The body parser will be used in close and keep-alive modes. It follows
the stream to keep in sync with both the request and the response message.
Both chunked transfer-coding and content-length are supported according to
RFC2616.
The multipart/byterange encoding has not yet been implemented and if not
seconded by any of the two other ones, will be forwarded till the close,
as requested by the specification.
Both the request and the response analysers converge into an HTTP_MSG_DONE
state where it will be possible to force a close (option forceclose) or to
restart with a fresh new transaction and maintain keep-alive.
This change is important. All tests are OK but any possible behaviour
change with "option httpclose" might find its root here.
When parsing body for URL parameters, we must not consider that
data are available from buf->data but from buf->data + msg->som.
This is not a problem right now but may become with keep-alive.
When parsing a request that does not start at the beginning of the
buffer, we may experience a buffer full issue. In order to avoid
this, we try to realign the buffer if it is not really full. That
will be required when we have to deal with pipelined requests.
Some wrong operations were performed on buffers, assuming the
offsets were relative to the beginning of the request while they
are relative to the beginning of the buffer. In practice this is
not yet an issue since both are the same... until we add support
for keep-alive.
It's not enough to know if the connection will be in CLOSE or TUNNEL mode,
we still need to know whether we want to read a full message to a known
length or read it till the end just as in TUNNEL mode. Some updates to the
RFC clarify slightly better the corner cases, in particular for the case
where a non-chunked encoding is used last.
Now we also take care of adding a proper "connection: close" to messages
whose size could not be determined.
Chunked encoding can be slightly more complex than what was implemented.
Specifically, it supports some optional extensions that were not parsed
till now if present, and would have caused an error to be returned.
Also, now we enforce check for too large values in chunk sizes in order
to ensure we never overflow.
Last, we're now able to return a request error if we can't read the
chunk size because the buffer is already full.
This state indicates that an HTTP message (request or response) is
complete. This will be used to know when we can re-initialize a
new transaction. Right now we only switch to it after the end of
headers if there is no data. When other analysers are implemented,
we can switch to this state too.
The condition to reuse a connection is when the response finishes
after the request. This will have to be checked when setting the
state.
The response 1xx was set too low and required a lot of tests along
the code in order to avoid some processing. We still left the test
after the response rewrite rules so that we can eliminate unwanted
headers if required.
This code really belongs to the http part since it's transaction-specific.
This will also make it easier to later reinitialize a transaction in order
to support keepalive.
We used to apply a limit to each buffer's size in order to leave
some room to rewrite headers, then we used to remove this limit
once the session switched to a data state.
Proceeding that way becomes a problem with keepalive because we
have to know when to stop reading too much data into the buffer
so that we can leave some room again to process next requests.
The principle we adopt here consists in only relying on to_forward+send_max.
Indeed, both of those data define how many bytes will leave the buffer.
So as long as their sum is larger than maxrewrite, we can safely
fill the buffers. If they are smaller, then we refrain from filling
the buffer. This means that we won't risk to fill buffers when
reading last data chunk followed by a POST request and its contents.
The only impact identified so far is that we must ensure that the
BF_FULL flag is correctly dropped when starting to forward. Right
now this is OK because nobody inflates to_forward without using
buffer_forward().
Up to now, we only had a flag in the session indicating if it had to
work in "connection: close" mode. This is not at all compatible with
keep-alive.
Now we ensure that both sides of a connection act independantly and
only relative to the transaction. The HTTP version of the request
and response is also correctly considered. The connection already
knows several modes :
- tunnel (CONNECT or no option in the config)
- keep-alive (when permitted by configuration)
- server-close (close the server side, not the client)
- close (close both sides)
This change carefully detects all situations to find whether a request
can be fully processed in its mode according to the configuration. Then
the response is also checked and tested to fix corner cases which can
happen with different HTTP versions on both sides (eg: a 1.0 client
asks for explicit keep-alive, and the server responds with 1.1 without
a header).
The mode is selected by a capability elimination algorithm which
automatically focuses on the least capable agent between the client,
the frontend, the backend and the server. This ensures we won't get
undesired situtations where one of the 4 "agents" is not able to
process a transaction.
No "Connection: close" header will be added anymore to HTTP/1.0 requests
or responses since they're already in close mode.
The server-close mode is still not completely implemented. The response
needs to be rewritten as keep-alive before being sent to the client if
the connection was already in server-close (which implies the request
was in keep-alive) and if the response has a content-length or a
transfer-encoding (but only if client supports 1.1).
A later improvement in server-close mode would probably be to detect
some situations where it's interesting to close the response (eg:
redirections with remote locations). But even then, the client might
close by itself.
It's also worth noting that in tunnel mode, no connection header is
affected in either direction. A tunnelled connection should theorically
be notified at the session level, but this is useless since by definition
there will not be any more requests on it. Thus, we don't need to add a
flag into the session right now.
The POST body analysis was split between two analysers for historical
reasons. Now we only have one analyser which checks content length
and waits for enough data to come.
Right now this analyser waits for <url_param_post_limit> bytes of
body to reach the buffer, or the first chunk. But this could be
improved to wait for any other amount of data or any specific
contents.
Implement decreasing health based on observing communication between
HAProxy and servers.
Changes in this version 2:
- documentation
- close race between a started check and health analysis event
- don't force fastinter if it is not set
- better names for options
- layer4 support
Changes in this version 3:
- add stats
- port to the current 1.4 tree
In order to support keepalive, we'll have to differentiate
normal sessions from tunnel sessions, which are the ones we
don't want to analyse further.
Those are typically the CONNECT requests where we don't care
about any form of content-length, as well as the requests
which are forwarded on non-close and non-keepalive proxies.
To sum up :
- len : it's now the max number of characters for the value, preventing
garbaged results.
- a new option "prefix" is added, this allows to use dynamic cookie
names (e.g. ASPSESSIONIDXXX).
Previously in the thread, I wanted to use the value found with
"capture cookie" but when i started to update the documentation, I
found this solution quite weird. I've made a small rework to not
depend on "capture cookie".
- There's the posssiblity to define the URL parser mode (path parameters
or query string).
We now set msg->col and msg->sov to the first byte of non-header.
They will be used later when parsing chunks. A new macro was added
to perform size additions on an http_msg in order to limit the risks
of copy-paste in the long term.
During this operation, it appeared that the http_msg struct was not
optimal on 64-bit, so it was re-ordered to fill the holes.
An HTTP message can be decomposed into several sub-states depending
on the transfer-encoding. We'll have to keep these state information
while parsing chunks, so we must extend the values. In order not to
change everything, we'll now consider that anything >= MSG_BODY is
the body, and that the value indicates the precise state. The
MSG_ERROR status which was greater than MSG_BODY was moved for this.
This patch extends and corrects the functionality introduced by
"Collect & provide http response codes received from servers":
- responses are now also accounted for frontends
- backend's and frontend's counters are incremented based
on responses sent to client, not received from servers
We also check the close status and terminate the server persistent
connection if appropriate. Note that since this change, we'll not
get any "Connection: close" headers added to HTTP/1.0 responses
anymore, which is good.
The code part which waits for an HTTP response has been extracted
from the old function. We now have two analysers and the second one
may re-enable the first one when an 1xx response is encountered.
This has been tested and works.
The calls to stream_int_return() that were remaining in the wait
analyser have been converted to stream_int_retnclose().
Store those elements in the transaction. RFC2616 is strictly followed.
Note that requests containing two different content-length fields are
discarded as invalid.
This patch has 2 goals :
1. I wanted to test the appsession feature with a small PHP code,
using PHPSESSID. The problem is that when PHP gets an unknown session
id, it creates a new one with this ID. So, when sending an unknown
session to PHP, persistance is broken : haproxy won't see any new
cookie in the response and will never attach this session to a
specific server.
This also happens when you restart haproxy : the internal hash becomes
empty and all sessions loose their persistance (load balancing the
requests on all backend servers, creating a new session on each one).
For a user, it's like the service is unusable.
The patch modifies the code to make haproxy also learn the persistance
from the client : if no session is sent from the server, then the
session id found in the client part (using the URI or the client cookie)
is used to associated the server that gave the response.
As it's probably not a feature usable in all cases, I added an option
to enable it (by default it's disabled). The syntax of appsession becomes :
appsession <cookie> len <length> timeout <holdtime> [request-learn]
This helps haproxy repair the persistance (with the risk of losing its
session at the next request, as the user will probably not be load
balanced to the same server the first time).
2. This patch also tries to reduce the memory usage.
Here is a little example to explain the current behaviour :
- Take a Tomcat server where /session.jsp is valid.
- Send a request using a cookie with an unknown value AND a path
parameter with another unknown value :
curl -b "JSESSIONID=12345678901234567890123456789012" http://<haproxy>/session.jsp;jsessionid=00000000000000000000000000000001
(I know, it's unexpected to have a request like that on a live service)
Here, haproxy finds the URI session ID and stores it in its internal
hash (with no server associated). But it also finds the cookie session
ID and stores it again.
- As a result, session.jsp sends a new session ID also stored in the
internal hash, with a server associated.
=> For 1 request, haproxy has stored 3 entries, with only 1 which will be usable
The patch modifies the behaviour to store only 1 entry (maximum).
When processing a GET or HEAD request in close mode, we know we don't
need to read anything anymore on the socket, so we can disable it.
Doing this can save up to 40% of the recv calls, and half of the
epoll_ctl calls.
For this we need a buffer flag indicating that we're not interesting in
reading anymore. Right now, this flag also disables both polled reads.
We might benefit from disabling only speculative reads, but we will need
at least this flag when we want to support keepalive anyway.
Currently we don't disable the flag on completion, but it does not
matter as we close ASAP when performing the shutw().
