Perlbal::Manual::ReverUseroContributed Perl DoPerlbal::Manual::ReverseProxy(3)NAMEPerlbal::Manual::ReverseProxy - Configuring Perlbal as a Reverse Proxy
VERSION
Perlbal 1.78.
DESCRIPTION
How to configure a Perlbal Reverse Proxy service.
READ ME FIRST
Please read Perlbal::Manual::Configuration first for a better
explanation on how to configure Perlbal. This document will make much
more sense after reading that.
Configuring Perlbal as a Reverse Proxy
Configuration of Perlbal as a Reverse Proxy is similar to configuration
as a Load Balancer.
Check Perlbal::Manual::LoadBalancer under "Using Perlbal as a Load
Balancer" for a sample configuration file and for a brief explanation
of the differences between a Load Balancer and a Reverse Proxy.
Parameters
You can set parameters via commands of either forms:
SET <service-name> <param> = <value>
SET <param> = <value>
always_trusted = bool
Whether to trust all incoming requests' X-Forwarded-For and
related headers. Set to true only if you know that all incoming
requests from your own proxy servers that clean/set those
headers.
Default is false.
backend_persist_cache = int
The number of backend connections to keep alive on reserve
while there are no clients.
Default is 2.
blind_proxy = bool
Flag to disable any modification of X-Forwarded-For, X-Host,
and X-Forwarded-Host headers.
Default is false.
buffer_backend_connect = size
How much content-body (POST/PUT/etc) data we read from a client
before we start sending it to a backend web node. If
"buffer_uploads" is enabled, this value is used to determine
how many bytes are read before Perlbal makes a determination on
whether or not to spool the upload to disk.
Default is 100k.
buffer_size = size
How much ahead of a client we'll get while copying from a
backend to a client. If a client gets behind this much, we stop
reading from the backend for a bit. Once all remaining data
fits in the buffer, the backend is released and may be reused.
Default is 256k.
buffer_size_reproxy_url = size
How much ahead of a client we'll get while copying from a
reproxied URL to a client. If a client gets behind this much,
we stop reading from the reproxied URL for a bit. The default
is lower than the regular "buffer_size" (50k instead of 256k)
because it's assumed that you're only reproxying to large files
on event-based webservers, which are less sensitive to many
open connections, whereas the 256k buffer size is good for
keeping heavy process-based free of slow clients.
Default if 50k.
buffer_upload_threshold_rate = int
If an upload is coming in at a rate less than this value in
bytes per second, it will be buffered to disk. A value of 0
means the rate will not be checked.
Default is 0.
buffer_upload_threshold_size = size
If an upload is larger than this size in bytes, it will be
buffered to disk. A value of 0 means the size will not be
checked.
Default is 250k.
buffer_upload_threshold_time = int
If an upload is estimated to take more than this number of
seconds, it will be buffered to disk. A value of 0 means the
time will not be estimated.
Default is 5.
buffer_uploads = bool
Used to enable or disable the buffer uploads to disk system. If
enabled, "buffer_backend_connect" bytes worth of the upload
will be stored in memory. At that point, the buffer upload
thresholds will be checked to see if we should just send this
upload to the backend or if we should spool it to the disk.
Default if false.
buffer_uploads_path = path/to/directory
Directory root for storing files used to buffer uploads.
client_sndbuf_size = size
How large to set the client's socket SNDBUF.
Default is 0.
connect_ahead = int
How many extra backend connections we keep alive in addition to
the current ones, in anticipation of new client connections.
Default is 0.
enable_error_retries = bool
Whether Perlbal should transparently retry requests to backends
if a backend returns a 500 server error.
Default is false.
enable_reproxy = bool
Enable 'reproxying' (end-user-transparent internal redirects)
to either local files or other URLs. When enabled, the backend
servers in the pool that this service is configured for will
have access to tell this Perlbal instance to serve any local
readable file, or connect to any other URL that this Perlbal
can connect to. Only enable this if you trust the backend web
nodes.
Default is false.
See the section "Reproxying" in this document for more
information.
error_retry_schedule = string of comma-separated seconds (full or
partial)
String of comma-separated seconds (full or partial) to delay
between retries. For example "0,2" would mean do at most two
retries, the first zero seconds after the first failure, and
the second 2 seconds after the second failure. You probably
don't need to modify the default value.
Default it 0,0.25,0.50,1,1,1,1,1
enable_ssl = bool
Enable SSL to the client.
Default is false.
high_priority_cookie = cookie_name
The cookie name to inspect to determine if the client goes onto
the high-priority queue.
See Perlbal::Manual::HighPriority for more information.
high_priority_cookie_contents = string
A string that the "high_priority_cookie" must contain to go
onto the high-priority queue.
See Perlbal::Manual::HighPriority for more information.
idle_timeout = int
Timeout in seconds for idle connections to the end user. It's
also the limit for how long a backend may take to respond or
transfer data.
Default is 30.
listen = ip:port
The ip:port to listen on. For a service to work, you must
either make it listen, or make another selector service map to
a non-listening service.
max_backend_uses = int
The maximum number of requests to be made on a single
persistent backend connection before releasing the connection.
A value of 0 means there is no limit and the connection will
only be discarded once the backend asks it to be or when
Perlbal is sufficiently idle.
Default is 0.
max_chunked_request_size = size
The maximum size that will be accepted for a chunked request
(which is written to disk, buffered uploads must be on). A
value of 0 means no limit.
Default is 209715200 (200MB).
persist_client = bool
Whether to enable HTTP keep-alives to the end user.
Default is false.
persist_backend = bool
Whether to enable HTTP keep-alives to the backend webnodes.
Default is false, but setting it to true is highly recommended
if Perlbal is the only client to your backends. If not, beware
that Perlbal will hog the connections, starving other clients.
persist_client_idle_timeout = int
Timeout in seconds for HTTP persist_client_idle_timeout keep-
alives to the end user.
Default is 30.
persist_client_timeout = int (DEPRECATED)
Set both the persist_client_timeout persist_client_idle_timeout
and idle_timeout.
Deprecated.
pool Name of previously-created pool object containing the backend
nodes that this reverse proxy sends requests to.
queue_relief_chance = int:0-100
Chance (percentage) to take a standard priority request when
we're in pressure relief mode.
Default is 0.
See Perlbal::Manual::HighPriority for more information.
queue_relief_size = int
Number of outstanding standard priority connections to activate
pressure relief at.
A value of 0 disables the high priority queue system entirely.
Default is 0.
See Perlbal::Manual::HighPriority for more information.
reproxy_cache_maxsize = int
Set the maximum number of cached reproxy results (X-REPROXY-
CACHE-FOR) that may be kept in the service cache. These cached
requests take up about 1.25KB of RAM each (on Linux x86), but
will vary with usage. Perlbal still starts with 0 in the cache
and will grow over time. Be careful when adjusting this and
watch your RAM usage like a hawk.
Default is 0, which means cache is disabled.
role = reverse_proxy|web_server|management|selector
What type of service. One of 'reverse_proxy' for a service that
load balances to a pool of backend webserver nodes,
'web_server' for a typical webserver', 'management' for a
Perlbal management interface (speaks both command-line or HTTP,
auto-detected), or 'selector', for a virtual service that maps
onto other services.
server_process
Executable which will be the HTTP server on stdin/stdout.
(ALPHA, EXPERIMENTAL)
ssl_cert_file = path/to/file
Path to certificate PEM file for SSL.
Default is "certs/server-cert.pem".
ssl_cipher_list = cipher list
OpenSSL-style cipher list.
Default is "ALL:!LOW:!EXP".
ssl_key_file = path/to/file
Path to private key PEM file for SSL.
Default is "certs/server-key.pem".
trusted_upstream_proxies = Net::Netmask filter
A comma separated list of Net::Netmask filters (e.g.
10.0.0.0/24, see Net::Netmask) that determines whether upstream
clients are trusted or not, where trusted means their
X-Forwarded-For/etc headers are not munged.
upload_status_listeners = comma separated list of hosts
Comma separated list of hosts in form 'a.b.c.d:port' which will
receive UDP upload status packets no faster than once a second
per HTTP request (PUT/POST) from clients that have requested an
upload status bar, which they request by appending the URL get
argument ?client_up_sess=[xxxxx] where xxxxx is 5-50 'word'
characters (a-z, A-Z, 0-9, underscore).
verify_backend = bool
Whether Perlbal should send a quick OPTIONS request to the
backends before sending an actual client request to them. If
your backend is Apache or some other process-based webserver,
this is highly recommended. All too often a loaded backend box
will reply to new TCP connections, but it's the kernel's TCP
stack Perlbal is talking to, not and actual Apache process yet.
Using this option reduces end-user latency a ton on loaded
sites.
Default if false.
verify_backend_path = path
What path the OPTIONS request sent by "verify_backend" should
use.
Default is "*".
server_tokens = bool
Whether to provide a "Server" header.
Perlbal by default adds a header to all replies (such as the
web_server role). By setting this default to "off", you can
prevent Perlbal from identifying itself.
Default is "on".
More on Parameters
backend_persist_cache vs. connect_ahead
The "backend_persist_cache" parameter refers to connections kept alive
after being used, while "connect_ahead" refers to connections opened in
anticipation.
For instance:
SET backend_persist_cache = 2
SET connect_ahead = 1
Let's assume, for simplification purposes, that your service only has
one server. Here's an example of what could happen:
· Perlbal starts
No connections open until the very first request comes in (this may
change in the future).
· one requests arrives
This request starts being served on the open connection; Perlbal
opens another connection because "connect_ahead"'s value tells it
to always open one in anticipation.
· a second request arrives
(the first request hasn't concluded yet)
The second connection is used, a third one is created so we still
have one in anticipation.
· the first request finishes
The connection is kept open; this means we now have three open
connections: two being used and one free (the first and the third
one are free).
· the second request finishes
The connection is killed, as we already have two other open
connections (the first and the third), and that's the number set by
"backend_persist_cache" for the number of connections to be kept
alive.
Reproxying
Perlbal supports the concept of reproxying. Basically, this gives it
the ability to ask a backend node for a file and get back a specific
header that says "this file is really over there, get it there."
Perlbal will then load that file or URL and send it to the user
transparently, without them ever knowing that they got reproxied to
another location.
Add the following line to your perlbal.conf to enable reproxying on a
per service basis ( reproxying is disabled by default in >= 1.38 ):
SET enable_reproxy = true
This can be useful for having URLs that get mapped to files on disk
without giving users enough information to map out your directory
structure. For example, you can create a file structure such as:
/home/pics/$userid/$pic
Then you can have URLs such as:
http://foo.com/mysite/users/$userid/picture/$pic
When this URL gets passed to the backend web node, it could return a
simple response that includes this header:
X-REPROXY-FILE: /home/pics/$userid/$pic
Perlbal will then use asynchronous IO to send the file to the user
without slowing down Perlbal at all.
This support also extends to URLs that can be located anywhere Perlbal
has access to. It's the same syntax, nearly:
X-REPROXY-URL: http://foo.com:80/resource.html
You can also specify multiple URLs:
X-REPROXY-URL: http://foo.com:80/resource.html http://baz.com:8080/res.htm
Just specify any number of space separated URLs. Perlbal will request
them one by one until one returns a response code of 200. At that point
Perlbal will proxy the response back to the user just like normal.
Note that the user's headers are NOT passed through to the web server.
To the target server, it looks simply like Perlbal is requesting the
resource for itself. This behavior may change at some point.
One final note: the server that returns the reproxy header can also
return a "X-REPROXY-EXPECTED-SIZE" header. If present, Perlbal will
consider a reproxy a failure if the file returned by the target system
is of a different size than what the expected size header says. On
failure, Perlbal tries the next URI in the list. If it's a file being
reproxied, a 404 is returned if the file size is different.
SEE ALSO
Perlbal::Manual::Configuration, Perlbal::Manual::FailOver,
Perlbal::Manual::LoadBalancer, Perlbal::Manual::Management.
perl v5.14.2 2011-09-03 Perlbal::Manual::ReverseProxy(3)
