Network.Wai.Handler.Warp

A fast, light-weight HTTP server handler for WAI.

HTTP/1.0, HTTP/1.1 and HTTP/2 are supported. For HTTP/2, Warp supports direct and ALPN (in TLS) but not upgrade.

Note on slowloris timeouts: to prevent slowloris attacks, timeouts are used at various points in request receiving and response sending. One interesting corner case is partial request body consumption; in that case, Warp's timeout handling is still in effect, and the timeout will not be triggered again. Therefore, it is recommended that once you start consuming the request body, you either:

• consume the entire body promptly
• call the pauseTimeout function

For more information, see https://github.com/yesodweb/wai/issues/351.

Run a Warp server

All of these automatically serve the same Application over HTTP/1, HTTP/1.1, and HTTP/2.

run :: Port -> Application -> IO ()

Run an Application on the given port. This calls runSettings with defaultSettings.

runEnv :: Port -> Application -> IO ()

Run an Application on the port present in the PORT environment variable. Uses the Port given when the variable is unset. This calls runSettings with defaultSettings.

Since 3.0.9

runSettings :: Settings -> Application -> IO ()

Run an Application with the given Settings. This opens a listen socket on the port defined in Settings and calls runSettingsSocket.

runSettingsSocket :: Settings -> Socket -> Application -> IO ()

This installs a shutdown handler for the given socket and calls runSettingsConnection with the default connection setup action which handles plain (non-cipher) HTTP. When the listen socket in the second argument is closed, all live connections are gracefully shut down.

The supplied socket can be a Unix named socket, which can be used when reverse HTTP proxying into your application.

Note that the settingsPort will still be passed to Applications via the serverPort record.

Settings

data Settings

Various Warp server settings. This is purposely kept as an abstract data type so that new settings can be added without breaking backwards compatibility. In order to create a Settings value, use defaultSettings and the various 'set' functions to modify individual fields. For example:

setTimeout 20 defaultSettings

defaultSettings :: Settings

The default settings for the Warp server. See the individual settings for the default value.

Setters

setPort :: Port -> Settings -> Settings

Port to listen on. Default value: 3000

Since 2.1.0

setHost :: HostPreference -> Settings -> Settings

Interface to bind to. Default value: HostIPv4

Since 2.1.0

setOnException :: (Maybe Request -> SomeException -> IO ()) -> Settings -> Settings

What to do with exceptions thrown by either the application or server. Default: defaultOnException

Since 2.1.0

setOnExceptionResponse :: (SomeException -> Response) -> Settings -> Settings

A function to create a Response when an exception occurs.

Default: defaultOnExceptionResponse

Since 2.1.0

setOnOpen :: (SockAddr -> IO Bool) -> Settings -> Settings

What to do when a connection is opened. When False is returned, the connection is closed immediately. Otherwise, the connection is going on. Default: always returns True.

Since 2.1.0

setOnClose :: (SockAddr -> IO ()) -> Settings -> Settings

What to do when a connection is closed. Default: do nothing.

Since 2.1.0

setTimeout :: Int -> Settings -> Settings

Timeout value in seconds. Default value: 30

Since 2.1.0

setManager :: Manager -> Settings -> Settings

Use an existing timeout manager instead of spawning a new one. If used, settingsTimeout is ignored.

Since 2.1.0

setFdCacheDuration :: Int -> Settings -> Settings

Cache duration time of file descriptors in seconds. 0 means that the cache mechanism is not used.

The FD cache is an optimization that is useful for servers dealing with static files. However, if files are being modified, it can cause incorrect results in some cases. Therefore, we disable it by default. If you know that your files will be static or you prefer performance to file consistency, it's recommended to turn this on; a reasonable value for those cases is 10. Enabling this cache results in drastic performance improvement for file transfers.

Default value: 0, was previously 10

Since 3.0.13

setFileInfoCacheDuration :: Int -> Settings -> Settings

Cache duration time of file information in seconds. 0 means that the cache mechanism is not used.

The file information cache is an optimization that is useful for servers dealing with static files. However, if files are being modified, it can cause incorrect results in some cases. Therefore, we disable it by default. If you know that your files will be static or you prefer performance to file consistency, it's recommended to turn this on; a reasonable value for those cases is 10. Enabling this cache results in drastic performance improvement for file transfers.

Default value: 0

setBeforeMainLoop :: IO () -> Settings -> Settings

Code to run after the listening socket is ready but before entering the main event loop. Useful for signaling to tests that they can start running, or to drop permissions after binding to a restricted port.

Default: do nothing.

Since 2.1.0

setNoParsePath :: Bool -> Settings -> Settings

Perform no parsing on the rawPathInfo.

This is useful for writing HTTP proxies.

Default: False

Since 2.1.0

setInstallShutdownHandler :: (IO () -> IO ()) -> Settings -> Settings

A code to install shutdown handler.

For instance, this code should set up a UNIX signal handler. The handler should call the first argument, which closes the listen socket, at shutdown.

Default: does not install any code.

Since 3.0.1

setServerName :: ByteString -> Settings -> Settings

Default server name if application does not set one.

Since 3.0.2

setMaximumBodyFlush :: Maybe Int -> Settings -> Settings

The maximum number of bytes to flush from an unconsumed request body.

By default, Warp does not flush the request body so that, if a large body is present, the connection is simply terminated instead of wasting time and bandwidth on transmitting it. However, some clients do not deal with that situation well. You can either change this setting to Nothing to flush the entire body in all cases, or in your application ensure that you always consume the entire request body.

Default: 8192 bytes.

Since 3.0.3

setFork :: (((forall a. IO a -> IO a) -> IO ()) -> IO ()) -> Settings -> Settings

Code to fork a new thread to accept a connection.

This may be useful if you need OS bound threads, or if you wish to develop an alternative threading model.

Default: void . forkIOWithUnmask

Since 3.0.4

setProxyProtocolNone :: Settings -> Settings

Do not use the PROXY protocol.

Since 3.0.5

setProxyProtocolRequired :: Settings -> Settings

Require PROXY header.

This is for cases where a "dumb" TCP/SSL proxy is being used, which cannot add an X-Forwarded-For HTTP header field but has enabled support for the PROXY protocol.

See http://www.haproxy.org/download/1.5/doc/proxy-protocol.txt and http://docs.aws.amazon.com/ElasticLoadBalancing/latest/DeveloperGuide/TerminologyandKeyConcepts.html#proxy-protocol.

Only the human-readable header format (version 1) is supported. The binary header format (version 2) is not supported.

Since 3.0.5

setProxyProtocolOptional :: Settings -> Settings

Use the PROXY header if it exists, but also accept connections without the header. See setProxyProtocolRequired.

WARNING: This is contrary to the PROXY protocol specification and using it can indicate a security problem with your architecture if the web server is directly accessable to the public, since it would allow easy IP address spoofing. However, it can be useful in some cases, such as if a load balancer health check uses regular HTTP without the PROXY header, but proxied connections do include the PROXY header.

Since 3.0.5

setSlowlorisSize :: Int -> Settings -> Settings

Size in bytes read to prevent Slowloris protection. Default value: 2048

Since 3.1.2

setHTTP2Disabled :: Settings -> Settings

Disable HTTP2.

Since 3.1.7

setLogger :: (Request -> Status -> Maybe Integer -> IO ()) -> Settings -> Settings

Setting a log function. Integer is the body length of a response.

Since 3.X.X

Getters

getPort :: Settings -> Port

Get the listening port.

Since 2.1.1

getHost :: Settings -> HostPreference

Get the interface to bind to.

Since 2.1.1

getOnOpen :: Settings -> SockAddr -> IO Bool

Get the action on opening connection.

getOnClose :: Settings -> SockAddr -> IO ()

Get the action on closeing connection.

getOnException :: Settings -> Maybe Request -> SomeException -> IO ()

Get the exception handler.

Exception handler

defaultOnException :: Maybe Request -> SomeException -> IO ()

Printing an exception to standard error if defaultShouldDisplayException returns True.

Since: 3.1.0

defaultShouldDisplayException :: SomeException -> Bool

Apply the logic provided by defaultOnException to determine if an exception should be shown or not. The goal is to hide exceptions which occur under the normal course of the web server running.

Since 2.1.3

Exception response handler

defaultOnExceptionResponse :: SomeException -> Response

Sending 400 for bad requests. Sending 500 for internal server errors.

Since: 3.1.0

exceptionResponseForDebug :: SomeException -> Response

Exception handler for the debugging purpose. 500, text/plain, a showed exception.

Since: 2.0.3.2

Data types

data HostPreference :: *

Which host to bind.

Note: The IsString instance recognizes the following special values:

• * means HostAny
• *4 means HostIPv4
• !4 means HostIPv4Only
• *6 means HostIPv6
• !6 means HostIPv6Only

Any other values is treated as a hostname. As an example, to bind to the IPv4 local host only, use "127.0.0.1".

Instances

Eq HostPreference

Ord HostPreference

Read HostPreference

Show HostPreference

IsString HostPreference

type Port = Int

TCP port number.

data InvalidRequest

Error types for bad Request.

Constructors

NotEnoughLines [String]

BadFirstLine String

NonHttp

IncompleteHeaders

ConnectionClosedByPeer

OverLargeHeader

BadProxyHeader String

Instances

Eq InvalidRequest

Show InvalidRequest

Exception InvalidRequest

Utilities

pauseTimeout :: Request -> IO ()

Explicitly pause the slowloris timeout.

This is useful for cases where you partially consume a request body. For more information, see https://github.com/yesodweb/wai/issues/351

Since 3.0.10

data FileInfo

File information.

Constructors

FileInfo

Fields

fileInfoName :: !FilePath

fileInfoSize :: !Integer

fileInfoTime :: HTTPDate

Modification time

fileInfoDate :: ByteString

Modification time in the GMT format

Instances

Eq FileInfo

Show FileInfo

getFileInfo :: Request -> FilePath -> IO FileInfo

Getting file information of the target file.

This function first uses a stat(2) or similar system call to obtain information of the target file, then registers it into the internal cache. From the next time, the information is obtained from the cache. This reduces the overhead to call the system call. The internal cache is refreshed every duration specified by setFileInfoCacheDuration.

This function throws an IO exception if the information is not available. For instance, the target file does not exist. If this function is used an a Request generated by a WAI backend besides Warp, it also throws an IO exception.

Since 3.1.10

withApplication :: IO Application -> (Port -> IO a) -> IO a

Runs the given Application on a free port. Passes the port to the given operation and executes it, while the Application is running. Shuts down the server before returning.

Since: 3.2.4

testWithApplication :: IO Application -> (Port -> IO a) -> IO a

Same as withApplication but with different exception handling: If the given Application throws an exception, testWithApplication will re-throw the exception to the calling thread, possibly interrupting the execution of the given operation.

This is handy for running tests against an Application over a real network port. When running tests, it's useful to let exceptions thrown by your Application propagate to the main thread of the test-suite.

The exception handling makes this function unsuitable for use in production. Use withApplication instead.

Since: 3.2.4

openFreePort :: IO (Port, Socket)

Opens a socket on a free port and returns both port and socket.

Since: 3.2.4

Version

warpVersion :: String

The version of Warp.