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Chapter 6. Configuring Jetty Connectors

Table of Contents

Connector Configuration Overview
Configuring SSL
Setting Port 80 Access for a Non-Root User

This chapter discusses various options for configuring Jetty connectors.

Connector Configuration Overview

Connectors are the mechanism through which Jetty accepts network connections for various protocols. Configuring a connector is a combination of configuring the following:

  • Network parameters on the connector itself (for example: the listening port).

  • Services the connector uses (for example: executors, schedulers).

  • Connection factories that instantiate and configure the protocol for an accepted connection.

Jetty primarily uses a single connector type called ServerConnector.

Note

Prior to Jetty 9, the type of the connector specified both the protocol and the implementation used (for example, selector-based non blocking I/O vs blocking I/O, or SSL connector vs non-SSL connector). Jetty 9 has only a selector-based non blocking I/O connector, and a collection of ConnectionFactories now configure the protocol on the connector.

The standard Jetty distribution comes with the following Jetty XML files that create and configure connectors; you should examine them as you read this section:

jetty-http.xml

Instantiates a ServerConnector that accepts HTTP connections (that may be upgraded to WebSocket connections).

jetty-ssl.xml

Instantiates a ServerConnector that accepts SSL/TLS connections. On it's own, this connector is not functional and requires one or more of the following files to also be configured to add ConnectionFactories to make the connector functional.

jetty-https.xml

Adds a HttpConnectionFactory to the ServerConnector configured by jetty-ssl.xml which combine to provide support for HTTPS.

jetty-http2.xml

Adds a Http2ServerConnectionFactory to the ServerConnector configured by jetty-ssl.xml to support the http2 protocol. Also prepends either protonego-alpn.xml or protonego-npn.xml so that the next protocol can be negotiated, which allows the same SSL port to handle multiple protocols.

jetty-spdy.xml

Adds a SPDYServerConnectionFactory to the ServerConnector configured by jetty-ssl.xml to support the SPDY protocol. Also prepends either protonego-alpn.xml or protonego-npn.xml so that the next protocol can be negotiated, which allows the same SSL port to handle multiple protocols.

protonego-alpn.xml

Adds an ALPNServerConnectionFactory to the ServerConnector configured by jetty-ssl.xml which allows the one SSL connector to support multiple protocols with the ALPN extension used to select the protocol to be used for each connection.

protonego-npn.xml

Adds a NPNServerConnectionFactory to the ServerConnector configured by jetty-ssl.xml which allows the one SSL connector to support multiple protocols with the NPN extension used to select the protocol to be used for each connection.

Typically you need to configure very little on connectors other than set the listening port (see Network Settings), and perhaps enable X-Forwarded-For customization (see HTTP Configuration). Most other settings are for expert configuration only.

Constructing a ServerConnector

The services a ServerConnector instance uses are set by constructor injection and once instantiated cannot be changed. Most of the services may be defaulted with null or 0 values so that a reasonable default is used, thus for most purposes only the Server and the connection factories need to be passed to the connector constructor. In Jetty XML (that is, in jetty-http.xml), you can do this with:

You can see the other arguments that can be passed when constructing a ServerConnector in the Javadoc. Typically the defaults are sufficient for almost all deployments.

Network Settings.

You configure connector network settings by calling setters on the connector before it is started. For example, you can set the port with the Jetty XML:

Values in Jetty XML can also be parameterized so that they may be passed from property files or set on the command line. Thus typically the port is set within Jetty XML, but uses the Property element to be customizable:

The network settings that you can set on the ServerConnector include:

Table 6.1. Connector Configuration

FieldDescription
hostThe network interface this connector binds to as an IP address or a hostname. If null or 0.0.0.0, bind to all interfaces.
portThe configured port for the connector or 0 a random available port may be used (selected port available via getLocalPort()).
idleTimeoutThe time in milliseconds that the connection can be idle before it is closed.
defaultProtocolThe name of the default protocol used to select a ConnectionFactory instance. This defaults to the first ConnectionFactory added to the connector.
stopTimeoutThe time in milliseconds to wait before gently stopping a connector.
acceptQueueSizeThe size of the pending connection backlog. The exact interpretation is JVM and operating system specific and you can ignore it. Higher values allow more connections to wait pending an acceptor thread. Because the exact interpretation is deployment dependent, it is best to keep this value as the default unless there is a specific connection issue for a specific OS that you need to address.
reuseAddressAllow the server socket to be rebound even if in TIME_WAIT. For servers it is typically OK to leave this as the default true.
soLingerTimeA value >=0 set the socket SO_LINGER value in milliseconds. Jetty attempts to gently close all TCP/IP connections with proper half close semantics, so a linger timeout should not be required and thus the default is -1.

HTTP Configuration

The HttpConfiguration class holds the configuration for HTTPChannel s, which you can create 1:1 with each HTTP connection or 1:n on a multiplexed SPDY connection. Thus a HTTPConfiguration object is injected into both the HTTP and SPDY connection factories. To avoid duplicate configuration, the standard Jetty distribution creates the common HttpConfiguration instance in jetty.xml , which is a Ref element then used in jetty-http.xml, jetty-https.xml and in jetty-http2.xml

A typical configuration of HttpConfiguration is:

This example HttpConfiguration may be used by reference to the ID "httpConfig":

For SSL based connectors (in jetty-https.xml and jetty-spdy.xml), the common "httpConfig" instance is used as the basis to create an SSL specific configuration with ID "tlsHttpConfig":

This adds a SecureRequestCustomizer which adds SSL Session IDs and certificate information as request attributes.

SSL Context Configuration

The SSL/TLS connectors for HTTPS and SPDY require a certificate to establish a secure connection. Jetty holds certificates in standard JVM keystores and are configured as keystore and truststores on a SslContextFactory instance that is injected into an SslConnectionFactory instance. An example using the keystore distributed with Jetty (containing a self signed test certificate) is in jetty-https.xml and example-jetty-spdy.xml . Read more about SSL keystores in Configuring SSL.

Proxy / Load Balancer Connection Configuration

Often a Connector needs to be configured to accept connections from an intermediary such as a Reverse Proxy and/or Load Balancer deployed in front of the server. In such environments, the TCP/IP connection terminating on the server does not originate from the client, but from the intermediary, so that the Remote IP and port number can be reported incorrectly in logs and in some circumstances the incorrect server address and port may be used.

Thus Intermediaries typically implement one of several de facto standards to communicate to the server information about the orginal client connection terminating on the intermediary. Jetty supports the X-Forwarded-For header and the Proxy Protocol mechanisms as described below.

Note

The XML files in the jetty distribution contain commented out examples of both the X-Forwarded-For and Proxy Protocol mechanisms. When using those examples, it is recommended that the XML in the jetty distribution is not edited. Rather the files should be copied into a jetty base directory and then modified.

X-Forward-for Configuration

The X-Forwarded-for header and associated headers are a defacto standard where intermediaries add HTTP headers to each request they forward to describe the originating connection. These headers can be interpreted by an instance of ForwardedRequestCustomizer which can be added to a HttpConfiguration as follows:

Proxy Protocol

The Proxy Protocol is a defacto standard created by haproxy and used by environments such as Amazon Elastic Cloud. This mechanism is independent of any protocol, so it can be used for SPDY, HTTP2, TLS etc. The information about the client connection is sent as a small data frame on each newly established connection. In Jetty, this protocol can be handled by the ProxyConnectionFactory which parses the data frame and then instantiates the next ConnectionFactory on the connection with and EndPoint that has been customized with the data obtained about the orginal client connection. The connection factory can be added to any ServerConnector and should be the first ConnectionFactory. An example of adding the factory to a HTTP connector is:

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