com.nike.wingtips.servlet

Class RequestTracingFilter

java.lang.Object

com.nike.wingtips.servlet.RequestTracingFilter

All Implemented Interfaces:

javax.servlet.Filter

Direct Known Subclasses:

RequestTracingFilterNoAsync

public abstract class RequestTracingFilter
extends java.lang.Object
implements javax.servlet.Filter

Makes sure distributed tracing is handled for each request. Sets up the span for incoming requests (either an entirely new root span or one with a parent, depending on what is in the incoming request's headers), and also sets the TraceHeaders.TRACE_ID on the response. This is designed to only run once per request.

NOTE: This is abstract because you'll need to override getUserIdHeaderKeys() if your service is expecting user ID header(s), and because the only-runs-once logic is dependent on whether you're in an async request environment or not, and more particularly whether or not you're in the middle of an async dispatch. If you're not in an async request environment then you can just use RequestTracingFilterNoAsync for your filter.

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	ERROR_REQUEST_URI_ATTRIBUTE Corresponds to RequestDispatcher.ERROR_REQUEST_URI.
static java.lang.String	FILTER_HAS_ALREADY_EXECUTED_ATTRIBUTE This attribute key will be set to a value of true via ServletRequest.setAttribute(String, Object) the first time this filter is run for any given request.
static java.lang.String	USER_ID_HEADER_KEYS_LIST_INIT_PARAM_NAME The param name for the "list of user ID header keys" init param for this filter.
protected java.util.List<java.lang.String>	userIdHeaderKeysFromInitParam

Constructor Summary

Constructors

Constructor and Description
RequestTracingFilter()

Method Summary

Methods

Modifier and Type	Method and Description
void	destroy()
void	doFilter(javax.servlet.ServletRequest request, javax.servlet.ServletResponse response, javax.servlet.FilterChain filterChain) Wrapper around doFilterInternal(HttpServletRequest, HttpServletResponse, FilterChain) to make sure this filter's logic is only executed once per request.
protected void	doFilterInternal(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response, javax.servlet.FilterChain filterChain) Performs the distributed tracing work for each request's overall span.
protected java.util.List<java.lang.String>	getUserIdHeaderKeys() The list of header keys that will be used to search the request headers for a user ID to set on the Span for the request.
void	init(javax.servlet.FilterConfig filterConfig)
protected abstract boolean	isAsyncDispatch(javax.servlet.http.HttpServletRequest request) The dispatcher type javax.servlet.DispatcherType.ASYNC introduced in Servlet 3.0 means a filter can be invoked in more than one thread over the course of a single request.
protected boolean	skipDispatch(javax.servlet.http.HttpServletRequest request)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FILTER_HAS_ALREADY_EXECUTED_ATTRIBUTE

public static final java.lang.String FILTER_HAS_ALREADY_EXECUTED_ATTRIBUTE

This attribute key will be set to a value of true via ServletRequest.setAttribute(String, Object) the first time this filter is run for any given request. This filter will then see this attribute on any subsequent executions with the same request and continue the filter chain without executing this filter's logic to make sure this filter's logic is only executed once per request.

See Also:

Constant Field Values

ERROR_REQUEST_URI_ATTRIBUTE

public static final java.lang.String ERROR_REQUEST_URI_ATTRIBUTE

Corresponds to RequestDispatcher.ERROR_REQUEST_URI. This will be populated in the request attributes during an error dispatch.

See Also:

Constant Field Values

USER_ID_HEADER_KEYS_LIST_INIT_PARAM_NAME

public static final java.lang.String USER_ID_HEADER_KEYS_LIST_INIT_PARAM_NAME

The param name for the "list of user ID header keys" init param for this filter. The value of this init param will be parsed for the list of user ID header keys to use when calling HttpSpanFactory.fromHttpServletRequest(HttpServletRequest, List) or HttpSpanFactory.getUserIdFromHttpServletRequest(HttpServletRequest, List). The value for this init param is expected to be a comma-delimited list.

See Also:

Constant Field Values

userIdHeaderKeysFromInitParam

protected java.util.List<java.lang.String> userIdHeaderKeysFromInitParam

Constructor Detail

RequestTracingFilter

public RequestTracingFilter()

Method Detail

init

public void init(javax.servlet.FilterConfig filterConfig)
          throws javax.servlet.ServletException

Specified by:

init in interface javax.servlet.Filter

Throws:

javax.servlet.ServletException

destroy

public void destroy()

Specified by:

destroy in interface javax.servlet.Filter

doFilter

public void doFilter(javax.servlet.ServletRequest request,
            javax.servlet.ServletResponse response,
            javax.servlet.FilterChain filterChain)
              throws java.io.IOException,
                     javax.servlet.ServletException

Wrapper around doFilterInternal(HttpServletRequest, HttpServletResponse, FilterChain) to make sure this filter's logic is only executed once per request.

Specified by:

doFilter in interface javax.servlet.Filter

Throws:

java.io.IOException

javax.servlet.ServletException

doFilterInternal

protected void doFilterInternal(javax.servlet.http.HttpServletRequest request,
                    javax.servlet.http.HttpServletResponse response,
                    javax.servlet.FilterChain filterChain)
                         throws javax.servlet.ServletException,
                                java.io.IOException

Performs the distributed tracing work for each request's overall span. Guaranteed to only be called once per request.

Throws:

javax.servlet.ServletException

java.io.IOException

skipDispatch

protected boolean skipDispatch(javax.servlet.http.HttpServletRequest request)

Returns:

true if doFilterInternal(HttpServletRequest, HttpServletResponse, FilterChain) should be skipped, false otherwise.

isAsyncDispatch

protected abstract boolean isAsyncDispatch(javax.servlet.http.HttpServletRequest request)

The dispatcher type javax.servlet.DispatcherType.ASYNC introduced in Servlet 3.0 means a filter can be invoked in more than one thread over the course of a single request. This method should return true if the filter is currently executing within an asynchronous dispatch.

Parameters:

request - the current request

getUserIdHeaderKeys

protected java.util.List<java.lang.String> getUserIdHeaderKeys()

The list of header keys that will be used to search the request headers for a user ID to set on the Span for the request. The user ID header keys will be searched in list order, and the first non-empty user ID header value found will be used as the Span.getUserId(). You can safely return null or an empty list for this method if there is no user ID to extract; if you return null/empty then the request span's Span.getUserId() will be null.

By default this method will return the list specified via the USER_ID_HEADER_KEYS_LIST_INIT_PARAM_NAME init param, or null if that init param does not exist.

Returns:

The list of header keys that will be used to search the request headers for a user ID to set on the Span for the request. This method may return null or an empty list if there are no user IDs to search for.