com.yahoo.search.searchers

Class ConnectionControlSearcher

java.lang.Object

com.yahoo.component.AbstractComponent

com.yahoo.component.chain.ChainedComponent

com.yahoo.processing.Processor

com.yahoo.search.Searcher

com.yahoo.search.searchers.ConnectionControlSearcher

All Implemented Interfaces:

com.yahoo.component.Component, Comparable<com.yahoo.component.Component>

public class ConnectionControlSearcher
extends Searcher

Searcher which can enforce HTTP connection close based on query properties.

This searcher informs the client to close a persistent HTTP connection if the connection is older than the configured max lifetime. This is done by adding the "Connection" HTTP header with the value "Close" to the result.

The searcher reads the query property "connectioncontrol.maxlifetime", which is an integer number of seconds, to get the value for maximum connection lifetime. Setting it to zero will enforce connection close independently of the age of the connection. Typical usage would be as follows:

1. Add the ConnectionControlSearcher to the default search chain of your application. (It has no special ordering considerations.)
2. For the default query profile of your application, set a reasonable value for "connectioncontrol.maxlifetime". The definition of reasonable will be highly application dependent, but it should always be less than the grace period when taking the container out of production traffic.
3. Deploy application. The container will now inform clients to close connections/reconnect within the configured time limit.

Author:

frodelu, Steinar Knutsen

Field Summary

Fields

Modifier and Type	Field and Description
private LongSupplier	clock
private static String	HTTP_CONNECTION_CLOSE_ARGUMENT
private static String	HTTP_CONNECTION_HEADER_NAME
private static com.yahoo.processing.request.CompoundName	KEEPALIVE_MAXLIFETIMESECONDS
private String	simpleName

Fields inherited from class com.yahoo.component.AbstractComponent

isDeconstructable

Constructor Summary

Constructors

Modifier	Constructor and Description
	ConnectionControlSearcher()
private	ConnectionControlSearcher(LongSupplier clock)

Method Summary

Modifier and Type	Method and Description
static ConnectionControlSearcher	createTestInstance(LongSupplier clock) Create a searcher instance suitable for unit tests.
private void	keepAliveProcessing(Query query, Result result) If the HTTP connection has been alive for too long, set the header "Connection: Close" to tell the client to close the connection after this request.
Result	search(Query query, Execution execution) Override this to implement your searcher.
private void	setCloseIfLifetimeExceeded(Query query, Result result, int maxLifetimeSeconds)

Methods inherited from class com.yahoo.search.Searcher

ensureFilled, fill, getLogger, process, toString

Methods inherited from class com.yahoo.component.chain.ChainedComponent

getAnnotatedDependencies, getDefaultAnnotatedDependencies, getDependencies, initDependencies

Methods inherited from class com.yahoo.component.AbstractComponent

clone, compareTo, deconstruct, getClassName, getId, getIdString, hasInitializedId, initId, isDeconstructable, setIsDeconstructable

Methods inherited from class java.lang.Object

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

Field Detail

simpleName

private final String simpleName

clock

private final LongSupplier clock

KEEPALIVE_MAXLIFETIMESECONDS

private static final com.yahoo.processing.request.CompoundName KEEPALIVE_MAXLIFETIMESECONDS

HTTP_CONNECTION_HEADER_NAME

private static final String HTTP_CONNECTION_HEADER_NAME

See Also:

Constant Field Values

HTTP_CONNECTION_CLOSE_ARGUMENT

private static final String HTTP_CONNECTION_CLOSE_ARGUMENT

See Also:

Constant Field Values

Constructor Detail

ConnectionControlSearcher

public ConnectionControlSearcher()

ConnectionControlSearcher

private ConnectionControlSearcher(LongSupplier clock)

Method Detail

createTestInstance

public static ConnectionControlSearcher createTestInstance(LongSupplier clock)

Create a searcher instance suitable for unit tests.

Parameters:

clock - a simulated or real clock behaving similarly to System.currentTimeMillis()

Returns:

a fully initialised instance

search

public Result search(Query query,
                     Execution execution)

Description copied from class: Searcher

Override this to implement your searcher.

Searcher implementation subclasses will, depending on their type of logic, do one of the following:

• Query processors: Access the query, then call execution.search and return the result
• Result processors: Call execution.search to get the result, access it and return
• Sources (which produces results): Create a result, add the desired hits and return it.
• Federators (which forwards the search to multiple subchains): Call search on the desired subchains in parallel and get the results. Combine the results to one and return it.
• Workflows: Call execution.search as many times as desired, using different queries. Eventually return a result.

Hits come in two kinds - concrete hits are actual content of the kind requested by the user, meta hits are hits which provides information about the collection of hits, on the query, the service and so on.

The query specifies a window into a larger result list that must be returned from the searcher through hits and offset; Searchers which returns list of hits in the top level in the result must return at least hits number of hits (or if impossible; all that are available), starting at the given offset. In addition, searchers are allowed to return any number of meta hits (although this number is expected to be low). For hits contained in nested hit groups, the concept of a window defined by hits and offset is not well defined and does not apply.

Error handling in searchers:

• Unexpected events: Throw any RuntimeException. This query will fail with the exception message, and the error will be logged
• Expected events: Create (new Result(Query, ErrorMessage) or add result.setErrorIfNoOtherErrors(ErrorMessage) an error message to the Result.
• Recoverable user errors: Add a FeedbackHit explaining the condition and how to correct it.

Specified by:

search in class Searcher

Parameters:

query - the query

Returns:

the result of making this query

keepAliveProcessing

private void keepAliveProcessing(Query query,
                                 Result result)

If the HTTP connection has been alive for too long, set the header "Connection: Close" to tell the client to close the connection after this request.

setCloseIfLifetimeExceeded

private void setCloseIfLifetimeExceeded(Query query,
                                        Result result,
                                        int maxLifetimeSeconds)