org.apache.druid.query.context

Class ResponseContext.Keys

java.lang.Object

org.apache.druid.query.context.ResponseContext.Keys

Enclosing class:

ResponseContext

public static class ResponseContext.Keys
extends Object

Global registry of response context keys. Also defines the standard keys associated with objects in the context.

If it's necessary to add new keys in the context then they should be listed in a separate class:

 public class SomeClass
 {
   static final Key EXTENSION_KEY_1 = new StringKey(
      "extension_key_1", Visibility.HEADER_AND_TRAILER, true),
   static final Key EXTENSION_KEY_2 = new CounterKey(
      "extension_key_2", Visibility.None);

   static {
     Keys.instance().registerKeys(new Key[] {
        EXTENSION_KEY_1,
        EXTENSION_KEY_2
     });
   }
 }

Make sure all extension keys are added with the {@link #registerKey(Key)} or {@link #registerKeys(Key[])} methods.

Create custom keys in one of two ways. As shown above, predefined key types exist for common values. Custom values can be created as shown in the code for this class.

Field Summary

Fields

Modifier and Type	Field and Description
static ResponseContext.Key	CPU_CONSUMED_NANOS The total CPU time for threads related to Sequence processing of the query.
static ResponseContext.Key	ETAG Entity tag.
static ResponseContext.Keys	INSTANCE One and only global list of keys.
static ResponseContext.Key	MISSING_SEGMENTS Lists missing segments.
static ResponseContext.Key	NUM_SCANNED_ROWS The number of rows scanned by ScanQueryEngine.
static ResponseContext.Key	QUERY_FAIL_DEADLINE_MILLIS Query fail time (current time + timeout).
static ResponseContext.Key	QUERY_TOTAL_BYTES_GATHERED Query total bytes gathered.
static ResponseContext.Key	REMAINING_RESPONSES_FROM_QUERY_SERVERS Map of most relevant query ID to remaining number of responses from query nodes.
static ResponseContext.Key	TIMEOUT_AT This variable indicates when a running query should be expired, and is effective only when 'timeout' of queryContext has a positive value.
static ResponseContext.Key	TRUNCATED Indicates if a ResponseContext was truncated during serialization.
static ResponseContext.Key	UNCOVERED_INTERVALS Lists intervals for which NO segment is present.
static ResponseContext.Key	UNCOVERED_INTERVALS_OVERFLOWED Indicates if the number of uncovered intervals exceeded the limit (true/false).

Method Summary

Modifier and Type	Method and Description
ResponseContext.Key	find(String name) Returns a registered key associated with the given name, or null if the key is not registered.
static ResponseContext.Keys	instance() Returns the single, global key registry for this server.
ResponseContext.Key	keyOf(String name) Returns a registered key associated with the name .
void	registerKey(ResponseContext.Key key) Primary way of registering context keys.
void	registerKeys(ResponseContext.Key[] keys) Register a group of keys.

Methods inherited from class java.lang.Object

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

Field Detail

UNCOVERED_INTERVALS

public static final ResponseContext.Key UNCOVERED_INTERVALS

Lists intervals for which NO segment is present.

UNCOVERED_INTERVALS_OVERFLOWED

public static final ResponseContext.Key UNCOVERED_INTERVALS_OVERFLOWED

Indicates if the number of uncovered intervals exceeded the limit (true/false).

REMAINING_RESPONSES_FROM_QUERY_SERVERS

public static final ResponseContext.Key REMAINING_RESPONSES_FROM_QUERY_SERVERS

Map of most relevant query ID to remaining number of responses from query nodes. The value is initialized in CachingClusteredClient when it initializes the connection to the query nodes, and is updated whenever they respond (@code DirectDruidClient). RetryQueryRunner uses this value to check if the MISSING_SEGMENTS is valid. Currently, the broker doesn't run subqueries in parallel, the remaining number of responses will be updated one by one per subquery. However, since it can be parallelized to run subqueries simultaneously, we store them in a ConcurrentHashMap.

See Also:

Query.getMostSpecificId()

MISSING_SEGMENTS

public static final ResponseContext.Key MISSING_SEGMENTS

Lists missing segments.

ETAG

public static final ResponseContext.Key ETAG

Entity tag. A part of HTTP cache validation mechanism. Is being removed from the context before sending and used as a separate HTTP header.

QUERY_TOTAL_BYTES_GATHERED

public static final ResponseContext.Key QUERY_TOTAL_BYTES_GATHERED

Query total bytes gathered.

QUERY_FAIL_DEADLINE_MILLIS

public static final ResponseContext.Key QUERY_FAIL_DEADLINE_MILLIS

Query fail time (current time + timeout).

TIMEOUT_AT

public static final ResponseContext.Key TIMEOUT_AT

This variable indicates when a running query should be expired, and is effective only when 'timeout' of queryContext has a positive value.

NUM_SCANNED_ROWS

public static final ResponseContext.Key NUM_SCANNED_ROWS

The number of rows scanned by ScanQueryEngine. Named "count" for backwards compatibility with older data servers that still send this, even though it's now marked as internal.

CPU_CONSUMED_NANOS

public static final ResponseContext.Key CPU_CONSUMED_NANOS

The total CPU time for threads related to Sequence processing of the query. Resulting value on a Broker is a sum of downstream values from historicals / realtime nodes. For additional information see CPUTimeMetricQueryRunner

TRUNCATED

public static final ResponseContext.Key TRUNCATED

Indicates if a ResponseContext was truncated during serialization.

INSTANCE

public static final ResponseContext.Keys INSTANCE

One and only global list of keys. This is a semi-constant: it is mutable at start-up time, but then is not thread-safe, and must remain unchanged for the duration of the server run.

Method Detail

instance

public static ResponseContext.Keys instance()

Returns the single, global key registry for this server.

registerKey

public void registerKey(ResponseContext.Key key)

Primary way of registering context keys.

Throws:

IllegalArgumentException - if the key has already been registered.

registerKeys

public void registerKeys(ResponseContext.Key[] keys)

Register a group of keys.

keyOf

public ResponseContext.Key keyOf(String name)

Returns a registered key associated with the name .

Throws:

IllegalStateException - if a corresponding key has not been registered.

find

public ResponseContext.Key find(String name)

Returns a registered key associated with the given name, or null if the key is not registered. This form is for testing and for deserialization when the existence of the key is suspect.