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:
```
{@code
 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	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

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	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 {@param 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 {@param 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.

Class ResponseContext.Keys

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

UNCOVERED_INTERVALS

UNCOVERED_INTERVALS_OVERFLOWED

REMAINING_RESPONSES_FROM_QUERY_SERVERS

MISSING_SEGMENTS

ETAG

QUERY_TOTAL_BYTES_GATHERED

QUERY_FAIL_DEADLINE_MILLIS

TIMEOUT_AT

NUM_SCANNED_ROWS

CPU_CONSUMED_NANOS

TRUNCATED

INSTANCE

Method Detail

instance

registerKey

registerKeys

keyOf

find