io.envoyproxy.controlplane.server.callback

Class SnapshotCollectingCallback<T>

java.lang.Object

io.envoyproxy.controlplane.server.callback.SnapshotCollectingCallback<T>

All Implemented Interfaces:

DiscoveryServerCallbacks

public class SnapshotCollectingCallback<T>
extends Object
implements DiscoveryServerCallbacks

Callback that keeps track of the number of streams associated with each node group and periodically clears out Snapshots from the cache that are no longer referenced by any streams.

Works by monitoring the stream to determine what group they belong to and keeps a running count as well as when a request is seen that targets a given node group.

Every collectionIntervalMillis milliseconds a cleanup job runs which looks for snapshots with no active streams that haven't been updated within the configured time frame. Checking the time since last update is done to prevent snapshots from being prematurely removed from the cache. It ensures that a group must have no active streams for collectAfterMillis milliseconds before being collected.

To be notified of snapshots that are removed, a set of callbacks may be provided which will be triggered whenever a snapshot is removed from the cache. Any other callback which maintains state about the snapshots that is cleaned up by one of these callbacks should be run *after* this callback. This helps ensure that if state is cleaned up while a request in inbound, the request will be blocked by the lock in this callback until collection finishes and the subsequent callbacks will see the new request come in after collection. If the order is reversed, another callback might have seen the new request but the refcount here hasn't been incremented, causing it to get cleaned up and wipe the state of the other callback even though we now have an active stream for that group.

Constructor Summary

Constructors

Constructor and Description
SnapshotCollectingCallback(SnapshotCache<T> snapshotCache, NodeGroup<T> nodeGroup, Clock clock, Set<Consumer<T>> collectorCallbacks, long collectAfterMillis, long collectionIntervalMillis) Creates the callback.

Method Summary

Modifier and Type	Method and Description
void	onStreamClose(long streamId, String typeUrl) onStreamClose is called just before the bi-directional gRPC stream is closed successfully for an envoy instance.
void	onStreamCloseWithError(long streamId, String typeUrl, Throwable error) onStreamCloseWithError is called just before the bi-directional gRPC stream is closed for an envoy instance due to some error that has occurred.
void	onStreamRequest(long streamId, io.envoyproxy.envoy.api.v2.DiscoveryRequest request) onStreamRequest is called for each DiscoveryRequest that is received on the stream.

Methods inherited from class java.lang.Object

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

Methods inherited from interface io.envoyproxy.controlplane.server.DiscoveryServerCallbacks

onStreamOpen, onStreamResponse

Constructor Detail

SnapshotCollectingCallback

public SnapshotCollectingCallback(SnapshotCache<T> snapshotCache,
                                  NodeGroup<T> nodeGroup,
                                  Clock clock,
                                  Set<Consumer<T>> collectorCallbacks,
                                  long collectAfterMillis,
                                  long collectionIntervalMillis)

Creates the callback.

Parameters:

snapshotCache - the cache to evict snapshots from

nodeGroup - the node group used to map requests to groups

clock - system clock

collectorCallbacks - the callbacks to invoke when snapshot is collected

collectAfterMillis - how long a snapshot must be referenced for before being collected

collectionIntervalMillis - how often the collection background action should run

Method Detail

onStreamRequest

public void onStreamRequest(long streamId,
                            io.envoyproxy.envoy.api.v2.DiscoveryRequest request)

Description copied from interface: DiscoveryServerCallbacks

onStreamRequest is called for each DiscoveryRequest that is received on the stream.

Specified by:

onStreamRequest in interface DiscoveryServerCallbacks

Parameters:

streamId - an ID for this stream that is only unique to this discovery server instance

request - the discovery request sent by the envoy instance

onStreamClose

public void onStreamClose(long streamId,
                          String typeUrl)

Description copied from interface: DiscoveryServerCallbacks

onStreamClose is called just before the bi-directional gRPC stream is closed successfully for an envoy instance.

Specified by:

onStreamClose in interface DiscoveryServerCallbacks

Parameters:

streamId - an ID for this stream that is only unique to this discovery server instance

typeUrl - the resource type of the stream, or DiscoveryServer.ANY_TYPE_URL for ADS

onStreamCloseWithError

public void onStreamCloseWithError(long streamId,
                                   String typeUrl,
                                   Throwable error)

Description copied from interface: DiscoveryServerCallbacks

onStreamCloseWithError is called just before the bi-directional gRPC stream is closed for an envoy instance due to some error that has occurred.

Specified by:

onStreamCloseWithError in interface DiscoveryServerCallbacks

Parameters:

streamId - an ID for this stream that is only unique to this discovery server instance

typeUrl - the resource type of the stream, or DiscoveryServer.ANY_TYPE_URL for ADS

error - the error that caused the stream to close