tap: Buffered Admin Tap Filter Implementation (#20142)

This change introduces a new output sink type for admin /tap requests which buffers traces internally before responding to the client.

This sink is best used to collect traces for requests that are frequently matched, or to work around system limitations such as improper support for streaming HTTP responses.

Signed-off-by: David Peet <davidpeet@tutanota.com>

Mirrored from https://github.com/envoyproxy/envoy @ 0fd80eef63bc9770186c4f4aa345ee63e464cab3

envoy/config/tap/v3/common.proto

@@ -7,6 +7,7 @@ import "envoy/config/core/v3/base.proto";
 import "envoy/config/core/v3/grpc_service.proto";
 import "envoy/config/route/v3/route_components.proto";
 
+import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";
 
 import "envoy/annotations/deprecation.proto";
@@ -182,6 +183,7 @@ message OutputConfig {
 }
 
 // Tap output sink configuration.
+// [#next-free-field: 6]
 message OutputSink {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.service.tap.v2alpha.OutputSink";
@@ -247,6 +249,16 @@ message OutputSink {
     // GrpcService to stream data to. The format argument must be PROTO_BINARY.
     // [#comment: TODO(samflattery): remove cleanup in uber_per_filter.cc once implemented]
     StreamingGrpcSink streaming_grpc = 4;
+
+    // Tap output will be buffered in a single block before flushing to the :http:post:`/tap` admin endpoint
+    //
+    // .. attention::
+    //
+    //   It is only allowed to specify the buffered admin output sink if the tap is being
+    //   configured from the :http:post:`/tap` admin endpoint. Thus, if an extension has
+    //   been configured to receive tap configuration from some other source (e.g., static
+    //   file, XDS, etc.) configuring the buffered admin output type will fail.
+    BufferedAdminSink buffered_admin = 5;
   }
 }
 
@@ -256,6 +268,23 @@ message StreamingAdminSink {
       "envoy.service.tap.v2alpha.StreamingAdminSink";
 }
 
+// BufferedAdminSink configures a tap output to collect traces without returning them until
+// one of multiple criteria are satisfied.
+// Similar to StreamingAdminSink, it is only allowed to specify the buffered admin output
+// sink if the tap is being configured from the `/tap` admin endpoint.
+message BufferedAdminSink {
+  // Stop collecting traces when the specified number are collected.
+  // If other criteria for ending collection are reached first, this value will not be used.
+  uint64 max_traces = 1 [(validate.rules).uint64 = {gt: 0}];
+
+  // Acts as a fallback to prevent the client from waiting for long periods of time.
+  // After timeout has occurred, a buffer flush will be triggered, returning the traces buffered so far.
+  // This may result in returning fewer traces than were requested, and in the case that no traces are
+  // buffered during this time, no traces will be returned.
+  // Specifying 0 for the timeout value (or not specifying a value at all) indicates an infinite timeout.
+  google.protobuf.Duration timeout = 2;
+}
+
 // The file per tap sink outputs a discrete file for every tapped stream.
 message FilePerTapSink {
   option (udpa.annotations.versioning).previous_message_type =