Add possibility to split oversized udp batches

If we use the BatchExportSpanProcessor combined with the
JaegerSpanExporter and use instrumentations that add a lot of metadata
to the spans like sqlalchemy, then we run occationally into the "Data
exceeds the max UDP packet size" warning causing dropped spans and
incomplete data.

The option to reduce the general batch-size to a very small number (in
my case >30) may cause a performance issue as the worker thread of the
batch exporter gets very busy. Instead this change allows the user to
ask the exporter to split oversized batches when they get detected and
send the splits separately instead of dropping them. Depending on the
usecase this is a better option than reducing the batch-size to a very
small value because every now and then they contain a couple of large
spans.

CHANGELOG.md

@@ -9,6 +9,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - Add `max_attr_value_length` support to Jaeger exporter
   ([#1633])(https://github.com/open-telemetry/opentelemetry-python/pull/1633)
+- Add `udp_split_oversized_batches` support to jaeger exporter
+  ([#1500](https://github.com/open-telemetry/opentelemetry-python/pull/1500))
 
 ### Changed
 - Rename `IdsGenerator` to `IdGenerator`

exporter/opentelemetry-exporter-jaeger/src/opentelemetry/exporter/jaeger/__init__.py

@@ -86,6 +86,7 @@
 from opentelemetry.sdk.environment_variables import (
     OTEL_EXPORTER_JAEGER_AGENT_HOST,
     OTEL_EXPORTER_JAEGER_AGENT_PORT,
+    OTEL_EXPORTER_JAEGER_AGENT_SPLIT_OVERSIZED_BATCHES,
     OTEL_EXPORTER_JAEGER_ENDPOINT,
     OTEL_EXPORTER_JAEGER_PASSWORD,
     OTEL_EXPORTER_JAEGER_USER,
@@ -122,6 +123,7 @@ class JaegerSpanExporter(SpanExporter):
         credentials: Credentials for server authentication.
         transport_format: Transport format for exporting spans to collector.
         max_tag_value_length: Max length string attribute values can have. Set to None to disable.
+        udp_split_oversized_batches: Re-emit oversized batches in smaller chunks.
     """
 
     def __init__(
@@ -136,6 +138,7 @@ def __init__(
         credentials: Optional[ChannelCredentials] = None,
         transport_format: Optional[str] = None,
         max_tag_value_length: Optional[int] = None,
+        udp_split_oversized_batches: bool = None,
     ):
         self.service_name = service_name
         self._max_tag_value_length = max_tag_value_length
@@ -155,8 +158,17 @@ def __init__(
             env_variable=environ_agent_port,
             default=DEFAULT_AGENT_PORT,
         )
+        self.udp_split_oversized_batches = _parameter_setter(
+            param=udp_split_oversized_batches,
+            env_variable=environ.get(
+                OTEL_EXPORTER_JAEGER_AGENT_SPLIT_OVERSIZED_BATCHES
+            ),
+            default=False,
+        )
         self._agent_client = AgentClientUDP(
-            host_name=self.agent_host_name, port=self.agent_port
+            host_name=self.agent_host_name,
+            port=self.agent_port,
+            split_oversized_batches=self.udp_split_oversized_batches,
         )
         self.collector_endpoint = _parameter_setter(
             param=collector_endpoint,

exporter/opentelemetry-exporter-jaeger/src/opentelemetry/exporter/jaeger/send/thrift.py

@@ -14,6 +14,7 @@
 
 import base64
 import logging
+import math
 import socket
 
 from thrift.protocol import TBinaryProtocol, TCompactProtocol
@@ -36,6 +37,7 @@ class AgentClientUDP:
         port: The port of the Jaeger server.
         max_packet_size: Maximum size of UDP packet.
         client: Class for creating new client objects for agencies.
+        split_oversized_batches: Re-emit oversized batches in smaller chunks.
     """
 
     def __init__(
@@ -44,13 +46,15 @@ def __init__(
         port,
         max_packet_size=UDP_PACKET_MAX_LENGTH,
         client=agent.Client,
+        split_oversized_batches=False,
     ):
         self.address = (host_name, port)
         self.max_packet_size = max_packet_size
         self.buffer = TTransport.TMemoryBuffer()
         self.client = client(
             iprot=TCompactProtocol.TCompactProtocol(trans=self.buffer)
         )
+        self.split_oversized_batches = split_oversized_batches
 
     def emit(self, batch: jaeger.Batch):
         """
@@ -66,11 +70,25 @@ def emit(self, batch: jaeger.Batch):
         self.client.emitBatch(batch)
         buff = self.buffer.getvalue()
         if len(buff) > self.max_packet_size:
-            logger.warning(
-                "Data exceeds the max UDP packet size; size %r, max %r",
-                len(buff),
-                self.max_packet_size,
-            )
+            if self.split_oversized_batches and len(batch.spans) > 1:
+                packets = math.ceil(len(buff) / self.max_packet_size)
+                div = math.ceil(len(batch.spans) / packets)
+                for packet in range(packets):
+                    start = packet * div
+                    end = (packet + 1) * div
+                    if start < len(batch.spans):
+                        self.emit(
+                            jaeger.Batch(
+                                process=batch.process,
+                                spans=batch.spans[start:end],
+                            )
+                        )
+            else:
+                logger.warning(
+                    "Data exceeds the max UDP packet size; size %r, max %r",
+                    len(buff),
+                    self.max_packet_size,
+                )
             return
 
         with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as udp_socket:

exporter/opentelemetry-exporter-jaeger/tests/test_jaeger_exporter_thrift.py

@@ -520,3 +520,58 @@ def test_max_tag_value_length(self):
         self.assertEqual("hello", tags_by_keys["key_string"])
         self.assertEqual("('tup", tags_by_keys["key_tuple"])
         self.assertEqual("some_", tags_by_keys["key_resource"])
+
+    def test_agent_client_split(self):
+        agent_client = jaeger_exporter.AgentClientUDP(
+            host_name="localhost",
+            port=6354,
+            max_packet_size=250,
+            split_oversized_batches=True,
+        )
+
+        translator = jaeger_exporter.Translate((self._test_span,))
+        small_batch = jaeger.Batch(
+            # pylint: disable=protected-access
+            spans=translator._translate(ThriftTranslator()),
+            process=jaeger.Process(serviceName="xxx"),
+        )
+
+        with unittest.mock.patch(
+            "socket.socket.sendto", autospec=True
+        ) as fake_sendto:
+            agent_client.emit(small_batch)
+            self.assertEqual(fake_sendto.call_count, 1)
+
+        translator = jaeger_exporter.Translate([self._test_span] * 2)
+        large_batch = jaeger.Batch(
+            # pylint: disable=protected-access
+            spans=translator._translate(ThriftTranslator()),
+            process=jaeger.Process(serviceName="xxx"),
+        )
+
+        with unittest.mock.patch(
+            "socket.socket.sendto", autospec=True
+        ) as fake_sendto:
+            agent_client.emit(large_batch)
+            self.assertEqual(fake_sendto.call_count, 2)
+
+    def test_agent_client_dont_send_empty_spans(self):
+        agent_client = jaeger_exporter.AgentClientUDP(
+            host_name="localhost",
+            port=6354,
+            max_packet_size=415,
+            split_oversized_batches=True,
+        )
+
+        translator = jaeger_exporter.Translate([self._test_span] * 4)
+        large_batch = jaeger.Batch(
+            # pylint: disable=protected-access
+            spans=translator._translate(ThriftTranslator()),
+            process=jaeger.Process(serviceName="xxx"),
+        )
+
+        with unittest.mock.patch(
+            "socket.socket.sendto", autospec=True
+        ) as fake_sendto:
+            agent_client.emit(large_batch)
+            self.assertEqual(fake_sendto.call_count, 4)

opentelemetry-sdk/src/opentelemetry/sdk/environment_variables/__init__.py

@@ -46,3 +46,6 @@
 OTEL_EXPORTER_JAEGER_CERTIFICATE = "OTEL_EXPORTER_JAEGER_CERTIFICATE"
 OTEL_EXPORTER_OTLP_INSECURE = "OTEL_EXPORTER_OTLP_INSECURE"
 OTEL_EXPORTER_OTLP_SPAN_INSECURE = "OTEL_EXPORTER_OTLP_SPAN_INSECURE"
+OTEL_EXPORTER_JAEGER_AGENT_SPLIT_OVERSIZED_BATCHES = (
+    "OTEL_EXPORTER_JAEGER_AGENT_SPLIT_OVERSIZED_BATCHES"
+)