writer: allow configuration of queue maxsize via env var (#1364)

* writer: allow configuration of queue maxsize via env var

* rename to DD_TRACE_MAX_TPS

Author: Kyle-Verhoog

ddtrace/internal/writer.py

@@ -1,5 +1,6 @@
 # stdlib
 import itertools
+import os
 import random
 import time
 import sys
@@ -16,8 +17,6 @@
 log = get_logger(__name__)
 
 
-MAX_TRACES = 1000
-
 DEFAULT_TIMEOUT = 5
 LOG_ERR_INTERVAL = 60
 
@@ -82,6 +81,7 @@ def write(self, spans=None, services=None):
 class AgentWriter(_worker.PeriodicWorkerThread):
 
     QUEUE_PROCESSING_INTERVAL = 1
+    QUEUE_MAX_TRACES_DEFAULT = 1000
 
     def __init__(
         self,
@@ -98,7 +98,9 @@ def __init__(
         super(AgentWriter, self).__init__(
             interval=self.QUEUE_PROCESSING_INTERVAL, exit_timeout=shutdown_timeout, name=self.__class__.__name__
         )
-        self._trace_queue = Q(maxsize=MAX_TRACES)
+        # DEV: provide a _temporary_ solution to allow users to specify a custom max
+        maxsize = int(os.getenv("DD_TRACE_MAX_TPS", self.QUEUE_MAX_TRACES_DEFAULT))
+        self._trace_queue = Q(maxsize=maxsize)
         self._filters = filters
         self._sampler = sampler
         self._priority_sampler = priority_sampler

tests/test_tracer.py

@@ -935,3 +935,9 @@ def test_detect_agentless_env(self):
     @run_in_subprocess(env_overrides=dict(AWS_LAMBDA_FUNCTION_NAME="my-func", DD_AGENT_HOST="localhost"))
     def test_detect_agent_config(self):
         assert isinstance(self.tracer.original_writer, AgentWriter)
+
+
+def test_tracer_custom_max_traces(monkeypatch):
+    monkeypatch.setenv("DD_TRACE_MAX_TPS", "2000")
+    tracer = ddtrace.Tracer()
+    assert tracer.writer._trace_queue.maxsize == 2000