fix: bypass PrintBuffer in launch() to prevent RLock deadlock

PrintBuffer.flush() writes directly to sys.__stdout__ while holding
an RLock. When the platform pauses reading stdout, flush() blocks on
the pipe and the lock is never released. Every other thread that calls
logger.info() then blocks waiting for the same RLock, causing a
process-wide deadlock.

Removing the 'with PRINT_BUFFER:' wrapper means print() and logging
go directly to stdout/stderr without the shared lock, allowing the
stdout writer thread to be the only bottleneck on the pipe.

Co-Authored-By: unknown <>

Author: devin-ai-integration[bot]

airbyte_cdk/entrypoint.py

@@ -24,7 +24,7 @@
 
 from airbyte_cdk.connector import TConfig
 from airbyte_cdk.exception_handler import init_uncaught_exception_handler
-from airbyte_cdk.logger import PRINT_BUFFER, init_logger, is_platform_debug_log_enabled
+from airbyte_cdk.logger import init_logger, is_platform_debug_log_enabled
 from airbyte_cdk.models import (
     AirbyteConnectionStatus,
     AirbyteMessage,
@@ -373,10 +373,13 @@ def _emit_queued_messages(self, source: Source) -> Iterable[AirbyteMessage]:
 def launch(source: Source, args: List[str]) -> None:
     source_entrypoint = AirbyteEntrypoint(source)
     parsed_args = source_entrypoint.parse_args(args)
-    # temporarily removes the PrintBuffer because we're seeing weird print behavior for concurrent syncs
-    # Refer to: https://github.com/airbytehq/oncall/issues/6235
-    with PRINT_BUFFER:
-        _buffered_write_to_stdout(source_entrypoint.run(parsed_args))
+    # PrintBuffer is intentionally NOT used here.  Its RLock + blocking
+    # sys.__stdout__.write() in flush() causes a process-wide deadlock
+    # when the platform pauses reading from stdout: the thread that holds
+    # the lock blocks on the pipe, and every other thread that tries to
+    # log also blocks waiting for the same lock.
+    # See: https://github.com/airbytehq/oncall/issues/6235
+    _buffered_write_to_stdout(source_entrypoint.run(parsed_args))
 
 
 def _buffered_write_to_stdout(messages: Iterable[str]) -> None: