This is an automated email from the ASF dual-hosted git repository. cmcfarlen pushed a commit to branch 10.1.x in repository https://gitbox.apache.org/repos/asf/trafficserver.git
commit 7f2c1b03dd2e56aee525d72072243057a0f34748 Author: Mo Chen <[email protected]> AuthorDate: Wed Apr 16 14:56:17 2025 -0500 USDT tracing improvements (#12179) - Add tracing documentation. - Fix uninitizlied sm_id in milestone_sm_start. (cherry picked from commit 122403b9a1593a3adae78dade751b1f9bfaef047) --- doc/developer-guide/debugging/index.en.rst | 1 + doc/developer-guide/debugging/tracing.en.rst | 72 ++++++++++++++++++++++++++++ src/proxy/http/HttpSM.cc | 4 +- 3 files changed, 75 insertions(+), 2 deletions(-) diff --git a/doc/developer-guide/debugging/index.en.rst b/doc/developer-guide/debugging/index.en.rst index 36f5cb8911..151609c2dd 100644 --- a/doc/developer-guide/debugging/index.en.rst +++ b/doc/developer-guide/debugging/index.en.rst @@ -31,4 +31,5 @@ Debugging and Analysis core-dump-analysis.en profiling.en memory-leaks.en + tracing.en diff --git a/doc/developer-guide/debugging/tracing.en.rst b/doc/developer-guide/debugging/tracing.en.rst new file mode 100644 index 0000000000..580ac12cc9 --- /dev/null +++ b/doc/developer-guide/debugging/tracing.en.rst @@ -0,0 +1,72 @@ +.. Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, + software distributed under the License is distributed on an + "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + KIND, either express or implied. See the License for the + specific language governing permissions and limitations + under the License. + +.. include:: ../../common.defs +.. default-domain:: cpp + +.. _developer-tracing: + +Tracing +********* + +ATS includes statically defined tracepoints. These are useful for debugging a running instance with minimal overhead. + +USDT +==== + +A number of tools can be used to read USDT tracepoints. Tools such as bpftrace, bcc, and perf use eBPF technology within the Linux kernel to provide tracing capabilities. + +These tools can list available tracepoints, attach to a tracepoint, and some can process trace data in real time with eBPF programs. + +Built-in tracepoints +==================== + +ATS includes a tracepoint at each HTTP state machine state. The state machine id, sm_id, is included as an argument to help isolate each transaction. These tracepoints +are named milestone_<state> and are located in the HttpSM.cc file. See :func:`TSHttpTxnMilestoneGet` for a list of the states. + +Example with bpftrace +===================== +.. code-block:: bash + + #!/usr/bin/env bpftrace + + BEGIN { + @ = (uint64)0; + } + + usdt:/opt/ats/bin/traffic_server:trafficserver:milestone_sm_start { + $sm_id = arg0; + if (@ == 0) { + @ = $sm_id; + } + @start_time = nsecs; + } + + usdt:/opt/ats/bin/traffic_server:trafficserver:milestone_* { + $sm_id = arg0; + if ($sm_id == @) { + printf("%s %d\n", probe, nsecs - @start_time); + } + } + + usdt:/opt/ats/bin/traffic_server:trafficserver:milestone_sm_finish { + $sm_id = arg0; + if ($sm_id == @) { + printf("End of state machine %d\n", $sm_id); + exit(); + } + } diff --git a/src/proxy/http/HttpSM.cc b/src/proxy/http/HttpSM.cc index 56b5f1cac7..051b001386 100644 --- a/src/proxy/http/HttpSM.cc +++ b/src/proxy/http/HttpSM.cc @@ -282,7 +282,6 @@ HttpSM::destroy() void HttpSM::init(bool from_early_data) { - ATS_PROBE1(milestone_sm_start, sm_id); milestones[TS_MILESTONE_SM_START] = ink_get_hrtime(); _from_early_data = from_early_data; @@ -292,7 +291,8 @@ HttpSM::init(bool from_early_data) server_txn = nullptr; // Unique state machine identifier - sm_id = next_sm_id++; + sm_id = next_sm_id++; + ATS_PROBE1(milestone_sm_start, sm_id); t_state.state_machine = this; t_state.http_config_param = HttpConfig::acquire();
