Questions: About using watch and json-output

[Robin3Chan]

Q1: Why there isn't any 'Latency Details' block in my 'first part'?

Q2: Why 'black_box_duration_ms' is bigger than 'total_duration_ms' ? And how to understand req_syscall_events and req_nic_events? I cannot find any event name or syscall name in those list. Does req_syscall_events represent send syscall?

{
    "start_time": "2025-03-05T09:08:51.110670228Z",
    "end_time": "2025-03-05T09:08:51.11083628Z",
    "protocol": "HTTP",
    "side": "server",
    "local_addr": "0.0.0.0",
    "local_port": 80,
    "remote_addr": "0.0.0.0",
    "remote_port": 13634,
    "pid": 361836,
    "is_ssl": false,
    "total_duration_ms": 0.165888,
    "black_box_duration_ms": 0.19456,
    "read_socket_duration_ms": -0.000001,
    "copy_to_socket_buffer_duration_ms": 0,
    "req_size_bytes": 118,
    "resp_size_bytes": 382,
    "req_plain_text_size_bytes": 0,
    "resp_plain_text_size_bytes": 0,
    "request": "xxxx",
    "response": "xxxx",
    "req_syscall_events": [
        {
            "ByteSize": 118,
            "Timestamp": 1741165731110670228
        }
    ],
    "resp_syscall_events": [
        {
            "ByteSize": 382,
            "Timestamp": 1741165731110821806
        }
    ],
    "req_nic_events": [],
    "resp_nic_events": [
        {
            "ByteSize": 382,
            "Timestamp": 1741165731110836280,
            "Attributes": {
                "time-lo": 1741165731110836280
            }
        }
    ]
}

[dosubot]

Hello @Robin3Chan! I'm here to help you with any bugs, questions, or contributions. Let's tackle this issue together while we wait for a human maintainer.

1. 'Latency Details' Block Missing: The absence of a 'Latency Details' block in your output could be due to the lack of detailed event data that Kyanos uses to construct these blocks. Ensure that the necessary events, such as nicIngressEvents, tcpInEvents, userCopyEvents, and readSyscallEvents, are being captured and logged. These events are crucial for generating the detailed latency breakdown.

2. 'black_box_duration_ms' Greater than 'total_duration_ms': This discrepancy might occur if there is an error in the event timestamps or if the events used to calculate black_box_duration_ms are not aligned correctly with those used for total_duration_ms. The black_box_duration_ms measures the unobservable time, which should logically be a subset of the total_duration_ms. Double-check the timestamps and ensure that the events are correctly captured and processed.

3. Understanding 'req_syscall_events' and 'req_nic_events':

   • req_syscall_events represents syscall events related to the request, detailing system calls made during the request process. These events help analyze the time spent in the kernel during network operations. They do not specifically represent send syscalls but include all relevant syscalls for the request.
   • req_nic_events represents network interface card (NIC) events related to the request, providing details about packet handling at the NIC level. In your case, the absence of req_nic_events suggests that no NIC-level events were captured for the request, which might affect the latency analysis ^[1][2].

To continue talking to Dosu, mention @dosu.

---

^{Help Dosu learn! Give it feedback: Great Response | Irrelevant Answer | Incorrect Sources | Too Verbose | Hallucination | Bug Report | Other}

[hengyoush]

1. The prerequisite for displaying the graph is having network card events, namely the req_nic_events (time when the network card receives the request for server side) and resp_nic_events (time when the network card sends the response for server side) mentioned in your second question. If there are missing events, the display will look like what you posted.
2. Why 'black_box_duration_ms' is bigger than 'total_duration_ms'? This could be a bug :). i'll take a look.
3. How to understand req_syscall_events and req_nic_events? This has been explained above.
4. Does req_syscall_events represent send syscall? For the server side, req_syscall_events corresponds to read syscall not the write syscall.
   @Robin3Chan

[hengyoush]

Could you please provide your OS environment (cat /etc/os-release) and the server-side application you are running? @Robin3Chan

[Robin3Chan]

Could you please provide your OS environment (cat /etc/os-release) and the server-side application you are running? @Robin3Chan

I'm running kyanos in a privileged k8s pod. The OS of k8s node is Rocky Linux 9.4 (Blue Onyx). The base docker image is Alpine.

$ cat /etc/os-release
NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.19.7
PRETTY_NAME="Alpine Linux v3.19"
HOME_URL="https://alpinelinux.org/"
BUG_REPORT_URL="https://gitlab.alpinelinux.org/alpine/aports/-/issues"

$ uname -a
Linux rocky14.1.106.76ic 5.14.0-427.31.1.el9_4.x86_64 #1 SMP PREEMPT_DYNAMIC Wed Aug 14 16:15:25 UTC 2024 x86_64 Linux

Server is a MySQL proxy. Btw, what's the meaning of black_box_duration_ms? Is it the same with 'process internal duration'? I found 'process internal duration' just sometimes appears when using 'kyanos watch', and it always bigger than 'total duration' in my env. @hengyoush

[hengyoush]

https://kyanos.io/watch.html

The meaning of black_box_duration_ms depends on the side of your application.