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main: Add support for "glog style" timestamps

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Add support for formatting logs following the popular glog crate style.
In particular this can use local or UTC time along with a single
character level.

As an implementation detail of that implement finegrained date time log
outputs including both local and UTC variants.

Signed-off-by: Rob Bradford <rbradford@meta.com>
Assisted-by: Claude:Opus-4.6
This commit is contained in:
Rob Bradford
2026-05-21 16:53:02 +01:00
committed by Bo Chen
parent 1924153185
commit e0c68dbfaa
3 changed files with 322 additions and 4 deletions
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58
docs/logging.md
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@@ -40,3 +40,61 @@ This level is for the benefit of developers. It should be used for sporadic and
Use `-vv` to enable.
For the most verbose of logging messages. It is acceptable to "spam" the log with repeated invocations of the same message. This level of logging would be combined with `--log-file`.
## Format
The `--log-format <FORMAT>` flag controls how each log record is rendered.
`<FORMAT>` is a template string where tokens enclosed in `{...}` are substituted
at log time. Literal `{` and `}` can be escaped as `{{` and `}}`.
The default format is:
```text
cloud-hypervisor: {boottime}s: <{thread}> {level}:{location} -- {msg}
```
### Common tokens
| Token | Substituted with |
|---------------|---------------------------------------------------------------|
| `{boottime}` | Seconds since process start (6 decimal places, right-aligned).|
| `{wallclock}` | UTC RFC 3339 (e.g. `2024-01-15T10:30:45.123456Z`). |
| `{glog}` | UTC glog timestamp `MMDD HH:MM:SS.uuuuuu`. |
| `{localglog}` | Local-time glog timestamp, same shape as `{glog}`. |
| `{thread}` | Thread name (`anonymous` if unnamed). |
| `{level}` | Log level word (`ERROR`/`WARN`/`INFO`/`DEBUG`/`TRACE`). |
| `{levelchar}` | Single-letter glog level: `E`/`W`/`I`/`D`/`T`. |
| `{location}` | `file:line`, or the `log` target if unavailable. |
| `{msg}` | Formatted log message. |
| `{pid}` | Process ID. |
| `{tid}` | Kernel thread ID (`gettid(2)`). |
### Broken-down date/time fields
Each UTC field has a `local`-prefixed variant that uses the system timezone.
All wallclock-derived tokens within a single record refer to the same instant.
| UTC | Local | Output |
|-------------|------------------|---------------------------------------|
| `{year}` | `{localyear}` | 4-digit year. |
| `{month}` | `{localmonth}` | 2-digit month. |
| `{day}` | `{localday}` | 2-digit day of month. |
| `{hour}` | `{localhour}` | 2-digit hour (24h). |
| `{minute}` | `{localminute}` | 2-digit minute. |
| `{second}` | `{localsecond}` | 2-digit second. |
| `{micros}` | `{localmicros}` | 6-digit microseconds. |
| `{offset}` | `{localoffset}` | Timezone offset (`+00:00` for UTC). |
### Examples
Glog header `I0521 08:02:15.542701`:
```text
--log-format '{levelchar}{localglog}'
```
Or built from individual fields:
```text
--log-format '{levelchar}{localmonth}{localday} {localhour}:{localminute}:{localsecond}.{localmicros}'
```