Add sysinfo journalctl action to Sansshell

[sfc-gh-pchu]

Description

Add journalctl action to Sansshell to read messages from journald

• input time for since and until should follow the same pattern as "YYYY-MM-DD HH:MM:SS", and in local timezone based on where the sanssh client is run
• the output timestamp is also in local timezone where the sanssh client is run

Note

Sansshell server will fetch the journal entries through package: github.com/coreos/go-systemd/v22 which will call systemd C API through cgo. So in order to successfully run build, pre-commit and golangci-lint. Below command need to be run to install systemd development package.

// for linux systems with apt package manager
sudo apt-get install -y libsystemd-dev
// for linux systems with yum package manager
sudo yum install systemd-devel

Usage

journalCtl [--since|--S=X] [--until|-U=X] [-tail=X] [-u|-unit=X] [-o|--output=X] [-x] :
        Get the log entries stored in journald by systemd-journald.service 
  -S string
        Sets the date (YYYY-MM-DD HH:MM:SS) we want to filter from (the date time is included)
  -U string
        Sets the date (YYYY-MM-DD HH:MM:SS) we want to filter until
  -output string
        Sets the format of the journal entries that will be shown. Right now only json and json-pretty are supported.
  -since string
        Sets the date (YYYY-MM-DD HH:MM:SS) we want to filter from
  -tail int
        If positive, the latest n records to fetch. By default, fetch latest 100 records. If negative, fetch all records (default 100)
  -unit string
        Sets systemd unit to filter messages
  -until string
        Sets the date (YYYY-MM-DD HH:MM:SS) we want to filter until (the date time is not included)
  -x    If true, augment log lines with explanatory texts from the message catalog.

Example

./sanssh --targets=localhost sysinfo journalctl -tail 5 -x
[2023-07-28 02:09:00.038149 +0000 UTC]  SDP_DevVM-pchu python3[1504]: Jul 28 02:09:00 1504 INFO] Sleeping
[2023-07-28 02:10:00.086197 +0000 UTC]  SDP_DevVM-pchu python3[1504]: Jul 28 02:10:00 1504 INFO] Sleeping
[2023-07-28 02:10:01.4509 +0000 UTC]  SDP_DevVM-pchu systemd[1]: Started Session 2968 of user root.
-- Subject: Unit session-2968.scope has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
-- 
-- Unit session-2968.scope has finished starting up.
-- 
-- The start-up result is done.
[2023-07-28 02:10:01.45659 +0000 UTC]  SDP_DevVM-pchu CROND[29297]: (root) CMD (/usr/lib64/sa/sa1 1 1)
[2023-07-28 02:11:00.080698 +0000 UTC]  SDP_DevVM-pchu python3[1504]: Jul 28 02:11:00 1504 INFO] Sleeping

[sfc-gh-srhodes]

Hmm, is this the first C library we're using? What happens if you try to cross-compile across architectures or compile for linux from macos?

[sfc-gh-pchu]

Yes, I think it is the first time we are using C library. Crossing compile linux from macos through GOOS=linux will always show this error message: pchu@XGX9120JFR sansshell-server % GOOS=linux go build . github.com/coreos/go-systemd/v22/internal/dlopen: build constraints exclude all Go files in /XXXXX/go/pkg/mod/github.com/coreos/go-systemd/[email protected]/internal/dlopen

And in devVM(linux env), if we directly compile it, another error will come out: # github.com/coreos/go-systemd/v22/sdjournal /Users/pchu/go/pkg/mod/github.com/coreos/go-systemd/[email protected]/sdjournal/journal.go:27:11: fatal error: 'systemd/sd-journal.h' file not found #include <systemd/sd-journal.h> ^~~~~~~~~~~~~~~~~~~~~~ 1 error generated.
It is easy to reproduce, here is the previous merge-gate failure: https://github.com/Snowflake-Labs/sansshell/actions/runs/5694246008.

The reason is that Go compiler is unable to find the systemd/sd-journal.h file while trying to compile the github.com/coreos/go-systemd/v22/sdjournal package. This file is part of the systemd library, which provides an API for interacting with the systemd journal.

The resolution is to install the development package for systemd utility library like systemd-devel or libsystemd-dev.
Then building the project in linux system(container) won't have any issue.

But I don't have a chance to cross-compile across architecture, let me test it.

[sfc-gh-srhodes]

This is a pretty big bump in difficulty in compiling sansshell. I'm not convinced the benefits of this are worth the cost. We're jumping from "all you need is a go compiler if you're not touching protos" to "you need to install a non-default c library".

Is there no pure go api for this?

[sfc-gh-pchu]

I understand it increases the complexity in compiling sansshell when introducing C package. I import sdjournal for following reasons:

• it is the most popular golang systemd packages
• the data fields it has can greatly fit into our use case and easy to extend.

But let me think other workaround.

[sfc-gh-elinardi]

Closing this in favor of #293