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memlogd: use kmsg format for reading the logs

Browse Source 
Switch to a more formally-specified `kmsg`-style format for reading
the logs.

- update the spec in docs/logging.md
- check for bad names in pkg/memlogd with unit test

Signed-off-by: David Scott <dave.scott@docker.com>
This commit is contained in:
David Scott
2018-07-05 14:24:37 +01:00
parent fe64f33430
commit a07ecf60d5
3 changed files with 131 additions and 43 deletions
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54
docs/logging.md
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@@ -42,32 +42,40 @@ network service, a service should be added to the yaml which connects to
`memlogd` and streams the logs. The example program `logread` in the `memlogd`
package demonstrates how to do this.
Usage examples:
### Message format
The format used to read logs is similar to [kmsg](https://www.kernel.org/doc/Documentation/ABI/testing/dev-kmsg):
```
<timestamp>,<log>;<body>
```
where `<timestamp>` is an RFC3339-formatted timestamp, `<log>` is the name of
the log (e.g. `docker-ce.out`) and `<body>` is the output. The `<log>` must
not contain the character `;`.
### Usage examples
```
/ # logread -f
2017-04-15T15:37:37Z memlogd memlogd started
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: waiting for carrier
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: carrier acquired
2017-04-15T15:37:37Z 002-dhcpcd.stdout DUID 00:01:00:01:20:84:fa:c1:02:50:00:00:00:24
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: IAID 00:00:00:24
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding address fe80::84e3:ca52:2590:fe80
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: soliciting an IPv6 router
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: soliciting a DHCP lease
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: offered 192.168.65.37 from 192.168.65.1 `vpnkit'
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: leased 192.168.65.37 for 7199 seconds
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding route to 192.168.65.0/24
2017-04-15T15:37:37Z 002-dhcpcd.stdout eth0: adding default route via 192.168.65.1
2017-04-15T15:37:37Z 002-dhcpcd.stdout exiting due to oneshot
2017-04-15T15:37:37Z 002-dhcpcd.stdout dhcpcd exited
2017-04-15T15:37:37Z rngd.stderr Unable to open file: /dev/tpm0
2018-07-05T13:22:32Z,memlogd;memlogd started
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: waiting for carrier
2018-07-05T13:22:32Z,onboot.001-dhcpcd.err;eth0: could not detect a useable init
system
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: carrier acquired
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;DUID 00:01:00:01:22:d0:d8:18:02:50:00:00:00:02
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: IAID 00:00:00:02
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding address fe80::d33a:3936:
2ee4:5c8c
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: soliciting an IPv6 router
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: soliciting a DHCP lease
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: offered 192.168.65.4 from 192.1
68.65.1 `vpnkit'
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: leased 192.168.65.4 for 7200 se
conds
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding route to 192.168.65.0/24
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;eth0: adding default route via 192.16
8.65.1
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;exiting due to oneshot
2018-07-05T13:22:32Z,onboot.001-dhcpcd.out;dhcpcd exited
^C
/ # logwrite echo testing123
testing123
/ # logread | tail -n1
2017-04-15T15:37:45Z echo.stdout testing123
/ # echo -en "GET / HTTP/1.0\n\n" | nc localhost 80 > /dev/null
/ # logread | grep nginx
2017-04-15T15:42:40Z nginx.stdout 127.0.0.1 - - [15/Apr/2017:15:42:40 +0000] "GET / HTTP/1.0" 200 612 "-" "-" "-"
```
Current issues and limitations: