Loki not alerting Alertmanager 404 not found是什么意思

The config looks good, similar as mine. I would troubleshoot it with following steps:

1. Exec to docker container and check if the rules file is not empty cat /etc/loki/rules/rules.yaml

2. Check the logs of loki. When rules are loaded properly logs like this will pop up:

level=info ts=2021-05-06T11:18:33.355446729Z caller=module_service.go:58 msg=initialising module=ruler
level=info ts=2021-05-06T11:18:33.355538059Z caller=ruler.go:400 msg="ruler up and running"
level=info ts=2021-05-06T11:18:33.356584674Z caller=mapper.go:139 msg="updating rule file" file=/data/loki/loki-stack-alerting-rules.yaml

3. During runtime loki also logs info messages about your rule (I will show you the one I am running, but slightly shortened)(notice status=200 and non-empty bytes=...):

level=info 
ts=... 
caller=metrics.go:83 
org_id=... 
traceID=... 
latency=fast 
query="sum(rate({component=\"kube-apiserver\"} |~ \"stderr F E.*failed calling webhook \\\"webhook.openpolicyagent.org\\\". an error on the server.*has prevented the request from succeeding\"[1m])) > 1" 
query_type=metric 
range_type=instant 
length=0s 
step=0s 
duration=9.028961ms 
status=200 
throughput=40MB 
total_bytes=365kB

4. Then make sure you can access alertmanager http://171.11.3.160:9093 from loki container without any issues (there can be a networking problem or you have set up basic authentication, etc.).

5. If the rule you set up (which you can test from grafana explore window) will exceed the threshold you set for 1 minute the alert should show up in alertmanager. It will be most likely ungrouped as you didn't add any labels to it.