With this PR, liveness check responds with 200 OK with "server-not-
initialized" header while objectLayer gets initialized. The header
is removed as objectLayer is initialized. This is to allow
MinIO distributed cluster to get started when running on an
orchestration platforms like Docker Swarm.
This PR also updates sample Swarm yaml files to use correct values
for healthcheck fields.
Fixes#8140
Health checking programs very frequently use /minio/health/live
to check health, hence we can avoid doing StorageInfo() and
ListBuckets() for FS/Erasure backend.
It was expected that in gateway mode, we do not know
the backend types whereas in NAS gateway since its
an extension of FS mode (standalone) this leads to
an issue in LivenessCheckHandler() which would perpetually
return 503, this would affect all kubernetes, openshift
deployments of NAS gateway.
Healthcheck handler in current implementation was
performing ListBuckets() to check for liveness of Minio
service. ListBuckets() implementation on the other hand
doesn't do quorum based listing and if one of the disks
returned error, an I/O error it would be lead to kubernetes
taking the minio pod down prematurely even if the disk
is not local to that minio server.
The reason is ListBuckets() call cannot be trusted to
provide us the valid information that we need, Minio is a
clustered application which is designed to handle disk
failures. Error on one of the disks doesn't mean the pod
should become fully non-operational.
This PR attempts to fix this by only checking for alive
disks which are local to each setup and also by simply
performing a Stat() operation, if the Stat() returned
error on all disks local to a particular server then
we can let kubernetes safely take it down, until then
we should be operational.
This PR adds readiness and liveness endpoints to probe Minio server
instance health. Endpoints can only be accessed without authentication
and the paths are /minio/health/live and /minio/health/ready for
liveness and readiness respectively.
The new healthcheck liveness endpoint is used for Docker healthcheck
now.
Fixes#5357Fixes#5514
