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Add DTR health check explanations

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Huu Nguyen 2017-02-16 13:26:35 -08:00 committed by Joao Fernandes
parent 30faaa3f55
commit 86baab300d
1 changed files with 33 additions and 5 deletions
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38
datacenter/dtr/2.2/guides/admin/configure/use-a-load-balancer.md
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@ -4,8 +4,9 @@ description: Learn how to configure a load balancer to balance user requests acr
keywords: docker, dtr, load balancer
---
Once you’ve joined multiple DTR replicas nodes for high-availability, you can
configure your own load balancer to balance user requests across all replicas.
Once you’ve joined multiple DTR replicas nodes for
[high-availability](set-up-high-availability.md), you can configure your own
load balancer to balance user requests across all replicas.
![](../../images/use-a-load-balancer-1.svg)
@ -23,9 +24,36 @@ Make sure you configure your load balancer to:
* Load balance TCP traffic on ports 80 and 443
* Not terminate HTTPS connections
* Use the `/health` endpoint on each DTR replica, to check if
the replica is healthy and if it should remain on the load balancing pool or
not
* Use the `/health` endpoint (note the lack of an `/api/v0/` in the path) on each
DTR replica, to check if the replica is healthy and if it should remain on the
load balancing pool or not
## Health check endpoints
The `/health` endpoint returns a JSON object for the replica being queried with
`"Healthy"` as one of the keys. Any response other than a 200 HTTP status code
and `"Healthy":true` means the replica is unsuitable for taking requests. If
the API server is still up, the returned JSON object will have an `"Error"` key
with more details. More specifically, these issues can be in any of these
services:
* Storage container (registry)
* Authorization (garant)
* Metadata persistence (rethinkdb)
* Content trust (notary)
Note that this endpoint is for checking the health of a *single* replica. To get
the health of every replica in a cluster, querying each individual replica is
the preferred way to do it in real time.
The `/api/v0/meta/cluster_status` endpoint returns a JSON object for the entire
cluster *as observed* by the replica being queried. Health status for the
replicas is available in the `"replica_health"` key. These statuses are taken
from a cache which is updated by each replica individually.
In addition, this endpoint returns a dump of the rethink system tables
which can be rather large (~45 KB) for a status endpoint.
## Where to go next