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Implement debugging with TXT records

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Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben
2020-03-06 09:13:27 +01:00
parent deb582259a
commit b00ff13ca0
6 changed files with 64 additions and 38 deletions
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18
plugin/traffic/README.md
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@@ -27,13 +27,21 @@ the *management cluster* (see `cluster` below in "Syntax"). By default the name
When bootstrapping *traffic* tries to retrieve the cluster endpoints for the management cluster,
when the cluster is not found *traffic* will return a fatal error.
The *traffic* plugin handles A, AAAA and SRV queries. Queries for non-existent clusters get a
NXDOMAIN, where the minimal TTL is also set to 5s.
The *traffic* plugin handles A, AAAA, SRV and TXT queries. TXT queries are purely used for debugging
as health status of the endpoints is ignored in that case.
Queries for non-existent clusters get a NXDOMAIN, where the minimal TTL is also set to 5s.
For A and AAAA queries each DNS response contains a single IP address that's considered the best
one. The TTL on these answer is set to 5s. It will only return successful responses either with an
answer or, otherwise, a NODATA response.
TXT replies will use the SRV record format augmented with the health status of each backend, as this
is useful for debugging.
~~~
web.lb.example.org. 5 IN TXT "100" "100" "18008" "endpoint-0.web.lb.example.org." "HEALTHY"
~~~
For SRV queries *all* healthy backends will be returned - assuming the client doing the query
is smart enough to select the best one. When SRV records are returned, the endpoint DNS names
are synthesized `endpoint-<N>.<cluster>.<zone>` that carries the IP address. Querying for these
@@ -55,8 +63,7 @@ traffic TO...
This enabled the *traffic* plugin, with a default node ID of `coredns` and no TLS.
* **TO...** are the control plane endpoints to bootstrap from. These must start with `grpc://`. The
port number defaults to 443, if not specified. These endpoint will be tried in the order given.
First successful connection will be used to resolve the management cluster `xds`.
port number defaults to 443, if not specified. These endpoints will be tried in the order given.
The extended syntax is available if you want more control.
@@ -66,7 +73,6 @@ traffic TO... {
id ID
tls CERT KEY CA
tls_servername NAME
ignore_health
}
~~~
@@ -93,8 +99,6 @@ traffic TO... {
* `tls_servername` **NAME** allows you to set a server name in the TLS configuration. This is
needed because *traffic* connects to an IP address, so it can't infer the server name from it.
* `ignore_health` can be enabled to ignore endpoint health status, this can aid in debugging.
## Naming Clusters
When a cluster is named this usually consists out of a single word, i.e. "cluster-v0", or "web".