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Fix documentation and start parsing localities

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Signed-off-by: Miek Gieben <miek@miek.nl>
This commit is contained in:
Miek Gieben
2020-01-24 12:00:07 +01:00
parent 93eaaf3bad
commit eaa7f0d6eb
3 changed files with 66 additions and 38 deletions
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69
plugin/traffic/README.md
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@@ -9,7 +9,7 @@
The *traffic* plugin is a balancer that allows traffic steering, weighted responses
and draining of clusters. The cluster information is retrieved from a service
discovery manager that implements the service discovery protocols from Envoy
[implements](https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol). It connect to the
[implements](https://www.envoyproxy.io/docs/envoy/latest/api-docs/xds_protocol). It connects to the
manager using the Aggregated Discovery Service (ADS) protocol.
A Cluster in Envoy is defined as: "A group of logically similar endpoints that Envoy connects to."
@@ -48,7 +48,7 @@ traffic TO...
This enabled the *traffic* plugin, with a default node ID of `coredns` and no TLS.
* **TO...** are the control plane endpoints to connect to. These must start with `grpc://`. The
* **TO...** are the control plane endpoints to connect to. These must start with `grpc://`. The
port number defaults to 443, if not specified.
The extended syntax is available if you want more control.
@@ -56,33 +56,44 @@ The extended syntax is available if you want more control.
~~~
traffic TO... {
node ID
locality REGION,ZONE,SUBZONE [REGION,ZONE,SUBZONE]...
locality REGION[,ZONE[,SUBZONE]] [REGION[,ZONE[,SUBZONE]]]...
tls CERT KEY CA
tls_servername NAME
ignore_health
}
~~~
* `node` **ID** is how *traffic* identifies itself to the control plane. This defaults to `coredns`.
* `locality` has a list of **REGION,ZONE,SUBZONE**s. These tell *traffic* where its running and what should be
considered local traffic. Each **REGION,ZONE,SUBZONE** will be used to match clusters again while generating
responses. The list should descend in proximity. A `*` describes a wild card match. I.e. when
there are 3 regions, US, EU, ASIA, and this CoreDNS is running in EU, you can use:
`locality EU,*,* US,*,*, ASIA,*,*`. Only when the cluster's locality isn't UNKNOWN will this
matching happen.
* `tls` **CERT** **KEY** **CA** define the TLS properties for gRPC connection. If this is omitted an
insecure connection is attempted. From 0 to 3 arguments can be provided with the meaning as described below
* `node` **ID** is how *traffic* identifies itself to the control plane. This defaults to
`coredns`.
* `tls` - no client authentication is used, and the system CAs are used to verify the server certificate
* `tls` **CA** - no client authentication is used, and the file CA is used to verify the server certificate
* `tls` **CERT** **KEY** - client authentication is used with the specified cert/key pair.
The server certificate is verified with the system CAs.
* `tls` **CERT** **KEY** **CA** - client authentication is used with the specified cert/key pair.
The server certificate is verified using the specified CA file.
* `locality` has a list of **REGION,ZONE,SUBZONE** sets. These tell *traffic* where its running
and what should be considered local traffic. Each **REGION,ZONE,SUBZONE** set will be used
to match clusters against while generating responses. The list should descend in proximity.
**ZONE** or **ZONE** *and* **SUBZONE** may be omitted. This signifies a wild card match.
I.e. when there are 3 regions, US, EU, ASIA, and this CoreDNS is running in EU, you can use:
`locality EU US ASIA`. Each list must be separated using spaces. The elements within a set
should be separated with only a comma.
* `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.
* `tls` **CERT** **KEY** **CA** define the TLS properties for gRPC connection. If this is omitted
an insecure connection is attempted. From 0 to 3 arguments can be provided with the meaning as
described below
- `tls` - no client authentication is used, and the system CAs are used to verify the server
certificate
- `tls` **CA** - no client authentication is used, and the file CA is used to verify the
server certificate
- `tls` **CERT** **KEY** - client authentication is used with the specified cert/key pair. The
server certificate is verified with the system CAs.
- `tls` **CERT** **KEY** **CA** - client authentication is used with the specified cert/key
pair. The server certificate is verified using the specified CA file.
* `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
@@ -99,27 +110,29 @@ is used in the configuration.
## Matching Algorithm
How are clients match against the data we receive from xDS endpoint? Ignoring `locality` for now,
it will go through the following steps:
How are clients match against the data we receive from xDS endpoint? Ignoring `locality` for now, it
will go through the following steps:
1. Does the cluster exist? If not return NXDOMAIN, otherwise continue.
2. Run through the endpoints, discard any endpoints that are not HEALTHY. If we are left with no
endpoint return a NODATA response, otherwise continue.
3. If weights are assigned use those to pick an endpoint, otherwise randomly pick one and return a
response to the client.
If `locality` *has* been specified there is an extra step between 2 and 3.
2a. Match the endpoints using the locality that groups several of them, it's the most specific match
from left to right in the `locality` list; if no **REGION,ZONE,SUBZONE** matches then try
**REGION,ZONE** and then **REGION**. If still not match, move on the to next one. If we found
none, we continue with step 4 above, ignoring any locality.
2a. Match the endpoints using the locality that groups several of them, it's the most specific
match from left to right in the `locality` list; if no **REGION,ZONE,SUBZONE** matches then try
**REGION,ZONE** and then **REGION**. If still not match, move on the to next one. If we found none,
we continue with step 4 above, ignoring any locality.
## Metrics
If monitoring is enabled (via the *prometheus* plugin) then the following metric are exported:
* `coredns_traffic_clusters_tracked{}` the number of tracked clusters.
* `coredns_traffic_clusters_tracked{}` the number of tracked clusters.
## Ready

7
plugin/traffic/setup.go
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@@ -124,3 +124,10 @@ func parseTraffic(c *caddy.Controller) (*Traffic, error) {
return t, nil
}
// parseLoc parses string s into loc's. Each loc must be space separated from the other, inside
// a loc we have region,zone,subzone, where subzone or subzone and zone maybe empty. If specified
// they must be comma separate (not spaces or anything).
func parseLoc(s string) ([]loc, error) {
return nil, nil
}

8
plugin/traffic/traffic.go
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@@ -21,6 +21,7 @@ type Traffic struct {
id string
health bool
origins []string
locality []loc
Next plugin.Handler
}
@@ -181,3 +182,10 @@ func soa(z string) []dns.RR {
// Name implements the plugin.Handler interface.
func (t *Traffic) Name() string { return "traffic" }
// loc holds the locality for this server. It a list of the set region, zone, subzone.
type loc struct {
region string
zone string
subzone string
}