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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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81
plugin/traffic/README.md
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@@ -9,7 +9,7 @@
The *traffic* plugin is a balancer that allows traffic steering, weighted responses The *traffic* plugin is a balancer that allows traffic steering, weighted responses
and draining of clusters. The cluster information is retrieved from a service and draining of clusters. The cluster information is retrieved from a service
discovery manager that implements the service discovery protocols from Envoy 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. 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." A Cluster in Envoy is defined as: "A group of logically similar endpoints that Envoy connects to."
@@ -48,41 +48,52 @@ traffic TO...
This enabled the *traffic* plugin, with a default node ID of `coredns` and no TLS. 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. port number defaults to 443, if not specified.
The extended syntax is available if you want more control. The extended syntax is available if you want more control.
~~~ ~~~
traffic TO... { traffic TO... {
node ID node ID
locality REGION,ZONE,SUBZONE [REGION,ZONE,SUBZONE]... locality REGION[,ZONE[,SUBZONE]] [REGION[,ZONE[,SUBZONE]]]...
tls CERT KEY CA tls CERT KEY CA
tls_servername NAME tls_servername NAME
ignore_health ignore_health
} }
~~~ ~~~
* `node` **ID** is how *traffic* identifies itself to the control plane. This defaults to `coredns`. * `node` **ID** is how *traffic* identifies itself to the control plane. This defaults to
* `locality` has a list of **REGION,ZONE,SUBZONE**s. These tell *traffic* where its running and what should be `coredns`.
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
* `tls` - no client authentication is used, and the system CAs are used to verify the server certificate * `locality` has a list of **REGION,ZONE,SUBZONE** sets. These tell *traffic* where its running
* `tls` **CA** - no client authentication is used, and the file CA is used to verify the server certificate and what should be considered local traffic. Each **REGION,ZONE,SUBZONE** set will be used
* `tls` **CERT** **KEY** - client authentication is used with the specified cert/key pair. to match clusters against while generating responses. The list should descend in proximity.
The server certificate is verified with the system CAs. **ZONE** or **ZONE** *and* **SUBZONE** may be omitted. This signifies a wild card match.
* `tls` **CERT** **KEY** **CA** - client authentication is used with the specified cert/key pair. I.e. when there are 3 regions, US, EU, ASIA, and this CoreDNS is running in EU, you can use:
The server certificate is verified using the specified CA file. `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 * `tls` **CERT** **KEY** **CA** define the TLS properties for gRPC connection. If this is omitted
because *traffic* connects to an IP address, so it can't infer the server name from it. an insecure connection is attempted. From 0 to 3 arguments can be provided with the meaning as
* `ignore_health` can be enabled to ignore endpoint health status, this can aid in debugging. 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 ## Naming Clusters
@@ -99,27 +110,29 @@ is used in the configuration.
## Matching Algorithm ## Matching Algorithm
How are clients match against the data we receive from xDS endpoint? Ignoring `locality` for now, How are clients match against the data we receive from xDS endpoint? Ignoring `locality` for now, it
it will go through the following steps: will go through the following steps:
1. Does the cluster exist? If not return NXDOMAIN, otherwise continue. 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. 2. Run through the endpoints, discard any endpoints that are not HEALTHY. If we are left with no
3. If weights are assigned use those to pick an endpoint, otherwise randomly pick one and return a endpoint return a NODATA response, otherwise continue.
response to the client.
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. 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 2a. Match the endpoints using the locality that groups several of them, it's the most specific
from left to right in the `locality` list; if no **REGION,ZONE,SUBZONE** matches then try 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 **REGION,ZONE** and then **REGION**. If still not match, move on the to next one. If we found none,
none, we continue with step 4 above, ignoring any locality. we continue with step 4 above, ignoring any locality.
## Metrics ## Metrics
If monitoring is enabled (via the *prometheus* plugin) then the following metric are exported: 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 ## Ready

7
plugin/traffic/setup.go
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@@ -124,3 +124,10 @@ func parseTraffic(c *caddy.Controller) (*Traffic, error) {
return t, nil 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
}

16
plugin/traffic/traffic.go
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@@ -17,10 +17,11 @@ import (
// Traffic is a plugin that load balances according to assignments. // Traffic is a plugin that load balances according to assignments.
type Traffic struct { type Traffic struct {
c *xds.Client c *xds.Client
id string id string
health bool health bool
origins []string origins []string
locality []loc
Next plugin.Handler Next plugin.Handler
} }
@@ -181,3 +182,10 @@ func soa(z string) []dns.RR {
// Name implements the plugin.Handler interface. // Name implements the plugin.Handler interface.
func (t *Traffic) Name() string { return "traffic" } 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
}