Why does Istio need Mixer?
Mixer provides a rich intermediation layer between the Istio components as well as Istio-based services, and the infrastructure backends used to perform access control checks and telemetry capture. This layer enables operators to have rich insights and control over service behavior without requiring changes to service binaries.
Mixer is designed as a stand-alone component, distinct from Envoy. This has numerous benefits:
Scalability. The work that Mixer and Envoy do is very different in nature, leading to different scalability requirements. Keeping the components separate enables independent component-appropriate scaling.
Resource Usage. Istio depends on being able to deploy many instances of its proxy, making it important to minimize the cost of each individual instance. Moving Mixer’s complex logic into a distinct component makes it possible for Envoy to remain svelte and agile.
Reliability. Mixer and its open-ended extensibility model represents the most complex parts of the data path processing pipeline. By hosting this functionality in Mixer rather than Envoy, it creates distinct failure domains which enables Envoy to continue operating even if Mixer fails, preventing outages.
Isolation. Mixer provides a level of insulation between Istio and the infrastructure backends. Each Envoy instance can be configured to have a very narrow scope of interaction, limiting the impact of potential attacks.
Extensibility. It was imperative to design a simple extensibility model to allow Istio to interoperate with as widest breath of backends as possible. Due to its design and language choice, Mixer is inherently easier to extend than Envoy is. The separation of concerns also makes it possible to use Istio policy and telemetry processing with different proxies, just as a mix of Envoy and NGINX.
Envoy implements sophisticated caching, batching, and prefetching, to largely mitigate the latency impact of needing to interact with Mixer on the request path.
How do I see all Mixer's configuration?
Configuration for instances, handlers, and rules is stored as Kubernetes
Configuration may be accessed by using
kubectl to query the Kubernetes
API server for the resources.
To see the list of all rules, execute the following:
$ kubectl get rules --all-namespaces NAMESPACE NAME AGE istio-system kubeattrgenrulerule 20h istio-system promhttp 20h istio-system promtcp 20h istio-system stdiohttp 20h istio-system stdiotcp 20h istio-system tcpkubeattrgenrulerule 20h
To see an individual rule configuration, execute the following:
$ kubectl -n <namespace> get rules <name> -o yaml
Handlers are defined based on Kubernetes Custom Resource Definitions for adapters.
First, identify the list of adapter kinds:
$ kubectl get crd -listio=mixer-adapter NAME AGE adapters.config.istio.io 20h bypasses.config.istio.io 20h circonuses.config.istio.io 20h deniers.config.istio.io 20h fluentds.config.istio.io 20h kubernetesenvs.config.istio.io 20h listcheckers.config.istio.io 20h memquotas.config.istio.io 20h noops.config.istio.io 20h opas.config.istio.io 20h prometheuses.config.istio.io 20h rbacs.config.istio.io 20h servicecontrols.config.istio.io 20h signalfxs.config.istio.io 20h solarwindses.config.istio.io 20h stackdrivers.config.istio.io 20h statsds.config.istio.io 20h stdios.config.istio.io 20h
Then, for each adapter kind in that list, issue the following command:
$ kubectl get <adapter kind name> --all-namespaces
stdios will be similar to:
NAMESPACE NAME AGE istio-system handler 20h
To see an individual handler configuration, execute the following:
$ kubectl -n <namespace> get <adapter kind name> <name> -o yaml
Instances are defined according to Kubernetes Custom Resource Definitions for instances.
First, identify the list of instance kinds:
$ kubectl get crd -listio=mixer-instance NAME AGE apikeys.config.istio.io 20h authorizations.config.istio.io 20h checknothings.config.istio.io 20h edges.config.istio.io 20h instances.config.istio.io 20h kuberneteses.config.istio.io 20h listentries.config.istio.io 20h logentries.config.istio.io 20h metrics.config.istio.io 20h quotas.config.istio.io 20h reportnothings.config.istio.io 20h servicecontrolreports.config.istio.io 20h tracespans.config.istio.io 20h
Then, for each instance kind in that list, issue the following command:
$ kubectl get <instance kind name> --all-namespaces
metrics will be similar to:
NAMESPACE NAME AGE istio-system requestcount 20h istio-system requestduration 20h istio-system requestsize 20h istio-system responsesize 20h istio-system tcpbytereceived 20h istio-system tcpbytesent 20h
To see an individual instance configuration, execute the following:
$ kubectl -n <namespace> get <instance kind name> <name> -o yaml
What is the full set of attribute expressions Mixer supports?
Please see the Expression Language Reference for the full set of supported attribute expressions.
Does Mixer provide any self-monitoring?
Mixer exposes a monitoring endpoint (default port:
15014). There are a few
useful paths to investigate Mixer performance and audit
/metricsprovides Prometheus metrics on the Mixer process as well as gRPC metrics related to API calls and metrics on adapter dispatch.
/debug/pprofprovides an endpoint for profiling data in pprof format.
/debug/varsprovides an endpoint exposing server metrics in JSON format.
Mixer logs can be accessed via a
kubectl logs command, as follows:
- For the
$ kubectl -n istio-system logs -l app=policy -c mixer
- For the
$ kubectl -n istio-system logs -l app=telemetry -c mixer
Mixer trace generation is controlled by command-line flags:
any of those flag values are set, trace data will be written directly to those locations. If no tracing options are provided, Mixer
will not generate any application-level trace information.
How can I write a custom adapter for Mixer?
Learn how to implement a new adapter for Mixer by consulting the Adapter Developer’s Guide.
Why does my rule not match?
Mixer rules must be valid to be applied at runtime. That means the match conditions are well-defined expressions in the language, the attributes are declared in an attribute manifest, and rules have no dangling references to handlers and instances.
The attribute values are typically normalized before evaluating rules on
them. For example, HTTP headers have lowercase keys in
response.headers attributes. An expression
request.headers["X-Forwarded-Proto"] == "http" does not match any request
even though HTTP headers are case-insensitive. Instead, use an expression
request.headers["x-forwarded-proto"] == "http".