Mixer FAQ

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.

Configuration for instances, handlers, and rules is stored as Kubernetes Custom Resources¹. Configuration may be accessed by using kubectl to query the Kubernetes API server for the resources.

Rules

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

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

Output for 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

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

Output for 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

Please see the Expression Language Reference² for the full set of supported attribute expressions.

Mixer exposes a monitoring endpoint (default port: 15014). There are a few useful paths to investigate Mixer performance and audit function:

• /metrics provides Prometheus metrics on the Mixer process as well as gRPC metrics related to API calls and metrics on adapter dispatch.
• /debug/pprof provides an endpoint for profiling data in pprof format³.
• /debug/vars provides an endpoint exposing server metrics in JSON format.

Mixer logs can be accessed via a kubectl logs command, as follows:

• For the istio-policy service:

$ kubectl -n istio-system logs -l app=policy -c mixer

• For the istio-telemetry service:

$ kubectl -n istio-system logs -l app=telemetry -c mixer

Mixer trace generation is controlled by command-line flags: trace_zipkin_url, trace_jaeger_url, and trace_log_spans. If 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.

Learn how to implement a new adapter for Mixer by consulting the Adapter Developer’s Guide⁴.

Mixer rules must be valid to be applied at runtime. That means the match conditions are well-defined expressions in the language², the attributes are declared in an attribute manifest⁷, 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 request.headers and 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".