# Istio Agent

This document describes the internal architecture of Istio agent.

## High Level overview

![High Level overview](docs/overview.svg)

At a high level, the Istio agent acts as an intermediate proxy between Istiod and Envoy. This is done
at two levels. For distributing workload certificates, Envoy will send [SDS](https://www.envoyproxy.io/docs/envoy/latest/configuration/security/secret)

import "k8s.io/apimachinery/pkg/runtime/schema/generated.proto";

// Package-wide variables from generator "generated".
option go_package = "k8s.io/api/certificates/v1beta1";

// Describes a certificate signing request
message CertificateSigningRequest {
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

// Package-wide variables from generator "generated".
option go_package = "k8s.io/api/storage/v1alpha1";

// CSIStorageCapacity stores the result of one CSI GetCapacity call.
// For a given StorageClass, this describes the available capacity in a
// particular topology segment.  This can be used when considering where to
// instantiate new PersistentVolumes.
//
// For example this can express things like:

Concurrency
===========

This document describes the concurrency considerations for http/2 connections and the connection pool within OkHttp.

## HTTP/2 Connections

The HttpURLConnection API is a blocking API. You make a blocking write to send a request, and a blocking read to receive the response.

#### Blocking APIs

const ConsoleLoggerTgt = "console+http"

// ExitFunc is called by Fatal() class functions, by default it calls os.Exit()
var ExitFunc = os.Exit

// Logger interface describes the methods that need to be implemented to satisfy the interface requirements.
type Logger interface {
	json(msg string, args ...interface{})
	quiet(msg string, args ...interface{})
	pretty(msg string, args ...interface{})
}

// This is a subresource of Pod.  A request to cause such an eviction is
// created by POSTing to .../pods/<pod name>/evictions.
message Eviction {
  // ObjectMeta describes the pod that is being evicted.
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // DeleteOptions may be provided
  // +optional

In versions of FastAPI before 0.99.0 (0.99.0 and above use the newer OpenAPI 3.1.0) when you used `example` or `examples` with any of the other utilities (`Query()`, `Body()`, etc.) those examples were not added to the JSON Schema that describes that data (not even to OpenAPI's own version of JSON Schema), they were added directly to the *path operation* declaration in OpenAPI (outside the parts of OpenAPI that use JSON Schema).

  }

  fun retryAfterFailure(): Boolean {
    return exchange?.hasFailure == true &&
      exchangeFinder!!.routePlanner.hasNext(exchange?.connection)
  }

  /**
   * Returns a string that describes this call. Doesn't include a full URL as that might contain
   * sensitive information.
   */
  private fun toLoggableString(): String {
    return (
      (if (isCanceled()) "canceled " else "") +

  //   must be a BER-encoded ASN.1 Certificate structure as described in section 4 of RFC5280.
  //  3. Non-PEM content may appear before or after the "CERTIFICATE" PEM blocks and is unvalidated,
  //   to allow for explanatory text as described in section 5.2 of RFC7468.
  //
  // If more than one PEM block is present, and the definition of the requested spec.signerName

	}
}

// minioCollector is the Custom Collector
type minioCollector struct {
	desc *prometheus.Desc
}

// Describe sends the super-set of all possible descriptors of metrics
func (c *minioCollector) Describe(ch chan<- *prometheus.Desc) {
	ch <- c.desc
}

// Collect is called by the Prometheus registry when collecting metrics.