# 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)

                    // The result would be something like DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'" \"-javaagent:$APP_HOME/lib/agents/foobar.jar\""
                    line + getAgentOptions("\$APP_HOME").joinToString(separator = " ", prefix = "\" ", postfix = "\"") {
                        // Wrap the agent switch in double quotes, as the expanded APP_HOME may contain spaces.

    // US region agents have name "EC2-XXX"
    doesNotContain("teamcity.agent.name", "EC2")
}

/**
 * We have some "shared" host where a Linux build agent and a Windows build agent
 * both run on the same bare metal. Some builds require exclusive access to the
 * hardware resources (e.g. performance test).
 */
fun Requirements.requiresNotSharedHost() {
    doesNotContain("agent.host.type", "shared")
}

import vcsroots.useAbsoluteVcs

object WarmupEc2Agent : BuildType({
    name = "Warmup EC2 Agent"
    id("Util_WarmupEc2Agent")

    vcs.useAbsoluteVcs(VersionedSettingsBranch.fromDslContext().vcsRootId())

    features {
        freeDiskSpace {
            // Lower the limit such that the agent work directories aren't cleaned during the AMI baking process
            requiredSpace = "100mb"
        }
    }

Envoy Version:       0.0.0

NAME                                                                SERVICE FQDN                          PORT     SUBSET     DIRECTION       TYPE       DESTINATION RULE
cluster/agent                                                       cluster/agent                         -        -          -               STATIC     

    assertThat(response.request.header("User-Agent")).isNotNull()
    assertThat(response.request.header("User-Agent")).isEqualTo("user request")
    assertThat(response.networkResponse!!.request.header("User-Agent")).isEqualTo(
      "intercepted request",
    )
  }

  @Test
  fun applicationInterceptorThrowsRuntimeExceptionAsynchronous() {
    interceptorThrowsRuntimeExceptionAsynchronous(false)
  }

import org.junit.jupiter.api.Test

class RequestTest {
  @Test
  fun constructor() {
    val url = "https://example.com/".toHttpUrl()
    val body = "hello".toRequestBody()
    val headers = headersOf("User-Agent", "RequestTest")
    val method = "PUT"
    val request =
      Request(
        url = url,
        headers = headers,
        method = method,
        body = body,
      )

val gradlePromotionBranches = "Gradle_GradlePromoteBranches"

fun VcsSettings.useAbsoluteVcs(absoluteId: String) {
    root(AbsoluteId(absoluteId))

    checkoutMode = CheckoutMode.ON_AGENT
    this.cleanCheckout = cleanCheckout
    showDependenciesChanges = true

Aber eine Variable wie `user-agent` ist in Python nicht gültig.

Darum wird `Header` standardmäßig in Parameternamen den Unterstrich (`_`) zu einem Bindestrich (`-`) konvertieren.

HTTP-Header sind außerdem unabhängig von Groß-/Kleinschreibung, darum können Sie sie mittels der Standard-Python-Schreibweise deklarieren (auch bekannt als "snake_case").

) {
    init {
        id("Promotion_SnapshotFromQuickFeedbackStepPromote")
        name = "Nightly Snapshot (from QuickFeedback) - Promote"
        description = "Promotes a previously built distribution on this agent on '${branch.branchName}' from Quick Feedback as a new nightly snapshot. This build checks out gradle-promote, so don't be misled by the 'master' branch."

        steps {
            buildStep(