# 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)

    // 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")
}

  @Test fun ofMapAcceptsEmptyValue() {
    val headers = mapOf("User-Agent" to "").toHeaders()
    assertThat(headers.value(0)).isEqualTo("")
  }

  @Test fun ofMapTrimsKey() {
    val headers = mapOf(" User-Agent " to "OkHttp").toHeaders()
    assertThat(headers.name(0)).isEqualTo("User-Agent")
  }

  @Test fun ofMapTrimsValue() {
    val headers = mapOf("User-Agent" to " OkHttp ").toHeaders()

    }

    public void test_getUserAgentType_IE9() {
        getMockRequest().addHeader("user-agent", "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.0; Trident/5.0)");
        assertEquals(UserAgentType.IE, userAgentHelper.getUserAgentType());
    }

    public void test_getUserAgentType_IE10() {
        getMockRequest().addHeader("user-agent", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)");

      label: "What is the URL of the page with the issue?"
    validations:
      required: true
  - type: input
    id: user-agent
    attributes:
      label: "What is your user agent?"
      description: "You can find your user agent here: https://www.google.com/search?q=what+is+my+user+agent"
    validations:
      required: true
  - type: textarea
    id: screenshot
    attributes:
      label: "Screenshot"

    assertFailsWith<NullPointerException> {
      (mapOf("User-Agent" to null) as Map<String, String>).toHeaders()
    }
  }

  @Test fun toMultimapGroupsHeaders() {
    val headers =
      Headers.headersOf(
        "cache-control",
        "no-cache",
        "cache-control",
        "no-store",
        "user-agent",
        "OkHttp",
      )
    val headerMap = headers.toMultimap()

-Dorg.gradle.daemon.idletimeout=120000 -Dorg.gradle.daemon.registry.base=C:\\some\\agent\\workspace\\build\\daemon -Dorg.gradle.native.dir=C:\\some\\agent\\workspace\\intTestHomeDir\\worker-1\\native -Dorg.gradle.deprecation.trace=true -Djava.io.tmpdir=C:\\some\\agent\\workspace\\subprojects\\osgi\\build\\tmp -Dfile.encoding=windows-1252 -Dorg.gradle.classloaderscope.strict=true -ea -ea "-Dorg.gradle.appname=gradle" -classpath "C:\\some\\agent\\workspace\\subprojects\\osgi\\build\\integ test\\bin\\..\\lib\\gra...

// SecretItemDiff represents a secret that has been diffed between nodeagent and proxy
type SecretItemDiff struct {
	Agent string `json:"agent"`
	Proxy string `json:"proxy"`
	SecretItem
}

// SecretItem is an intermediate representation of secrets, used to provide a common
// format between the envoy proxy secrets and node agent output which can be diffed
type SecretItem struct {
	Name        string `json:"resource_name"`

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"
        }
    }

RELEASE_LDFLAGS='-extldflags -static -s -w'
endif

# List of all binaries to build
# We split the binaries into "agent" binaries and standard ones. This corresponds to build "agent".
# This allows conditional compilation to avoid pulling in costly dependencies to the agent, such as XDS and k8s.
AGENT_BINARIES:=./pilot/cmd/pilot-agent
STANDARD_BINARIES:=./istioctl/cmd/istioctl \
  ./pilot/cmd/pilot-discovery \
  ./pkg/test/echo/cmd/client \