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index.html.md.erb
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index.html.md.erb
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---
title: Cloud Foundry Components
---
<strong><%= modified_date %></strong>
Cloud Foundry components include a self-service application execution engine, an
automation engine for application deployment and lifecycle management, and a
scriptable command line interface (CLI), as well as integration with development
tools to ease deployment processes.
Cloud Foundry has an open architecture that includes a buildpack mechanism for
adding frameworks, an application services interface, and a cloud provider
interface.
Refer to the descriptions below for more information about Cloud Foundry
components.
Some descriptions include links to more detailed documentation.
## <a id='routing'></a>Routing
### <a id='router'></a>Router
The [router](./router.html) routes incoming traffic to the appropriate
component, either a Cloud Controller component or a hosted application running on a Diego Cell.
The router periodically queries the Diego Bulletin Board System (BBS) for which cells and containers each application is currently running on. Then it recomputes new routing tables based on the IP addresses of each cell virtual machine (VM) and the host-side port numbers for the cell's containers.
## <a id='authentication'></a>Authentication
### <a id='uaa'></a> OAuth2 Server (UAA) and Login Server
The OAuth2 server (the [UAA](./uaa.html)) and Login Server work together to
provide identity management.
## <a id='app-lifecycle'></a>App Lifecycle
### <a id='cc'></a> Cloud Controller and Diego Brain
The [Cloud Controller](./cloud-controller.html) (CC) directs the deployment of applications.
When a developer pushes an application to Cloud Foundry, she is targeting the
Cloud Controller. The Cloud Controller then directs the Diego Brain through the [CC-Bridge](../diego/diego-architecture.html#bridge-components) to coordinate individual [Diego cells](#diego-cell) to stage and run applications.
<%=vars.pre_diego_cc%>
The Cloud Controller also maintain records of [orgs, spaces, user roles](../roles.html), <%= vars.services_link %>, and more.
### <a id='nsync-bbs'></a> nsync, BBS, and Cell Reps
To keep applications available, cloud deployments must constantly monitor their states and reconcile them with their expected states, starting and stopping processes as required. In pre-Diego architecture, the [Health Manager (HM9000)](../diego/dea-vs-diego.html#hm9k) performed this function. The nsync, BBS, and Cell Reps use a more distributed approach.
The nsync, BBS, and Cell Rep components work together along a chain to keep apps running. At one end is the user. At the other end are the instances of applications running on widely-distributed VMs, which may crash or become unavailable.
Here is how the components work together:
* **nsync** receives a message from the Cloud Controller when the user scales an app. It writes the number of instances into a `DesiredLRP` structure in the Diego BBS database.
* **BBS** uses its convergence process to monitor the `DesiredLRP` and `ActualLRP` values. It launches or kills application instances as appropriate to ensure the `ActualLRP` count matches the `DesiredLRP` count.
* **Cell Rep** monitors the containers and provides the `ActualLRP` value.
## <a id='app-storage-execution'></a>App Storage and Execution
### <a id='blob'></a> Blobstore
The blobstore is a repository for large binary files, which Github cannot easily manage because Github is designed for code. Blobstore binaries include:
* Application code packages
* Buildpacks
* Droplets
You can configure the blobstore as either an internal server or an external S3 or S3-compatible endpoint. <%= vars.blobstore_kb %>
### <a id='diego-cell'></a> Diego Cell
Application instances, application tasks, and staging tasks all run as Garden containers on the Diego Cell VMs. The Diego cell rep component manages the lifecycle of those containers and the processes running in them, reports their status to the Diego BBS, and emits their logs and metrics to [Loggregator](#metrics-logging).
<%=vars.pre_diego_node%>
## <a id='services'></a>Services
### <a id='broker'></a> Service Brokers
Applications typically depend on <%= vars.services %> such as databases
or third-party SaaS providers.
When a developer provisions and binds a service to an application, the service
broker for that service is responsible for providing the service instance.
## <a id='messaging'></a>Messaging
### <a id='bbs-consul'></a> Consul and BBS
Cloud Foundry component VMs communicate with each other internally through HTTP and HTTPS protocols, sharing temporary messages and data stored in two locations:
* A [Consul server](../diego/diego-architecture.html#consul) stores longer-lived control data, such as component IP addresses and distributed locks that prevent components from duplicating actions.
* Diego's [Bulletin Board System](../diego/diego-architecture.html#bbs) (BBS) stores more frequently updated and disposable data such as cell and application status, unallocated work, and heartbeat messages. The BBS is currently implemented in [etcd](https://coreos.com/etcd/).
The route-emitter component uses the NATS protocol to broadcast the latest routing tables to the routers. In pre-Diego CF architecture, the [NATS Message Bus](../diego/dea-vs-diego.html#nats) carried all internal component communications.
## <a id='metrics-logging'></a>Metrics and Logging
### <a id='metrics'></a> Metrics Collector and Loggregator
The metrics collector gathers metrics and statistics from the components.
Operators can use this information to monitor a Cloud Foundry deployment.
The <%= vars.loggregator_name_or_link %> (log aggregator) system streams application logs to developers.