Top 50 Consul interview questions and answers

Consul interview questions and answers

Table of Contents

1) What Is Checkpoint? / Does Consul Call Home?

Consul makes use of a HashiCorp service called Checkpoint which is used to check for updates and critical security bulletins. Only anonymous information, which cannot be used to identify the user or host, is sent to Checkpoint. An anonymous ID is sent which helps de-duplicate warning messages. This anonymous ID can be disabled. In fact, using the Checkpoint service is optional and can be disabled.

2) Does Consul Rely On Udp Broadcast Or Multicast?

Consul uses the Serf gossip protocol which relies on TCP and UDP unicast. Broadcast and Multicast are rarely available in a multi-tenant or cloud network environment. For that reason, Consul and Serf were both designed to avoid any dependence on those capabilities.

3) Is Consul Eventually Or Strongly Consistent?

Consul has two important subsystems, the service catalog and the gossip protocol. The service catalog stores all the nodes, service instances, health check data, ACLs, and KV information. It is strongly consistent, and replicated using the consensus protocol.

The gossip protocol is used to track which nodes are part of the cluster and to detect a node or agent failure. This information is eventually consistent by nature. When the servers detects a change in membership, or receive a health update, they update the service catalog appropriately.

Because of this split, the answer to the question is subtle. Almost all client APIs interact with the service catalog and are strongly consistent. Updates to the catalog may come via the gossip protocol which is eventually consistent, meaning the current state of the catalog can lag behind until the state is reconciled.

4) Does Consul Support Delta Updates For Watchers Or Blocking Queries?

Consul does not currently support sending a delta or a change only response to a watcher or a blocking query. The API simply allows for an edge-trigger return with the full result. A client should keep the results of their last read and compute the delta client side.

By design, Consul offloads this to clients instead of attempting to support the delta calculation. This avoids expensive state maintenance on the servers as well as race conditions between data updates and watch registrations.

5) What Network Ports Does Consul Use?

The Ports Used section of the Configuration documentation lists all ports that Consul uses.

6) Does Consul Require Certain User Process Resource Limits?

There should be only a small number of open file descriptors required for a Consul client agent. The gossip layers perform transient connections with other nodes, each connection to the client agent (such as for a blocking query) will open a connection, and there will typically be connections to one of the Consul servers. A small number of file descriptors are also required for watch handlers, health checks, log files, and so on.

For a Consul server agent, you should plan on the above requirements and an additional incoming connection from each of the nodes in the cluster. This should not be the common case, but in the worst case if there is a problem with the other servers you would expect the other client agents to all connect to a single server and so preparation for this possibility is helpful.

The default ulimits are usually sufficient for Consul, but you should closely scrutinize your own environment’s specific needs and identify the root cause of any excessive resource utilization before arbitrarily increasing the limits.

7) What Is The Per-key Value Size Limitation For Consul’s Key/value Store?

The limit on a key’s value size is 512KB. This is strictly enforced and an HTTP 413 status will be returned to any client that attempts to store more than that limit in a value. It should be noted that the Consul key/value store is not designed to be used as a general purpose database. See Server Performance for more details.

8) What Data Is Replicated Between Consul Datacenters?

In general, data is not replicated between different Consul datacenters. When a request is made for a resource in another datacenter, the local Consul servers forward an RPC request to the remote Consul servers for that resource and return the results. If the remote datacenter is not available, then those resources will also not be available, but that won’t otherwise affect the local datacenter. There are some special situations where a limited subset of data can be replicated, such as with Consul’s built-in ACL replication capability, or external tools like consul-replicate.

9) What Is A Consul Server?

Consul is a distributed, highly available, datacenter-aware, service discovery and configuration system. It can be used to present services and nodes in a flexible and powerful interface that allows clients to always have an up-to-date view of the infrastructure they are a part of.

10. What Is Hashicorp Consul?

HashiCorp Consul is an open source tool that solves these new complexities by providing service discovery, health checks, load balancing, a service graph, mutual TLS identity enforcement, and a configuration key-value store. These features make Consul an ideal control plane for a service mesh.

11. What Is Docker Consul?

We are pleased to announce the release of our official Docker image for Consul. Consul is a modern datacenter runtime that provides service discovery, configuration, and orchestration capabilities. Consul is our first tool to have an official Docker image.

12. What Is Consul Agent?

The Consul agent is the core process of Consul. The agent maintains membership information, registers services, runs checks, responds to queries, and more. The agent must run on every node that is part of a Consul cluster. Any agent may run in one of two modes: client or server.

13) What is Consul?

Consul is an open-source platform developed by HashiCorp for service networking. Consul is a service mesh solution that includes a full-featured control plane that includes service discovery, configuration, and segmentation. Each of these capabilities can be utilised independently or in combination to create a complete service mesh. Consul needs the use of a data plane and offers both a proxy and native integration mechanism. Consul comes with a built-in proxy that makes things work right away, but it also supports third-party proxy integrations like Envoy.

14) What are the key features of Consul?

Consul is built with DevOps and application developers in consideration, especially designed for modern, elastic infrastructures.

Service Discovery
Consul clients can register a service, such as api or mysql, and other clients can utilise Consul to find service providers. Applications can quickly locate the services they require by using DNS or HTTP.
Health Checkup
Consul clients provide and monitor cluster health and help the service discovery components to use these to avoid sending traffic to unhealthy hosts.
KV Store
Consul’s hierarchical key/value store can be used for a lot of areas, including dynamic configuration, feature flagging, coordination, and leader election.
Secure Service Communication
To establish mutual TLS connections, Consul can generate and distribute TLS certificates for services. Intentions can be used to specify which services are permitted to communicate with one another. Instead of using complex network topologies and static firewall rules, service segmentation may be easily managed with intentions that can be altered in real time.
Multi Datacenter
Consul has the ability to support several data centers. This indicates that Consul users won’t have to worry about adding more abstraction layers to expand to multiple locations.

15) Explain Consul Architecture?

As can be seen, Consul manages three separate servers. The functioning architecture uses the Raft algorithm, which allows us to choose a leader from among the three servers. Labels such as Follower and Leader are applied to these servers. The follower, as the name implies, is in charge of adhering to the leader’s decisions. For any communication, all three servers are connected together.

The concept of RPC is used by each server to communicate with its own client. The Gossip Protocol, allows clients to communicate with one another. The internet communication facility can be made available via TCP or the gossip technique of communication. This communication is made with one of the three servers directly.

16) What is Raft Algorithm in Consul?

Raft is a consensus algorithm to manage a replicated log. It is based on the CAP Theorem concept, which says that when a network partition exists, one must choose between consistency and availability. At any given time, not all three fundamentals of the CAP Theorem can be achieved. At the very least, one must make a tradeoff for any two of them.

A Raft Cluster is made up of multiple servers, usually in odd numbers. If we have five servers, for example, the system can sustain two failures. Each server is in one of three states at any given time: Leader, Follower, or Candidate. In a typical operation, there is just one leader and every other server is a follower. These followers are in a passive condition, meaning they don’t make requests on their own and instead reply to requests from the candidate and the leaders.

17) What is consul used for?

Consul is the control plane of the service mesh. Consul is a multi-networking tool that offers a fully-featured service mesh solution that solves the networking and security challenges of operating microservices and cloud infrastructure. Consul offers a software-driven approach to routing and segmentation.

18) What is consul history?

A consul held the highest elected political office of the Roman Republic (509 to 27 BC), and ancient Romans considered the consulship the highest level of the cursus honorum (an ascending sequence of public offices to which politicians aspired). Consuls were elected to office and held power for one year.

19) What is Consul package?

GitHub – hashicorp/consul: Consul is a distributed, highly available, and data center aware solution to connect and configure applications across dynamic, distributed infrastructure. Actions. Packages. Security.

20) Is Consul a database?

The databases have a health check script that tells the servers (in black) that they are healthy and can be advertised as available. Consul acts as a DNS server, so when you query it via DNS, it will return the most available IP for the name you are querying.

21) What is Consul sidecar?

Consul service mesh allows you to deploy applications into a zero-trust network. A zero-trust network is a network where nothing is trusted automatically. All connections must be both authenticated and authorized.

22) What is terraform Consul?

Consul is a service networking platform which provides service discovery, service mesh, and application configuration capabilities. The Consul provider exposes resources used to interact with a Consul cluster.

23) What is consul AWS?

HashiCorp Consul is a tool that provides cloud networking automation by using a central registry for service-based networking.

24) Does consul support state locking?

Stores the state in the Consul KV store at a given path. This backend supports state locking.

25) What is Terraform used for?

HashiCorp Terraform is an infrastructure as code tool that lets you define both cloud and on-prem resources in human-readable configuration files that you can version, reuse, and share. You can then use a consistent workflow to provision and manage all of your infrastructure throughout its lifecycle.

26) How do you store Terraform state?

This state is stored by default in a local file named “terraform. tfstate”, but it can also be stored remotely, which works better in a team environment. Terraform uses this local state to create plans and make changes to your infrastructure.

27) What is local in Terraform?

Terraform locals are named values that you can refer to in your configuration. You can use local values to simplify your Terraform configuration and avoid repetition. Local values (locals) can also help you write more readable configuration by using meaningful names rather than hard-coding values.

28) What is map type in Terraform?

Terraform variable Map Type Explained!!! Maps are a collection of string keys and string values. These can be useful for selecting values based on predefined parameters such as the server configuration by the monthly price. We’ve replaced our sensitive strings with variables, but we still are hard-coding AMIs.

29) What is Consul package?

30) What was one major job of the consuls?

The consuls were the chairmen of the Senate, which served as a board of advisers. They also commanded the Roman army (both had two legions) and exercised the highest juridical power in the Roman empire. Therefore, the Greek historian Polybius of Megalopolis likened the consuls to kings.

31) Who was consul the most times?

Gaius Marius
Gaius Marius was one of the most important leaders of the Roman Republic. He was elected to consul a record seven times.

32) Is consul a service mesh?

Consul is a service mesh solution that offers a software-driven approach to: Security (mTLS & ACLs) Observability. Traffic management.

33) Does consul do load balancing?

Default load balancing policy

Consul automatically balances traffic across all the healthy instances of the resolved service using the round_robin policy. You can verify this by using the curl command from the node running the client service.

34) How do you access the consul UI?

If you have a local development agent, started with consul agent -dev , you can open a browser window and navigate to the UI, which is available at the /ui path on the same port as the HTTP API (port 8500 ).

35) How do I find a consul leader?

The Consul leader is elected via an implementation of the Raft Protocol from amongst the Quorum of Consul Servers. Only Consul instances that are configured as Servers participate in the Raft Protocol communication. The Consul Agent (the daemon) can be started as either a Client or a Server.

36) What is a Consul cluster?

Consul is a service mesh solution providing a full featured control plane with service discovery, configuration, and segmentation functionality. Each of these features can be used individually as needed, or they can be used together to build a full service mesh.

37) How do I access the vault UI?

Launch a web browser, and enter http://127.0.0.1:8200/ui in the address. The Vault server is uninitialized and sealed. Before continuing, the server’s storage backend requires starting a cluster or joining a cluster.

38) What is consul backend?

The Consul storage backend is used to persist Vault’s data in Consul’s key-value store. In addition to providing durable storage, inclusion of this backend will also register Vault as a service in Consul with a default health check. High Availability – the Consul storage backend supports high availability.

39) What is raft in Consul?

Raft is a consensus algorithm that is based on Paxos. Compared to Paxos, Raft is designed to have fewer states and a simpler, more understandable algorithm.

40) How do I check my Consul status?

The easiest way to view initial health status is by visiting the Consul Web UI at http://localhost:8500/ui . Click through to a specific service such as the counting service. The status of the service on each node will be displayed. Click through to inspect the output of the health check.

41) Why do we need Consul?

Consul is a Hashicorp based tool for discovering and configuring a variety of different services in your infrastructure. It is based and built on Golang. One of the core reasons to build Consul was to maintain the services present in the distributed systems.

42) Is Consul a database?

43) How do you access the consul UI?

44) Where is Consul used?

45) What is Consul medium?

HashiCorp Consul is an open-source tool that solves these new complexities by providing service discovery, health checks, load balancing, a service graph, mutual TLS identity enforcement, and a configuration key-value store.

46) What is Consul package?

47) How does Consul Connect work?

Consul Connect provides service-to-service connection authorization and encryption using mutual Transport Layer Security (TLS). Applications can use sidecar proxies in a service mesh configuration to establish TLS connections for inbound and outbound connections without being aware of Connect at all.

48) How do you set up a Consul?

These setup steps should be completed on all Consul hosts.

Install Consul.
Verify the installation.
Prepare the security credentials.
Configure Consul agents.
Server specific configuration.
Client specific configuration.
Apply Enterprise license.
Configure the Consul process.

49) Is Consul an API gateway?

Introduction. Consul API Gateway implements the Kubernetes Gateway API Specification. This specification defines a set of custom resource definitions (CRD) that can create logical gateways and routes based on the path or protocol of a client request.

50) What is Consul bootstrap?

Bootstrapping is the process of joining these initial server nodes into a cluster. Read the architecture documentation to learn more about the internals of Consul. It is recommended to have three or five total servers per datacenter.

51) Where is Consul config file?

/etc/consul
Place them in a file at /etc/consul. d/server/config. json just as you did in the first host. Save and close the files you have created when you are finished.

52) Is consul a service mesh?