Interview Questions.

Question 1. What Is Checkpoint? / Does Consul Call Home?

Answer :

Consul makes use of a HashiCorp service referred to as Checkpoint that's used to test for updates and essential protection bulletins. Only nameless facts, which can't be used to discover the user or host, is sent to Checkpoint . An nameless ID is despatched which facilitates de-replica warning messages. This nameless ID may be disabled. In truth, the use of the Checkpoint provider is non-obligatory and may be disabled.

Question 2. Does Consul Rely On Udp Broadcast Or Multicast?

Answer :

Consul makes use of the Serf gossip protocol which relies on TCP and UDP unicast. Broadcast and Multicast are not often to be had in a multi-tenant or cloud community surroundings. For that cause, Consul and Serf were each designed to keep away from any dependence on the ones abilities.

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Question three. Is Consul Eventually Or Strongly Consistent?

Answer :

Consul has two crucial subsystems, the service catalog and the gossip protocol. The carrier catalog stores all the nodes, provider times, health test records, ACLs, and KV information. It is strongly regular, and replicated the use of the consensus protocol.

The gossip protocol is used to track which nodes are part of the cluster and to come across a node or agent failure. This facts is ultimately consistent with the aid of nature. When the servers detects a alternate in membership, or acquire a health update, they update the carrier catalog correctly.

Because of this split, the solution to the question is subtle. Almost all customer APIs have interaction with the service catalog and are strongly regular. Updates to the catalog may come through the gossip protocol which is sooner or later steady, which means the modern-day kingdom of the catalog can lag behind till the kingdom is reconciled.

Question four. Does Consul Support Delta Updates For Watchers Or Blocking Queries?

Answer :

Consul does not currently guide sending a delta or a exchange most effective reaction to a watcher or a blocking question. The API definitely lets in for an facet-trigger return with the entire end result. A purchaser need to maintain the consequences in their closing read and compute the delta patron side.

By layout, Consul offloads this to customers in preference to attempting to support the delta calculation. This avoids luxurious nation renovation on the servers as well as race conditions among data updates and watch registrations.

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Question 5. What Network Ports Does Consul Use?

Answer :

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

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Question 6. Does Consul Require Certain User Process Resource Limits?

Answer :

There have to be handiest a small wide variety of open document descriptors required for a Consul customer agent. The gossip layers carry out brief connections with different nodes, each connection to the customer agent (along with for a blocking question) will open a connection, and there'll commonly be connections to one of the Consul servers. A small quantity of report descriptors also are required for watch handlers, health exams, log documents, and so forth.

For a Consul server agent, you should plan at the above requirements and an additional incoming connection from every of the nodes in the cluster. This ought to no longer be the not unusual case, however in the worst case if there is a problem with the alternative servers you would count on the alternative consumer sellers to all connect with a unmarried server and so training for this possibility is beneficial.

The default ulimits are typically enough for Consul, but you need to closely scrutinize your personal environment's unique wishes and identify the basis reason of any excessive resource utilization before arbitrarily increasing the bounds.

Question 7. What Is The Per-key Value Size Limitation For Consul's Key/value Store?

Answer :

The limit on a secret is fee size is 512KB. This is exactly enforced and an HTTP 413 reputation will be returned to any purchaser that tries to save more than that limit in a price. It should be stated that the Consul key/price save isn't designed to be used as a general cause database. See Server Performance for more details.

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Question eight. What Data Is Replicated Between Consul Datacenters?

Answer :

In preferred, records isn't replicated among unique Consul datacenters. When a request is made for a aid in every other datacenter, the local Consul servers ahead an RPC request to the far off Consul servers for that useful resource and go back the consequences. If the faraway datacenter is not to be had, then those resources may even not be to be had, but that might not in any other case have an effect on the nearby datacenter. There are some special conditions in which a constrained subset of records can be replicated, consisting of with Consul's built-in ACL replication capability, or external equipment like consul-replicate.

Question 9. What Is A Consul Server?

Answer :

Consul is a dispensed, particularly available, datacenter-aware, carrier discovery and configuration gadget. It may be used to present offerings and nodes in a flexible and powerful interface that allows customers to constantly have an up to date view of the infrastructure they are part of.

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Question 10. What Is Hashicorp Consul?

Answer :

HashiCorp Consul is an open source device that solves those new complexities by imparting carrier discovery, fitness assessments, load balancing, a service graph, mutual TLS identification enforcement, and a configuration key-cost keep. These features make Consul an excellent control aircraft for a carrier mesh.

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Question eleven. What Is Docker Consul?

Answer :

We are thrilled to announce the release of our reliable Docker photo for Consul. Consul is a modern-day datacenter runtime that offers provider discovery, configuration, and orchestration skills. Consul is our first device to have an legit Docker photograph.

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Question 12. What Is Consul Agent?

Answer :

The Consul agent is the core process of Consul. The agent maintains club statistics, registers services, runs exams, responds to queries, and more. The agent have to run on each node this is a part of a Consul cluster. Any agent may additionally run in considered one of two modes: patron or server.

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