What is etcd?

Summary

Whitney Lee from IBM explains etcd, an open-source key-value store crucial for managing distributed systems, notably as a core component of Kubernetes. Fully replicated and consistently reliable, etcd uses the Raft algorithm for consensus, ensuring every node has the most recent data. It's highly available, secure with TLS, and offers a simple HTTP JSON interface. The watch function is highlighted for syncing Kubernetes configurations, emphasizing etcd's role in maintaining data consistency across distributed environments.

Takeaways

• 🗝️ etcd is an open-source key-value data store used for managing distributed systems.
• 🔒 It is known for being a core component of Kubernetes, storing state, configuration, and metadata.
• 💡 etcd serves as a single source of truth at any given time, ensuring consistency across the system.
• 🔄 Full replication in etcd means every node in the cluster has access to the complete data set.
• 📝 etcd is reliably consistent, ensuring every data read returns the most recent data.
• 🤖 Built on the Raft algorithm for distributed consensus, etcd maintains data integrity across nodes.
• 🔄 In an etcd cluster, a leader node and follower nodes work together to update and replicate data.
• 🔍 Clients can read and write to any node in the cluster without needing to identify the leader.
• 🛡️ etcd is highly available with no single point of failure, tolerating network partitions and hardware failures.
• ⚡️ etcd is fast, capable of handling 10,000 writes per second, though performance is dependent on disk speed.
• 🔒 Security is ensured with transport layer security and optional SSL client certificate authentication.
• 🛠️ etcd is easy to use, allowing web applications to interact with it through simple HTTP JSON tools.
• 👀 The watch function in etcd is crucial for syncing Kubernetes configuration and state data, ensuring system reconfiguration when necessary.

Q & A

What is etcd and what is its primary function?

etcd is an open-source key-value data store designed to manage and store data for distributed systems. Its primary function is to ensure data consistency and reliability across the system, often serving as a single source of truth.

How is etcd used in Kubernetes?

In Kubernetes, etcd is one of the core components used to store and manage state data, configuration data, and metadata. It ensures that Kubernetes has a reliable and consistent source of data for cluster operations.

What does it mean for etcd to be fully replicated?

Full replication in etcd means that every node in an etcd cluster has a complete copy of the data store, ensuring that the data is consistent and accessible across all nodes.

What is the significance of the Raft algorithm in etcd?

The Raft algorithm is crucial for distributed consensus in etcd. It ensures that all nodes in the cluster agree on the current state of the data, maintaining consistency even when changes are made.

How does etcd handle updates to the data store?

When an update is requested, the leader node in etcd does not immediately change its local data store. Instead, it forwards the request to followers. Once the majority of nodes have updated, the leader then updates its own store and acknowledges the successful write to the client.

Can a client interact with any node in an etcd cluster?

Yes, a client can make read and write requests to any node in the etcd cluster without needing to identify the leader node, as the cluster handles the routing and consistency internally.

What happens if a node in the etcd cluster has not yet updated to the most recent data?

If a client makes a read request to a node that hasn't updated, that node, being a follower, will forward the request to the leader, which will then provide the current value to the client.

How does etcd ensure high availability in a cluster?

etcd ensures high availability by having no single point of failure. If the leader node goes down, the followers can hold an election to elect a new leader, thus maintaining the cluster's operation and data integrity.

What is the performance benchmark for etcd in terms of write operations?

etcd is benchmarked at 10,000 writes per second, demonstrating its capability to handle a high volume of data updates efficiently.

How does etcd ensure data security?

etcd uses transport layer security and optional SSL client certificate authentication to secure the data. This is important as etcd often stores vital and highly sensitive configuration data.

What is the watch function in etcd and how is it used by Kubernetes?

The watch function in etcd allows it to monitor and compare data changes. Kubernetes uses this function to ensure that if the configuration data and state data ever go out of sync, etcd will notify the Kubernetes API to reconfigure the cluster accordingly.

How can a web application interact with etcd?

A web application can read and write data to etcd using simple HTTP JSON tools, making it straightforward to integrate etcd into various applications.

Outlines

00:00

💾 Distributed Data Consistency with etcd

Whitney Lee introduces etcd, an open-source key-value store, as a crucial tool for maintaining consistent and reliable data storage across distributed systems. As a core component of Kubernetes, etcd serves as a single source of truth for state, configuration, and metadata. The video explains etcd's full replication feature, ensuring every node in the cluster has access to the complete data set and is updated consistently through the Raft algorithm, which facilitates distributed consensus. The process of data updating is detailed, highlighting how changes are propagated from the leader to followers and back, ensuring data consistency. Additionally, the video touches on etcd's high availability, its ability to handle network partitions and hardware failures, and its performance capabilities, benchmarked at 10,000 writes per second.

05:04

🔒 Security and Simplicity of etcd for Kubernetes

The second paragraph delves into etcd's security features, emphasizing the use of transport layer security and optional SSL client certificate authentication to protect vital and highly sensitive configuration data. The ease of use is highlighted through the simple HTTP JSON tools that allow web applications to interact with etcd. A special mention is given to the 'watch' function, which Kubernetes uses to monitor and synchronize configuration and state data, ensuring the cluster reconfigures as needed. The video concludes by encouraging viewers to engage with the content through questions and subscriptions, and promoting IBM CloudLabs as a resource for skill development and badge earning in Kubernetes.

Keywords

💡etcd

etcd is an open-source distributed key-value store designed for high reliability and consistency. It is integral to the functioning of distributed systems, such as Kubernetes, where it serves as a single source of truth for state and configuration data. In the video, etcd is highlighted for its replication and consistency features, ensuring that every node in the cluster has access to the most recent data.

💡Kubernetes

Kubernetes is an open-source container orchestration system for automating application deployment, scaling, and management. It is mentioned in the script as one of the core components that rely on etcd for storing its state data and configuration data. The script emphasizes etcd's role in maintaining Kubernetes' operational integrity.

💡Replication

Replication in the context of etcd refers to the process where every node in the cluster has a complete copy of the data store. This ensures that the system remains consistent and reliable, even if one node fails. The script explains how etcd achieves this by having the leader node forward data change requests to the followers, which then update their local stores and confirm the change back to the leader.

💡Consistency

Consistency in the video script pertains to the property of a distributed system where every read operation returns the most recent data. etcd ensures this by using the Raft algorithm for distributed consensus, as explained in the script, which guarantees that the data across all nodes is synchronized and up-to-date.

💡Raft Algorithm

The Raft algorithm is a consensus algorithm used in distributed systems to ensure that all nodes agree on the state of the system. In the script, it is the underlying mechanism that etcd uses to maintain consistency and reliability across the cluster by electing a leader and ensuring that all nodes follow the leader's updates.

💡Leader and Followers

In an etcd cluster, there is a leader node responsible for managing updates to the data store, and follower nodes that replicate the leader's state. The script describes how the leader node processes write requests and how followers update their local data stores in response to the leader's instructions, maintaining the cluster's consistency.

💡High Availability

High availability in the script refers to the capability of the etcd cluster to remain operational and functional even in the event of a node failure. The script explains that if the leader node goes down, the followers can elect a new leader, ensuring that the system continues to operate without interruption.

💡Network Partitions

Network partitions are a type of fault in distributed systems where the network is split into isolated segments, potentially causing inconsistencies. The script mentions that etcd can gracefully handle network partitions, which is crucial for maintaining the system's reliability and availability.

💡Benchmark

In the context of the script, benchmarking refers to the process of testing and measuring the performance of etcd, specifically its ability to handle a high number of writes per second. The script states that etcd is benchmarked at 10,000 writes per second, indicating its high performance capabilities.

💡Transport Layer Security (TLS)

TLS is a cryptographic protocol used to provide secure communication over a network. In the script, etcd uses TLS for secure data transmission, which is critical for protecting sensitive configuration data. The script also mentions optional SSL client certificate authentication for an additional layer of security.

💡Watch Function

The watch function in etcd allows applications to monitor specific keys for changes. In the script, it is highlighted as a feature that Kubernetes leverages to ensure that its configuration and state data remain in sync. If they ever go out of sync, etcd will notify the Kubernetes API to reconfigure the cluster.

Highlights

etcd is an open source key-value data store used for managing data in distributed systems.

etcd is a core component of Kubernetes, storing state, configuration, and metadata.

etcd serves as a single source of truth at any given time in a distributed system.

etcd is fully replicated, with every node in the cluster having access to the full data store.

etcd ensures reliable consistency by returning the most recent data on every read.

etcd is built on the Raft algorithm for distributed consensus.

In an etcd cluster, there is always a leader node and follower nodes.

The leader node forwards write requests to followers before updating its own data store.

A successful write is acknowledged when the majority of nodes are updated.

Clients can read and write to any node in the etcd cluster without concern for the leader.

Follower nodes forward read requests to the leader if they haven't updated yet.

etcd is highly available with no single point of failure and can handle network partitions and hardware failures.

If the leader node fails, followers can elect a new leader to manage replication.

etcd is capable of 10,000 writes per second, with performance tied to disk speed.

etcd persists data to disk, ensuring data integrity.

etcd uses transport layer security and optional SSL client authentication for security.

etcd is simple to use with HTTP JSON tools for data read and write operations.

The watch function in etcd allows for synchronization checks and notifications for system reconfiguration.

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Transcripts

How can you ensure that your data is stored consistently

and reliably across a distributed system? My name is Whitney Lee and I'm a Cloud

Developer here at IBM. etcd is an open source key value data

store used to manage and store data that help

keep distributed systems running. etcd is most well known for being one of

the core components of Kubernetes, where it stores and manages Kubernetes

state data, configuration data, and metadata. etcd can be relied upon

to be a single source of truth at any given point in time.

Today I'm going to go over some of the features of etcd that allow it to be so

effective in this way.

etcd is fully replicated.

This means that every node in an etcd cluster

has access to the full data store. etcd is also reliably consistent.

Every data read in an etcd cluster is going to return the most recent data

right. Let's talk about how this works. etcd

is built on top of the Raft algorithm that is used for distributed consensus.

So, let's make a very simple etcd cluster of only four nodes. An etcd cluster

always has a leader and then the other nodes in the cluster

are followers. It's a key value data store, so in this

case at key one we have the value of seven.

Let's say a web application comes in

and lets the leader node know at key one we want to store the value of 17 instead

of 7. The leader node does not change its own

local data store, instead it forwards that request to each

of the followers. When a follower changes its local data

store it returns that to the leader, so the

leader knows. When our leader node can see that the

majority of the nodes have been updated to the most current

data that's when the leader will update its own current data store

and return a successful write to the client.

Now client doesn't actually have to concern itself

about which node in the cluster is the leader. The client can make

read and write requests to any node in the cluster.

So, let's say, this all happens over a matter of milliseconds,

but let's say that the client makes a read request to the node that hasn't

updated yet and says what's the value at key one?

Well this follower node knows it's a follower node and knows it's not

authorized to answer the client directly. So what it's going to do is forward that

request into the leader node which will then respond the cluster's

current value at key 1 is 17. And so it will get a response of 17 to

the client. And that's how etcd is replicated.

So every every node in the cluster has access to the full data store

and it's consistent every data read is going to return

the most recent data right. etcd is also highly available.

This means that there's no single point of failure in the etcd cluster.

It can tolerate gracefully tolerate network partitions and hardware failure

too. So, let's say that our leader node goes

down. The followers can declare themselves a

candidate, they'll hold an election where each one

votes based on availability and a new node will be elected the

leader. That leader will go on to manage the

replication for the cluster and the data is unaffected.

etcd is also fast.

etcd is benchmarked at 10,000 writes per second.

With that said, etcd does persist data to disk.

So, etcd's performance is tied to your storage disk speed.

etcd is secure. etcd uses transport layer security with

optional SSL client certificate authentication.

etcd stores vital and highly sensitive configuration data,

so it's important to keep it protected. Finally etcd is simple to use.

A web application can read and write data to etcd uses a

simple http JSON tools.

So the other thing to talk about in etcd that's important

is the watch function. Kubernetes leverages this.

So, as i talked about at the beginning, etcd stores Kubernetes configuration data

and its state data.

So, etcd can use this watch function to compare these to each other. If they

ever go out of sync, etcd will let the Kubernetes

API know and the kubernetes API will reconfigure

the cluster accordingly.

etcd can be used to store your data reliably and consistently across your

distributed system. Thank you. if you have questions please

drop us a line below. If you want to see more videos like this

in the future, please like and subscribe. And don't forget you can

grow your skills and earn a badge with IBM CloudLabs,

which are free browser-based, interactive Kubernetes labs.