In an instant, the IP phone converts your voice into digital data. Since those days the network speeds were slow and people had limited bandwidth, video chat was almost impossible without interruptions. You can think of a partition as an ordered dictionary. It’s easy and free to post your thinking on any topic. It was time to migrate to a database more suited to the task. We changed our query code to track empty buckets and avoid them in the future for a channel. Minecraft is a close second, with 569,000 members This meant that if a user caused this query again then at worst Cassandra would be scanning only in the most recent bucket. Upgrade your emoji, enjoy bigger file uploads, stand out in your favorite Discords, and more. Supporting large group channels (we have seen You can also write to any node and it will resolve conflicts automatically using “last write wins” semantics on a per column basis. When compared to audio, video requires significantly more CPU power and bandwidth. It became clear we had to somehow bound the size of partitions because a single Discord channel can exist for years and perpetually grow in size. Because of that the data is usually in the disk cache. While solving this problem, we noticed we were being very inefficient with our writes. It collects and processes RTCP reports from receivers and notifies senders how much bandwidth is available for video. This breaks down as follows: 2016 – $5 million; 2017 – $10 million; 2018 – $30 million; 2019 – $70 million; 2020 – $120 million; How Much Money Can Discord Make in the Future? This is actually part of our company culture: build quickly to prove out a product feature, but always with a path to a more robust solution. The term “server” will instead be used here to describe our backend infrastructure. Lastly, WebRTC uses the Secure Real-time Transport Protocol (SRTP) for media encryption. And also you … The text rooms are very much like forums (though if you want an actual gaming forum, you should look elsewhere). Nothing was surprising, we got exactly what we expected. It has to replicate deletes to other nodes and do it even if other nodes are temporarily unavailable. In the future, we want to use this information to automatically detect and reduce voice degradation issues. The signaling component fully controls the SFU and is responsible for generating stream identifiers and encryption keys, forwarding speaking indication, etc. Learn more, Follow the writers, publications, and topics that matter to you, and you’ll see them on your homepage and in your inbox. Cassandra partition keys can be compounded, so our new primary key became ((channel_id, bucket), message_id). This had the possibility of resurrecting messages that were deleted and adding more chances for conflict for concurrent writes to other columns. The downside is that if your voice drops below that level, the sound cuts off completely. With the implementation of choosing whether you wish to chat with friends in a 1-on-1 conversation, to joining a … Zangi generally consumes 216KB of data for a 1-minute voice call. You can now select a voice channel of your choice. Everything on Discord was stored in a single MongoDB replica set and this was intentional, but we also planned everything for easy migration to a new database (we knew we were not going to use MongoDB sharding because it is complicated to use and not known for stability). The channels can be configured a number of ways, and set aside for specific purposes, such as announcements, contests, or music. If you are passionate about working with audio and video, check out our jobs page! Thanks to all our engineering efforts on both the client and server architecture, we are able to serve more than 2.6 million concurrent voice users with egress traffic of more than 220 Gbps (bits-per-second) and 120 Mpps (packets-per-second). Cassandra does this by treating deletes as a form of write called a “tombstone.” On read, it just skips over tombstones it comes across. Explore, If you have a story to tell, knowledge to share, or a perspective to offer — welcome home. There were two possible solutions for handling this problem: We went with the second option, which we did by choosing a column that was required (in this case author_id) and deleting the message if it was null. Scalable Video Coding could be the solution to provide seamless video experience. We can just add nodes to scale it and it can tolerate a loss of nodes without any impact on the application. Cassandra is known to have faster writes than reads and we observed exactly that. It said: Deleted Messages are deleted permanently. The problem is that even though this is a small amount of messages it makes it harder to serve this data to the users. This results in significant bandwidth and CPU savings — however, both client and server must be prepared to cease receiving audio data any time and rewrite audio/video packet sequence numbers. Importing messages into Cassandra went without a hitch and we were ready to try in production. We knew that in the coming year we would add even more ways for users to issue random reads: the ability to view your mentions for the last 30 days then jump to that point in history, viewing plus jumping to pinned messages, and full-text search. When you are online, your client maintains a WebSocket connection to a Discord Gateway (we call this the gateway WebSocket connection). All the voice channels within a guild are assigned to the same Discord Voice server. We are running more than 850 voice servers in 13 regions (hosted in more than 30 data centers) all over the world. During less "outdoor" months i hover around 150-200ish MB of data. Introducing a new system into production is always scary so it’s a good idea to try to test it without impacting users. In line with fast, consistent read performance, here’s an example of a jump to a message from over a year ago in a channel with millions of messages: Everything went smoothly, so we rolled it out as our primary database and phased out MongoDB within a week . On the top left corner of your screen, tap the “ Three horizontal lines ” icon. Clients tear down their voice WebSocket connection to the old Discord Voice server and create a new voice WebSocket connection to the new Discord Voice server. Discord lets friends chat with each other either one-to-one or as a group via a server. Now, click on “ Connect to voice “. 2. level 1. Voice chat heavy Discord servers send almost no messages. We observed this regardless of what data was being accessed, and performance stayed consistent during a week of testing. It is quite common that a Discord Voice server suffers a DDoS attack (which we observe from the rapid increase of incoming IP packets). Thanks to Nelly, Matt Nowack, and Brian Armstrong. First, WebRTC relies on the Session Description Protocol (SDP) to negotiate audio/video information between participants (which can be close to ten kilobytes in size round-trip). Reduce your bandwidth and CPU consumption during periods of silence — even very large voice channels only have a few concurrent speakers at any given time. When a client displays “Voice Connected,” it means that the client successfully exchanged UDP messages with the selected Discord Voice server. Around November 2015, we reached 100 million stored messages and at this time we started to see the expected issues appearing: the data and the index could no longer fit in RAM and latencies started to become unpredictable. Discord combines the text and image sharing of Skype and Teamspeak 3's high speed voice connection to create this reliable software platform. We decided to bucket our messages by time. In Discord, voice/video communication is initiated by entering a voice channel or call. The Discord Guilds server watches the service discovery system and assigns the least utilized voice server in the given region to the guild. The first thing to mention is that Discord is focused on voice chat. Once 500 channels are reached, no more channels can be created. The client updates its voice state object using the gateway WebSocket connection. The first K is the partition key and is used to determine which node the data lives on and where it is found on disk. Medium is an open platform where 170 million readers come to find insightful and dynamic thinking. Tombstones live for a configurable amount of time (10 days by default) and are permanently deleted during compaction when that time expires. With a camera in every smartphone and traversing the globe increasingly common, video-calling is a great way to keep in touch with loved ones. It implements a transport and encryption for both browser and standalone applications and translates between the two as it forwards media packets. Using the WebRTC native library allows us to use a lower level API from WebRTC (webrtc::Call) to create both send stream and receive stream. It pushes all the voice state objects to the newly selected server and notifies clients about the new voice server. This includes the voice backend server address and port, encryption method and keys, codec, and stream identification (about 1000 bytes). For example, administrators can disable audio/video for offending participants. In case of infrastructure failure, participants can simply re-connect to a new backend server. Since it was public we joined it to take a look. In Discord’s free plan, the user can share files to the limit of 8MB and can extend this limit up to … Buckets had to be derivable from the message_id or a timestamp. Arguably, one of the best databases for iterating quickly is MongoDB. Finally, the SFU is also responsible for handling the real-time control transport protocol (RTCP), which is used for video quality optimization. We decided early on to store all chat history forever so users can come back at any time and have their data available on any device. In July, we announced 40 million messages a day, in December we announced 100 million, and as of this blog post we are well past 120 million. I text chat a lot in Discord using mobile data, and I don't think it takes that much. This means that certain features work better in the installed application than in the browser. The main reason is that gamers need high-quality, lag-free voice chat to communicate with each other when playing different games. We are currently running a 12 node cluster with a replica factor of 3 and will just continue to add new Cassandra nodes as needed. We exchange all necessary information between client and server (less than 1200 bytes round trip) and SDP is synthesized from this information at the clients. Screen sharing requires even more bandwidth due to higher frame rate and resolution than your ordinary webcam. The Discord Voice server is responsible for transmitting every member’s audio to the channel. We exchange a minimal amount of information when joining a voice channel. The downside of this method is that rarely active Discords will have to query multiple buckets to collect enough messages over time. It’s easy and free to post your thinking on any topic. Explore, If you have a story to tell, knowledge to share, or a perspective to offer — welcome home. A bunch of servers regions will pop up. It is a required field! The primary key became (channel_id, message_id), where the message_id is a Snowflake. Our SFU is tailored to our use case offering maximum performance and thus the lowest cost. Arguably, one of the best databases for iterating quickly is MongoDB. Once You’re in Server Settings: Slide yourself on over to the “Server Region” option on the right side. It took only 15mb to 1hr & 30min call. The original version of Discord was built in just under two months in early 2015. When a Discord Voice server dies, it fails the periodic ping and gets removed from the service discovery system. You can connect to audio calls even with minimal internet speed and can eat up less than 60MB in about 3 hours. Luckily every ID on Discord is actually a Snowflake (chronologically sortable), so we were able to use them instead. If you are the first voice participant in the guild, Discord Guilds server is responsible for assigning a Discord Voice server to the guild using the process described below. Here, expert and undiscovered voices alike dive into the heart of any topic and bring new ideas to the surface. The SFU also acts as a bridge between native and browser applications. The latest reports in 2013 suggests that Skype uses 200-300mb of data (up & down combined) per hour of usage on a video call, and around 40-50mb per hour on a voice only call. Supporting large group channels (we have seen 1000 people taking turns speaking) requires client-server networking architecture because peer-to-peer networking becomes prohibitively expensive as the number of participants increases. Each voice server periodically reports its health and load, and this information is curated and placed into our service discovery system (we use etcd) as we’ve discussed in a previous blog post. Which helps us understand as to how does Discord make money? If you are using discord to speak or video chat, it will take up somewhere near 60Mbs every five minutes or so. Keep in mind that it could vary significantly based on background apps your phone may be running. We believe we can safely reduce the number of nodes in the cluster by bumping this to 2TB. We lowered the lifespan of tombstones from 10 days down to 2 days because we run. Least Data Usage Apps Zangi Safe Messenger. Let’s start with the app that uses the least data on voice and video calls without compromising quality. This is a lot of data that is ever increasing in velocity, size, and must remain available. Doubling those to account for the two-way flow, that’s a total of 7.25 MB/minute minimum, 27 MB/minute maximum. As such its annual revenues are mostly estimated. Discord’s audio and video features are implemented using WebRTC. When you are connected to a voice channel, the connection status is represented by the voice state object. In a year, this kind of server is unlikely to reach 1,000 messages. Figuring out that the message is corrupt and deleting it from database. Slack and Discord both the tools, allows the users to share a wide range of files across their respective applications. Access raw audio data to perform voice activity detection and share both game audio and video. Discord, on the other hand, is free, can be used on a browser, isn’t heavy, is safer, and involves every feature a gamer requires to hold a voice chat while playing. Immediately after launching we started getting errors in our bug tracker telling us that author_id was null. This meant that when loading a channel we could tell Cassandra exactly where to range scan for messages. We are investing heavily in our voice and video clients and infrastructure to make Discord the best voice and video experience for gamers. The Discord Guilds server confirms the failure, consults the service discovery system, and assigns a new Discord Voice server to the guild. They both generate a tombstone. Due to the success of this project we have since moved the rest of our live production data to Cassandra and that has also been a success. Much like how music can be made available in an MP3 or AAC format, phone calls are compressed using a variety of codecs. Just returning 50 messages to a user can result in many random seeks on disk causing disk cache evictions. Actually Whatsapp is the lowest data using app (when you enable the "low data usage" in whatsapp call settings). This is an estimate of course, but similar to YouTube, it is a streaming video application (including VoIP). But by simply switching on the “low data usage” mode, users can save much more data, consuming only 134KB per minute. We were writing 12 tombstones into Cassandra most of the time for no reason. Clients send periodic ping messages to ensure that the firewall remains open all the time. This allows us to provide a much more reliable connection when you’re behind a NAT, as well as keep your IP address secret from other parties in the channel. Writes were sub-millisecond and reads were under 5 milliseconds. The problem is since these servers usually have under 100 members the rate at which this data is requested is low and unlikely to be in disk cache. They have thousands of members sending thousands of messages a day and easily rack up millions of messages a year. Provide system-wide push to talk functionality. Discord Gateway and Discord Guilds are running at Google Cloud Platform. Every audio/video communication in Discord is multiparty. Discord fits the bill perfectly, providing reliable voice communication all around. We noticed Cassandra was running 10 second “stop-the-world” GC constantly but we had no idea why. Write the whole message back when editing the message. For clarity, we will use the term “guild” to represent a collection of users and channels — they are called “servers” in the client. The data they are requesting is usually very recent only. Routing all your network traffic through Discord servers also ensures that your IP address is never leaked whether you use text, voice, or video — preventing anyone from finding out your IP address and launching a DDoS attack against you. The native WebRTC library lets you implement your own transport layer using the webrtc::TransportAPI. The original version of Discord was built in just under two months in early 2015. Discord is a newcomer to the chat scene, but it’s made a big splash. Newer versions of Cassandra are better at handling more data on a single node. Cassandra advertises that it can support 2GB partitions! 1Gb of data will be spent up within a day of you aren't all that careful. We use a handful of providers and use physical servers in their data centers. A big part of Discord is about sharing your gaming experiences with your friends. A category can have at most 50 channels - text and voice combined. Ducking, or volume attenuation, means that. Once 50 channels are reached, no more channels can be created inside that category. This means that the communication is always initiated by the client, which reduces both client and backend complexity and also increases resilience against errors. They almost always are requesting messages sent in the last hour and they are requesting them often. When a Discord Voice server is selected, all the voice state objects (also maintained by Discord Guilds) are pushed to voice server so it knows how to set up audio/video forwarding. We then sequentially query partitions until enough messages are collected. Every client is notified about the new voice server and creates a voice WebSocket connection to the new voice server to start media setup. To query for recent messages in the channel we generate a bucket range from current time to channel_id (it is also a Snowflake and has to be older than the first message). Discord enables a noise gate by default for voice chat. Since Cassandra is eventually consistent it cannot just delete data immediately. How can it be null? Cassandra is an AP database which means it trades strong consistency for availability which is something we wanted. When offending users are moderated (server mute), their audio packets are dropped. Write on Medium, Captivate Your Community with Stage Channels, How Discord Scaled Elixir to 5,000,000 Concurrent Users, How Discord Handles Two and Half Million Concurrent Voice Users using WebRTC, Inside 8-bit Music Theory’s Growing Video Game Soundtrack Server, How Discord Maintains Performance While Adding Features. In a follow-up to this post we will explore how we make billions of messages searchable. We went from over 100 million total messages to more than 120 million messages a day, with performance and stability staying consistent. We are hiring, so come join us if this type of stuff tickles your fancy. But is it … All of our signaling servers are written in Elixir allowing lots of code re-use. What gives?! The two Ks comprise the primary key. All the servers will be listed on the left. We setup our code to double read/write to MongoDB and Cassandra. From the very start, we made very conscious engineering and product decisions to keep Discord well suited for voice chat while playing your favorite game with your friends. This is actually part of our company culture: build quickly to prove out a product feature, b… The only way our team can support all these platforms is to take advantage of code re-use and WebRTC. To our surprise, the channel had only 1 message in it. Send extra information along with audio/video packets (such as indicating priority speaker). The clustering key acts as both a primary key within the partition and how the rows are sorted. Since we have control of the native library, we do some things differently in the native app than what you see in the browser’s WebRTC implementation. Deleting a column and writing null to a column are the exact same thing. It has now been just over a year since we made the switch and, despite “the big surprise,” it has been smooth sailing. If you’re asking how much mobile data does Discord voice chat use, the answer seems to be around 28 MB per hour. Large public Discord servers send a lot of messages. How do we do it? It was at that moment that it became obvious they deleted millions of messages using our API, leaving only 1 message in the channel. Discord is a VoIP, instant messaging and digital distribution platform designed for creating communities. If the SFU crashes, it is restarted right away causing minimal service interruption (few dropped packets). Discord is a voice, video and text communication service to talk and hang out with your friends and communities. WebRTC is available in all modern browsers and also as a native library to embed into applications. We have a handful of engineers working on both client and server components and looking after operations as well. Large partitions put a lot of GC pressure on Cassandra during compaction, cluster expansion, and more. Clients are also notified about the selected Discord Voice server. Every audio/video communication in Discord is multiparty. The best way to describe Cassandra to a newcomer is that it is a KKV store. Instead of DTLS/SRTP, we decided to use the faster Salsa20 encryption. We started digging and found a Discord channel that was taking 20 seconds to load. Click the best option for your group! You could easily have listviews hosting server icons and friendlists, another listview for chat threads, and on native code the same would take what... 20~50MB memory? Having made the choice, we needed to prove that it would actually work. A better way is to stop data-hungry apps from using too much data in the first place. How to voice chat in Among us using discord server | Chat with Friends - YouTube. It is a challenge to balance the amount of bandwidth and CPU/GPU resources used to provide the best video quality, especially when a group of gamers in a channel may be on a range of different devices. Most video call apps use a minimum of about 500 kbps (3.75 MB/minute) for one-way standard definition calls and a maximum of around 1.8 Mbps (13.5 MB/s) for one-way high-definition video. Discord Business Model Discord has more than 87 million users , and is planning to rule over the $1.7 billion worth of voice chat … Because our browser app uses the browser WebRTC API, we make use of SDP/ICE/DTLS/SRTP. We are adding hardware video encoding to our desktop application for a better experience. How much data does Facetime use? This provisioning includes lots of redundancy to handle data center failures and DDoS attacks. Netflix and Apple run clusters of hundreds of nodes so we know we can punt thinking too much about this for a while. These properties combined allow for very powerful data modeling. When a client displays “Awaiting Endpoint,” it means that the Discord Guilds server is looking for the best Discord Voice server. Here, expert and undiscovered voices alike dive into the heart of any topic and bring new ideas to the surface. An old Reddit post by a Discord staff member tried to clarify the situation around privacy. The state on the SFU is reconstructed by the signaling component without any client interaction. We looked at the largest channels on Discord and determined if we stored about 10 days of messages within a bucket that we could comfortably stay under 100MB. The encryption keys are set up using Datagram Transport Layer Security (DTLS), which is based on the Transport Layer Security protocol used in your browser every day. It quickly became clear that our reads were extremely random and our read/write ratio was about 50/50. It’s backed by DataStax, but still open source and community driven. Cassandra was the only database that fulfilled all of our requirements. In addition, we avoid sending audio data during periods of silence — a frequent occurrence especially with larger groups. When you join a voice channel, you are assigned to a Discord Voice server. The noise gate helps eliminate electronic and background noise by cutting off all sound below a certain threshold. This means they send a message or two every few days. Discord is a voice, video and text communication service to talk and hang out with your friends and communities. It really depends what you're doing, if you tend to load images lots, embeds enabled, voice chat etc. The messages were stored in a MongoDB collection with a single compound index on channel_id and created_at. Although SFU crashes are rare, we use the same mechanism for zero-downtime SFU updates. Four billion minutes of conversation happen on Discord each day (The Verge) What is Discord’s largest server? You’re free to experiment with all of the server regions freely. We want to avoid doing this one and don’t think we will have to do it. We believe this will continue to work for a long time but as Discord continues to grow there is a distant future where we are storing billions of messages per day. The app provides voice and text chat for groups, with an emphasis on gaming. Since every client connects to our media relay server, we do not need ICE. Private text chat heavy Discord servers send a decent number of messages, easily reaching between 100 thousand to 1 million messages a year. Slack vs Discord: Integrated File Sharing. When we started importing existing messages into Cassandra we immediately began to see warnings in the logs telling us that partitions were found over 100MB in size. A server can have at most 500 channels - text, voice, and categories combined. Discord Guilds then pushes all the voice state objects to the new voice server. It is a voluntary program that focuses on influencing to take part in purchases. Our homegrown SFU (written in C++) is responsible for forwarding audio and video traffic within channels. When the guild owner decides to select a new voice region, we perform a very similar procedure as described above. We perform the same procedure as for Discord Voice server failure: remove the impacted Discord Voice server from the service discovery system, select a new Discord Voice server for the guild, push all the voice state objects to the newly selected Discord Voice server, and notify clients of the new voice server for reconnection. Discord Voice server contains two components: a signaling component and a media relay component called the selective forwarding unit or SFU. Routing audio/video through media servers offers other advantages as well, such as moderation. In practice this has proved to be fine because for active Discords enough messages are usually found in the first partition and they are the majority. The signaling component constantly monitors the SFU. A server can have at most 250 roles. There are several backend services that make voice possible, but we will focus on three of them — Discord Gateway, Discord Guilds and Discord Voice. Cassandra! From here, select a server. However, providing specific features to our gamers is well worth the extra effort. channel_id became the partition key since all queries operate on a channel, but created_at didn’t make a great clustering key because two messages can have the same creation time. Select “Save Changes,” and you’re good to go!
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