Neelesh Kamkolkar, Product Manager Tableau Server 9.0 Scalability: Powering Self Service Analytics at Scale
2 Table of Contents Motivation...4 Background...4 Executive Summary...5 Tableau Server Powers Tableau Public...6 Dogfooding at Cloud Scale...7 New Architecture Updates...8 New Minimum Hardware Requirements...9 Performance Improvements...9 Parallel Queries...9 Query Fusion...10 Cache Server External Query Cache...10 Horizontal Scale for Data Engine... 12 Other Improvements... 12 Scalability Testing Goals... 12 Testing Approach & Methodology...13 Virtual Machines...14 Physical Machines... 14 System Saturation and Think Time...15 Little s Law... 17 Think Time... 17 Workload Mix Changes...18 New Methodology... 19 Test Workbook Examples...20
3 Extract Characteristics...21 Standardized Isolated Environment...22 Deployment Topology...22 Measurement & Reporting... 23 Transaction...24 Throughput...24 Saturation Throughput...24 Response Time...24 Concurrent Users...24 Results... 25 Comparing Scalability of Tableau Server 9.0 with 8.3... 25 Linearly Scaling Throughput...26 Overall Hardware Observations...26 Memory...27 Disk Throughput...28 Network Usage...28 8-Core Single Machine Comparison...29 Increased Memory Requirements...31 High Availability Impact... 32 Applying Results...33 Backgrounder Considerations...33 Best Practices DIY Scale Testing... 34 TabJolt - Tooling for Scalability Testing... 34 Best Practices for Optimization In The Real World... 35 Summary... 36
4 Motivation Many of our customers are making a strategic choice to deliver self-service analytics at scale. It s natural for our customers (IT and business alike) to want to understand how Tableau Server scales to support all their users globally. In addition, customers want to plan ahead for capacity and hardware budget allocations to accommodate increased adoption of Tableau. As part of our Tableau 9.0 release process, we set a goal to understand how Tableau Server 9.0 compares in scalability characteristics with Tableau Server 8.3. We also wanted to understand whether Tableau Server 9.0 scaled linearly and how increased loads affected its availability. Background If you are used to traditional BI or are new to Tableau, it may help to understand some core differences with how Tableau works. Unlike traditional BI reports that are designed and developed for a limited set of requirements, Tableau visualizations are built for interactivity. Users can ask any number of questions about their data, without having to go through a traditional software development life cycle to create new visualizations. To provide self-service analytics at scale and help keep users in the flow of analysis we have built on top of existing innovative technologies for Tableau Server 9.0. With Tableau, the age-old idea of query first, visualize next is completely changed. Patented technologies, including VizQL, seamlessly combine query and visualization into one process. Users focus on their business problems and on asking questions of their data. Instead of the old way, selecting data and picking from pre-built chart types. They iteratively drag and drop dimensions, blend datasets, and create calculations on various measures. During this process, Tableau creates clear visualizations and seamlessly runs needed queries at the same time. This is a different paradigm that you should factor in as you try to understand the scalability of Tableau Server. If you come from a traditional BI world, you are probably used to load-testing static reports that meet a specific service level agreement (SLA). A static report has a fixed scope, fixed set of queries and is often optimized by a developer, one at a time, over many weeks.
5 Tableau visualizations, on the other hand, may regenerate or submit new queries on behalf of the user s exploratory actions. Optimizations that enable quick retrieval of data can help the user stay in the flow of analytics instead of waiting for the results of a query. In Tableau 9.0, we have invested significantly in performance in addition to many other areas that enable a user to remain in the flow of analytics. This whitepaper explains how Tableau Server 9.0 performs and scales with increasing user load across various configurations and how it compares in scalability to Tableau Server 8.3. Executive Summary Tableau 9.0 is the biggest release in the history of our company. Since November 2014, very early in the 9.0 release cycle, we started performance and scalability testing of new features as they were still being developed. We iteratively incorporated design feedback for new features into the performance and load testing for Tableau Server 9.0. There are a number of factors that can impact performance and scalability, including workbook design, server configuration, infrastructure tuning, and networking. Based on our goals and testing methodology we demonstrated that: 1. Tableau Server 9.0 is nearly linearly scalable across all scenarios tested. 2. Tableau Server 9.0 showed a 200+% improvement in throughput and significant reduction in response times compared to 8.3 3. Tableau Server 9.0 showed increased memory and network usage compared to 8.3 With many new architectural updates in Tableau Server 9.0, we chose cluster topologies based on iterative testing for new server design and common customer scenarios. In the table below (Figure 1), each row represents a Tableau Server 9.0 cluster configuration of 1 Node - 16 Cores, 2 Node - 32 Cores, and 3 Node - 48 Cores. We observed that in various configurations Tableau Server 9.0 could support the following count of users when the system was at saturation. The table of concurrent users included below represents the number of end users accessing visualizations and interacting with them concurrently, at server saturation using Little s Law.
6 In our test scenarios, we assume that roughly 10% of the total end users in an organization or department are concurrently accessing and interacting with visualizations. Based on our testing and workloads, we observed that Tableau Server 9.0 can support up to 927 total users on a 16-core single machine deployment, and scales up to 2809 total users on a 48-core, 3-node cluster setup as shown in the table. Deployment Configuration 1 Node 16 Cores 2 Node 32 Cores 3 Node 48 Cores Tableau Server 9.0 Concurrent Users 92.75 138.04 280.93 Tableau Server 9.0 Total Users 927 1380 2809 Figure 1: Tableau Server 9.0 scalability summary In addition, we demonstrated that Tableau Server 9.0 scales nearly linearly by adding more nodes in the cluster. While in the table above we assumed a 10% user concurrency (that is, 10% of the total number of people in an organization are expected to be simultaneously viewing or interacting with visualizations), your level of user concurrency may vary. In some cases we have seen concurrency as low as 1%. In this whitepaper, we will start by providing some real-world examples of Tableau Server scalability. We will describe new changes in architecture in Tableau Server 9.0 and also our testing approach and methodologies to help you better understand Tableau Server 9.0 scalability. Lastly, we will provide some guidance on how you can apply the lessons from our experiments in your environments. Tableau Server Powers Tableau Public Tableau Server is being deployed at cloud and enterprise scales across many organizations. This includes several deployments at Tableau Software. Tableau Public is our free, premium cloud service that lets anyone publish interactive data to the web. Tableau Public supports a massive number of workbooks, authors, and real-time views. We just recently increased the data extract size from 1 million rows to 10 million rows and increased total storage to 10GB for every Tableau Public user.
7 With over 100,000 authors, over 450 million views, and 500,000 visualizations, Tableau Public plays a key role in allowing us to use our own products. Dogfooding at Cloud-Scale Using our own products to do our work on a daily basis is a core Tableau cultural value. Tableau Public gives us a cloud-scale test environment to test new versions of Tableau Server. As part of the product release process, we deploy Tableau Server pre-release software to Tableau Public. This enables us not only to deploy our products at large scale in a production, mission-critical environment, but also to understand, find, and fix issues related to scalability. We deployed Tableau Server 9.0 to Tableau Public in the 9.0 Beta cycle. This gave us ample opportunity to not only learn about how the new architecture is scaling in a real production situation but also helped up to find and fix issues before we released the product to corporate customers. Figure 2: Point in time view of Tableau Public usage Tableau Public has served more than 450 million impressions in its lifetime with over 27 million in just the last month. It also supports more than 100,000 authors who are creating and publishing over 500,000 visualizations to Tableau Public.
8 The Tableau Public configuration is similar to a corporate deployment of Tableau Server with a few exceptions. All Tableau Public users are limited to a fixed extract size of up to 10 million rows of data. Since it s an open, free platform, users on Tableau Public don t expect the same level of security when accessing public data. Additionally, Tableau Public uses a custom front-end called Author Profiles for managing workbooks instead of the Application Server (Vizportal) process. However, Tableau Public runs tens of thousands of queries every single day and while the data sizes are relatively small, they have a high degree of variability. Tableau Public, powered by Tableau Server 9.0, has been a strong testing ground for the architecture updates we made in Tableau Server 9.0. New Architecture Updates In Tableau Server 9.0, many of the new capabilities are rooted in a strong architectural foundation that extends and expands the pre-existing enterprise architecture of Tableau Server. We have added several new server processes to Tableau Server to support these new capabilities. To understand how to manage scalability with Tableau Server 9.0, it s important to get familiar with these components and understand their role. For simplification in Figure 3, we have rolled up multiple server processes into a logical architecture of higher-level service layer groups. Gateway (Reverse Proxy) User Tier Content Management Services* Visualization Services Data Provider Services API Services Storage Tier Management Tier Repository (Postgres) File Store* Cluster Controller* Coordination Service* Backgrounder Figure 3: Logical architecture for a single server node
9 Multiple server processes work together to provide services at various tiers. The gateway is the component that directs traffic to all server nodes. You can put an external load balancer in front of the server cluster (not shown in Figure 3) and have a gateway on every node for improved high availability. The user tier consists of content management, visualization, data provider and API services. The storage tier has the content Repository and a new File Store process. Structured relational data like metadata, permissions info and Tableau workbooks are in the Repository. The File Store process, is for user s data (Tableau data extracts) and enables data extract file redundancy across the cluster. The Management tier provides a set of services that allows a server administrator to effectively manage the cluster and ensure high availability. For details on individual server process please review the administration guide. New Minimum Hardware Requirements With the new services on server supporting new capabilities, the minimum requirement for the 64-bit server installer have gone up to 4 cores and 8GB RAM. While the minimum is 4 cores for installation, we do not recommend load or scale testing a single node server using a 4-core machine. A single 4-core server is typically for small trials and prototyping. Large enterprise deployments should consider using 16-core servers for each node. Performance Improvements Performance improvements help in providing better response times to end users and promoting company-wide usage. Performance improvements have been made across the entire analytics flow. However, there are many variables that impact performance and your results may vary depending on your situation. Below, we will cover a few of the important improvements that will help guide your deployment for both performance and scale. Parallel Queries Parallel queries are designed to enable Tableau to use the back-end databases more effectively, speeding up the users interactions with a visualization. In Tableau Server 9.0 we now look at a visualization s queries sent to the backend databases and when appropriate, de-duplicate them and issue multiple queries simultaneously.
10 This means that Tableau Server can have multiple connections open to your back-end database and leverage more database resources where possible. This allows compatible databases to work on queries in parallel instead of sequentially, resulting in significantly faster query results. Whether this capability benefits you specifically depends on the how your back-end databases handle parallel work presented to them. Query Fusion As the name suggests, we take multiple separate queries from a dashboard and fuse them together where possible, reducing the number of queries sent to the back-end database. This is particularly beneficial for live connections. However, if your dashboard is not generating any queries that are combinable, this optimization will not help you. Multiple Queries Fused Query Identify identical queries excluding columns returned When output columns differ by aggregation/calcs Fuse to single query with all columns necessary Figure 4: Query Fusion in Tableau Server 9.0 Cache Server External Query Cache If you have just loaded a workbook and run all the queries for the first time, in many cases, when you close and re-open the workbook the data may not have changed in the backend.
11 If this is characteristic of your data freshness and usage scenarios, then loading these workbooks a second time will be significantly faster for your end users. With the external query cache we save the results from previous queries for fast access by future users. The Cache Server process is powered by Redis, which is a highly scalable key value cache used by many large internet-scale providers. Application Server API Server Data Server Backgrounder Vizql Server Cache Server Abstract Query Cache DB DB Figure 5: A simplified view of how caching works The figure shows a simplified version of Cache Server interactions between processes. For simplicity, other processes that don t interact with Cache Server processes are not shown. Each process has an in-memory cache called the query cache. The server process first tries to look for what it needs in the query cache. If it doesn t find it in the in-memory cache, it tries to find what it needs in the Cache Server. If the result is in the Cache Server, it is copied to the in-memory cache and returned. If it s not in either place, the query is run on the database and the results are cached in a Cache Server as well as the in-memory cache of the process that needed it. Caches in each Cache Server are accessible by all server processes and nodes in the whole cluster.
12 Horizontal Scale for Data Engine New for the Tableau Server 9.0 Data Engine, which is the component responsible for loading extracts into memory and querying, is now horizontally scalable to N nodes in a cluster. Previously it was limited to 2 nodes. This also allows you to build highly scalable clusters when using Tableau extracts. Other Improvements In addition, we made many improvements across the Data Engine by adding support for parallel queries (noted above) and vectorization, improved rendering, faster extract creation, support for temp tables in the Data Server and more. There are a lot of additional new capabilities and features across the Tableau 9.0 product line. In the above section we reviewed just the key new server components and their roles. Scalability Testing Goals Early in November 2014, we set out to understand how Tableau Server 9.0 scalability characteristics compared with Tableau Server 8.3 with increasing loads. We also wanted to understand whether Tableau Server 9.0 scaled linearly and whether it bent or broke with increasing loads while maintaining an average response time of three seconds or less. It was not a goal for us to preserve consistency of the methodology, workloads and workload mixes with the previous iteration of this whitepaper. We had to iteratively update and inform all of these based on the design and architecture changes planned for the new release. For example, we focused on workloads that exercised the new features of Tableau Server 9.0, and we were realistic from a customer perspective. Given the departure from workload and changes in methodology, which we will share later in the paper, you should not compare the Tableau Server scalability results published in this whitepaper with the scalability numbers published in previous whitepapers. The variations in testing are significant enough that a direct comparison is not possible. For the purposes of this paper, and for comparing scalability with the previous release, we explicitly ran the same tests against both Tableau Server 9.0 and Tableau Server 8.3 using the same hardware. We followed the same methodology both times.
13 Testing Approach & Methodology A lot of the methodology we used for this paper is informed not only by commonlyused best practices but also by the design changes we were making in Tableau Server 9.0. For example, in addition to using customer-facing workbooks, we were selective about the additional workbooks we added to the test mix. This is because we needed workbooks that would represent user actions that explicitly exercise the new features being built. Holistically, there are a number of different workloads that can run on Tableau Server, from end users loading visualizations, to automatic subscriptions, extract refresh jobs and more. As part of the methodology, we have focused on the end user workloads predominantly because part of our goal was to understand how many end users the system can support at saturation. When you plan for overall capacity, you should plan and account for capacity needed to run the backgrounders in addition to the concurrent user load. Typically, you want to deploy between N/2 to N/4 number of backgrounders on a machine where N is the number of cores on a machine. Detailed guidance and consideration on backgrounders is already part of the server administration guide. In the user-facing tier, the primary processes on Tableau Server that service user requests are the VizQL Server and the new and improved Application Server. There are other processes like the API server, which only services API client requests. We have excluded that from our test methodology to stay focused on the end user workloads. The VizQL server process is CPU-bound by design and needs sufficient resources allocated to ensure proper performance and scalability.
14 Virtual Machines Many customers deploy Tableau Server on virtual machines and run successful scalable deployments. It is not the goal of the whitepaper to exhaustively distinguish between physical and virtual infrastructure environments or across the various virtualization platforms that are available. The level of performance and scalability you can get on a virtualization platform also depends on the configuration and tuning of the virtualization parameters for a given platform. For example, using CPU overloading on VMware ESX is not recommended for Tableau Server, because with heavier workloads, other applications may compete with Tableau Server resource needs. Instead, you should consider running Tableau Server on VMs with dedicated CPU affinity. There are virtualization platform vendor-specific whitepapers you should review for best practices for your chosen virtualization platform. A couple of examples for VMware are listed below for your consideration. Performance Best Practices for vsphere 5.5 guide Deploying Extremely Latency-Sensitive Applications in vsphere 5.5 Tableau Server 9.0 runs as a server class application on top of any virtualization platform. It requires sufficient compute resources and should be deployed with that in mind. We recommend you seek guidance from your virtualization platform vendor to perform tuning for your server deployment. Physical Machines Each physical machine deployment will vary depending on many factors. For the purposes of these experiments, we wanted to minimize variability with virtualization platforms and their specific tuning. So, we deployed Tableau Server 9.0 clusters on physical machines with homogenous hardware configuration in a network-isolated lab. For each test pass, we ran a predefined set of workloads and load mix against 16, 32, 48 cores across various cluster topologies. Through each iteration we recorded not only the key performance indicators, but also system metrics and application server metrics using JMX. For each of the runs, we correlated the data and analyzed how the system behaved under increasing user loads. At the end of each of the iterations, given the architectural changes, we reviewed the results with our architecture team to inform future testing and methodology updates. We also found and fixed scalability bugs as part of our agile development process.
15 We ran many experiments that informed the deployment topologies for the final tests. These experiments included studies of how server scalability is impacted with various server component interactions. We will share these results as part of this whitepaper. In all, we ran over 1000 test iterations across one topology with each of the iterations roughly taking two hours to complete. We measured and collected a variety of system metrics and application metrics during the load tests to understand how the system scaled with increasing loads while adding more workers to the cluster. System Saturation and Think Time Often, infrastructure teams will want to measure and monitor CPU on the various server processes and the machine. Typically, infrastructure teams want to allow for sufficient CPU capacity headroom for burst load. For example, 80% utilization on CPU could be a good indicator of saturation from an infrastructure point of view. However, Tableau Server 9.0 is a workhorse and requires sufficient compute capacity to do its work. It is not uncommon, at times, to see some processes in a server cluster taking up 100% of a CPU s cycles. This is by design and something the infrastructure teams should consider as part of their monitoring strategy. We measured the system saturation as a point during the load test where we attain peak throughput saturation in combination with a ceiling on average response times not exceeding three seconds. If the average latency exceeded three seconds, we ignored any further increase in throughput of clients because we wanted to take a conservative view on the reported numbers. What this means in the context of our experiments is that Tableau Server could allow more incremental user load on the system at the expense of increased latencies for new users coming on to the system. In addition, we set a goal of < 1% error rates (socket, HTTP, or other) for picking the point where we measured saturation.
16 Below is a summary view of the measurements we took at system saturation comparing Tableau 8.3 and Tableau 9.0. The view shows KPIs like TPS, average response time, concurrent users (using Little s Law), and error rate. Figure 6: One test scenario showing system saturation point Once we determined the throughput and response times at saturation, we then used Little s Law to extrapolate the number of concurrent users on the system.
17 Little s Law The goal of these tests was to determine the point at which the system reaches capacity, including the total number of users at that point. Little s Law helps us illustrate this point very well. Imagine a small coffee shop that has one barista who can only help one customer at a time. People enter, buy coffee, and leave. A basic cup of coffee is served up quickly and more complex drinks take longer. In addition, if the barista were to take additional time to review instructions on preparing a drink, then the total time for servicing the user is the time taken to review instructions plus the time required to make the drink. The end-to-end service time drives the rate at which they serve people and send them on their way. However, if the number of customers arriving exceeds the number of customers leaving, eventually the coffee shop will fill up and no one else can enter. The coffee shop is maxed out. The variables that determine the maximum number of customers in the shop at any one time are the length of time they spend there, the complexity of their drink order, and the number of workers serving them. To apply the coffee shop analogy to Tableau Server, let s imagine each barista represented a VizQL server process. The coffee is analogous to the loading of a visualization or an end user interacting with a dashboard. Then, the number of end users concurrently loading and interacting with visualizations becomes the product of the average response time and the saturated throughput. Concurrent Users = Average Response Time x Saturated Throughput You may be wondering, what could represent the CPU in this analogy? We could imagine the CPU being the hardware the barista uses to actually do the work the espresso machine, the juicer, the mixer, the coffee dispenser, etc. An espresso machine that can pour one shot at a time compared to four shots a time can have a material difference on how efficiently the barista can service customers. Think Time Often, load and performance testing teams include something called think time to their response times or load testing scenarios. While this is a realistic concept, in the context of analytics, think time can be difficult to predict.
18 For example, when looking at a visualization, I may quickly find what I want a very short think time. However, this may lead to a lengthy, iterative exploration of the data. This additional exploration could all be considered the end users think time. Traditional approaches have used this to mimic end user delay. In our approach, we decided to test for real concurrency and ignored adding a specific think time delay in our tests. In effect, our think time was zero. On user ramp, there are many possible models. We ramped up one user per second, with zero think time between their actions, until we reached saturation as defined above. Workload Mix Changes We started doing performance and scalability testing very early in the release cycle. Along the way, we made some key decisions that informed our approach. We wanted to use a workload mix that would ensure we exercise the new capabilities in the server and represent a realistic usage scenario including real customer workbooks. In our previous whitepaper, on the same topic, defining or classifying a workload as simple/complex/moderate proved to be challenging. It often led to subjective interpretations of what the terms meant. For example, a workbook can look visually simple, but may have complexity associated with the data required for it. This would make it a compute-intensive workbook and one that benefits significantly from the product investments we made in Tableau Server 9.0. In order to simplify and exercise new features, we created a credible workload mix across (a) a mix of realistic workbooks including customer workbooks (b) a mix of users viewing and interacting with workbooks.
19 The figure below shows a visual representation of the load mix so you can see how we have mixed the workloads for our tests. VizQL Server Load Ramp: one user/second 65% View 60% Browser Render 35% Interact Load Mix 40% Server Render Multiple Workbooks Figure 7: Showing the load mix used to represent multiple workload types for Tableau Server 9.0 New Methodology The workload mix departs from the simple, moderate, complex workbook notion that we used in the past whitepapers. Instead of running the server to saturation with a workbook of one type (simple, complex, moderate) and using a user mix of viewers and interactors, we wanted to make it more realistic. We introduced a pool of workbooks that range in complexity. This pool included workbooks that exercised the brand new features of Tableau Server and also customers workbooks. Depending on the workbook s design, it may use browser rendering or server rendering. Browser rendering is a capability that existed in previous versions of Tableau Server. It allows modern browsers to do some of the workbook rendering, reducing the servers workload. In cases where a workbook is very complex, for performance reasons, Tableau clients push the heavier rendering work on to the server. In response, the server does the heavy lifting and just sends back tiles that make up the visualization. This is referred to as server rendering.
20 Tableau visualizations can therefore use modern browser capabilities where appropriate or push heavier work to the server. The choice is dependent upon the workbook s complexity, but is transparent to the user. The updated workload mix and the new methodology of selecting from a pool of workbooks, are some of the key reasons for why you should not compare the previously published results for 8.1 with results for 9.0 in this paper. Test Workbook Examples While we cannot publish the sample workbooks we used as they include customer workbooks, here are some examples of the types dashboards in use. User interaction workloads include navigating through a Tableau Story Point, filled maps with varying layers and increasing number of marks, selection, categorical filter by index, tab switching, filter actions and more. Below is an example of a Story Point workbook used for testing. Season Name Member to death ratio (X member for 1 death) Autumn Spring Summer Winter 0.0 3.8 # of climbers and # of Expeditions growth over time Annapurna I An A na n. p... Cho Oyu Dhaulagiri I Everest Kangchenjunga K K a. a... Lhotse 600 Lhotse Shar Makalu Manaslu Yalun g Kan g 100 80 # MEMBERS 400 200 156 165 60 40 # EXPEDITION 32 0 2.25 51.1371. 13.01 40 3.38 10.35 21 1.86 91.1711 1.00 35 3.49 36 1.00 11 1.17 2.89 40 3.71 151.11 20 0 1969 1979 1985 1991 1997 2004 2009 2004 1958 1980 1986 1992 1998 2004 1955 1970 1978 1984 1990 1996 2002 2008 1933 1950 1960 1967 1973 1979 1985 1991 1997 2003 1925 1951 1980 1986 1992 1998 2004 1989 1989 1973 1979 1985 1991 1998 2004 2001 1965 1983 1989 2007 1961 1974 1981 1987 1993 1999 2005 1954 1973 1979 1985 1991 1997 2003 1974 1985 8000ers map Summit to Death ratio Death trends over time Annapurna I -> Click on a peak to find more about it Kangchenjunga Number Of Member Deaths 150 100 50 0 More Red means higher % of Death per 100 summitter Darker Green means safer Dhaulagiri I Lhotse Everest Cho Oyu 0 500 1,000 1,500 2,000 2,500 3,000 # MEMBERS ON SUMMIT Number Of Member Deaths 40 20 0 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s Peak Name Annapurna I Annapurna I - Mid.. Dhaulagiri I Kangchenjunga Kangchenjunga So.. Lhotse Middle Makalu Yalung Kang Max. HEIGHT in Meters 8,000 to 8,850 Annapurna I - East.. Cho Oyu Everest Kangchenjunga C.. Lhotse Lhotse Shar Manaslu Figure 8: A Story Point workbook that shows climbing and accident trends in the Himalayas.
21 Figure 9: Number of Taxi Rides workbook with sample interactions Another test workbook shown above looks visually simple but took a long time to load in previous releases. This was due to the same query being re-run separately for each of the 4 views. This workbook was based on a taxi rides data set and the specific interactions we exercised were the following: Select Categorical Filter By Index, Tab Switching, Select November on the Calendar, Pick the Date 17th, Filter to Cash, Switch Tab. Other test workbooks were designed to test for performance under heavy loads with 1,000,000 marks showing various trending analysis. All of these workbooks were built using extracts. Extract Characteristics We chose to test with workbooks based on extracts. This eliminates any variability that a live back-end data source can bring to the tests. Realistic live connection scenarios vary significantly depending on how the databases are used and what other loads are running on the databases themselves. The extracts we used ranged in row count from 3000 rows to 93 million rows of data (~3.5GB in extract size).
22 In addition to workloads, there are many variables that can impact system performance and scalability. In order to manage this variability and to drive consistency among test runs, we standardized on several aspects of the test. Standardized Isolated Environment First, we standardized on the hardware. We ran these scalability tests in our performance lab on physical machines with the following specifications. Server Type Operating System CPU Memory Dell PowerEdge R620 Microsoft Windows Server 2012 R2 Standard 64 Bit 2.6 GHz 2x8 cores (16 core total), and hyper-threading enabled 64 GB Figure 10: Hardware specification of the benchmarking environment Deployment Topology Across each of the cluster nodes (workers), except the primary, we maintained the following configuration of server processes: Figure 11: Showing the server deployment topology for the scalability testing.
23 We scaled the workload using load generators driving the workload mix described above. During test execution, we collected system metrics, performance metrics, and application metrics using JMX. We saved the results in a relational data store. We then analyzed the results using Tableau Desktop. The figure below shows a logical but simplified view of the test execution. It s simplified only in that each cluster node does not show all the server processes running on the machine. TabJolt Load Generators Tab Jolt 1 Tab Jolt 2 Gateway Server Clusters VizQI x 2 App Server x 1 Data Engine x 1 Tab Jolt 3 Gateway VizQI x 2 App Server x 1 Data Engine x 0 Test Results Gateway VizQI x 2 App Server x 1 Data Engine x 0 Tableau Desktop Analytics Gateway VizQI x 2 App Server x 1 Data Engine x 0 Figure 12: The logical and simplified view of the test environment Each of the test iterations collected a lot of data, but before we jump into the results, let s understand some of the metrics and the definitions. Measurement & Reporting We measured a number of metrics to understand the system performance and scalability including system metrics for CPU, Memory, Disk, and performance and scalability metrics such as response times, throughput, run duration etc. To understand the data discussed in this whitepaper, let s quickly review some definitions.
24 Transaction A transaction is the end-user experience of loading a Tableau visualization and/or interacting with a view. For example, if you are loading a visualization, the entire set of requests (HTTP) that load the visualization represents a single transaction. The response time is measured and reported for a transaction from the client s perspective (that is from where the load is being generated). Throughput Throughput is the number of transactions per second (TPS). E.g. 5 TPS = 432,000 transactions in a 24-hour period. Tableau Public, for example, has supported a peak of 1.3M page views in a day. Saturation Throughput Saturation throughput is the number of transactions per second across all clients hitting the system when the system is in saturation. Our approach to determining saturation point is described earlier in this paper. Response Time Response time is measured as the amount of time it takes the server to respond to the end user request. Concurrent Users To understand concurrency in the context of Tableau Server, we will start by defining what concurrency is not. Many times we speak to performance teams that assume that user concurrency is defined as the number of users logged into Tableau Server. While that is a logical metric, is it not representative of concurrency in this whitepaper. Number of logged in users only measures the scalability of the Application Server process. A user login exercises a narrow path in the system and is not the same critical path that loads and interacts with a visualization which does a lot of the compute-intensive work. For Tableau Server, concurrency is defined as the number of end users that are actively loading and interacting with visualizations at a specified response time and throughput goal. This is a core metric that informs the number of users that we can support on a given system under test, at saturation. We use Little s Law to extrapolate the number of concurrent users number based on average response times and saturated throughput across our experimentation and test execution.
25 Given that Tableau Server s scalability is informed by how VizQL server processes are able to process and satisfy end user requests to load and interact with visualizations, we ran a series of tests to measure that. Now that we ve seen how we perform test execution, the deployment we used, and the metrics, let s review the results. Results With all the new features and architecture updates in Tableau Server 9.0, we ran several experiments to inform the following scenarios. We ran the same workload using the same methodology, on both Tableau Server 9.0 and Tableau Server 8.3, across the same topology and hardware in the same lab so we could compare scalability across the releases. Comparing Scalability of Tableau Server 9.0 with 8.3 With 16 cores or more, we see an increase in performance and scalability for Tableau Server 9.0 compared to Tableau Server 8.3. Specifically, we saw Tableau Server 9.0 scale from 927 total users on a single 16-core machine to 2809 total users on a 3-node, 48-core server cluster with average response time well under the goal of three seconds and an error rate below 1%. For a typical workload, we demonstrated that Tableau Server 9.0 saturated throughput increased from 209 TPS on a single node 16-core machine to 475 TPS on a 3-node 48-core machine. Reminding ourselves that TPS corresponds to the number of visualizations loaded and interacted with in a second, we see a nearly linearly scaling system where you can scale out by adding more worker nodes to your cluster. Topology Saturated Throughput TPS Response Time (Sec) Concurrent Users Total Users Error Rate 1 Node 16 Cores 209.7 0.44 92.75 927 0.78% 2 Node 32 Cores 303.4 0.46 138.04 1380 0.58% 3 Node 48 Cores 475.5 0.59 280.93 2809 0.16% Figure 13: Tableau Server 9.0 scalability summary
26 We re-ran the same tests using Tableau Server 8.3 on the same hardware, with the same methodology. We captured the results in the table below. Topology Saturated Throughput TPS Response Time (Sec) Concurrent Users Total Users Error Rate 1 Node 16 Cores 61.0 1.47 89.88 899 0.46% 2 Node 32 Cores 144.6 0.69 99.82 998 0.06% 3 Node 48 Cores 152.6 1.36 206.76 2068 0.12% Figure 14: Tableau Server 8.3 scalability summary We observed that Tableau Server 8.3 scaled from 899 total users on a single 16- core machine compared to 927 on the same configuration for Tableau Server 9.0. In addition, Tableau Server 8.3 saturated at 2068 total users on a 3-node 48-core cluster compared to 2809 total users on Tableau Server 9.0. However, Tableau 8.3 saturated relatively quicker, at 61 TPS on a 16-core machine compared to 209 TPS for Tableau Server 9.0. In the larger scale tests we found Tableau Server 8.3 saturated at 152 TPS on a 3-node 48-core cluster, compared to 475 TPS for Tableau Server 9.0. Linearly Scaling Throughput Across all of our testing, we demonstrated that Tableau Server 9.0 throughput scales nearly linearly and is more consistent compared to Tableau Server 8.3 for the same workloads, methodologies, and infrastructure used. For those customers planning to run Tableau Server on a single 8-core machine, we ran a separate set of specific tests to inform this scenario. Please see the 8-Core Single Machine Comparison section later in this paper. Overall Hardware Observations In addition to the specific scalability observations reviewed above and how server scale was impacted with cores and horizontal scaling, we captured infrastructure metrics and observations. In the section below, we will review memory, disk and network impact for each of the above core topologies for 16, 32, and 48-core machines.
27 Memory Compared to Tableau Server 8.3, we observed that Tableau Server 9.0 requires between 40% more memory on a single 16-core machine to 70% more RAM on a 3-node 48-core cluster. Figure 15: RAM utilization across 16, 32, 48 core clusters Increased RAM is a result of many of the changes we presented earlier in the whitepaper and as part of your upgrade from 8.x, you should consider adding more RAM to your 9.0 systems.
28 Disk Throughput For the disks we used in our experiments, Tableau Server 9.0 showed reduced disk throughput over a distributed cluster. With a single machine 16-core scenario, we see a 14% increase in disk throughput consumed between 8.3 and 9.0. However, a 3-node 48-core cluster actually shows a 30% reduction in disk throughput during the load tests between server versions. In Tableau Server 9.0, we are persisting cluster state to disk, and each of the new components in Tableau Server 9.0 logs to disk. Figure 16: Disk utilization comparison Network Usage In Tableau Server 9.0, we now have several components that work together with the new distributed query cache. In addition, we also have a coordination service that maintains the state across the cluster. In comparison to 8.3, this shows relatively large increases in network chatter. However, we did not observe a significant impact from the network chatter on scalability or performance.
29 Figure 17: Network utilization comparison So on its own, Tableau Server 9.0 scales and performs well in spite of the increased network traffic. The takeaway for a real deployment is to consider deploying Tableau Server on 10GB networks when available. 8-Core Single Machine Comparison For customers running Tableau Server on 8-core machines, we wanted to inform how Tableau Server 9.0 would behave in comparison to 8.3 after an upgrade. We ran a battery of tests with the same methodology to compare the results across 9.0 and 8.3.
30 For the single 8-core machine scenario, we observed that Tableau Server 9.0 is significantly better when you look at saturated throughput and response times, when compared to 8.3, as shown in the table below. Key Indicator Tableau Server 8.3 1 Node 8 Cores Tableau Server 9.0 1 Node 8 Cores Saturated Throughput (TPS) 34.2 129.9 Response Time (Secs) 1.80 0.46 Concurrent Users 61.56 59.45 Error Rate 1.71% 0.78% Figure 18: Comparing Server 8.3 and Server 9.0 on 8 core machine With Tableau Server 9.0, we observed a significantly higher saturation throughput of 130 TPS and lower average response times of 0.46 seconds with a lower error rate of <1%. With Tableau Server 8.3, we see a significantly lower throughput of 34 TPS and an average response time of 1.8 seconds. We were able to maintain the error rate goal of < 1% on Tableau Server 9.0, but Tableau Server 8.3 on a single machine with 8-cores had more errors, often related to client time-outs as the response times started to increase with load.
31 Increased Memory Requirements Comparing our single 8-core machine and our 16-core machines, Tableau Server 9.0 used 38% more RAM in our 16-core tests and 68% more RAM on our 8-core tests. Figure 19: RAM utilization comparison across 8.3 and 9.0 for single machine deployments In addition, in multi-machine cluster deployments, Tableau Server 9.0 utilizes about 60-80% more memory at peak usage compared to Tableau Server 8.3. We have increased the minimum hardware requirements for Tableau Server 9.0 to 8GB to accommodate the additional server processes supporting new 9.0 features. For example, each Cache Server process at startup will consume 500MB of RAM. While it s efficient at what it does, the more Cache Server processes you have on a machine, the more RAM that will be set aside. In addition, new processes like File Store consume additional RAM. These didn t exist in prior versions of Tableau Server.
32 What this means is, based on the specific tests in this whitepaper, if you have a single-machine 8-core Tableau Server 8.3 instance, doing an in-place upgrade to 9.0 could help your end users experience a performance boost. However, you may get slightly poorer scaling due to resource contention. Compared to 8.3, on a single machine we saw fewer errors with 9.0. The specific performance gains you see may vary depending on many factors. We hope that this helps inform your planning needs for capacity as you consider upgrading from 8.x to 9.0. We made a lot of improvements to high availability (HA) in Tableau Server 9.0. In addition to introducing new server processes like the File Store, Cluster Controller, Co-ordination Service, etc., we are doing new work to move extracts onto all of the nodes in the cluster that have a Data Engine. We wanted to test what impact, if any, the updates to HA would have on scalability. The following section covers our observations. High Availability Impact In thinking about HA and non-ha, one key thing to remember is that we added several new components to the server to support the new architecture for HA. In order to test HA, we wanted to ensure we included the new application server workload into the mix. We ran the new workload on the same hardware as before. In Tableau Server 9.0, you must have at least three machines to run an HA configuration. For more details, please read the server administration guide. In one test, we enabled HA by adding a passive repository for failover and a File Store and Data Engine processes to every node in the cluster. When compared to the non-ha deployment, when HA is enabled, we noticed a very small impact on throughput and response times. This is minor and anticipated because we are doing more work to keep the Postgres repositories and the extracts in sync. However, we see about a 10% percent increase in memory usage across all workers when running an HA configuration. The increase in memory usage did not impact the TPS significantly. We observed a <1% reduction in TPS when HA was enabled. The error rate (mostly socket-read timeouts) increased 0.1% to 0.3%, although still under our threshold of < 1% error rate. In addition, when running in HA mode, each publish action to the server (in case of extract use) will require File Store processes to synchronize the new extracts across all the nodes in the cluster. In previous versions, you could only run Data Engine processes on up to two nodes in a cluster. In Tableau Server 9.0, you can run Data Engine process on any number of nodes.
33 Each machine running the Data Engine process also requires a File Store process. Given this configuration possibility, you should be aware that the more nodes you set up for extract redundancy, the more costs you will incur in synchronizing the extracts across the nodes. This cost is primarily reflected in network usage and should inform your decision to deploy server workers across slow links. Applying Results At this point, you are probably wondering how this applies to you and how you can determine the capacity you need for your deployments. In this paper, we demonstrated that Tableau Server scales nearly linearly for user concurrency. One approach you could take is to leverage the guidance in this paper to find the capacity you may need and use it as a baseline. Your actual results will vary because you will not be using the same system we used for our tests in this whitepaper. Backgrounder Considerations Much of what we discussed was in the context of user-facing workloads. The most critical of those being view loading and interacting and portal interactions. The Backgrounder server process does much of the work related to extract refreshes, subscriptions and other scheduled background jobs. These jobs don t compete with capacity if you schedule them to run at off-peak hours. When this is not possible, you should plan for and add capacity needed for your backgrounders and non-user-facing workloads to run concurrently with user facing processes. Backgrounders are designed to consume an entire core s capacity because they are designed to finish the work as quickly as possible. When you run multiple backgrounders, you should consider the fact that a background server process may impact other services running on the same machine. A good best practice is to ensure that for N cores available to Tableau Server on your machine, you run between N/4 and N/2 backgrounders on that machine. While not required, you could separate out background server processes to dedicated hardware, as necessary, to isolate it s impact to the end user workloads. If you are looking to conduct your own load testing to find out how Tableau Server scales in your environment with your workloads, here are some best practices.
34 Best Practices DIY Scale Testing Often times, you may want to do your own scalability and load testing so you can determine how Tableau Server scales in your environment and in your workloads. When trying this on your own, here are the top four things you should factor in: 1. Don t treat Tableau Server as a black box. Tableau is designed to scale up and scale out. However, treating it as a black box may give you unexpected results because scaling Tableau Server depends on many aspects of workload, configuration, system environment, and your overall system under test load. 2. Pick the right tool for testing. Tableau Server is a workhorse and does complex and resource-intensive work. There are many tools available to drive loads on Tableau Server. While Tableau doesn t directly support any of these tools, you should pick the one that allows for the greatest ease of use and represents your production environment the closest. Another consideration is ensuring you have the appropriate expertise in tooling and in Tableau Server. 3. Select representative workbooks. Most often when we hear about performance or scale complaints, it is because the workbooks being used are not authored with best practices in mind. If a single-user test on your workbook shows a very slow response time, then you should optimize the workbook before you embark on a load-testing project. 4. When testing workbooks using live connections remember that with the introduction of parallelization in Tableau Server 9.0, you may not need as many VizQL servers as you may have deployed in your previous version of Tableau Server. Start with the new default configuration and scale up your processes incrementally. TabJolt - Tooling for Scalability Testing Tableau recently released TabJolt, a point-and-run load and performance testing tool that is designed to work easily with Tableau Server. It eliminates the need for script development and maintenance and allows for faster iteration. This tool is available as-is, for free, from github. You can learn more about it from the release blog.
35 Best Practices for Optimization In The Real World In addition to a system that is optimally designed, there are best practices that can be used to greatly improve performance and reduce average response time. Use Tableau Data Extracts If your database queries are slow, consider using extracts to increase query performance. Extracts store data in memory and locally on the server so that users can access the data without making requests to the database. They can easily be filtered and aggregated for when users don t need row-level detail, significantly improving response time. Schedule updates during off-peak times Often data sources are being updated in real time but users only need data daily or weekly. Scheduling extracts for off-peak hours can reduce peak-time load on both the database and Tableau Server. In addition, you could add additional backgrounders on existing machines or use dedicated hardware if you have sufficient core capacity. Consider this option for faster completion of extracts. Avoid expensive operations during peak times Publishing, especially large files, is a very resource-consuming task. And it s often easy to influence publishing behavior. Ask users to publish during off-peak hours, avoiding busy times like Monday mornings. To learn when your servers are being used the most, visit the Administrator views, then create policy based on actual usage. Depending on how you have configured Tableau Server 9.0, publishing also means that a copy of the extracts is made on each of the cluster nodes for high availability. Doing this during off-peak times will also allow you to maximize network bandwidth. Cache views As multiple users begin to access Tableau Server, the response time will initially increase due to contention for shared resources. With caching turned on, views from each request coming into the system will be cached and then rendered more quickly for the next viewer of the same dashboard. The Cache Server process, new in Tableau Server 9.0, can be warmed up by scheduling an email that requests common views following completed extract refreshes. That way viewers are using the cached data from your earlier request. You may use other approaches to warming up the cache, using an automated tool to load up key visualizations that regularly see high traffic. The user can manually invalidate the external query cache, which is what the Cache Server process maintains, at any time to refresh their data from the data source and force regenerate the cache. This way, the users can always get a fresh copy of the data regardless if a version is already in cache.
36 Less is more - In prior releases, you may have had to run multiple VizQL server processes on a single machine to handle load. However, the introduction of a core technology called protocol groups allows for parallel queries, VizQL server can now use multiple connections to back-end databases. You may find that in Tableau Server 9.0 you get better scale by actually reducing the number of VizQL processes to less than four. The new default configuration of running two VizQL server processes per machine is now a best practice. Summary In this whitepaper, we went into detail and provided context on our approach, appropriate changes in the methodology, and the final results of our Tableau Server 9.0 server scalability results. We demonstrated that Tableau Server 9.0 scales linearly and performs better when compared to Tableau Server 8.3. We observed that Tableau Server 9.0 could support up to 927 total users on a single 16-core machine and scales up to 2809 total users on a 3-node 48- core cluster setup, with 10% of users actively loading and interacting with visualizations. We hope that you use this whitepaper as a source of guidance for your own Tableau Server 9.0 deployments. Given that every environment, workload and deployment will look different, your results may vary.
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