FAQ: Data Services Real Time Set Up

Transcription

1 FAQ: Data Services Real Time Set Up Assumptions How to load balancer Real-Time job? How does a Web Service Real-Time job utilize multiple job servers? Setup with at least two Web Servers and two Job Servers / Access Server The Access Server acts as a software load balancer distributing real-time message requests from 1-to-many service providers (job server instances). In order to provide failover for the Access Server and/or Web Server (when using web services) you would need to use external load balancer solution. One example using an external load balancer (See more detailed diagrams below) Load balancer Web Services -> Access Server Web Services -> Access Server As for optimizing Real Time jobs or using multiple job servers, you can designate multiple service providers as noted below. Note: when Job Server service/daemon is not running the Access Server will be do wn.. In addition, when web services are being used there is a connection pool between the web service layer and the Access Server(s). The connection pool settings can be adjusted on the web server to enhance scalability and performance. For further information, see Data Services Integrator s Guide. When more than one environment is setup for failover and/or load balancing you would typically replicate the environments. There is no automated way to do this right now. Long term engineering is planning on improving the product to make it easier to replicate environments. For now are detailed steps on how to manually replicate the management console and access server configuration through copying and manipulation of the XML configuration files. When a web services request is made they are sent to the DS Web Service layer via HTTP/SOAP protocols and the Web Service routes them to the Access Server. When using the Message Client API s, requests are sent to the Access server directly bypassing the web service layer and thus providing improve performance. You need to setup Real-time Services and for each service define which job servers will handle the requests and how many service providers (AL_ENGINE processes) will be instantiated to service the requests on each job server. You MUST manage the minimum and maximum instances properly in order to gain scalability of the service on each job server. DOP does NOT scale real-time jobs, but the number of s ervice providers (Processes) does. You need to balance loads with memory consumption per physical deployment and number of services a job server is supporting. Recommendation: We recommend using separate job server (physical/virtual) to handle batch processing vs. real-time to help ensure SLA s for real-time requests are met. For further performance

2 Can web service requests be sent directly to the Access Server or go through the web tier from the Load Balancer? Does Job Server return the result set to the calling Web Services? optimization, see SAP BusinessObjects Data Services Performance Optimization Guide and SAP BusinessObjects Data Services Integrator's Guide The load balancer would go before the web server in the case of web service requests, which is implemented via a Java application running on the web server. In the case of the Java/C++ message client, it will work directly with the DS Access Server. Keep in mind that this API s TCP/IP connection is persistent. The Load balancer must maintain the connection to the same access server each time using the load balancers persistent connection capabilities. When using a load balancer with message clients, message clients should be setup to automatically reconnect and retry if a failure occurs. At that point the load balancer will automatically forward the request to an active node to gain a new connection. The load balancer in this case will balance connections across 1-to-many Access Servers but each invoke() call will have to send the request back to the exact same Access Server, which will balance the load across 1-to-many job servers setup as service providers for that service being invoked. Request/response are a continuous flow (synchronous) in and back out through the same processes. It is not asynchronous. However, most web service tool kits provide an asynchronous interface which will provide a call-back and spawn a separate thread to manage the synchronous request to Data Services. Data Services is setup to handle connection failures between application components. The job server and Access Server's availability is ensured by job service, which will be pinging for the servers every 30 sec. If the Access Server stopped for some unknown reason, the Job Service will restart that again. There is parameter in DSConfig.txt to reduce this time, but I think 30 sec is ideal. However the customer should ensure they setup their client to properly manage any failures that could occur due to a connection failure in Data Services which results in an exception on the client or if the connection between the client and web service or Access Server fails. What would be the optimal placement of an access server? How can an external load balancer know that a DS environment is running properly? Place one Access Server on an y one of the Job Servers. As noted above, each Real-Time job is associated with a list of Job Servers where the Real-Time Job, RTJ, can run. So everybody is sending XMLs to the Access Server, and it looks for an idle service provider and sends the XML to that one. For failover you might want to have a second Access Server so at the end you will probably have one Access Server per Job Server and make sure that 1/3 rd of the requests are sent to one of the Access Servers. You scale up you can have 1-many job servers providing services through 1 access server. At some point the Access Server/Web Server could become the bottleneck and thus you may need additional for performance or purely failover needs. As for the SAP connectivity I would use the term RFC. We talk to SAP via the RFC protocol. The access server acts as a software load balancer within the application across 1-to-many job servers setup to handle real-time requests. However the Access Server would be your single point of failure so most customers use a hardware based load balancer. Each load balancer technology has different methodologies for monitoring a particular node (Data Services instance) in a pool to ensure it is accessible. Sometimes it s a simple TCP/IP connection test, other times it s making an HTTP request and analyzing the content returned. Most allow an HTTP request with a given HTTP body and the ability to compare that against a truth string to ensure availability others have the ability to use SNMP a special configuration when calling web services (sending SOAP messages) etc.. The customer will need to ensure they select the best method of monitoring that suits their needs. In general the simple

3 TCP/IP Connection test is just checking the web server for availability but NOT the Access/Job Servers. So the best methodology to have more confidence in a node being up is to create a tes t real-time job with minimal overhead and have the load balancer send a test soap document to the request. A tool like SOAP UI will generate a test input SOAP document and give you the return document to easily configure the load balancer. This works well for the web services interface but will NOT work for the message client libraries. The message is a proprietary binary format and cannot easily be generated by a load balancer to test node availability when connecting directly with the access server. So for now a simple TCP/IP connection test to the access server should suffice. One of the most common devices used by our customers is the F5 Big-IP solution. More details on its monitoring capabilities can be found here: pdf.html/configuration_guide_for_big-ip_local_traffic_management.pdf Can I run DS Web Services on its own server one different server from the job server? Where is the Web Admin configuration saved? How should DS Web Admin server be configured for Real-Time job fail over? Yes. In fact we typically recommend the web server tier be installed on a separate server from the job server tier. We currently do not charge for deploying the web server to different servers customers just pay for the deployment of job servers. Admin.xml and should be behind the firewall. The management console web application and the web services/sap interfaces are all a single intertwined application from an installation perspective and cannot be installed separately. Thus, to setup the management console for high availability/load balancing today you have two options: 1. Install 2 or more environments and pair up the web server instance with it s own access server and 1-many job servers. Setup each environment manually by logging into the management consoles using the direct host name (not through a load balancer). Setup replicated environments in terms of repo s and services. 2. Install the environments and setup 1 environment. Then follow the steps to replicate the configuration of the management console AND the access server (if using real-time services) through copying and modifying the necessary XML files (see the appendix with detail at the end of this document. Customers commonly ask about how they should handle the repository when it comes to ensuring high availability. You have two options: 1. Use the RDBMS vendors failover support such as Oracle RAC if using Oracle. Many customers don t own these features of their RDBMS and are hesitant to invest in this way. From an engineering perspective we re really only done testing with Oracle s RAC capabilities and have not done official testing with any other vendors failover capabilities. 2. If the customer doesn t want to invest in the RDBMS vendors solutions then the second most common methodology is to use 2 or more copies of your production repository 1 copy for each replicated environment. Describe the steps to test Data Services Real-Time You can first test your real-time job in the Designer. Open the reader and loader and specify the

4 job location of an input XML file that matches your defined schema and open the loader and define the location and file name of the output XML file you want it to create. Make sure you specify in the loader to delete and recreate the file or it will append each run of the job into the existing file. Ensure that your output looks correct first when running from the designer. Next test the real-time service through 1 of two ways depending on if the customer will be using the message client libraries OR the web service interface: 1. Message Client libraries In the SDK folder where the message client libraries are installed with Data Services you will find a samples folder. There is some basic sample code for both the Java and C++ API s. Use the samples to test a real-time service if you will be using the message client library. Pre-requisites: 1. Create a Real-Time job and test through the designer 2. Configure a Real-Time service in DS Management Console 3. Modify the sample code to call your real-time service as you named it in the management console and change the input XML to match the schema you defined in Data Services. Ensure that you ve properly defined a namespace in your XSD s that you use as a source and target. 2. Web Services if the customer will be using the web service interface there are many tools out there to perform simple testing without generating the web service clients through a software development tool. There is a great free tool called SOAP UI which is fairly reliable tool for ensuring you web service is working correctly Pre-requisites: 4. Create a Real-Time job and test through the designer 5. Configure a Real-Time service in DS Management Console 6. Add the real-time service as a web service. 7. Install free tool soapui Start soapui and add WSDL URL, i.e. the Real-Time service defined in the Management Console. Expand the job and display default XML. Replace the default XML with the test XML content and run. You will see the result set on the right pane. Also you will see the requests increasing for the real-time service in the DS Management Console for each request Some other very useful tools are XMLSpy which allows you to graphically create XSD s, validate them, and generate sample XML files. SOAPScope is a great tool for testing web services and we ve used this internally many times for testing purposes. This tool isn t all that expensive and can be used for development teams to automate the testing of their services as well. Well worth a look. Over the past many releases we ve ran into a number of issues with the handling of namespaces in web service tools and a few bugs in Data Services that we ve addressed to ensure this works properly whether a customer defines a namespace or not in their XSD s. But the best practice is to always define a namespace for your XSD s. Make sure you do the following: 1. Define a default namespace 2. Define a target namespace (typically the same as the default namespace) 3. Define the elementformdefault attribute of the schema element to be true.

5 Here is an example: <xsd:schema xmlns:xsd=" xmlns=" targetnamespace=" elementformdefault="qualified"> NOTES: 1. Ensure that you are defining unique namespaces for your reader and your loader 2. Ensure that your namespaces are unique across real-time jobs. 3. Your namespace doesn t need to be a URL but that s typically standard as it s an easy way to ensure that you have a unique namespace. It can be any string you want to use. Typically organizations define a standard such as the company domain and different paths after the domain for various groups/applications. Performance Tuning Some main things to watch when it comes to performance: 1. When you create your real-time services the number of Min/Max instances determines how the real-time service will scale up. For each instance 1 AL_ENGINE process is created on the server. Each AL_ENGINE process can handle 1 real-time message request at a time. So you ll want to change these from the default of 1 to something else based on the number of service providers your setting up on each job server and the number of CPU s/cores. 2. Connection Pool there is a connection pool for the web service connections to the access server. The documentation covers the options you ll need to tweak in order to properly manage this pool. We ve seen a few customers that have had to tweak these settings from the defaults in order to further scale up the solution for better throughput. 3. Watch the different statistics in the management console around avg. response times, queue lengths etc. so you can see if requests are piling up in the queues and response times are not in alignment with what you need to meet an SLA. NOTE: The first message request through a given AL_ENGINE process will always take longer than each subsequent request due to a small amount of initialization that can only happen when the first request comes through. That may skew you request times you see in the management console. 4. Each AL_ENGINE process for real-time jobs can take a good amount of memory even for simple jobs so monitor the memory use on the server and ensure you have enough for all the services and the number of service providers (Max/Min settings) you intend to have on a given job server. 5. We typically recommend that customers deploy at least 2 stand alone web/access/job servers to ensure high availability. We typically expect customers to deploy those on servers that are NOT shared with a job server that will be performing batch operations. This recommendation is to ensure that they will meet their performance SLA s for their real-time services by not consuming most if not all of the system resources when running a batch job. However, if a customer will have low or no real-time requests at night and can schedule their batch jobs then there is no reason they couldn t share the same job server for batch/real-time operations. NOTE: If a customer is to have more than 1 environment for HA/LB they will need to pay for the CPU s for each job server they are using ONLY for those job servers that are truly active. If they have an Active/Passive configuration where a particular environment would ONLY be used upon another

6 How do I update my data quality reference data for real-time services? How should a customer setup a load balancer to determine which environments to send requests to? How are RDBMS connections handled when a failure occurs? environment failing they do not have to pay for the passive setup. Typically customers will have 2 or more replicated environments (web/access/job servers) and for each of those environments have a separate file system containing the address directories and potentially a separate cleansing package repository. This way they can bring down 1 environment at a time to update the reference data and the load balancer will automatically send request to the still active environments. There are many ways this can be tackled and each administrator will probably have their own preference but they commonly ask for features in the software to enable them to easily do this. Some common mechanisms we ve seen: 1. Simple open/close a TCP/IP connection to each web server or acc ess server (message client libraries) instance. If it succeeds in making a connection it considers the environment available. 2. Make a web service request (SOAP/HTTP) to the web server to call a simple real-time service. 3. Call the ping real-time service method from the load balancer. 4. Some load balancers also have software daemons which run on the servers where our applications are housed that monitor and report system used back to the load balancer Typically we d recommend #2 and the customer create a very simple job that responds quickly. This is more fool proof than option #1 and #2 since those are really only testing the availability of the web service and not the Access Server or Job Server instances. NOTE: You can configure the Windows Service and unix/linux daemon for DS (which controls BOTH the Access and Job Server) to autorestart if they were to fail for some reason. Also if a service provider (AL_ENGINE instance for a real-time service) fails DS will always start new AL_ENGINE process to maintain at least the minimum number you ve defined for each service. We have a solution to address the loss of repository connections when trying to access the repository during job execution. This covers the following scenarios: 1) Access to repo by DQ transforms (i.e. DQ transform writing data to the repository for report data) 2) General DS accesses to the repository for writing operational metadata to AL_HISTORY, AL_STATISTICS at end of dataflow/job execution. 3) The fix is applicable for both real-time and batch for the above scenarios. In addition, the DB reader for candidate selector (Match transform) is also made connection tolerant in real-time mode. It automatically reconnects a broken connection before processing a real-time message. The supported databases are Oracle, SQLServer, DB2 or MySQL. Due to a technical issue with the client, we cannot support this functionality for Sybase as a repository RDBMS. When connections are lost and reconnecting is taking place, trace will show: Database connection to <sj-asamudra> broken. Retrying with retry count <6> and sleep interval <10>

7 seconds Database connection to <sj-asamudra> broken. Successfully obtained connection after <2> attempts. In the event the db re-connect failure, you will see the following message (this time, it is an error, as the job could not access repo to update al_history) and engine aborts execution: Database connection to <sj-asamudra> broken. Failed to obtain connection after <6> attempts. Please verify that the database server is accessible. Note: You will still see green icon in admin in this case. These database retry s are configurable within the DSConfig file: Recycle_DB_Connection_Retry_Count=6 Recycle_DB_Connection_Retry_Sleep_Interval_In_Seconds=10 Setting Recycle_DB_Connection_Retry_Count=0 will turn-off this feature, useful while testing. Identifying and debugging XML Schema or other web service issues at design time? Sometimes there could be certain issues with the XML schema definitions being used or other problems where the real-time service cannot be properly added to the WSDL. This is not common but has come up a few times. When that happens the key is usually that you won t see your real-time service in the list of real-time services after adding it in the management console. If this happens you should view the WSDL in the management console and you will usually see an error message at the very top about your real-service and what the issue was. If you see this the best thing is to make sure you ve tested your job in the designer and if need be re-add the service. However, you can find additional detail that might be beneficial in some log files on the web service tier: Depending on where the error occurs, the logs should be in $LINK_DIR/log folder. Take a look at webservice.log, webadmin.log or error.log et cetera. These should be submitted to customer support if you re not able to address the issue yourself. How is the number of real-time service providers management with the Min/Max settings? How to replicate the management console and if you are using Real-Time services how to replicate the configuration stored with the Access Server When a real-time service is started the min number of service providers will automatically be started. If the #of service requests in a queue is larger than the # of service providers, it will create new provider instances up until the max instances is reached. If a service provider instance is idle for 10 minutes AND the #of instances is > minimum instances it will shutdown. Scenario: tested the replication of Data Services Web Server Configuration using 2 Servers, following are the steps for that, same steps can be followed for more than 2 servers. See below for more detail. Sample failover / load balancing architecture Visio diagrams are listed at the end of this document. How to replicate the management console and how to replicate the configuration stored with the access server if you re using real-time services:

8 1 Install Data Services Web Server on the 2 different servers (machines) 2 Configure repositories, access server, CMS Connection and other parameter on the Web server 1 (access the Management console by directly connection to this server, don't connect using F5 switch) 3 Stop both the Web servers 4 Copy following files from Web Server 1 from $LINK_DIR/conf to Web Server 2 $LINK_DIR/conf directory a dmin.xml mdreport.ini (if it exists) dqreport.xml (if it exists, this file is created if, function areas, and rules are configured in Data Validation else this file will not be there) sapconnections.xml (if it exists, this file is created if SAP RFC Server Interface is configured, else this file will not be there) 5 After copy is completed, on Web Server 2, open the admin.xml and update the AccessServer details, the access server name and port info will be stored in the XML tag named server-name and server-port in the <accessservers> XML node <server-name>vanpgwin195</server-name> <server-port>4000</server-port> 6 Restart both the Web Server Note:- Do not change any configuration by accessing the management console URL via F5 switch, which can result in configuration files getting out of sync, the other limitation is you will not be able to monitor the real time services from DS Management Console via F5, since the Access Server information for different http session can come from any of the web server, depending on the web server that is processing the request it will display a different access server, and while trying to access the info for RT services the page may give errors The Access Server and real time service configuration is stored in AS.xml file in Access Server directory 1 Start Access Server on Machine 1 2 Configure Real Time Services, by opening the management console directly on the Web server machine to which this Access Server is associated 3 Stop the Access Server on both machines 4 Copy the AS.xml of the Access Server configured on Machine 1 to Access Server directory of Machine 2 5 Change the job server information of each service, the job server info is stored <JobServer> xml tag in th e host and port attributes. Replace the highlighted attributed with the job server host and port of this machine <JobServer connection=" -SVANPGWIN195 -NOracle -UDS122 -P;994973A404D5BDB1552BC53D9587EAFDF3101D2A01633F444501B944F039A864"enabled="1"host="SJ-W-01-TEST"max="1"min="1"port=" 3595"/> 6 Start both the Access servers

9 Useful Diagrams to depict failover/load balancing setup

10

11