Liquibase is a great tool, and comparable to Git for databases. While it might not technically be a source control system, it's packed with similar functionality.
Methods like blue-green and canary deployments, along with A/B testing, have been staples of DevOps. This article will clarify the differences between each one.
Distributed transaction tracing is a useful way to monitor or evaluate your microservices architecture for performance, particularly when measuring end-to-end requests.
How do you answer the age-old question, "Is it done right?" Here's a whirlwind tour from defining software characteristics to static code analysis tools.
In this article, excerpted from the book Docker in Action, I will show you how to open access to shared memory between containers. Linux provides a few tools for sharing memory between processes running on the same computer. This form of inter-process communication (IPC) performs at memory speeds. It is often used when the latency associated with network or pipe based IPC drags software performance below requirements. The best examples of shared memory based IPC usage is in scientific computing and some popular database technologies like PostgreSQL. Docker creates a unique IPC namespace for each container by default. The Linux IPC namespace partitions shared memory primitives like named shared memory blocks and semaphores, as well as message queues. It is okay if you are not sure what these are. Just know that they are tools used by Linux programs to coordinate processing. The IPC namespace prevents processes in one container from accessing the memory on the host or in other containers. Sharing IPC Primitives Between Containers I’ve created an image named allingeek/ch6_ipc that contains both a producer and consumer. They communicate using shared memory. Listing 1 will help you understand the problem with running these in separate containers. Listing 1: Launch a Communicating Pair of Programs # start a producer docker -d -u nobody --name ch6_ipc_producer \ allingeek/ch6_ipc -producer # start the consumer docker -d -u nobody --name ch6_ipc_consumer \ allingeek/ch6_ipc -consumer Listing 1 starts two containers. The first creates a message queue and starts broadcasting messages on it. The second should pull from the message queue and write the messages to the logs. You can see what each is doing by using the following commands to inspect the logs of each: docker logs ch6_ipc_producer docker logs ch6_ipc_consumer If you executed the commands in Listing 1 something should be wrong. The consumer never sees any messages on the queue. Each process used the same key to identify the shared memory resource but they referred to different memory. The reason is that each container has its own shared memory namespace. If you need to run programs that communicate with shared memory in different containers, then you will need to join their IPC namespaces with the --ipc flag. The --ipc flag has a container mode that will create a new container in the same IPC namespace as another target container. Listing 2: Joining Shared Memory Namespaces # remove the original consumer docker rm -v ch6_ipc_consumer # start a new consumer with a joined IPC namespace docker -d --name ch6_ipc_consumer \ --ipc container:ch6_ipc_producer \ allingeek/ch6_ipc -consumer Listing 2 rebuilds the consumer container and reuses the IPC namespace of the ch6_ipc_producer container. This time the consumer should be able to access the same memory location where the server is writing. You can see this working by using the following commands to inspect the logs of each: docker logs ch6_ipc_producer docker logs ch6_ipc_consumer Remember to cleanup your running containers before moving on: # remember: the v option will clean up volumes, # the f option will kill the container if it is running, # and the rm command takes a list of containers docker rm -vf ch6_ipc_producer ch6_ipc_consumer There are obvious security implications to reusing the shared memory namespaces of containers. But this option is available if you need it. Sharing memory between containers is safer alternative to sharing memory with the host.
This technical tip explains how to add a watermark to a document in Microsoft Word document inside Android Applications. Sometimes you need to insert a watermark into a Word document, for instance if you would like to print a draft document or mark it as confidential. In Microsoft Word, you can quickly insert a watermark using the Insert Watermark command. Not many people using this command realize that such “watermark” is just a shape with text inserted into a header or footer and positioned in the centre of the page. While Aspose.Words doesn't have a single insert watermark command like Microsoft Word, it is very easy to insert any shape or image into a header or footer and thus create a watermark of any imaginable type. The code below inserts a watermark into a Word document. [Java Code Sample] package AddWatermark; import java.awt.Color; import java.io.File; import java.net.URI; import com.aspose.words.Document; import com.aspose.words.Shape; import com.aspose.words.ShapeType; import com.aspose.words.RelativeHorizontalPosition; import com.aspose.words.RelativeVerticalPosition; import com.aspose.words.WrapType; import com.aspose.words.VerticalAlignment; import com.aspose.words.HorizontalAlignment; import com.aspose.words.Paragraph; import com.aspose.words.Section; import com.aspose.words.HeaderFooterType; import com.aspose.words.HeaderFooter; public class Program { public static void main(String[] args) throws Exception { // Sample infrastructure. URI exeDir = Program.class.getResource("").toURI(); String dataDir = new File(exeDir.resolve("../../Data")) + File.separator; Document doc = new Document(dataDir + "TestFile.doc"); insertWatermarkText(doc, "CONFIDENTIAL"); doc.save(dataDir + "TestFile Out.doc"); } /** * Inserts a watermark into a document. * * @param doc The input document. * @param watermarkText Text of the watermark. */ private static void insertWatermarkText(Document doc, String watermarkText) throws Exception { // Create a watermark shape. This will be a WordArt shape. // You are free to try other shape types as watermarks. Shape watermark = new Shape(doc, ShapeType.TEXT_PLAIN_TEXT); // Set up the text of the watermark. watermark.getTextPath().setText(watermarkText); watermark.getTextPath().setFontFamily("Arial"); watermark.setWidth(500); watermark.setHeight(100); // Text will be directed from the bottom-left to the top-right corner. watermark.setRotation(-40); // Remove the following two lines if you need a solid black text. watermark.getFill().setColor(Color.GRAY); // Try LightGray to get more Word-style watermark watermark.setStrokeColor(Color.GRAY); // Try LightGray to get more Word-style watermark // Place the watermark in the page center. watermark.setRelativeHorizontalPosition(RelativeHorizontalPosition.PAGE); watermark.setRelativeVerticalPosition(RelativeVerticalPosition.PAGE); watermark.setWrapType(WrapType.NONE); watermark.setVerticalAlignment(VerticalAlignment.CENTER); watermark.setHorizontalAlignment(HorizontalAlignment.CENTER); // Create a new paragraph and append the watermark to this paragraph. Paragraph watermarkPara = new Paragraph(doc); watermarkPara.appendChild(watermark); // Insert the watermark into all headers of each document section. for (Section sect : doc.getSections()) { // There could be up to three different headers in each section, since we want // the watermark to appear on all pages, insert into all headers. insertWatermarkIntoHeader(watermarkPara, sect, HeaderFooterType.HEADER_PRIMARY); insertWatermarkIntoHeader(watermarkPara, sect, HeaderFooterType.HEADER_FIRST); insertWatermarkIntoHeader(watermarkPara, sect, HeaderFooterType.HEADER_EVEN); } } private static void insertWatermarkIntoHeader(Paragraph watermarkPara, Section sect, int headerType) throws Exception { HeaderFooter header = sect.getHeadersFooters().getByHeaderFooterType(headerType); if (header == null) { // There is no header of the specified type in the current section, create it. header = new HeaderFooter(sect.getDocument(), headerType); sect.getHeadersFooters().add(header); } // Insert a clone of the watermark into the header. header.appendChild(watermarkPara.deepClone(true)); } }
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