Very casual whiteboard type chat sessions on a regular basis in SF, NYC, Redwood Shores, Mountain View, and Atlanta. Stop by!
Also check out the meetup users groups in lots of other cities.
How Journaling and Replication Interact
Version 1.8 of MongoDB supports journaling in the storage engine for crash safety and fast recovery. An interesting question arises then regarding how journaling interacts with replication. A traditional approach might be to wait for the commit (i.e., journal physical write confirmed) before replicating any data. MongoDB does not do this. Instead, it allows data to replicate even if the journal write has yet to occur or be confirmed. We then must ask “but what happens if we crash before journaling but the data replicated out?” With replica sets , it turns out this is ok. In a replica set the rule is that the freshest node will be elected primary. Thus if the crashed node comes back up, but the node which received the unjournaled data is ahead, it will be primary. We might then ask about a cascade of failures. This is ok too as replica sets have a notion of rolling back to a consistent point of view. How do we know our data won’t be rolled back? The answer is that a write is truly committed in a replica set when it has been written at a majority of set members. We can confirm this with the getLastError command. For example, if our write has made it to the journal on two out of three total set members, we know the data is committed even if nodes fail in a cascading sequence, and even if a minority of nodes are permanently lost. Why bother replicating so quickly? It lets us minimize latency between secondaries and primaries. In addition more writes will be successful than traditionally when a crash occurs. Yet the latency reduction is the biggest advantage: fsyncing to disks can be slow – replication lag (if on a LAN) can be less than the time to fsync to disk. Plus both can then be underway concurrently.
Hear From the MongoDB World 2022 Diversity Scholars
The MongoDB Diversity Scholarship program is an initiative to elevate and support members of underrepresented groups in technology across the globe. Scholars receive complimentary access to the MongoDB World developer conference in New York, on-demand access to MongoDB University to prepare for free MongoDB certification, and mentorship via an exclusive discussion group. This year at MongoDB World, our newest cohort of scholars got the opportunity to interact with company leadership at a luncheon and also got a chance to share their experience in a public panel discussion at the Community Café. Hear from some of the 2022 scholars, in their own words. Rebecca Hayes, System Analyst at Alliance for Safety and Justice I did an internal transition from managing Grants/Contracts to IT and just finished a data science certificate (Python, Unix/Linux, SQL) through my community college. My inspiration for pursuing STEM was wanting to understand how reality is represented in systems and how data science can be used to change the world. What was your most impactful experience as part of the Diversity Scholarship? Most impactful were the conversations I had with other attendees at the conference. I talked to people from all sectors who were extremely knowledgeable and passionate about shaping the future of databases. The opportunity to hear from MongoDB leaders and then understand how the vision behind the product was being implemented made me feel inspired for my future in STEM. How has the MongoDB World conference inspired you in your learning or your career path? MongoDB World inspired me to understand the real world applications of databases. I left knowing what's possible with a product like MongoDB and the limits of SQL and traditional databases. After the conference, I wrote this article on Medium reflecting on what I learned at the conference. What is your advice to colleagues pursuing STEM and/or on a similar path as you? Embrace what makes you unique. Just because things take time doesn't mean they won't happen. When learning programming and data science, think about how your work relates to the real world and share those thoughts with others. Seek out new perspectives, stay true to yourself, and keep an open mind. Delphine Nyaboke, Junior Software Engineer at Sendy I am passionate about energy in general. My final year project was on solar mini-grid design and interconnection. I have a mission of being at the intersection of energy and AI What inspired me to get into tech is the ability to solve societal problems without necessarily waiting for someone else to do it for you. This can be either in energy or by code. What was your most impactful experience as part of the Diversity Scholarship? My most impactful experience, apart from attending and listening in on the keynotes, was to attend the breakout sessions. They had lovely topics full of learnings and inspiration, including Engineering Culture at MongoDB; Be a Community Leader; Principles of Data Modeling for MongoDB; and Be Nice, But Not Too Nice just to mention but a few. How has the MongoDB World conference inspired you in your learning or your career path? MongoDB World has inspired me to keep on upskilling and being competitive in handling databases, which is a key skill in a backend engineer like myself. I will continue taking advantage of the MongoDB University courses and on-demand courses available thanks to the scholarship. What is your advice to colleagues pursuing STEM and/or on a similar path as you? STEM is a challenging yet fun field. If you’re tenacious enough, the rewards will trickle in soon enough. Get a community to be around, discuss what you’re going through together, be a mentor, get a mentor, and keep pushing forward. We need like-minded individuals in our society even in this fourth industrial revolution, and we are not leaving anyone behind. Video: Watch the panel in its entirety Raja Adil, Student at Cal Poly SLO Currently, I am a software engineer intern at Salesforce. I started self-teaching myself software development when I was a junior in high school during the COVID-19 pandemic, and from there I started doing projects and gaining as much technical experience as I could through internships. Before the pandemic I took my first computer science class, which was taught in C#. At first, I hated it as it looked complex. Slowly, I started to enjoy it more and more, and during the pandemic I started learning Python on my own. I feel blessed to have found my path early in my career. What was your most impactful experience as part of the Diversity Scholarship? My most impactful experience was the network and friends I made throughout the four days I was in New York for MongoDB World. I also learned a lot about the power of MongoDB, as opposed to relational databases, which I often use in my projects. How has the MongoDB World conference inspired you in your learning or your career path? The MongoDB World conference was amazing and has inspired me a ton in my learning path. I definitely want to learn even more about MongoDB as a database, and in terms of a career path, I would love to intern at MongoDB as a software engineer down the line. What is your advice to colleagues pursuing STEM and/or on a similar path as you? My advice would be to network as much as you can and simply make cool projects that others can use. Evans Asuboah, Stetson University I am an international student from Ghana. I was born and raised by my dad, who is a cocoa farmer, and my mum, who is a teacher. I got into tech miraculously, because my country's educational system matches majors to students according to their final high school grades. Initially, I wanted to do medicine, but I was offered computer science. I realized that computer science could actually be the tool to help my community and also use the knowledge to help my dad on the farm. What was your most impactful experience as part of the Diversity Scholarship? The breakout room sessions. As scholars, we had the chance to talk to MongoDB employees, and the knowledge and experiences changed my thoughts and increased my desire to persevere. I have learned never to stop learning and not to give up. How has the MongoDB World conference inspired you in your learning or your career path? Meeting these amazing people, connecting with the scholars, being at the workshops, and talking to the startups at the booths has made me realize the sky is the limit. I dare to dream and believe until I see the results. What is your advice to colleagues pursuing STEM and/or on a similar path as you? 1. Explore MongoDB; 2. You are the only one between you and your dream; 3. Take the initiative and meet people; 4. Never stop learning. Daniel Erbynn, Drexel University I love traveling and exploring new places. I am originally from Ghana, and I got the opportunity to participate in a summer program after high school called Project ISWEST, which introduced me to coding and computer science through building a pong game and building an Arduino circuit to program traffic lights. This made me excited about programming and the possibilities of solving problems in the tech space. What was your most impactful experience as part of the Diversity Scholarship? My most impactful experience was meeting with other students and professionals in the industry, learning from them, making lifelong connections, and getting the opportunity to learn about MongoDB through the MongoDB University courses. How has the MongoDB World conference inspired you in your learning or your career path? This conference has inspired me to learn more about MongoDB and seek more knowledge about cloud technology. What is your advice to colleagues pursuing STEM and/or on a similar path as you? Don’t be afraid to reach out to people you want to learn from, and create projects you are passionate about. Build your skills with MongoDB University's free courses and certifications . Join our developer community to stay up-to-date with the latest information and announcements.