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Pay it down software9/5/2023 ![]() So doing both is very hard.Editor's Note: This post has recently been updated from a previous version. "We're a Web company we're a real-time payment system - oh, dear. ![]() "Sometimes we feel a little schizophrenic," he says. So far, the mix of distributed Linux and open source software and rapid application development of open source code have been a success, Mengerink says. "You'd have to go box by box and fight your way." "So there is no such thing as a sitewide compromise," he say. Each box is configured as if it were operating in an untrusted network. Security policies and code also are added to the machines - Mengerink would not give specifics - which creates a built-in layer of mistrust among machines on the data-center network. "The combination of Linux and open source allows us to do the modifications we need to scale and have that extreme rigidity of security," Mengerink says. As a basic step, superfluous services, packages and other software are stripped out. Linux servers in PayPal's data center run Red Hat kernels with custom tweaks that add extra layers of security to the systems. This approach PayPal developers take in molding the Linux kernel and other open source code they use helps to make the overall system more secure, Mengerink says. Their take is, no feelings would be hurt if we just used the most stable, known versions of things." "The people in operations are a little more conservative than that. They would be on the beta version of the newest latest and greatest all the time, with some kernel patch they found from some college Web site," he says. "The one struggle we have is a classic struggle, is our decision to align development and the live site," Mengerink says. This model also helps PayPal developers frequently churn out new versions of the Web site's main applications, which can be both a positive and negative thing. "Open source clearly makes this a lot more cost effective as well, since you don't have the same licensing costs that would be associated" with duplicating a live site in the lab. "When you have developers testing a system on the exact same environment that you have in production, the probability for weird things happening is a lot lower. This lets PayPal coders write new versions of the PayPal production applications, which can then be switched on live with minimal disruptions. ![]() Because of the low-cost hardware and software PayPal uses on its production system, it can almost replicate the state of its entire live site in the application development lab. Using open source Red Hat Linux also provides several advantages on the development side. Open source pays off in app development lab Then the database on its side sees a nice, old-fashioned durable connection, and doesn't feel like it's being melted down by a connection storm." The application just doesn't care there is this middle layer. As far as the application is concerned, it just thinks it is making calls out to a database. "So there is a tier that buffers between those Web and database layers. "The speed with which the processes come and go is blindingly fast," Mengerink says. A custom-made database connection-management system links Web processes from the Linux-based Web and middleware tiers of the PayPal site to the Sun/Oracle back end. On the back end, these thousands of systems communicate with just a few large Sun Solaris boxes, which run an Oracle database that stores all customer data. "We just allocate a higher portion of the to running batch processes, and we crunch through all that data in three hours every night." Thompson says this kind of work, typically done on mainframes or large symmetric multiprocessing boxes in other payment organizations, is spread across the middle-tier Linux servers in the data center. PST, PayPal runs its batch processing for reconciling payments. The generic Linux Lego-block-style servers that make up the company's Web tier can be easily shifted around for a variety of tasks.įor example, every day at 1 a.m. The distributed model also lets the company make massive shifts and resource allocation when needed.
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