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Links for 2013-08-21

  • LMDB response to a LevelDB-comparison blog post

    This seems like a good point to note about LMDB in general:

    We state quite clearly that LMDB is read-optimized, not write-optimized. I wrote this for the OpenLDAP Project; LDAP workloads are traditionally 80-90% reads. Write performance was not the goal of this design, read performance is. We make no claims that LMDB is a silver bullet, good for every situation. It’s not meant to be – but it is still far better at many things than all of the other DBs out there that *do* claim to be good for everything.

    (tags: lmdb leveldb databases openldap storage persistent)

  • How to avoid crappy ISP caches when viewing YouTube video

    Must give this a try when I get home — I frequently have latency problems watching YT on my UPC connection, and I bet they have a crappily-managed, overloaded cache box on their network.

    (tags: streaming youtube caching isps caches firewalls iptables hacks video networking)

  • How to configure ntpd so it will not move time backwards

    The “-x” switch will expand the step/slew boundary from 128ms to 600 seconds, ensuring the time is slewed (drifted slowly towards the correct time at a max of 5ms per second) rather than “stepped” (a sudden jump, potentially backwards). Since slewing has a max of 5ms per second, time can never “jump backwards”, which is important to avoid some major application bugs (particularly in Java timers).

    (tags: ntpd time ntp ops sysadmin slew stepping time-synchronization linux unix java bugs)

  • Snowizard

    ‘a Java port of Twitter’s Snowflake thrift service presented as an HTTP-based Dropwizard service’.

    an HTTP-based service for generating unique ID numbers at high scale with some simple guarantees. supports returning ID numbers as: JSON and JSONP; Google’s Protocol Buffers; Plain text. At GE, we were more interested in the uncoordinated aspects of Snowflake than its throughput requirements, so HTTP was fine for our needs. We also exposed the core of Snowflake as an embeddable module so it can be directly integrated into our applications. We don’t have the guarantees that the Snowflake-Zookeeper integration was providing, but that was also acceptable to us. In places where we really needed high throughput, we leveraged the snowizard-core embeddable module directly.
    Odd OSS license, though — BSDish?

    (tags: java open-source ids soa services snowflake http)

  • Containers and Docker: How Secure Are They?

    pretty extensive article. (via Tony Finch)

    (tags: via:fanf security containerization docker containers lxc linux ops)

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