Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

Sync'd writes (and write-thru) can be slow due to the absence of caching, but so are most journalled file-systems.

When part of what you are trying to 'commit' has nothing to do with the database (ie, transition a server to a new state), then you are still not atomic. In BrowserUk's example,

Agreed. That example only works if repeating the performed, but unlogged command over is effectively a noop.

Mind you, breaking processing up into steps such that any given step can be repeated 2 or more times without affecting the overall result is something of a black art in itself. The basic steps are: a) don't discard source data for a given step, until the output data for that step has been successfully processed by the next step. b) discard any source data for this step that is 'incomplete'. Sentinel values are useful for this c) Once the input data for this step--ie. the output of the previous step--has been successfully processed, delete the associated input data to the previous step. Of course, in critical systems, 'delete' is probably spelt 'move to archive'.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^3: Atomic Config Updater with History? by BrowserUk
in thread Atomic Config Updater with History? by pileofrogs

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?

What's my password?
Create A New User
Domain Nodelet?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others exploiting the Monastery: (2)
As of 2021-10-23 18:09 GMT
Find Nodes?
    Voting Booth?
    My first memorable Perl project was:

    Results (88 votes). Check out past polls.