[go-nuts] simple sprintF output question
https://play.golang.org/p/XZimA47p9qM Why isnt this formatted with two bytes below 10 and is merely 0-9 instead of 00, 01, 02 etc etc with a left padded zero? The documentation of %x for sprintf made me think that this would keep a left padded zero on my string for 0-9, so I merely abstracted my sprintf to check if it's lower than 10 and then pad it to make it look like a proper mac address. I would love to come up with some better verbiage for the description in the documentation for 0-9 so people arent surprised and need to left pad it like I had to for a mac address %x base 16, lower-case, two characters per byte -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[go-nuts] Re: Panic recovery and mutex lock question
OK I think I have my questions answered, I think the moral is dont intermix
or add code above your lock if you are worried about any panics calling it
before, this way you know that you are in a lock right when the function
hits it and can always defer the unlock until after. I suppose in some
really bad code with a panic handler someone could accidentally throw a
panic deeper down in a function and since that code was above the Lock the
panic handler wouldnt know whether its open or not. I just wish sometimes
we could know whether a lock is open or not on a given sync.RWMutex as a
public variable. Oh well...
I really like some of Juliusz's examples to separate out the locks with
anonymous functions because it keeps the logic safer from anyone adding
code or function calls that can be more dangerous for things like panic
handlers.
Thanks everyone, I think I am good on this question and my brother solved
some of our web socket lock issues in our code dealing with websockets.
https://github.com/DanielRenne/GoCore/commit/1a6418c2734f985955571ff6015f8d82736890ae
I still get scared any minute a client websocket or some unhandled thing
might cause a lock, but only time will tell. Node.js websockets are easy
because theres only one thread!
If anyone feels like reviewing master of this project and helping us find
some potential bad code, we need some golang experts to review any lock
practices we can improve on problems before they become problems and
refactor any bad code out. Sometimes I wish we found this melody library
which handles all the locking for websockets with
gorilla package. https://github.com/olahol/melody Oh well. That package
might not even work for our use case anyway.
I removed some unlocks he put in on the recovery because the second defer
will always be called regardless of panic right? There is no way
golang will skip any deferred on a panic for any reason right?
https://github.com/DanielRenne/GoCore/commit/9685fb3f6fabe612e005238119349144da3bba18
Thanks for listening to my rants everyone! If anyone explores some of our
bad code and wants to help us just reply here or email me direct from
github https://github.com/davidrenne/
On Tuesday, October 17, 2017 at 8:15:23 PM UTC-4, David Renne wrote:
>
> Hi there,
>
> I was wondering if the code ever panics and we have a if recover :=
> recover(); recover != nil {
>
> in a defer func and we are using sync.RWMutexes which do not have a defer
> to unlock for example.
>
> What kinds of things can happen if the code unexpectedly panics when we
> are in a Lock() in the code and then something panics before it Unlocks.
> My defer funcs almost never unlock the syncRW mutexes or any RLock()'s that
> were called to unlock.
>
> Should maybe if we are in the recover() block should we then call Unlock()
> or RUnlock on all sync.RWMutex's that the function is recovering from? How
> would one know if you are in a lock or not if we made it far enough to open
> the lock to know which ones to unlock if it truly keeps the lock open?
>
> Since we rarely get panics and we are dealing with some deadlocks, I am
> asking myself this question and dont really know how to test it easily to
> verify what really happens.
>
--
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[go-nuts] log. Sprintf
I had a question that I cant seem to figure out. I know fmt is a bad package to use if you have any concurrent workers because it uses f.Write() and is not thread safe apparently. But I like using Sprintf because I can format strings and return as a string. How can I implement something to use the log package in a manner that I can have a concurrently safe log function which acts like Sprintf()? It's just so strange to me and I have always been curious of why there isnt a log.Sprintf(). -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[go-nuts] Re: Panic recovery and mutex lock question
Thank you Ian.
I guess I was wondering still if we had existing code with multiple mutexes
being locked or rLocked where we didnt have the defer unlocks and those
panic.
I guess I dont understand why you would want the lock entirely for the
entire execution of the function until the defer. It seems more efficient
to only Lock and unlock between the specific lines of code where you are
mutating a shared variable.
Still my question would be the same, on these existing locks if a panic
happened and it exited prematurely, is it just safe to put any mutexes we
are locked or RLocked inside of the recover if statement? Just in case
those are Locked or RLocked, will an Unlock or RUnlock always be okay and
not panic further if they are not locked and we call Unlock or RUnlock?
I swear I have seen golang get mad when you try to unlock something that
has not been locked. So I am trying to envision more the best way about
this.
I think its too risky right now to convert all UnLocks and RUnlocks to a
defered unlock because we have been through so many deadlock situations in
the past. I am a bit reluctant to keep something locked for the entire
execution of a function everywhere.
On Tuesday, October 17, 2017 at 8:15:23 PM UTC-4, David Renne wrote:
>
> Hi there,
>
> I was wondering if the code ever panics and we have a if recover :=
> recover(); recover != nil {
>
> in a defer func and we are using sync.RWMutexes which do not have a defer
> to unlock for example.
>
> What kinds of things can happen if the code unexpectedly panics when we
> are in a Lock() in the code and then something panics before it Unlocks.
> My defer funcs almost never unlock the syncRW mutexes or any RLock()'s that
> were called to unlock.
>
> Should maybe if we are in the recover() block should we then call Unlock()
> or RUnlock on all sync.RWMutex's that the function is recovering from? How
> would one know if you are in a lock or not if we made it far enough to open
> the lock to know which ones to unlock if it truly keeps the lock open?
>
> Since we rarely get panics and we are dealing with some deadlocks, I am
> asking myself this question and dont really know how to test it easily to
> verify what really happens.
>
--
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