error.jl
# This file is a part of Julia. License is MIT: http://julialang.org/license
# pseudo-definitions to show how everything behaves
#
# throw(label, val) = # throw a value to a dynamically enclosing block
#
# function rethrow(val)
# global current_exception = val
# throw(current_handler(), current_exception)
# end
#
# rethrow() = rethrow(current_exception)
#
# function throw(val)
# global catch_backtrace = backtrace()
# rethrow(val)
# end
## native julia error handling ##
error(s::AbstractString) = throw(ErrorException(s))
"""
error(msg...)
Raise an `ErrorException` with the given message.
See also [`logging`](@ref).
"""
error(s...) = throw(ErrorException(Main.Base.string(s...)))
"""
rethrow([e])
Throw an object without changing the current exception backtrace. The default argument is
the current exception (if called within a `catch` block).
"""
rethrow() = ccall(:jl_rethrow, Bottom, ())
rethrow(e) = ccall(:jl_rethrow_other, Bottom, (Any,), e)
"""
backtrace()
Get a backtrace object for the current program point.
"""
backtrace() = ccall(:jl_backtrace_from_here, Array{Ptr{Void},1}, (Int32,), false)
"""
catch_backtrace()
Get the backtrace of the current exception, for use within `catch` blocks.
"""
catch_backtrace() = ccall(:jl_get_backtrace, Array{Ptr{Void},1}, ())
## keyword arg lowering generates calls to this ##
kwerr(kw, args...) = throw(MethodError(typeof(args[1]).name.mt.kwsorter, (kw,args...)))
## system error handling ##
"""
systemerror(sysfunc, iftrue)
Raises a `SystemError` for `errno` with the descriptive string `sysfunc` if `iftrue` is `true`
"""
systemerror(p, b::Bool; extrainfo=nothing) = b ? throw(Main.Base.SystemError(string(p), Libc.errno(), extrainfo)) : nothing
## assertion functions and macros ##
assert(x) = x ? nothing : throw(Main.Base.AssertionError())
macro assert(ex, msgs...)
msg = isempty(msgs) ? ex : msgs[1]
if isa(msg, AbstractString)
msg = msg # pass-through
elseif !isempty(msgs) && (isa(msg, Expr) || isa(msg, Symbol))
# message is an expression needing evaluating
msg = :(Main.Base.string($(esc(msg))))
elseif isdefined(Main, :Base) && isdefined(Main.Base, :string) && applicable(Main.Base.string, msg)
msg = Main.Base.string(msg)
else
# string() might not be defined during bootstrap
msg = :(Main.Base.string($(Expr(:quote,msg))))
end
return :($(esc(ex)) ? $(nothing) : throw(Main.Base.AssertionError($msg)))
end
immutable ExponentialBackOff
n::Int
first_delay::Float64
max_delay::Float64
factor::Float64
jitter::Float64
function ExponentialBackOff(n, first_delay, max_delay, factor, jitter)
all(x->x>=0, (n, first_delay, max_delay, factor, jitter)) || error("all inputs must be non-negative")
new(n, first_delay, max_delay, factor, jitter)
end
end
"""
ExponentialBackOff(; n=1, first_delay=0.05, max_delay=10.0, factor=5.0, jitter=0.1)
A `Float64` iterator of length `n` whose elements exponentially increase at a
rate in the interval `factor` * (1 ± `jitter`). The first element is
`first_delay` and all elements are clamped to `max_delay`.
"""
ExponentialBackOff(; n=1, first_delay=0.05, max_delay=10.0, factor=5.0, jitter=0.1) =
ExponentialBackOff(n, first_delay, max_delay, factor, jitter)
start(ebo::ExponentialBackOff) = (ebo.n, min(ebo.first_delay, ebo.max_delay))
function next(ebo::ExponentialBackOff, state)
next_n = state[1]-1
curr_delay = state[2]
next_delay = min(ebo.max_delay, state[2] * ebo.factor * (1.0 - ebo.jitter + (rand() * 2.0 * ebo.jitter)))
(curr_delay, (next_n, next_delay))
end
done(ebo::ExponentialBackOff, state) = state[1]<1
length(ebo::ExponentialBackOff) = ebo.n
"""
retry(f::Function; delays=ExponentialBackOff(), check=nothing) -> Function
Returns an anonymous function that calls function `f`. If an exception arises,
`f` is repeatedly called again, each time `check` returns `true`, after waiting the
number of seconds specified in `delays`. `check` should input `delays`'s
current state and the `Exception`.
# Examples
```julia
retry(f, delays=fill(5.0, 3))
retry(f, delays=rand(5:10, 2))
retry(f, delays=Base.ExponentialBackOff(n=3, first_delay=5, max_delay=1000))
retry(http_get, check=(s,e)->e.status == "503")(url)
retry(read, check=(s,e)->isa(e, UVError))(io)
```
"""
function retry(f::Function; delays=ExponentialBackOff(), check=nothing)
(args...) -> begin
state = start(delays)
while true
try
return f(args...)
catch e
done(delays, state) && rethrow(e)
if check !== nothing
state, retry_or_not = check(state, e)
retry_or_not || rethrow(e)
end
end
(delay, state) = next(delays, state)
sleep(delay)
end
end
end