error.jl
# This file is a part of Julia. License is MIT: https://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
"""
throw(e)
Throw an object as an exception.
"""
throw
## native julia error handling ##
"""
error(message::AbstractString)
Raise an `ErrorException` with the given message.
"""
error(s::AbstractString) = throw(ErrorException(s))
"""
error(msg...)
Raise an `ErrorException` with the given message.
"""
function error(s::Vararg{Any,N}) where {N}
@_noinline_meta
throw(ErrorException(Main.Base.string(s...)))
end
"""
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)
struct InterpreterIP
code::Union{CodeInfo,Core.MethodInstance,Nothing}
stmt::Csize_t
end
# convert dual arrays (ips, interpreter_frames) to a single array of locations
function _reformat_bt(bt, bt2)
ret = Vector{Union{InterpreterIP,Ptr{Cvoid}}}()
i, j = 1, 1
while i <= length(bt)
ip = bt[i]::Ptr{Cvoid}
if ip == Ptr{Cvoid}(-1%UInt)
# The next one is really a CodeInfo
push!(ret, InterpreterIP(
bt2[j],
bt[i+2]))
j += 1
i += 3
else
push!(ret, Ptr{Cvoid}(ip))
i += 1
end
end
ret
end
function backtrace end
"""
catch_backtrace()
Get the backtrace of the current exception, for use within `catch` blocks.
"""
function catch_backtrace()
bt = Ref{Any}(nothing)
bt2 = Ref{Any}(nothing)
ccall(:jl_get_backtrace, Cvoid, (Ref{Any}, Ref{Any}), bt, bt2)
return _reformat_bt(bt[], bt2[])
end
## keyword arg lowering generates calls to this ##
function kwerr(kw, args::Vararg{Any,N}) where {N}
@_noinline_meta
throw(MethodError(typeof(args[1]).name.mt.kwsorter, (kw,args...)))
end
## 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 macro ##
"""
@assert cond [text]
Throw an [`AssertionError`](@ref) if `cond` is `false`. Preferred syntax for writing assertions.
Message `text` is optionally displayed upon assertion failure.
!!! warning
An assert might be disabled at various optimization levels.
Assert should therefore only be used as a debugging tool
and not used for authentication verification (e.g., verifying passwords),
nor should side effects needed for the function to work correctly
be used inside of asserts.
# Examples
```jldoctest
julia> @assert iseven(3) "3 is an odd number!"
ERROR: AssertionError: 3 is an odd number!
julia> @assert isodd(3) "What even are numbers?"
```
"""
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)) ? $(nothing) : throw(AssertionError($msg)))
end
struct 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`](@ref) 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(Float64) * 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
Return 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, 128; all=false)
```
"""
function retry(f::Function; delays=ExponentialBackOff(), check=nothing)
(args...; kwargs...) -> begin
state = start(delays)
while true
try
return f(args...; kwargs...)
catch e
done(delays, state) && rethrow(e)
if check !== nothing
result = check(state, e)
state, retry_or_not = length(result) == 2 ? result : (state, result)
retry_or_not || rethrow(e)
end
end
(delay, state) = next(delays, state)
sleep(delay)
end
end
end
