Updates for retry changes in 0.6. (#368)

* Updates for retry changes in 0.6.

* Added retry info to README.

README.md

@@ -162,6 +162,8 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * There are versions of `InexactError`, `DomainError`, and `OverflowError` that take the same arguments as introduced in Julia 0.7-DEV ([#20005], [#22751], [#22761]).
 
+* `retry` for the more flexible `retry` method introduced in 0.6 which includes support for kwargs ([#19331], [#21419]).
+
 ## Renamed functions
 
 

src/Compat.jl

@@ -140,8 +140,65 @@ macro compat(ex...)
     esc(_compat(ex[1]))
 end
 
+
 export @compat
 
+if VERSION < v"0.6.0-dev.2042"
+    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`](@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)
+    Base.start(ebo::ExponentialBackOff) = (ebo.n, min(ebo.first_delay, ebo.max_delay))
+    function Base.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
+    Base.done(ebo::ExponentialBackOff, state) = state[1]<1
+    Base.length(ebo::ExponentialBackOff) = ebo.n
+
+    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
+                        state, retry_or_not = check(state, e)
+                        retry_or_not || rethrow(e)
+                    end
+                end
+                (delay, state) = next(delays, state)
+                sleep(delay)
+            end
+        end
+    end
+else
+    import Base.ExponentialBackOff
+    import Base.retry
+end
+
 import Base: redirect_stdin, redirect_stdout, redirect_stderr
 if VERSION < v"0.6.0-dev.374"
     for (F,S) in ((:redirect_stdin, :STDIN), (:redirect_stdout, :STDOUT), (:redirect_stderr, :STDERR))

test/runtests.jl

@@ -105,6 +105,53 @@ cd(dirwalk) do
 end
 rm(dirwalk, recursive=true)
 
+let
+    # Subset of tests copied from base test/error.jl
+    function foo_error(c, n)
+        c[1] += 1
+        if c[1] <= n
+            error("foo")
+        end
+        return 7
+    end
+
+    # Success on first attempt
+    c = [0]
+    @test Compat.retry(foo_error)(c, 0) == 7
+    @test c[1] == 1
+
+    # Success on second attempt
+    c = [0]
+    @test Compat.retry(foo_error)(c,1) == 7
+    @test c[1] == 2
+
+    # 2 failed retry attempts, so exception is raised
+    c = [0]
+    ex = try
+        Compat.retry(foo_error, delays=Compat.ExponentialBackOff(n=2))(c, 3)
+    catch e
+        e
+    end
+
+    c = [0]
+    ex = try
+        Compat.retry(
+            foo_error,
+            check=(s,e)->(s, try e.http_status_code == "503" end != true)
+        )(c, 2)
+    catch e
+        e
+    end
+    @test typeof(ex) == ErrorException
+    @test ex.msg == "foo"
+    @test c[1] == 2
+
+    # Functions with keyword arguments
+    foo_kwargs(x; y=5) = x + y
+    @test Compat.retry(foo_kwargs)(3) == 8
+    @test Compat.retry(foo_kwargs)(3; y=4) == 7
+end
+
 for os in [:apple, :bsd, :linux, :unix, :windows]
     from_base = if VERSION >= v"0.7.0-DEV.914"
         Expr(:., Expr(:., :Base, Base.Meta.quot(:Sys)), Base.Meta.quot(Symbol("is", os)))