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diff --git a/lib/tesla/middleware/fuse.ex b/lib/tesla/middleware/fuse.ex
index 2b615b2..a77e101 100644
--- a/lib/tesla/middleware/fuse.ex
+++ b/lib/tesla/middleware/fuse.ex
@@ -1,85 +1,92 @@
if Code.ensure_loaded?(:fuse) do
defmodule Tesla.Middleware.Fuse do
@moduledoc """
Circuit Breaker middleware using [fuse](https://github.com/jlouis/fuse)
Remember to add `{:fuse, "~> 2.4"}` to dependencies (and `:fuse` to applications in `mix.exs`)
Also, you need to recompile tesla after adding `:fuse` dependency:
```
mix deps.clean tesla
mix deps.compile tesla
```
## Example usage
```
defmodule MyClient do
use Tesla
plug Tesla.Middleware.Fuse,
- opts: {{:standard, 2, 10_000}, {:reset, 60_000}}
+ opts: {{:standard, 2, 10_000}, {:reset, 60_000}},
+ keep_orig_error: true,
should_melt: fn
{:ok, %{status: status}} when status in [428, 500, 504] -> true
{:ok, _} -> false
{:error, _} -> true
end
end
```
## Options
- `:name` - fuse name (defaults to module name)
- `:opts` - fuse options (see fuse docs for reference)
+ - `:keep_orig_error` - boolean to indicate if, in case of melting (based on `should_melt`), it should return the upstream's error or the fixed one `{:error, unavailable}`.
+ It's false by default, but it will be true in `2.0.0` version
- `:should_melt` - function to determine if response should melt the fuse
## SASL logger
fuse library uses [SASL (System Architecture Support Libraries)](http://erlang.org/doc/man/sasl_app.html).
You can disable its logger output using:
```
config :sasl, sasl_error_logger: :false
```
Read more at [jlouis/fuse#32](https://github.com/jlouis/fuse/issues/32) and [jlouis/fuse#19](https://github.com/jlouis/fuse/issues/19).
"""
@behaviour Tesla.Middleware
# options borrowed from http://blog.rokkincat.com/circuit-breakers-in-elixir/
# most probably not valid for your use case
@defaults {{:standard, 2, 10_000}, {:reset, 60_000}}
@impl Tesla.Middleware
def call(env, next, opts) do
opts = opts || []
context = %{
name: Keyword.get(opts, :name, env.__module__),
+ keep_orig_error: Keyword.get(opts, :keep_orig_error, false),
should_melt: Keyword.get(opts, :should_melt, &match?({:error, _}, &1))
}
case :fuse.ask(context.name, :sync) do
:ok ->
run(env, next, context)
:blown ->
{:error, :unavailable}
{:error, :not_found} ->
:fuse.install(context.name, Keyword.get(opts, :opts, @defaults))
run(env, next, context)
end
end
- defp run(env, next, %{should_melt: should_melt, name: name}) do
+ defp run(env, next, %{should_melt: should_melt, name: name, keep_orig_error: keep_orig_error}) do
res = Tesla.run(env, next)
- if should_melt.(res), do: :fuse.melt(name)
-
- res
+ if should_melt.(res) do
+ :fuse.melt(name)
+ if keep_orig_error, do: res, else: {:error, :unavailable}
+ else
+ res
+ end
end
end
end
diff --git a/test/tesla/middleware/fuse_test.exs b/test/tesla/middleware/fuse_test.exs
index 7a32e9d..8664096 100644
--- a/test/tesla/middleware/fuse_test.exs
+++ b/test/tesla/middleware/fuse_test.exs
@@ -1,114 +1,115 @@
defmodule Tesla.Middleware.FuseTest do
use ExUnit.Case, async: false
defmodule Report do
def call(env, next, _) do
send(self(), :request_made)
Tesla.run(env, next)
end
end
defmodule Client do
use Tesla
plug Tesla.Middleware.Fuse
plug Report
adapter fn env ->
case env.url do
"/ok" ->
{:ok, env}
"/unavailable" ->
{:error, :econnrefused}
end
end
end
- defmodule ClientWithCustomShouldMeltFunction do
+ defmodule ClientWithCustomSetup do
use Tesla
plug Tesla.Middleware.Fuse,
+ keep_orig_error: true,
should_melt: fn
{:ok, %{status: status}} when status in [504] -> true
{:ok, _} -> false
{:error, _} -> true
end
plug Report
adapter fn env ->
case env.url do
"/ok" ->
{:ok, env}
"/error_500" ->
{:ok, %{env | status: 500}}
"/error_504" ->
{:ok, %{env | status: 504}}
"/unavailable" ->
{:error, :econnrefused}
end
end
end
setup do
Application.ensure_all_started(:fuse)
:fuse.reset(Client)
- :fuse.reset(ClientWithCustomShouldMeltFunction)
+ :fuse.reset(ClientWithCustomSetup)
:ok
end
test "regular endpoint" do
assert {:ok, %Tesla.Env{url: "/ok"}} = Client.get("/ok")
end
test "custom should_melt function - not melting 500" do
- custom_client = ClientWithCustomShouldMeltFunction
+ custom_client = ClientWithCustomSetup
assert {:ok, %Tesla.Env{status: 500}} = custom_client.get("/error_500")
assert_receive :request_made
assert {:ok, %Tesla.Env{status: 500}} = custom_client.get("/error_500")
assert_receive :request_made
assert {:ok, %Tesla.Env{status: 500}} = custom_client.get("/error_500")
assert_receive :request_made
assert {:ok, %Tesla.Env{status: 500}} = custom_client.get("/error_500")
assert_receive :request_made
assert {:ok, %Tesla.Env{status: 500}} = custom_client.get("/error_500")
assert_receive :request_made
end
test "custom should_melt function - melting 504" do
- custom_client = ClientWithCustomShouldMeltFunction
+ custom_client = ClientWithCustomSetup
assert {:ok, %Tesla.Env{status: 504}} = custom_client.get("/error_504")
assert_receive :request_made
assert {:ok, %Tesla.Env{status: 504}} = custom_client.get("/error_504")
assert_receive :request_made
assert {:ok, %Tesla.Env{status: 504}} = custom_client.get("/error_504")
assert_receive :request_made
assert {:error, :unavailable} = custom_client.get("/error_504")
refute_receive :request_made
assert {:error, :unavailable} = custom_client.get("/error_504")
refute_receive :request_made
end
test "unavailable endpoint" do
- assert {:error, :econnrefused} = Client.get("/unavailable")
+ assert {:error, :unavailable} = Client.get("/unavailable")
assert_receive :request_made
- assert {:error, :econnrefused} = Client.get("/unavailable")
+ assert {:error, :unavailable} = Client.get("/unavailable")
assert_receive :request_made
- assert {:error, :econnrefused} = Client.get("/unavailable")
+ assert {:error, :unavailable} = Client.get("/unavailable")
assert_receive :request_made
assert {:error, :unavailable} = Client.get("/unavailable")
refute_receive :request_made
assert {:error, :unavailable} = Client.get("/unavailable")
refute_receive :request_made
end
end

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