hairpin.bend
bend-kit-hairpin@0.10.0.0 · 463 lines · 0 definitions
1# Hairpin: an HTTP client with a base URL, default headers, a pool, cookies, mTLS, redirects, and proven retries. Source: https://github.com/paymog/bend-kit/tree/main/hairpin
2import Base
3import bend-kit-http@0.36.0.0/http.bend as Http
4import bend-kit-time@0.2.0.0/time.bend as Time
5import bend-kit-url@0.4.1.0/url.bend as Url
6import bend-kit-json@0.6.1.1/json.bend as Json
7import bend-kit-bytes@0.3.2.0/bytes.bend as Bytes
8import bend-kit-retry@0.2.0.0/retry.bend as Retry
9
10# base: "" for none. headers: lowercase names. ms: the step timeout. policy: attempts, backoff, and deadline of each request.
11# ca: a PEM CA file to trust; "" trusts the default store.
12type Opts is Data:
13 Opts{base: String, headers: Map<&2, List<&2, String>>, ms: U32, mode: Http.Mode, policy: Retry.Policy, cert: Maybe<&2, Http.Cert>, ca: String}
14
15# breaker: the circuit breaker of every request on this client.
16type Client is Type:
17 Client{opts: Opts, pool: Http.Pool, jar: Maybe<&2, Http.Jar>, breaker: Retry.Breaker}
18
19# ErrHttp: the last attempt failed. ErrDenied: no attempt started, for why.
20type Err is Data:
21 ErrHttp{error: Http.Err}
22 ErrDenied{why: Retry.Deny}
23
24# One attempt, the first included; backoff from 500 ms, doubled to at most 30 s; no deadline.
25def policy() -> Retry.Policy:
26 Retry.Policy{1n, 500n, 30000, None{}}
27
28# A pool of up to cap idle sockets per origin, no base, no default headers, 30 s steps, follow redirects,
29# no retries, and no circuit breaker.
30def new.with(+cap: U32) -> Client:
31 Client{Opts{"", Http.empty(), 30000, Http.ModeFollow{}, policy(), None{}, ""}, Http.pool.new.with(cap), None{}, Retry.BreakerOff{}}
32
33def new() -> Client:
34 new.with(8)
35
36def base(c: Client, url: String) -> Client:
37 Client{Opts{b, h, ms, mode, p, cert, ca}, pool, j, br} = c
38 Client{Opts{url, h, ms, mode, p, cert, ca}, pool, j, br}
39
40# A default header. It replaces an earlier default of the same name; a request header of that name replaces it.
41def header(c: Client, k: String, v: String) -> Client:
42 Client{Opts{b, h, ms, mode, p, cert, ca}, pool, j, br} = c
43 Client{Opts{b, Http.set(h, String.to_lower(k), v), ms, mode, p, cert, ca}, pool, j, br}
44
45def timeout(c: Client, ms: U32) -> Client:
46 Client{Opts{b, h, old, mode, p, cert, ca}, pool, j, br} = c
47 Client{Opts{b, h, ms, mode, p, cert, ca}, pool, j, br}
48
49def redirect(c: Client, mode: Http.Mode) -> Client:
50 Client{Opts{b, h, ms, old, p, cert, ca}, pool, j, br} = c
51 Client{Opts{b, h, ms, mode, p, cert, ca}, pool, j, br}
52
53# Up to n retries after the first attempt: n + 1 attempts in all.
54def retry(c: Client, n: U32) -> Client:
55 Client{Opts{b, h, ms, mode, Retry.Policy{old, base, cap, d}, cert, ca}, pool, j, br} = c
56 Client{Opts{b, h, ms, mode, Retry.Policy{1n+U32.to_nat(n), base, cap, d}, cert, ca}, pool, j, br}
57
58# No attempt of a request starts ms or more after the request starts.
59def deadline(c: Client, ms: U32) -> Client:
60 Client{Opts{b, h, t, mode, Retry.Policy{a, base, cap, old}, cert, ca}, pool, j, br} = c
61 Client{Opts{b, h, t, mode, Retry.Policy{a, base, cap, Some{U32.to_nat(ms)}}, cert, ca}, pool, j, br}
62
63# A circuit breaker in front of every request, starting closed.
64def circuit(c: Client, circ: Retry.Circuit) -> Client:
65 Client{o, pool, j, old} = c
66 Client{o, pool, j, Retry.Breaker.new(circ)}
67
68# The breaker, for inspection.
69def breaker.of(c: Client) -> Client & Retry.Breaker:
70 Client{o, pool, j, +br} = c
71 (Client{o, pool, j, br}, br)
72
73# Paths to a PEM client chain and its private key, presented to every HTTPS origin.
74def cert(c: Client, chain: String, key: String) -> Client:
75 Client{Opts{b, h, ms, mode, p, old, ca}, pool, j, br} = c
76 Client{Opts{b, h, ms, mode, p, Some{Http.Cert{chain, key}}, ca}, pool, j, br}
77
78# Path to a PEM CA file, trusted in place of the default store. Like the certificate, it follows same-origin redirects only.
79def ca(c: Client, path: String) -> Client:
80 Client{Opts{b, h, ms, mode, p, cert, old}, pool, j, br} = c
81 Client{Opts{b, h, ms, mode, p, cert, path}, pool, j, br}
82
83# Every request stores and sends cookies through jar. Its clock moves to Time.now() before each try.
84def jar(c: Client, jar: Http.Jar) -> Client:
85 Client{o, pool, old, br} = c
86 Client{o, pool, Some{jar}, br}
87
88# The jar, if the client has one.
89def jar.of(c: Client) -> Client & Maybe<&2, Http.Jar>:
90 Client{o, pool, +j, br} = c
91 (Client{o, pool, j, br}, j)
92
93def close(c: Client) -> IO(Unit):
94 Client{o, pool, j, br} = c
95 Http.pool.close(pool)
96
97def target.pick(none: Bool, b: String, ref: String) -> Maybe<&2, String>:
98 match none:
99 case True{}:
100 Some{ref}
101 case False{}:
102 Http.resolve(b, ref)
103
104# ref against the base (RFC 3986 §5.2); with no base, ref as given. None when the base is not absolute.
105def target(+b: String, ref: String) -> Maybe<&2, String>:
106 target.pick(String.is_empty(b), b, ref)
107
108def target.abs(m: Maybe<&2, String>) -> Maybe<&2, Url.Abs>:
109 match m:
110 case None{}:
111 None{}
112 case Some{s}:
113 Url.absolute(s)
114
115# The defaults under the request headers, names lowercased; a request header replaces a default of its name.
116# Host, Connection, Content-Length, and Transfer-Encoding are the client's own, so both sides drop them.
117def merge(defaults: Map<&2, List<&2, String>>, headers: Map<&2, List<&2, String>>) -> Map<&2, List<&2, String>>:
118 Http.req.put(Map.to_list(&2, List<&2, String>, headers), Http.req.put(Map.to_list(&2, List<&2, String>, defaults), Http.empty()))
119
120def jar.now(j: Maybe<&2, Http.Jar>) -> IO(Maybe<&2, Http.Jar>):
121 match j:
122 case None{}:
123 IO.pure(Maybe<&2, Http.Jar>, None{})
124 case Some{jar}:
125 do IO<Maybe<&2, Http.Jar>>:
126 now : Time.Instant <- Time.now()
127 return Some{Http.jar.at(jar, now)}
128
129def once.final(+enc: String, x: Http.Pool & Result<&1, &1, Http.Err, Http.Res> & Maybe<&2, Http.Jar>) ->
130 IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Res>):
131 (p, r, j) = x
132 do IO<Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Res>>:
133 d : Result<&1, &1, Http.Err, Http.Res> <- Http.fetch.final(enc, r)
134 return (p, j, d)
135
136# One try: the redirect loop on the pool, with the jar, the certificate, and the CA file, then the body decoded.
137def once(+ms: U32, +mode: Http.Mode, +cert: Maybe<&2, Http.Cert>, +ca: String, +enc: String, p: Http.Pool, j: Maybe<&2, Http.Jar>,
138 +method: String, +u: Maybe<&2, Url.Abs>, +headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) ->
139 IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Res>):
140 do IO<Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Res>>:
141 now : Maybe<&2, Http.Jar> <- jar.now(j)
142 x : Http.Pool & Result<&1, &1, Http.Err, Http.Res> & Maybe<&2, Http.Jar> <-
143 Http.pool.hops(mode, ms, Http.Hops{p, Http.fetch.start(method, headers, body, u, enc), cert, now, ca})
144 once.final(enc, x)
145
146def hint.ms(m: Maybe<&2, U32>) -> Maybe<&2, Nat>:
147 match m:
148 case None{}:
149 None{}
150 case Some{ms}:
151 Some{U32.to_nat(ms)}
152
153# m is Http.retry.judge's verdict for an idempotent request: Some{Retry-After} when another try may help.
154# None is Settled, so the breaker counts any other response or error as a success.
155# A non-idempotent request with that verdict is Unsafe: the breaker counts it, but it never repeats.
156def outcome(+idem: Bool, m: Maybe<&2, String>, now: Time.Instant) -> Retry.Outcome:
157 match m:
158 case None{}:
159 Retry.Settled{}
160 case Some{+v}:
161 Bool.pick(Retry.Outcome, idem, Retry.Transient{hint.ms(Http.retry.after(v, now))}, Retry.Unsafe{})
162
163def lift(-R: Type, r: Result<&1, &1, Http.Err, R>) -> Result<&1, &1, Err, R>:
164 match r:
165 case Fail{e}:
166 Fail{ErrHttp{e}}
167 case Done{res}:
168 Done{res}
169
170# The live state of one request between attempts. R: a response or a stream. last: the result of the last
171# attempt, None before the first.
172type Step<-R: Type> is Type:
173 Step{pool: Http.Pool, jar: Maybe<&2, Http.Jar>, breaker: Retry.Breaker, budget: Retry.Budget, body: Bytes.Bytes,
174 last: Maybe<&1, Result<&1, &1, Err, R>>, plan: Retry.Plan}
175
176# The clock, read only when a decision depends on it; 0 otherwise, which no such decision reads.
177def clock(need: Bool) -> IO(Nat):
178 match need:
179 case True{}:
180 Time.mono.ms()
181 case False{}:
182 IO.pure(Nat, 0n)
183
184def breaker.on(br: Retry.Breaker) -> Bool:
185 match br:
186 case Retry.BreakerOff{}:
187 False{}
188 case Retry.BreakerOn{c, s}:
189 True{}
190
191def transient(o: Retry.Outcome) -> Bool:
192 match o:
193 case Retry.Transient{after}:
194 True{}
195 case Retry.Settled{}:
196 False{}
197 case Retry.Unsafe{}:
198 False{}
199 case Retry.Failed{}:
200 False{}
201
202def some(m: Maybe<&2, Nat>) -> Bool:
203 match m:
204 case None{}:
205 False{}
206 case Some{t}:
207 True{}
208
209def deadline.some(b: Retry.Budget) -> Bool:
210 Retry.Budget{l, d} = b
211 some(d)
212
213# The wall clock dates a Retry-After, so it is read only for a transient failure.
214def outcome.io(+idem: Bool, m: Maybe<&2, String>) -> IO(Retry.Outcome):
215 match m:
216 case None{}:
217 IO.pure(Retry.Outcome, Retry.Settled{})
218 case Some{v}:
219 do IO<Retry.Outcome>:
220 wall : Time.Instant <- Time.now()
221 return outcome(idem, Some{v}, wall)
222
223# Jitter for the backoff, drawn only when a retry may follow.
224def jitter.io(need: Bool) -> IO(Nat):
225 match need:
226 case True{}:
227 do IO<Nat>:
228 rnd : Result<&1, &1, U32 & String, U32> <- IO.random_u32()
229 return U32.to_nat(Http.retry.jitter(rnd))
230 case False{}:
231 IO.pure(Nat, 0n)
232
233def settle.at(-R: Type, +now: Nat, +rnd: Nat, +p: Retry.Policy, +n: Nat, +o: Retry.Outcome, br: Retry.Breaker, +b: Retry.Budget,
234 body: Bytes.Bytes, pool: Http.Pool, jar: Maybe<&2, Http.Jar>, r: Result<&1, &1, Http.Err, R>) -> Step<R>:
235 Step{pool, jar, Retry.Breaker.done(br, now, Retry.failed(o)), b, body, Some{lift(R, r)}, Retry.plan(o, p, b, n, now, rnd)}
236
237# The attempt has ended: tell the breaker, and plan the next step.
238def settle.outcome(-R: Type, +p: Retry.Policy, +n: Nat, +o: Retry.Outcome, +br: Retry.Breaker, b: Retry.Budget, body: Bytes.Bytes,
239 pool: Http.Pool, jar: Maybe<&2, Http.Jar>, r: Result<&1, &1, Http.Err, R>) -> IO(Step<R>):
240 do IO<Step<R>>:
241 now : Nat <- clock(Bool.or(breaker.on(br), transient(o)))
242 rnd : Nat <- jitter.io(transient(o))
243 return settle.at(R, now, rnd, p, n, o, br, b, body, pool, jar, r)
244
245def settle.judged(-R: Type, +p: Retry.Policy, +idem: Bool, +n: Nat, br: Retry.Breaker, b: Retry.Budget, body: Bytes.Bytes,
246 pool: Http.Pool, jar: Maybe<&2, Http.Jar>, j: Result<&1, &1, Http.Err, R> & Maybe<&2, String>) -> IO(Step<R>):
247 (r, m) = j
248 do IO<Step<R>>:
249 o : Retry.Outcome <- outcome.io(idem, m)
250 settle.outcome(R, p, n, o, br, b, body, pool, jar, r)
251
252# The default judge: Http.retry.judge, as if the request were idempotent; outcome then applies idem.
253def judge(r: Result<&1, &1, Http.Err, Http.Res>) -> Result<&1, &1, Http.Err, Http.Res> & Maybe<&2, String>:
254 Http.retry.judge(True{}, r)
255
256def settle(~R: Type, ~judge: Result<&1, &1, Http.Err, R> -> Result<&1, &1, Http.Err, R> & Maybe<&2, String>,
257 +p: Retry.Policy, +idem: Bool, +n: Nat, br: Retry.Breaker, b: Retry.Budget, body: Bytes.Bytes,
258 x: Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R>) -> IO(Step<R>):
259 (pool, jar, r) = x
260 settle.judged(R, p, idem, n, br, b, body, pool, jar, judge(r))
261
262# The inputs of one attempt. u: the target, None when it is not absolute. headers: the merged headers.
263type Call is Data:
264 Call{enc: String, method: String, u: Maybe<&2, Url.Abs>, headers: Map<&2, List<&2, String>>}
265
266# One attempt that reads a whole response: the redirect loop on the pool, with the jar and the certificate.
267def try.res(o: Opts, call: Call, pool: Http.Pool, jar: Maybe<&2, Http.Jar>, body: Bytes.Bytes) ->
268 IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Res>):
269 Opts{base, h, +ms, +mode, p, +cert, +ca} = o
270 Call{+enc, +method, +u, +headers} = call
271 once(ms, mode, cert, ca, enc, pool, jar, method, u, headers, body)
272
273def try.stream.got(pool: Http.Pool, x: Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Stream>) ->
274 Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Stream>:
275 (jar, s) = x
276 (pool, jar, s)
277
278# One attempt that opens a stream on its own connection, outside the pool: the redirect loop with the mode,
279# the jar, and the certificate, then the body decoded by enc.
280def try.stream(o: Opts, call: Call, pool: Http.Pool, jar: Maybe<&2, Http.Jar>, body: Bytes.Bytes) ->
281 IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Stream>):
282 Opts{base, h, +ms, mode, p, cert, ca} = o
283 Call{+enc, method, u, headers} = call
284 do IO<Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Stream>>:
285 now : Maybe<&2, Http.Jar> <- jar.now(jar)
286 r : Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Stream> <-
287 Http.stream.hops(mode, ms, Http.StreamHops{Http.stream.start(method, Http.accept.enc(headers, enc), body, u), cert, now, ca})
288 x : Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, Http.Stream> <- Http.stream.init.jar(enc, r)
289 return try.stream.got(pool, x)
290
291def close.res(r: Http.Res) -> IO(Unit):
292 IO.pure(Unit, Unit{})
293
294def close.last(~R: Type, ~close: R -> IO(Unit), last: Maybe<&1, Result<&1, &1, Err, R>>) -> IO(Unit):
295 match last:
296 case None{}:
297 IO.pure(Unit, Unit{})
298 case Some{r}:
299 match r:
300 case Fail{e}:
301 IO.pure(Unit, Unit{})
302 case Done{x}:
303 close(x)
304
305def attempt.run(~R: Type, ~judge: Result<&1, &1, Http.Err, R> -> Result<&1, &1, Http.Err, R> & Maybe<&2, String>,
306 ~try: Opts -> Call -> Http.Pool -> Maybe<&2, Http.Jar> -> Bytes.Bytes -> IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R>),
307 +o: Opts, +call: Call, +idem: Bool, +n: Nat, pool: Http.Pool, jar: Maybe<&2, Http.Jar>, br: Retry.Breaker,
308 b: Retry.Budget, r: Bytes.Bytes & Bytes.Bytes) -> IO(Step<R>):
309 Opts{base, h, ms, mode, +p, cert, ca} = o
310 (body, spare) = r
311 do IO<Step<R>>:
312 x : Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R> <- try(o, call, pool, jar, spare)
313 settle(~R, ~judge, p, idem, n, br, b, body, x)
314
315def denied(-R: Type, why: Retry.Deny, last: Maybe<&1, Result<&1, &1, Err, R>>) -> Maybe<&1, Result<&1, &1, Err, R>>:
316 match last:
317 case None{}:
318 Some{Fail{ErrDenied{why}}}
319 case Some{r}:
320 Some{r}
321
322# A refused stream closes only when the next attempt is admitted, so a denied attempt still returns it.
323def attempt.gate(~R: Type, ~judge: Result<&1, &1, Http.Err, R> -> Result<&1, &1, Http.Err, R> & Maybe<&2, String>,
324 ~try: Opts -> Call -> Http.Pool -> Maybe<&2, Http.Jar> -> Bytes.Bytes -> IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R>),
325 ~close: R -> IO(Unit),
326 x: Retry.Breaker & Retry.Budget & Retry.Gate, +o: Opts, +call: Call, +idem: Bool, +n: Nat, pool: Http.Pool,
327 jar: Maybe<&2, Http.Jar>, body: Bytes.Bytes, last: Maybe<&1, Result<&1, &1, Err, R>>) -> IO(Step<R>):
328 (br, b, g) = x
329 match g:
330 case Retry.GateNo{why}:
331 IO.pure(Step<R>, Step{pool, jar, br, b, body, denied(R, why, last), Retry.PlanStop{}})
332 case Retry.GateGo{}:
333 do IO<Step<R>>:
334 close.last(~R, ~close, last)
335 attempt.run(~R, ~judge, ~try, o, call, idem, n, pool, jar, br, b, Bytes.slice(body, 0, 4294967295))
336
337# Ask the gate; when it admits, make attempt n (0 first) of this layer. With no deadline and no breaker,
338# admission does not read the clock.
339def attempt(~R: Type, ~judge: Result<&1, &1, Http.Err, R> -> Result<&1, &1, Http.Err, R> & Maybe<&2, String>,
340 ~try: Opts -> Call -> Http.Pool -> Maybe<&2, Http.Jar> -> Bytes.Bytes -> IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R>),
341 ~close: R -> IO(Unit),
342 +o: Opts, +call: Call, +idem: Bool, +n: Nat, s: Step<R>) -> IO(Step<R>):
343 Step{pool, jar, +br, +b, body, last, plan} = s
344 do IO<Step<R>>:
345 now : Nat <- clock(Bool.or(breaker.on(br), deadline.some(b)))
346 attempt.gate(~R, ~judge, ~try, ~close, Retry.admit(br, b, now), o, call, idem, n, pool, jar, body, last)
347
348def pause(ms: Nat) -> IO(Unit):
349 match ms:
350 case 0n:
351 IO.pure(Unit, Unit{})
352 case 1n+k:
353 IO.sleep(U32.from_nat(1n+k))
354
355# left: attempts this layer may still make. n: attempts made so far. Each turn follows the plan of the last step.
356def go(~R: Type, ~judge: Result<&1, &1, Http.Err, R> -> Result<&1, &1, Http.Err, R> & Maybe<&2, String>,
357 ~try: Opts -> Call -> Http.Pool -> Maybe<&2, Http.Jar> -> Bytes.Bytes -> IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R>),
358 ~close: R -> IO(Unit),
359 left: Nat, +n: Nat, +o: Opts, +call: Call, +idem: Bool, s: Step<R>) -> IO(Step<R>):
360 match left:
361 case 0n:
362 IO.pure(Step<R>, s)
363 case 1n+rest:
364 Step{pool, jar, br, b, body, last, plan} = s
365 match plan:
366 case Retry.PlanStop{}:
367 IO.pure(Step<R>, Step{pool, jar, br, b, body, last, Retry.PlanStop{}})
368 case Retry.PlanWait{ms}:
369 do IO<Step<R>>:
370 pause(ms)
371 next : Step<R> <- attempt(~R, ~judge, ~try, ~close, o, call, idem, n, Step{pool, jar, br, b, body, last, Retry.PlanStop{}})
372 go(~R, ~judge, ~try, ~close, rest, 1n+n, o, call, idem, next)
373
374def result.of(-R: Type, m: Maybe<&1, Result<&1, &1, Err, R>>) -> Result<&1, &1, Err, R>:
375 match m:
376 case None{}:
377 Fail{ErrDenied{Retry.DenySpent{}}}
378 case Some{r}:
379 r
380
381def request.done(-R: Type, +o: Opts, s: Step<R>) -> Client & Retry.Budget & Result<&1, &1, Err, R>:
382 Step{pool, jar, br, b, body, last, plan} = s
383 (Client{o, pool, jar, br}, b, result.of(R, last))
384
385def attempts(p: Retry.Policy) -> Nat:
386 Retry.Policy{a, base, cap, d} = p
387 a
388
389# The budget of one plain request: the policy's attempts, and its deadline from now. The clock is read only for a deadline.
390def budget(c: Client) -> IO(Client & Retry.Budget):
391 Client{+o, pool, jar, br} = c
392 Opts{base, h, ms, mode, Retry.Policy{+a, bs, cap, +d}, cert, ca} = o
393 do IO<Client & Retry.Budget>:
394 now : Nat <- clock(some(d))
395 return (Client{o, pool, jar, br}, Retry.Budget.new(a, now, d))
396
397def run(~R: Type, ~judge: Result<&1, &1, Http.Err, R> -> Result<&1, &1, Http.Err, R> & Maybe<&2, String>,
398 ~try: Opts -> Call -> Http.Pool -> Maybe<&2, Http.Jar> -> Bytes.Bytes -> IO(Http.Pool & Maybe<&2, Http.Jar> & Result<&1, &1, Http.Err, R>),
399 ~close: R -> IO(Unit),
400 c: Client, b: Retry.Budget, +idem: Bool, enc: String, method: String, url: String,
401 headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Client & Retry.Budget & Result<&1, &1, Err, R>):
402 Client{+o, pool, jar, br} = c
403 Opts{+base, +h, ms, mode, +p, cert, ca} = o
404 +call = {Call{enc, method, target.abs(target(base, url)), merge(h, headers)} : Call}
405 do IO<Client & Retry.Budget & Result<&1, &1, Err, R>>:
406 s : Step<R> <- go(~R, ~judge, ~try, ~close, attempts(p), 0n, o, call, idem, Step{pool, jar, br, b, body, None{}, Retry.PlanWait{0n}})
407 return request.done(R, o, s)
408
409# One request inside a caller's retry layer, with every choice explicit. Every attempt takes from b, the
410# caller's shared budget, and obeys its deadline; the client's own policy caps the attempts of this call.
411# The budget left comes back beside the result: pass it to the next call, so nested layers never reset or
412# multiply it. The client's own deadline does not apply here; b's does.
413# judge: Some{Retry-After} when another attempt may help. idem: the request is safe to repeat, so a judged
414# failure is retried; else the breaker counts it and it never repeats. enc: the Accept-Encoding codings.
415def request.as(~judge: Result<&1, &1, Http.Err, Http.Res> -> Result<&1, &1, Http.Err, Http.Res> & Maybe<&2, String>,
416 c: Client, b: Retry.Budget, +idem: Bool, +enc: String, +method: String, url: String,
417 headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Client & Retry.Budget & Result<&1, &1, Err, Http.Res>):
418 run(~Http.Res, ~judge, ~try.res, ~close.res, c, b, idem, enc, method, url, headers, body)
419
420# A streamed request under the same budget, deadline, backoff, and breaker as request.as. The stream opens its
421# own connection outside the pool. It follows the client's redirect mode, presents its certificate, and sends
422# and stores cookies through its jar, as request.as does. judge reads the status and headers through
423# Http.stream.res. A refused stream closes before the next attempt; the last one comes back open, so the
424# caller can read its body.
425def open.as(~judge: Result<&1, &1, Http.Err, Http.Stream> -> Result<&1, &1, Http.Err, Http.Stream> & Maybe<&2, String>,
426 c: Client, b: Retry.Budget, +idem: Bool, +enc: String, +method: String, url: String,
427 headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) -> IO(Client & Retry.Budget & Result<&1, &1, Err, Http.Stream>):
428 run(~Http.Stream, ~judge, ~try.stream, ~Http.stream.close, c, b, idem, enc, method, url, headers, body)
429
430# request.as with judge, the idempotency of method, and every coding Http decodes.
431def request.in(c: Client, b: Retry.Budget, +method: String, url: String, headers: Map<&2, List<&2, String>>,
432 body: Bytes.Bytes) -> IO(Client & Retry.Budget & Result<&1, &1, Err, Http.Res>):
433 do IO<Client & Retry.Budget & Result<&1, &1, Err, Http.Res>>:
434 enc : String <- Http.codings()
435 request.as(~judge, c, b, Http.pool.idempotent(method), enc, method, url, headers, body)
436
437def request.drop(x: Client & Retry.Budget & Result<&1, &1, Err, Http.Res>) -> Client & Result<&1, &1, Err, Http.Res>:
438 (c, b, r) = x
439 (c, r)
440
441def request.budget(+method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes,
442 x: Client & Retry.Budget) -> IO(Client & Retry.Budget & Result<&1, &1, Err, Http.Res>):
443 (c, b) = x
444 request.in(c, b, method, url, headers, body)
445
446# url resolves against the base; headers go over the defaults. Redirects follow the client's mode, at most 20.
447# Each request gets a fresh budget from budget(c). Before each attempt the deadline, the
448# budget, and the breaker must admit it. GET, HEAD, OPTIONS, TRACE, PUT, and DELETE try again after a connect
449# error, a timeout, or 408, 429, 500, 502, 503, or 504, as Http.retry.judge says, on the same pool.
450# When the attempts run out, the last result comes back; when none started, ErrDenied says why.
451def request(c: Client, +method: String, url: String, headers: Map<&2, List<&2, String>>, body: Bytes.Bytes) ->
452 IO(Client & Result<&1, &1, Err, Http.Res>):
453 do IO<Client & Result<&1, &1, Err, Http.Res>>:
454 y : Client & Retry.Budget <- budget(c)
455 x : Client & Retry.Budget & Result<&1, &1, Err, Http.Res> <- request.budget(method, url, headers, body, y)
456 return request.drop(x)
457
458def get(c: Client, url: String) -> IO(Client & Result<&1, &1, Err, Http.Res>):
459 request(c, "GET", url, Http.empty(), Bytes.new(0))
460
461# POST v as compact JSON, with content-type: application/json.
462def post.json(c: Client, url: String, v: Json.Val) -> IO(Client & Result<&1, &1, Err, Http.Res>):
463 request(c, "POST", url, Http.set(Http.empty(), "content-type", "application/json"), Json.encode.bytes(v))