generation.bend source

generation.bend on the hub · documented module

# W3C Trace Context Level 2 propagation, with its rules proved as laws. Source: https://github.com/LucasGois1/bend-trace-context## Generation on the host's cryptographic source# =============================================## The first line is the package's description on BendHub, which shows the# first line of the file that a release publishes: this file.## Generated contexts on the host's cryptographic source: WebCrypto in# JavaScript and the operating system's generator natively. They apply the# rules of trace_context.bend: four words per trace ID candidate and two per# span ID candidate, most significant first, eight candidates per identifier,# no all-zero identifier, no reuse of the parent's span ID or of a received# trace ID, and an immediate stop at the first source error. There is no time,# counter or other fallback. TC.Context.root_with and its siblings take a# caller's source instead.## The generation machine itself is pure: section 6 of LAWS.bend states its# behavior over replayed tapes. This file only connects it, and the native# HTTP shortcuts of native_http.bend, to the host source of entropy.bend.## Every operation here relies on entropy.bend's foreign effect, so a check of# a file that imports this module reports them and answers SOME PROOFS FAIL.# No law imports it: the laws state the same operations on a caller's# source, which is how PROOF.bend proves them without host code.import Baseimport ./trace_context.bend as TCimport ./native_http.bend as Adapterimport ./entropy.bend as Entropy# The host source as the machine reads it: each read returns one word result# from Entropy.read_u32, and the state is Unit because the host keeps none.def Source.host(state: Unit) -> IO(Unit & Result<&1, &1, U32 & String, U32>):  IO.bind(Result<&1, &1, U32 & String, U32>, Unit & Result<&1, &1, U32 & String, U32>,    Entropy.read_u32(), word => IO.pure(Unit & Result<&1, &1, U32 & String, U32>, (state, word)))# The host source has no state to hand back.def on_host(-A: Type, action: IO(Unit & A)) -> IO(A):  IO.bind(Unit & A, A, action, done => IO.pure(A, Pair.snd(Unit, A, done)))# Start a trace. The trace ID asserts random-trace-id and the root is not# sampled, so it is emitted with flags 02.def Context.root() -> IO(Result<&2, &2, TC.GenerationError, TC.LocalContext>):  on_host(Result<&2, &2, TC.GenerationError, TC.LocalContext>, TC.Context.root_with(~Unit, ~Source.host, Unit{}))# Continue a remote or local parent with a new operation.def Context.child(parent: TC.Parent, sampling: TC.Sampling) -> IO(Result<&2, &2, TC.GenerationError, TC.LocalContext>):  on_host(Result<&2, &2, TC.GenerationError, TC.LocalContext>,    TC.Context.child_with(~Unit, ~Source.host, Unit{}, parent, sampling))# Start a new trace instead of continuing a received context.def Context.restart(previous: TC.RemoteContext) -> IO(Result<&2, &2, TC.GenerationError, TC.LocalContext>):  on_host(Result<&2, &2, TC.GenerationError, TC.LocalContext>,    TC.Context.restart_with(~Unit, ~Source.host, Unit{}, previous))# Give a service its own operation for a received message: a child of the# context that extraction keeps, the message's or the base, a root without# one, or a new trace in its place at a trust boundary# (TC.Context.continue_or_start_with).def Context.continue_or_start(+extraction: TC.Extraction, reception: TC.Reception, sampling: TC.Sampling,  +policy: TC.FailurePolicy) -> IO(TC.FailurePolicy.result(policy, TC.Service)):  on_host(TC.FailurePolicy.result(policy, TC.Service),    TC.Context.continue_or_start_with(~Unit, ~Source.host, Unit{}, extraction, reception, sampling, policy))# Give one message that the service sends a new child of the service's# operation, or the fallback when none can be generated# (TC.Context.send_with).def Context.send(+limits: TC.Limits, service: TC.Service, sampling: TC.Sampling, +policy: TC.FailurePolicy,  +carrier: List<&2, TC.Header>) -> IO(TC.FailurePolicy.result(policy, TC.Sent)):  on_host(TC.FailurePolicy.result(policy, TC.Sent),    TC.Context.send_with(~Unit, ~Source.host, Unit{}, limits, service, sampling, policy, carrier))# The service's own operation for a received request, from the header map of# the request, on the host's cryptographic source: native_http.bend's# continue_or_start_with on Source.host. `base` is the context to keep when# the request carries no usable traceparent.def NativeHttp.continue_or_start(+limits: TC.Limits, headers: Adapter.HeaderMap(), base: Maybe<&2, TC.BaseContext>,  reception: TC.Reception, sampling: TC.Sampling, +policy: TC.FailurePolicy) ->  IO(TC.FailurePolicy.result(policy, TC.Service)):  on_host(TC.FailurePolicy.result(policy, TC.Service),    Adapter.continue_or_start_with(~Unit, ~Source.host, Unit{}, limits, headers, base, reception, sampling, policy))# Give one request that the service sends the context of a new operation, on# the host's cryptographic source: native_http.bend's send_with on# Source.host, which replaces the context fields of `headers`, the request's# own header map.def NativeHttp.send(+limits: TC.Limits, service: TC.Service, sampling: TC.Sampling, +policy: TC.FailurePolicy,  headers: Adapter.HeaderMap()) -> IO(TC.FailurePolicy.result(policy, Adapter.Outbound)):  on_host(TC.FailurePolicy.result(policy, Adapter.Outbound),    Adapter.send_with(~Unit, ~Source.host, Unit{}, limits, service, sampling, policy, headers))