Skopos

Declarative HTTP polling, as code.

Warning

Skopos is experimental and pre-1.0. The spec, CLI flags, and Go API are expected to change in breaking ways between releases. Pin a version if you depend on it.

Skopos turns a YAML document describing an HTTP API — its authentication, requests, and pagination — into a working pull-based ingest agent. The spec is the program; the runner interprets it.

It's aimed at two kinds of users:

• Operators and platform teams who want HTTP polling defined declaratively alongside the rest of their infrastructure-as-code, in a format that's easy to read, review, and diff.
• Application authors who want to expose a simple, schema-validated interface that lets their end users configure polling against arbitrary third-party APIs — without writing per-vendor code.

Skopos ships as both a single static binary and a Go library, so you can reach for whichever fits the use case — a CLI for operations, or an embedded runner inside your own service.

Overview

• One spec, many API shapes. Authentication modes include bearer, basic, API key, OAuth2 (client credentials and password grant), AWS SigV4, session cookies, and dispatched multi-mode auth. Pagination modes include cursor token, page number, offset, Link header, next-URL-in-body, scroll ID, and async submit/poll/fetch.
• Stateful between runs. Cursors and bookkeeping live in a pluggable store (in-memory, file, or your own implementation) and survive restarts.
• CLI or library, same behaviour. Use the skopos binary for operations, or import the runner as a Go package — both interpret the same spec.
• Built to be operated. Optional per-request tracing with automatic secret redaction, structured diagnostics from skopos validate, and a configurable cap on pages per drain.
• Pure Go, no plugins. A single binary or a single import path. No sidecars, no external services required.

Install

CLI binary via go install

Builds the latest released skopos into $GOBIN:

go install github.com/p1llus/skopos/cmd/skopos@latest

Go library

Add Skopos to your module and import the client and schema packages:

go get github.com/p1llus/skopos@latest

import (
    "github.com/p1llus/skopos/client"
    "github.com/p1llus/skopos/schema"
)

See Creating your own client below for a minimal embedding example.

Prebuilt archive + signature verification

Each release publishes per-OS archives, a checksums.txt, and a keyless cosign Sigstore bundle (checksums.txt.sigstore.json) on GitHub Releases.

Archive names follow skopos_<semver>_<os>_<arch>.<ext> (semver has no leading v in filenames; the Git tag does).

TAG=v0.1.0
VERS=${TAG#v}
OS_ARCH=linux_amd64   # or darwin_amd64, darwin_arm64, linux_arm64, windows_amd64

curl -fsSLO "https://github.com/p1llus/skopos/releases/download/${TAG}/checksums.txt"
curl -fsSLO "https://github.com/p1llus/skopos/releases/download/${TAG}/checksums.txt.sigstore.json"
curl -fsSLO "https://github.com/p1llus/skopos/releases/download/${TAG}/skopos_${VERS}_${OS_ARCH}.tar.gz"

cosign verify-blob \
  --bundle checksums.txt.sigstore.json \
  --certificate-identity "https://github.com/p1llus/skopos/.github/workflows/release.yml@refs/tags/${TAG}" \
  --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \
  checksums.txt

sha256sum --check --ignore-missing checksums.txt

Quickstart

The skopos binary comes with prebuilt templates to help get started

# 1. (Optional) Start the testserver in another terminal. It hosts a stub endpoint
#    for every bundled template and exits on Ctrl-C.
go run github.com/p1llus/skopos/cmd/testserver@latest

# 2. Browse the templates embedded in the binary, then print one out
#    as a starting spec. Default values point to the correct testserver endpoint
skopos template list
skopos template show bearer_simple > spec.yml

# 3. Validate the spec.
skopos validate -i spec.yml

# 4. Run once. Events are emitted as JSONL on stdout.
skopos run -i spec.yml --once

Example event output

{"id":"evt-000001","seq_num":1,"timestamp":"2026-05-15T06:28:29.552249238Z"}
{"id":"evt-000002","seq_num":2,"timestamp":"2026-05-15T06:28:30.552249238Z"}
{"id":"evt-000003","seq_num":3,"timestamp":"2026-05-15T06:28:31.552249238Z"}
{"id":"evt-000004","seq_num":4,"timestamp":"2026-05-15T06:28:32.552249238Z"}
{"id":"evt-000005","seq_num":5,"timestamp":"2026-05-15T06:28:33.552249238Z"}

You can define a output file if you don't want events to appear in stdout, below example also enables tracing:

skopos run -i spec.yml --once --out events.jsonl --trace trace.jsonl

Override settings with configuration file

If you either want to quickly swap between different configurations or do not want to provide them in the CLI each time you run, you can run skopos init -o config.yml

skopos init -o config.yml

# skopos run configuration
# All fields are optional. CLI flags take precedence over values set here.
# Omit a field to use the built-in default.

# input: path to the spec file to run. Equivalent to -i / --input.
# input: spec.yml

# state: path to the JSON state file for persisting the cursor between runs.
# Equivalent to --state. Omit to use an in-memory store (state lost on exit).
# state: state.json

# out: path to write JSONL events to. Equivalent to --out.
# Defaults to stdout when omitted.
# out: events.jsonl

# trace: path to write per-exchange JSONL trace records to.
# Equivalent to --trace. Trace is disabled when omitted.
# trace: trace.jsonl

# once: run a single drain and exit. Equivalent to --once.
# once: false

# interval: sleep this duration between drains in continuous mode.
# Equivalent to --interval. Omit (or set to 0) for one-shot mode.
# interval: 30s

# http_timeout: per-request HTTP timeout. Defaults to 30s when omitted.
# http_timeout: 30s

# max_pages: cap on the number of pagination iterations per drain.
# Defaults to 10000 when omitted.
# max_pages: 10000

Example trace output

trace.jsonl carries one record per HTTP exchange, with secrets redacted:

{"iteration":1,"method":"GET","url":"http://localhost:9999/bearer_simple/events","query":{"limit":"<format:string>","since":"<ref state.last_timestamp>"},"request_headers":{"Accept":"application/json, application/x-ndjson;q=0.9, */*;q=0.1","Authorization":"<redacted>"},"status":200,"response_body":"body 403 bytes, object-like","started_at":"2026-05-15T06:28:47.777479114Z","elapsed":16011226}

Swap bearer_simple for any other template name to try a different API shape against the same testserver. Run skopos --help (or skopos <command> --help) for the full list of commands and flags.

Templates

Bundled templates cover every authentication and pagination pattern the runner supports today. List them with skopos template list, then print one to a file as a starting point:

skopos template show bearer_simple > spec.yml

The full template source lives in templates/ — that's the easiest place to browse the patterns side-by-side.

Creating your own client

To embed Skopos in your own Go program — for example to route events into a database or message queue, or to persist cursors somewhere other than a local file — the runner is exposed as a library. Bring your own implementations of Sink (where events go) and Store (where cursors live):

package main

import (
    "context"
    "log"
    "os"

    "github.com/p1llus/skopos/client"
    "github.com/p1llus/skopos/schema"
)

func main() {
    f, err := os.Open("spec.yml")
    if err != nil {
        log.Fatal(err)
    }
    defer f.Close()

    doc, err := schema.Load(f)
    if err != nil {
        log.Fatal(err)
    }
    if diags := schema.Validate(doc); len(diags) > 0 {
        log.Fatalf("invalid spec: %v", diags)
    }

    runner := &client.Runner{
        Doc:   doc,
        Store: client.NewFileStore("state.json"), // or your own Store
        Sink:  client.NewJSONLSink(os.Stdout),    // or your own Sink
    }
    if err := runner.Drain(context.Background()); err != nil {
        log.Fatal(err)
    }
}

For scheduling, custom HTTP clients, sharing state across goroutines, and writing your own sinks or stores, see docs/usage.md.

Documentation

Doc	What's in it
Spec reference	Every field in the YAML spec, with examples
Runtime contract	How the runner interprets a spec, end to end
API patterns	Catalogue of API shapes Skopos can speak to
Embedding guide	Using Skopos as a Go library inside your own service
State stores	Plugging in a custom cursor store (SQLite, BoltDB, …)
More examples	Golden-file fixtures, one per bundled template
Go API reference	Generated package docs on pkg.go.dev

License

Skopos is licensed under the Apache License, Version 2.0. See LICENSE for the full text.

SPDX-License-Identifier: Apache-2.0