README
¶
Examples
Each example is a single main.go that connects to a JetStream-enabled NATS
server ($NATS_URL, default nats://localhost:4222), starts an engine and its
workers, and prints what happens:
docker run --rm -p 4222:4222 nats:2.14.2 -js
go run ./examples/hello
make examples # run them all
| Example | Shows |
|---|---|
| hello | The smallest program: a two-step flow, a worker, start and wait; reading a previous node's output |
| approval | Human in the loop: a task that interrupts with a question and is resumed with the answer; an await node with a timeout route; a choice on the signal |
| research | Parallel branches (fanout + quorum join) writing to shared state through reducer channels (append, merge, sum); a budget on a counter |
| mapreduce | A dynamic map over a list computed at run time, bounded parallelism, ordered results, reducers as the reduce step |
| resilience | Retries with backoff, per-attempt timeouts (the late result is ignored), output JSON Schema, permanent errors |
| timetravel | History, state at any sequence, rerun of a failed node after a fix, fork from the past |
| agentloop | A tool-using loop: a planner routing with dynamic edges, a message channel, a recursion limit and a call budget — no LLM required |
| subflow | A flow calling another flow; child output and counters flow back; cancelling the parent cancels the child |
| events | Executions started by a cron schedule and by messages on a subject (deduplicated by Nats-Msg-Id) |
Each example uses its own namespace (example-<name>), so they do not
interfere. While an example runs you can inspect it with the CLI and the UI:
go run ./cmd/packtrail -ns example-timetravel list
go run ./cmd/packtrail-ui -namespace example-timetravel
Directories
¶
| Path | Synopsis |
|---|---|
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Example agentloop: the shape of a tool-using agent, built from generic parts — packtrail knows nothing about LLMs.
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Example agentloop: the shape of a tool-using agent, built from generic parts — packtrail knows nothing about LLMs. |
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Example approval: human in the loop, two ways.
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Example approval: human in the loop, two ways. |
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Example events: executions started by time and by messages.
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Example events: executions started by time and by messages. |
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Example hello: the smallest packtrail program.
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Example hello: the smallest packtrail program. |
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internal
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devserver
Package devserver gives the examples a NATS connection to the server named by $NATS_URL (default nats://127.0.0.1:4222), which must have JetStream enabled.
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Package devserver gives the examples a NATS connection to the server named by $NATS_URL (default nats://127.0.0.1:4222), which must have JetStream enabled. |
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exutil
Package exutil holds the few lines every example repeats.
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Package exutil holds the few lines every example repeats. |
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Example mapreduce: a dynamic fan-out over a list computed at run time.
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Example mapreduce: a dynamic fan-out over a list computed at run time. |
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Example research: parallel branches writing to shared state.
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Example research: parallel branches writing to shared state. |
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Example resilience: what happens when workers misbehave.
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Example resilience: what happens when workers misbehave. |
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Example subflow: composing flows.
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Example subflow: composing flows. |
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Example timetravel: the event log as a debugging tool.
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Example timetravel: the event log as a debugging tool. |
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