epigrep 0.2.0

Temporal event-pattern matching over partitioned, timestamped event sequences, with explicit semantics and near-miss explanations.

epigrep

Grep is good at lines. Epigrep is for sequences.

Epigrep finds temporal patterns in partitioned, timestamped event sequences — the kind of question that is awkward in grep, SQL, or ad-hoc pandas: "a config reload followed by an OOM within two minutes, with no readiness success in between, per pod." You describe the sequence; Epigrep returns the matches, their spans and captured values, and — for the near-misses — an explanation of why they did not match.

The matching semantics are explicit and tested against a reference matcher; underneath, it is a small Rust core with a Python API.

• Documentation: https://rikkhill.github.io/epigrep/
• Source: https://github.com/rikkhill/epigrep

Install

pip install epigrep

Prebuilt wheels cover Linux (x86_64, aarch64), macOS (Apple Silicon), and Windows (x64); other platforms build from the source distribution, which needs a Rust toolchain.

Quick start

from epigrep import Event, Pattern, explain, match

events = [
    Event("api-0", 0,  "config_reload",     {"pod": "api-0"}),
    Event("api-0", 30, "readiness_success", {"pod": "api-0"}),
    Event("api-0", 70, "oom_killed",        {"pod": "api-0"}),
    Event("api-1", 0,  "config_reload",     {"pod": "api-1"}),
    Event("api-1", 90, "oom_killed",        {"pod": "api-1"}),
]

pattern = (
    Pattern.event("config_reload")
    .then("oom_killed", within=120, no="readiness_success")
    .build()
)

for m in match(pattern, events):
    print(m.partition, list(m.indices))   # api-1 [3, 4]

# Why didn't the others match?
for nm in explain(pattern, events):
    print(nm.partition, nm.reason)        # api-0 absence_blocked

api-1 matches: a reload, then an OOM 90s later, nothing in between. api-0 does not — a readiness_success lands in the gap, so the no= clause rules it out, and explain() tells you that rather than leaving you to work it out.

What you get back

For each start position, Epigrep returns either:

• a match — participating event indices, the span (start and end timestamps), and any captured attribute values; or
• a near-miss — for starts that cannot complete, the deepest partial path it reached and the reason the next step failed (predicate_failed, absence_blocked, window_exceeded, or no_successor), with structured detail.

schema(events) summarises the event types and attributes present. Pandas dataframe helpers are available when pandas is installed; matching and explanation do not require it.

Patterns

Two construction surfaces are stable: the builder (above) for code written by hand, and a JSON pattern format for tools and agents that emit and validate patterns programmatically.

from epigrep import Pattern, pattern_from_json

ast = Pattern.event("A").then("B", within=5).build().to_json()
pattern = pattern_from_json(ast)   # validated; safe to match

A terse text DSL also exists (parse_pattern), but it is experimental and outside the 0.1 stability guarantee — prefer the builder or JSON format.

Semantics

Matching has an explicit, tested contract: ordering and tie-breaking, partitioning, match-consumption modes, inclusive windows, absence-between, capture/register equality, overlapping matches, and near-miss guarantees. A naive reference matcher is the source of truth; a second, independent implementation is checked against it by property tests. See the documentation.

Status

Alpha (0.1.0). The Python API and JSON pattern format are the intended stable surface; the text DSL is experimental. MIT licensed.