Top Five Frequent Error Logs | Dataford Interview Questions

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Problem

In Meta infrastructure systems, engineers often need to summarize large volumes of Scuba-style server logs. Given a list of log lines, return the top 5 most frequent error messages.

A log line is considered an error message only if it starts with the prefix "ERROR: ". The message is the substring after that prefix. Count identical messages together and return up to 5 messages ordered by descending frequency. If two messages have the same frequency, return them in lexicographically ascending order.

Formal Specification

Implement a function that takes a list of strings logs and returns a list of strings.

Input: logs, a list of log lines
Output: a list containing up to 5 error messages

Ignore all non-error log lines.

Constraints

1 <= len(logs) <= 10^5
0 <= len(logs[i]) <= 200
Each log line is an ASCII string
A valid error line starts exactly with "ERROR: "
Return at most 5 messages
If fewer than 5 distinct error messages exist, return all of them

Function Signature

def top_five_errors(logs):