Log Parsing Error Extraction

MediumPython

Problem

Zscaler operational logs use the format timestamp|level|component|message. Write a function that parses these log lines, keeps only entries whose level is exactly ERROR, and counts which requested error patterns occur in each error message.

A pattern contributes at most one count per log line, even if it appears multiple times. Matching is case-sensitive and uses literal substring matching. Malformed lines, including lines with fewer than four fields, must be ignored. The message may contain additional | characters, so split only at the first three separators.

Formal Specification

Implement count_error_patterns(logs, patterns).

logs is a list of strings.
patterns is a list of distinct, non-empty strings.
Return a dictionary mapping every pattern to its number of matching ERROR log lines, including patterns with count zero.
Preserve the order of patterns in the returned dictionary.

Constraints

1 <= len(logs) <= 10^4
1 <= len(patterns) <= 50
Each log line has at most 2,000 characters
Each pattern has at most 100 characters
Patterns are distinct, non-empty, and case-sensitive

Function Signature

def count_error_patterns(logs, patterns):

Formal Specification

Implement count_error_patterns(logs, patterns).

logs is a list of strings.
patterns is a list of distinct, non-empty strings.
Return a dictionary mapping every pattern to its number of matching ERROR log lines, including patterns with count zero.
Preserve the order of patterns in the returned dictionary.