Dot-Notation Context Filtering Example

This example demonstrates how to configure and execute Logly's Dot-Notation Context Path Filtering. You can write clean rules targeting nested properties (e.g. "user.id", "service.name") inside structured metadata contexts to automatically drop or allow records dynamically.

For detailed concepts, see the Enterprise Filtering Guide.

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Code Listing

The following is the complete source from [examples/context_filter.zig](file:///c:/Users/smuha/Downloads/logly.zig/examples/context_filter.zig):

const std = @import("std");
const logly = @import("logly");

pub fn main() !void {
    var gpa = std.heap.DebugAllocator(.{}){}; 
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    _ = logly.Terminal.enableAnsiColors();

    std.debug.print("=== Logly v0.2.0 Dot-Notation Context Filtering Example ===\\n\\n", .{});

    // Create logger (display-only: no file writes)
    // Disable async writes so messages appear immediately for this demo
    var config = logly.Config.displayOnly();
    config.auto_flush = true;
    const logger = try logly.Logger.initWithConfig(allocator, config);
    defer logger.deinit();

    // Create a filter with dot-notation context path matching
    var filter = logly.Filter.init(allocator);
    defer filter.deinit();

    // Allow records where context["user.id"] == "42"
    try filter.addContextPathMatch("user.id", "42", .allow);

    // Deny records where context["service.name"] == "legacy"
    try filter.addContextPathMatch("service.name", "legacy", .deny);

    // Attach filter to logger
    logger.setFilter(&filter);

    std.debug.print("--- Filter rules configured ---\n", .{});
    std.debug.print("  Rule 1: allow   context['user.id'] == '42'\n", .{});
    std.debug.print("  Rule 2: deny    context['service.name'] == 'legacy'\n\n", .{});

    // Scenario 1: user.id = "42", service.name = "auth" → allowed by rule 1, not denied by rule 2
    try logger.bind("user.id", .{ .string = "42" });
    try logger.bind("service.name", .{ .string = "auth" });
    std.debug.print("[Scenario 1] user.id=42, service.name=auth → ALLOWED:\n", .{});
    try logger.info("User 42 performed an action.", @src());
    try logger.flush();

    // Scenario 2: user.id = "99", service.name = "auth" → doesn't match allow rule 1 → denied
    try logger.bind("user.id", .{ .string = "99" });
    std.debug.print("[Scenario 2] user.id=99, service.name=auth → FILTERED (no allow rule matches):\n", .{});
    try logger.info("User 99 performed an action (should be filtered).", @src());
    try logger.flush();

    // Scenario 3: user.id = "42", service.name = "legacy" → rule 2 deny fires
    try logger.bind("user.id", .{ .string = "42" });
    try logger.bind("service.name", .{ .string = "legacy" });
    std.debug.print("[Scenario 3] user.id=42, service.name=legacy → DENIED by rule 2:\n", .{});
    try logger.info("Legacy service message (should be denied).", @src());
    try logger.flush();

    // Scenario 4: Clear all bindings — no context_path_match rules fire → pass-through
    logger.clearBindings();
    std.debug.print("[Scenario 4] No context bindings → filter falls through:\n", .{});
    try logger.info("No context — filter pass-through.", @src());
    try logger.flush();

    std.debug.print("\n=== Dot-Notation Context Filter Example Complete ===\n", .{});
}

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Execution Output

When you compile and run this example with zig build run-context_filter or zig build example-context_filter, the console will display:

=== Logly v0.2.0 Dot-Notation Context Filtering Example ===

--- Filter rules configured ---
  Rule 1: allow   context['user.id'] == '42'
  Rule 2: deny    context['service.name'] == 'legacy'

[Scenario 1] user.id=42, service.name=auth → ALLOWED:
2026-05-24 11:15:00.123 [INFO] User 42 performed an action. (examples/context_filter.zig:41)

[Scenario 2] user.id=99, service.name=auth → FILTERED (no allow rule matches):

[Scenario 3] user.id=42, service.name=legacy → DENIED by rule 2:

[Scenario 4] No context bindings → filter falls through:
2026-05-24 11:15:00.125 [INFO] No context — filter pass-through. (examples/context_filter.zig:60)

=== Dot-Notation Context Filter Example Complete ===