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I am learning Zig a little bit and I encountered this interesting case: fn handleConnection(conn: std.Io.net.Stream, io: std.Io) !void { var buffer: [1024]u8 = .{0} ** 1024; var inBuf: [1024]u8 = .{0} ** 1024; const reader = conn.reader(io, &inBuf); var writer = conn.writer(io, &buffer); var ri = reader.interface; var http_server = std.http.Server.init(&ri, &writer.interface); // TODO: read a protobuf message (: var req = try http_server.receiveHead(); defer _ = conn.shutdown(io, std.Io.net.ShutdownHow.both) catch {}; try req.respond("hello world\n", std.http.Server.Request.RespondOptions{}); } Why this crashes? The crash message looks like: Segmentation fault at address 0x328 /home/gstatkevicius/Downloads/zig-x86_64-linux-0.16.0/lib/std/Io/net.zig:1305:40: 0x11f6b84 in readVec (std.zig) const n = io.vtable.netRead(io.userdata, r.stream.socket.handle, dest) catch |err| { ^ /home/gstatkevicius/Downloads/zig-x86_64-linux-0.16.0/lib/std/Io/Reader.zig:1135:29: 0x107df7b in fillMore (std.zig) _ = try r.vtable.readVec(r, &bufs); ^ /home/gstatkevicius/Downloads/zig-x86_64-linux-0.16.0/lib/std/http.zig:398:28: 0x11f171d in receiveHead (std.zig) in.fillMore() catch |err| switch (err) { ^ /home/gstatkevicius/Downloads/zig-x86_64-linux-0.16.0/lib/std/http/Server.zig:47:49: 0x11efaca in receiveHead (std.zig) const head_buffer = try s.reader.receiveHead(); ^ /home/gstatkevicius/dev/zetrics/src/main.zig:52:42: 0x11d754e in handleConnection (main.zig) var req = try http_server.receiveHead(); ^ /home/gstatkevicius/dev/zetrics/src/main.zig:38:29: 0x11d7e51 in main (main.zig) try handleConnection(try server.accept(io), io); ^ /home/gstatkevicius/Downloads/zig-x86_64-linux-0.16.0/lib/std/start.zig:737:30: 0x11d8a5e in callMain (std.zig) return wrapMain(root.main(.{ ^ /home/gstatkevicius/Downloads/zig-x86_64-linux-0.16.0/lib/std/start.zig:190:5: 0x11d7201 in _start (std.zig) asm volatile (switch (native_arch) { ^ fish: Job 1, 'zig run src/main.zig' terminated by signal SIGABRT (Abort) This version doesn’t crash: ...

Hello Hugo After having received a bill for 200$ from the previous hosting provider, after some serious vulnerability was discovered in WordPress, and inspired by the “indie web” movement, I decided that I will too move to just static pages. It is much easier to deploy, there’s zero vendor lock-in, etc. I can now just open up a text file, scribble something, and out it will go. From the saved money (>100$), I will instead buy something nice. ...

github.com/prometheus/client_golang has a nice feature where a histogram can simultaneously be both an exponential (native) histogram and a classic (explicit bucket) one. Then, depending on what formats are accepted by the scraper, either both the native histogram version and the classical one are exposed, or just the classical one (text format). There has been an initiative to expose native histograms in text format, but it hasn’t yet solidified. Unfortunately, in the OpenTelemetry standards, a histogram at any point can only have either explicit buckets or exponential buckets. From https://opentelemetry.io/docs/specs/otel/metrics/data-model/#model-details: ...

Okay, jsonnet does not have such a bad experience nowadays - there is a pretty good LSP server implementation thanks to the team at Grafana, there’s jsonnetfmt that makes the jsonnet code style the same across projects, and we have LLMs that make it much easier to learn any new language. Also, since it is an interpreted language that simply yields JSON, it is very easy to prototype and test changes. This was especially apparent during the recent hackathon where our team used jsonnet to implement a “dynamic dashboard generator” in Grafana, and we won the prize. Since all Grafana dashboards are JSONs, it is very to generate them with a language specifically geared towards it. ...

Rust has a well-known borrow checker and a whole programming model that ensures there will be no data races. In particular, it is only possible to have one mutable reference or many read-only references but not both types at the same time. Technically, you might think that because Go is pass-by-value i.e. the arguments that you’re giving to a function are copied into some memory location before calling the function, it is impossible to have races in Go too. However, some types like slices and maps are implemented as references so you have to take a lot of care when returning them from a function because the caller might modify them. ...

We have been using gRPC in Thanos since Thanos inception - it has served us great and it has a ton of useful functionality, it solves a lot of problems, it is easy to use, and so on. However, I feel like some stuff is lacking, especially performance that will most likely never be fixed (or, I should say, changed). The framework just does not solve 100% of the things that the Thanos project needs right now. Let’s go through the list of my pet peeves. ...

It all started in, I believe, the eventful year of 2001. I was 6 years old. Our family was lucky enough to get our own first personal computer! Completely for us and used by all members of our family back then. I consider that to be incredible luck given that Lithuania recently regained its independence after the Soviet occupation. I think we got internet connected to our house around 2003 so for a few years we were offline. My mom was still studying back then and she used the computer a lot for her studies. But me and my brother mostly used it for entertainment - music, games, videos. Someone left some pre-installed games like Dave Mirra Freestyle BMX and Worms Blast on the computer, and we played the heck out of them. ...

Hashrings are everywhere in distributed systems. Combined with a write-ahead log that uses an unbounded amount of RAM during WAL replay, they are a terrible idea. If there is a constant stream of metrics coming into Thanos, you want to push back on the producers of those metrics in case of one or a few node’s downtime. Having a dynamic hashring i.e. a hashring that immediately updates as soon as it notices that one node is down, prevents that. The same stream is now going to fewer nodes. And so on until, most likely, your whole stack collapses. In practice, this means that you should not remove a node from the hashring if it is unhealthy or unready. ...

I recently ran into this “fun” problem where the Compactor was stuck compacting the same blocks repeatedly. Only after lots of trial and error, I have found out that sharding using hashmod on some labels that are also dedup labels in vertical compaction was the culprit. Vertical compaction is like horizontal compaction but vertical compaction compacts blocks that have overlaps in time. And also vertical compaction removes the specified replica labels. Apparently, Thanos Compactor depends on having a “global” view of all blocks to filter out blocks that had been compacted into higher compaction level blocks. The interesting part is this filter: https://github.com/thanos-io/thanos/blob/f7ba14066fc35095e13ca3f675915c509310f476/cmd/thanos/compact.go#L235. It filters out blocks that can be formed from two or more overlapping blocks that fully matches the source blocks of the older blocks. It uses data in the meta.json file of each block to understand what are the sources of each block. ...

In the Thanos project the e2e tests are written in part using assertions on the metrics data. I have encountered a few challenges with those assertions that I wanted to share with you. Always check for the maximum possible value Writing tests on /metrics data means your testing harness continuously checks /metrics data to see whether some metric equals some value. If the metric takes some time to reach the maximum value, you might erroneously write an equals check that checks for a smaller value. Later on, this will lead to a flaky test situation. ...