Stuck construction bots

[mr_fancy_pants]

We have a very large and sprawling base (~1.3k roboports), all of which is covered by the same logistics network. This game started as multiplayer and has been continued as multiplayer for the most part, though with some playtime via single player.

Currently there are a large number of ghost entities placed via blueprints which the construction bots have not yet built. Now, that may not sound like a bug, but said ghost entities have been lingering for multiple hours now, still not built, while everything around them that was blueprinted at the same time was constructed multiple hours ago. All of the materials necessary for construction are available in network, there are lots of available construction bots (~5500/6000), and there is lots of storage space available in storage chests in network. Even if they were to run out of power mid flight, the bots should have been able to go from one end of the base to the other multiple times by now.

This all started happening around the time I expanded the base to the south, blueprinting the long southern wall. Due to the Roboport coverage, I fully expected that to take a long time to construct (and it did - though there are some "stuck" ghost entities in it too). I don't recall now the timing of the solar array blueprinting in relation to the southern wall, but they probably overlapped. I believe at one point the southern wall logistics network was disconnected from the rest of the network, as a biter attack took out some power poles and/or Roboports. However, currently the southern logistics network is connected to the rest of the network via multiple points.

I first noticed the problem when I saw that the solar array expansion still hadn't been completed. When I went to investigate, I noticed that there was a number of items still queued for deconstruction in the way of some of the blueprinted items. Clearing the buildings (belts, mostly) queued for deconstruction manually allowed a number of the blueprinted buildings to be placed immediately, as there was a construction bot waiting there. I left the bots to their work (again), thinking they would figure things out eventually, and added (many) more storage chests just in case. A couple hours later, I started placing blueprints in the newly secured southern area and noticed again that some of the blueprinted buildings were not getting constructed, even though everything around them had been constructed a long time ago, I manually constructed most of what was missing here, but there are still a few ghosts left in that area. At this point I again noticed that the bots had made zero progress on the solar array construction, and tried to force the issue by walking past the ghost buildings with a Personal Roboport and the requisite items, but to no effect. If I manually place the items ghosted for the blueprint, I can see that the number of available construction bots increases by one per ghost removed.

I've been letting the game run while writing this bug report while keeping an eye on the number of available construction bots. Over the course of half an hour or so, the number of available construction bots has never risen above 5520/6027. The number will waver slightly as they respond to biter attacks, but it never rises back above 5520/6027. This confirms a more casual observation I had earlier, that there seemed to be 500 or so "stuck" construction bots, as even when I wasn't constructing anything, there was still some 500 construction bots unavailable.

Unfortunately, I can't tell where the 500ish unavailable bots are exactly, but they seem to be assigned to the ghost items on the map, as the Personal Roboport bots don't respond to them, and clearing each ghost frees up a construction bot. I assumed this problem would clear if I waited long enough, but it's not improving over the course of multiple hours, and the problem of ghost buildings never getting constructed is also affecting newly placed blueprints.

Just now I scoured the entire south wall and noticed one area where construction bots were flying to a destination over a large area not covered by Roboports, realizing they would run out of power before they got there, turning around, running out of power, and then eventually getting back to the original Roboport to charge, only to repeat the cycle again. These construction bots seemed happen to repeat this cycle forever. I added some additional Roboports to cover the uncovered area and they were then able to make it to their destination, and several of the ghosted buildings got built. However, there are still several hundred construction bots unavailable and corresponding building ghosts, which may be repeating this same pattern somewhere else I haven't noticed yet.

Why would the construction bots repeatedly choose a path that they know they won't complete? It would be much much better if they either:

a) completed the path anyways, even though it'll take a long time because they'll run out of power part of the way there, or
b) chose a longer path (ie, not a straight line), but with more intermediate charging points available

Particularly smart bots would choose the faster of the above two options.

Alternatively, if we could at least see where construction bots are (via a map overlay or similar), or get some sort of warning when they're stuck in a loop like described, we could at least manually address this problem. As it is, it is very difficult to diagnose.

I have attached a save file near some of the oldest ghost entities in the solar array.

[Loewchen]

What you describe is to be expected, when building one very big logistic network that is is concave in shape or has holes in it that can not be crossed without recharging. The "missing" robots are most likely drained of power on a hour long journey to the next roboport. To prevent these problems, best use separated networks or when making a single one, let the coverage build a regular convex area.
If you think there is a different cause, then please provide a save file where the issue can be observed in smaller scale.

[Neemys]

I take a quick look at your save, near station named AwesomeS, there is lots of bot that go get power again that have diverted a lot from their initial route. Can't see where they were headed as even with a zoom of 0.01 (where my computer have trouble running the game) their target are outside of viewing screen. They were headed to the north of your base. Seem like bots are still having trouble heading from one point of your base to the other, Maybe your bots with solar panel are there. Stuck as they can't reach their destination without running out of energy. Don't have time to check by adding more roboport in this area.

And the bots will never try to find another path. Thats how the game is written. Such change belong to suggestion, but I'm sure it has already been done.

Like Loewchen said, you should try to either to build a convex area or use multiple smaller logistics area.

[mr_fancy_pants]

Ok, I can accept that the pathing of the bots is a design decision. It was definitely a surprise to me to see the bots fly out only to land back at exactly the same Roboport again, my experience thus far is that they would continue flying to their destination after reaching 0 J, albeit very slowly.

I did a walkaround of the edges of the base and was able to locate and unstick most of the construction bots with some extra Roboports. There are still 40 or so unaccounted for, which are probably stuck somewhere I haven't looked yet... finding those may be annoying.

In situations like these it would be extremely helpful to be able to see bot locations on the overall map, or to have some sort of warning about bots that aren't making forward progress to their destination, or to be able to see where the bot assigned to a particular ghost is (then you could verify they're making progress yourself).

[steinio]

VisibleBots shows all bots as white markers on the map.
Maybe this could help.

https://mods.factorio.com/mods/keyboard ... sible_Bots

Greetings steinio

[mr_fancy_pants]

Ah, excellent. Yes, that mod is very helpful. Thanks.