Compile getting [error] ** Too many db tables **

I’ve hit an error compiling a Phoenix app that I’ve never seen before.

** (exit) an exception was raised:
    ** (SystemLimitError) a system limit has been reached
        (stdlib), [:set, :protected])
        (stdlib) digraph.erl:78:
        (elixir) lib/module/locals_tracker.ex:232: Module.LocalsTracker.init/1
        (stdlib) gen_server.erl:328: :gen_server.init_it/6
        (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3


[error] ** Too many db tables **

Elixir 1.5.1
Phoenix 1.3.0

It happens at different files each compile, so it’s not consistently happening at one point in the app or another.

Any ideas? Thanks.


I can only tell you that the error message means the system is running out of ets tables. The default limit is 1400 but it can be changed by a flag to the erlang runtime.

For example:
iex --erl '+e 10000'

That said, don’t blindly just increase this level. It is usually a sign that something is not quite right and that you must actually understand the problem :smiley:

You see this once in a while in running systems but the question is why it is happening during compilation. Is the error always in the locals_tracker module? It may be cause of it but you may also run out of ets tables else where and the locals_tracker only happen to be the one reaching the limit.

In a running system I would set-up traces to see when is being called and monitor it to find out who is the offender but I don’t know how to do this during compilation :confused:

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Thanks, yeah it’s an odd one…
Only other information I can add is that we have about 600 modules in this app. I don’t know if there are any limits there?

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Well, from a quick look at locals_tracker it is responsible for “tracking calls in order to extract Elixir modules’ behaviour during compilation time”.

So it is certainly possible that the number of modules in an application could have something to do with it Unfortunately it is beyond my knowledge how the elixir compilation works.

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Oh my… That’s a lot. Try to reduce that number or split them into multiple apps under an umbrella.

Additionally you should file a bug that something in the build chain crashes when there are too many modules.

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I was trying to determine if the number of modules is part of the bug or if it was something else before filing one.

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During compilation there are a lot of ets-tables created, and as far as I can remember, one for each module to hold the modules metadata such that it can be accessed from other compilers easily (one writer, many readers).

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Submitted an issue to the Elixir github:

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