Prev Next

Erlang / Erlang Advanced Interview questions

How do you troubleshoot a memory leak caused by large binaries not being garbage collected?

Large (>64 byte) binaries live off the process heap and are reference-counted, but the counter only drops when the owning process's heap is actually garbage collected — a process that receives many large binaries but rarely triggers a GC cycle (because its own small heap of local variables never fills up) can hold references to megabytes of off-heap binary data far longer than expected.

%% inspect suspects
erlang:process_info(Pid, binary).             %% list of {BinId, Size, RefCount}
recon:bin_leak(10).                             %% recon helper: top 10 processes by binary refs

Common fixes:

  1. Force a GC explicitly on long-lived, low-activity processes holding binaries via erlang:garbage_collect(Pid), either periodically or after processing a large payload.
  2. Shrink the reference's lifetime — if only a small slice of a large binary is actually needed long-term, copy just that slice with binary:copy/1 so the full original can be released.
  3. Check for accidental retention in a process dictionary entry or long-lived accumulator that's never cleared.
Why can a process hold onto large binary references longer than expected?
What does binary:copy/1 help with in this context?

More Related questions...

What is the difference between linking and monitoring a process? Why would you choose monitor over link for a client process? What is a dirty scheduler and when should a NIF use one? Explain the internal working of Erlang's per-process garbage collector? Why does Erlang use generational (per-process) garbage collection instead of a single global GC? What is EPMD and what role does it play in distributed Erlang? Why do distributed Erlang nodes require a shared cookie? Explain the internal working of the Erlang distribution handshake between two nodes? What is the two-version code loading rule and what happens when a third version is loaded? Explain the internal working of code:purge/1 and code:soft_purge/1? What is a gen_event and when would you choose it over gen_server? What is the difference between error, exit, and throw in Erlang? Why is exit/1 different from exit/2? What is an OTP application (.app file) and how does it differ from a single module? Explain the execution flow of application:start/1 and its dependency resolution? What is a release in OTP and how does it differ from an application? Explain the internal working of a relup-based hot upgrade? What is the code_change/3 callback used for in gen_server? How does the global module handle process name registration across a cluster? Why can global name registration cause a network partition ("split brain") problem? What is the pg (process groups) module used for? What are Erlang maps and how do they differ from records? When should you choose a map over a record for structured data? What is the difference between ets:match, ets:select, and ets:foldl? How can you use match specifications to filter ETS data efficiently? What do the write_concurrency and read_concurrency ETS options optimize for? How can you optimize binary pattern matching for parsing variable-length network protocols? Why is copying a large list between processes more expensive than copying a large binary? What is tail call optimization in Erlang and why does it matter for long-running loops? How do you write a properly tail-recursive accumulator-based function? Explain the internal working of selective receive and why message order in the queue matters? What is erlang:process_flag(priority,...) used for? Why should high-priority processes be used sparingly in Erlang? What is rpc:call/4 and how does it work across distributed nodes? What is the difference between rpc:call and simply sending a message to a remote PID? How does erlang:send/3 with the nosuspend option change message-sending behavior? What is Dialyzer and how does success typing differ from static typing? Why doesn't Dialyzer catch every type error the way a traditional type checker would? How do you define and use a custom behavior with the -callback attribute? What is the difference between a behavior callback module and a plain library module? Explain the internal working of exception propagation through nested try/catch blocks? When should you use throw instead of returning an {error, Reason} tuple? How do you troubleshoot a memory leak caused by large binaries not being garbage collected? What is the significance of the binary reference count and off-heap binary garbage collection? Why is the Erlang distribution protocol not encrypted by default, and how can you secure inter-node traffic? Why is Mnesia's two-phase commit necessary for distributed transactions? How do you troubleshoot slow ETS lookups on a heavily-used table? Why might increasing the number of BEAM schedulers not improve throughput linearly?
Show more question and Answers...

AI

Comments & Discussions

Interviews Questions

About Javapedia.net

Javapedia.net is for Java and J2EE developers, technologist and college students who prepare of interview. Also this site includes many practical examples.

This site is developed using J2EE technologies by Steve Antony, a senior Developer/lead at one of the logistics based company.

Follow Javapedia updates

contact: javatutorials2016[at]gmail[dot]com

Kindly consider donating for maintaining this website. Thanks.

Copyright © 2026, javapedia.net, all rights reserved. · .

DMCA.com Protection Status