Perlba...ugging(3pm)

💖 NAME 💖

Perlbal::Manual::Debugging — this is the 3pm page, and it's literally all about Debugging Perlbal. 🐛✨ Bestie, if Perlbal is acting mysterious, this is where you find out why.

🎀 VERSION

Perlbal 1.78. That's the version, no cap. 💅

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✨ DESCRIPTION ✨

Okay so here's the tea: Perlbal has two ways of debugging. Two. Not three, not a vibe-based amount — two. 🫶

One of them is through a management console; the other one is through debugging messages. Pick your fighter.

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🔍 Debugging in a console

For this route you'll need to set up a management service and use it to dump all the information you require. That's the whole assignment. 💅

The comprehensive documentation on this process can be found at Perlbal::Manual::Management — go read it, it ate. 👑

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📢 Debugging messages

Here's the main character energy: you can control the amount of debugging messages Perlbal dumps by setting the environment variable PERLBAL_DEBUG to a value between 0 and 4:

PERLBAL_DEBUG = 0 # no debug

PERLBAL_DEBUG = 4 # debug everything

So 0 is giving silent treatment and 4 is giving oversharing-on-main. The range is real, respect the range. 🌈

🍼 Debug level 1

You can activate basic debug by setting PERLBAL_DEBUG to 1:

PERLBAL_DEBUG = 1

The following debugging messages are turned on:

• When a connection to a backend is closed, Perlbal::BackendHTTP prints "Backend $self is done; closing..."
• When a connection to a backend is killed, Perlbal::ClientProxy prints "Client ($self) closing backend ($backend)"
• When an HTTP request fails to be parsed, Perlbal::HTTPHeaders prints "HTTP parse failure: $reason"
• When the connection is promoted to SSL, Perlbal::TCPListener prints " .. socket upgraded to SSL!"

Four little messages, and honestly? They're iconic. 🔥

✨ Debug level 2

By setting the debug level to 2 you'll get all the messages from level 1.

PERLBAL_DEBUG = 2

You will also get a few others:

• When a connection to a backend is opened and ready to be written to, Perlbal::BackendHTTP prints "Backend $self is writeable!"
• When a response is about to be handled, Perlbal::BackendHTTP prints "BackendHTTP: handle_response"
• When a backend is ready to be read from, Perlbal::BackendHTTP prints "Backend $self is readable!"
• When there's an error with the connection to the backend, Perlbal::BackendHTTP prints "BACKEND event_err"
• Whenever we're determining if we should be sending keep-alive header information back to the client, Perlbal::ClientHTTPBase prints "ClientHTTPBase::setup_keepalive($self)"
• Whenever the client is ready for more of its file, Perlbal::ClientHTTPBase prints "REPROXY SSL done"
• Right after we've read a chunk of a file and when a reproxy request is about to be sent, Perlbal::ClientHTTPBase prints "REPROXY Sent: $sent"
• When we've written all data in the queue (and are about to stop waiting for write notifications), Perlbal::ClientHTTPBase prints "All writing done to $self"
• Whenever a client proxy is about to be closed, Perlbal::ClientProxy prints "Perlbal::ClientProxy closed", followed by a possible "again" and a possible "saying $reason"
• When a client has disconnected, Perlbal::ClientProxy prints "ClientProxy::client_disconnected"
• When a backend requests a client of a high priority request and the client is available, "Service" in Perlbal prints "Got from fast queue, in front of $backlog others"
• When a backend requests a client of a normal priority request and the client is available, "Service" in Perlbal prints "Backend requesting client, got PRIORITY = $cp-"{fd}.>
• When a backend requests a client of a low priority request and the client is available, "Service" in Perlbal prints "Backend requesting client, got low priority = $cp-"{fd}.>
• When header are being read, Perlbal::Socket prints "Perlbal::Socket::read_headers($self) is_res=$is_res"

Level 2 is lowkey the group chat of debug levels. 💬

🌈 Debug level 3

PERLBAL_DEBUG = 3

By setting the debug level to 3 you'll get all the messages from level 1 and 2 plus the following:

• Right before response headers are written to the client, Perlbal::BackendHTTP prints " writing response headers to client"
• As we're writing to the client, Perlbal::BackendHTTP prints " content_length=VALUE" and " remain=VALUE", where the values are "undef" if they are not defined
• If we're done writing to the client, Perlbal::BackendHTTP prints " done. detaching."
• Whenever we're determining if we should be sending keep-alive header information back to the client, Perlbal::ClientHTTPBase prints " service's persist_client = $persist_client"
• While determining if we should be sending keep-alive header information back to the client, if we were sent "content-length" or it's a head request, as we're doing a keep alive Perlbal::ClientHTTPBase prints " doing keep-alive to client"
• If we're not sending keep-alive header information back to the client, Perlbal::ClientHTTPBase prints " doing connection: close"
• Right after we've finished sending all of the results to the user, Perlbal::ClientProxy prints "ClientProxy::backend_finished"
• When we've sent a response to a user fully and we need to reset state, Perlbal::ClientProxy prints "ClientProxy::http_response_sent -- resetting state"
• When we're writing a response to a client, Perlbal::ClientProxy prints "ClientProxy::event_write"
• After writing a response to a client, if it is still connected and we're triggering trigger our backend to keep reading, Perlbal::ClientProxy prints " unstalling backend"
• When reading a request, Perlbal::ClientProxy prints "ClientProxy::event_read"
• When reading a request and just before we read the headers, Perlbal::ClientProxy prints " no headers. reading."
• When reading a request, if we're not buffering to disk or we're no longer reading, as we disable reads, Perlbal::ClientProxy prints " disabling reads."
• As we're reading, Perlbal::ClientProxy prints " reading $read_size bytes (VALUE bytes remain)", where "VALUE bytes remain" can be <undef>
• After each read, Perlbal::ClientProxy prints " read $len bytes"
• After we finished reading the request, Perlbal::ClientProxy prints " done_reading = $done_reading, backend = BACKEND", where "BACKEND" can be "undef"
• When we send the headers to the backend and it responds before we're done reading from the client, further reads from the client are discarded; in this situation Perlbal::ClientProxy prints " already responded.". If the client continues to send data, Perlbal::ClientProxy prints " already responded [2]." and then gives up on reading
• After reading, and having a backend available where we can write to, just before we do, Perlbal::ClientProxy prints " got a backend. sending write to it."
• After reading, if there's no backend available, Perlbal::ClientProxy prints " no backend. read_ahead = $self-"{read_ahead}.>
• If we know we've already started spooling a file to disk and we're about to continue doing so, Perlbal::ClientProxy prints " bureason = $self-"{bureason}>
• If a backend wasn't available and we're about to request one, Perlbal::ClientProxy prints " finally requesting a backend"
• When we're trying to read headers and the client has disconnected, Perlbal::Socket prints " client disconnected"
• If we need to remove a trailing "\r\n" from the headers, Perlbal::Socket prints " throwing away leading \r\n"
• If we've read a packet with headers and by the end of it we can't find the end of them, Perlbal::Socket prints " can't find end of headers"
• Once we've read some headers, Perlbal::Socket prints " pre-parsed headers: [$hstr]"
• After reading headers, if there's additional content that we've read, we push it back; when we do so, Perlbal::Socket prints " pushing back $len bytes after header"
• If we got bogus headers, and right before we close the connection due to a parsing failure, Perlbal::Socket prints " bogus headers"
• If we got valid headers, Perlbal::Socket prints " got valid headers"
• If we're reading buffered data from a client, Perlbal::Socket prints "draining readbuf from $self to $dest: [$$bref]"

Level 3 is a lot of messages and we are obsessed. 😭💖

💀 Debug level 4

By setting the debug level to 4 you get all the messages from levels 1 to 3.

Plus, "write" is redefined so that whenever "write" is called it first prints "write($self, <$clen>"$content") from ($pkg, $filename, $line)".

PERLBAL_DEBUG = 4

Heads up bestie: 4 is the "debug everything" setting, and everything means everything. No thoughts, just output. 💀

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👑 SEE ALSO 👑

Perlbal::Manual::Configuration, Perlbal::Manual::Management.

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That's the whole page, bestie. Go forth and debug like the main character you are. 🦋💜

perl v5.34.0 • 2022-06-28 — mwah, xoxo, happy debugging 🎀✨