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Simple connection
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Create a custom protocol
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Creating the protocol
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GossipSub
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Discovery Manager
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Game
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Creating the protocol
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< / div >
< / div >
< div class = "md-content" data-md-component = "content" >
< article class = "md-content__inner md-typeset" >
< h1 id = "protobuf-usage" > Protobuf usage< / h1 >
< p > In the < a href = "../tutorial_2_customproto/" > previous tutorial< / a > , we created a simple "ping" protocol.
Most real protocol want their messages to be structured and extensible, which is why
most real protocols use < a href = "https://developers.google.com/protocol-buffers" > protobuf< / a > to
define their message structures.< / p >
< p > Here, we'll create a slightly more complex protocol, which parses & generate protobuf
messages. Let's start by importing our dependencies, as usual:
< div class = "highlight" > < pre > < span > < / span > < code > < a id = "__codelineno-0-1" name = "__codelineno-0-1" href = "#__codelineno-0-1" > < / a > < span class = "kn" > import< / span > < span class = "w" > < / span > < span class = "n" > chronos< / span >
< a id = "__codelineno-0-2" name = "__codelineno-0-2" href = "#__codelineno-0-2" > < / a > < span class = "kn" > import< / span > < span class = "w" > < / span > < span class = "n" > stew< / span > < span class = "o" > /< / span > < span class = "n" > results< / span > < span class = "w" > < / span > < span class = "c" > # for Opt[T]< / span >
< a id = "__codelineno-0-3" name = "__codelineno-0-3" href = "#__codelineno-0-3" > < / a >
< a id = "__codelineno-0-4" name = "__codelineno-0-4" href = "#__codelineno-0-4" > < / a > < span class = "kn" > import< / span > < span class = "w" > < / span > < span class = "n" > libp2p< / span >
< / code > < / pre > < / div > < / p >
< h2 id = "protobuf-encoding-decoding" > Protobuf encoding & decoding< / h2 >
< p > This will be the structure of our messages:
< div class = "highlight" > < pre > < span > < / span > < code > < a id = "__codelineno-1-1" name = "__codelineno-1-1" href = "#__codelineno-1-1" > < / a > < span class = "kd" > message< / span > < span class = "w" > < / span > < span class = "nc" > MetricList< / span > < span class = "w" > < / span > < span class = "p" > {< / span >
< a id = "__codelineno-1-2" name = "__codelineno-1-2" href = "#__codelineno-1-2" > < / a > < span class = "w" > < / span > < span class = "kd" > message< / span > < span class = "w" > < / span > < span class = "nc" > Metric< / span > < span class = "w" > < / span > < span class = "p" > {< / span >
< a id = "__codelineno-1-3" name = "__codelineno-1-3" href = "#__codelineno-1-3" > < / a > < span class = "w" > < / span > < span class = "kt" > string< / span > < span class = "w" > < / span > < span class = "na" > name< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "mi" > 1< / span > < span class = "p" > ;< / span >
< a id = "__codelineno-1-4" name = "__codelineno-1-4" href = "#__codelineno-1-4" > < / a > < span class = "w" > < / span > < span class = "kt" > float< / span > < span class = "w" > < / span > < span class = "na" > value< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "mi" > 2< / span > < span class = "p" > ;< / span >
< a id = "__codelineno-1-5" name = "__codelineno-1-5" href = "#__codelineno-1-5" > < / a > < span class = "w" > < / span > < span class = "p" > }< / span >
< a id = "__codelineno-1-6" name = "__codelineno-1-6" href = "#__codelineno-1-6" > < / a >
< a id = "__codelineno-1-7" name = "__codelineno-1-7" href = "#__codelineno-1-7" > < / a > < span class = "w" > < / span > < span class = "k" > repeated< / span > < span class = "w" > < / span > < span class = "n" > Metric< / span > < span class = "w" > < / span > < span class = "na" > metrics< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "mi" > 2< / span > < span class = "p" > ;< / span >
< a id = "__codelineno-1-8" name = "__codelineno-1-8" href = "#__codelineno-1-8" > < / a > < span class = "p" > }< / span >
< / code > < / pre > < / div >
We'll create our protobuf types, encoders & decoders, according to this format.
To create the encoders & decoders, we are going to use minprotobuf
(included in libp2p).< / p >
< p > While more modern technics
(such as < a href = "https://github.com/status-im/nim-protobuf-serialization" > nim-protobuf-serialization< / a > )
exists, minprotobuf is currently the recommended method to handle protobuf, since it has
been used in production extensively, and audited.
< div class = "highlight" > < pre > < span > < / span > < code > < a id = "__codelineno-2-1" name = "__codelineno-2-1" href = "#__codelineno-2-1" > < / a > < span class = "k" > type< / span >
< a id = "__codelineno-2-2" name = "__codelineno-2-2" href = "#__codelineno-2-2" > < / a > < span class = "w" > < / span > < span class = "n" > Metric< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "k" > object< / span >
< a id = "__codelineno-2-3" name = "__codelineno-2-3" href = "#__codelineno-2-3" > < / a > < span class = "w" > < / span > < span class = "n" > name< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "nb" > string< / span >
< a id = "__codelineno-2-4" name = "__codelineno-2-4" href = "#__codelineno-2-4" > < / a > < span class = "w" > < / span > < span class = "n" > value< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "nb" > float< / span >
< a id = "__codelineno-2-5" name = "__codelineno-2-5" href = "#__codelineno-2-5" > < / a >
< a id = "__codelineno-2-6" name = "__codelineno-2-6" href = "#__codelineno-2-6" > < / a > < span class = "w" > < / span > < span class = "n" > MetricList< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "k" > object< / span >
< a id = "__codelineno-2-7" name = "__codelineno-2-7" href = "#__codelineno-2-7" > < / a > < span class = "w" > < / span > < span class = "n" > metrics< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "nb" > seq< / span > < span class = "o" > [< / span > < span class = "n" > Metric< / span > < span class = "o" > ]< / span >
< a id = "__codelineno-2-8" name = "__codelineno-2-8" href = "#__codelineno-2-8" > < / a >
< a id = "__codelineno-2-9" name = "__codelineno-2-9" href = "#__codelineno-2-9" > < / a > < span class = "sx" > {.push< / span > < span class = "w" > < / span > < span class = "sx" > raises< / span > :< span class = "w" > < / span > < span class = "sx" > [].}< / span >
< a id = "__codelineno-2-10" name = "__codelineno-2-10" href = "#__codelineno-2-10" > < / a >
< a id = "__codelineno-2-11" name = "__codelineno-2-11" href = "#__codelineno-2-11" > < / a > < span class = "sx" > proc< / span > < span class = "w" > < / span > < span class = "sx" > encode(m< / span > :< span class = "w" > < / span > < span class = "sx" > Metric): ProtoBuffer< / span > < span class = "w" > < / span > < span class = "sx" > =< / span >
< a id = "__codelineno-2-12" name = "__codelineno-2-12" href = "#__codelineno-2-12" > < / a > < span class = "sx" > result< / span > < span class = "w" > < / span > < span class = "sx" > = initProtoBuffer()< / span >
< a id = "__codelineno-2-13" name = "__codelineno-2-13" href = "#__codelineno-2-13" > < / a > < span class = "sx" > result.write(1< / span > ,< span class = "w" > < / span > < span class = "sx" > m.name)< / span >
< a id = "__codelineno-2-14" name = "__codelineno-2-14" href = "#__codelineno-2-14" > < / a > < span class = "sx" > result.write(2< / span > ,< span class = "w" > < / span > < span class = "sx" > m.value)< / span >
< a id = "__codelineno-2-15" name = "__codelineno-2-15" href = "#__codelineno-2-15" > < / a > < span class = "sx" > result.finish()< / span >
< a id = "__codelineno-2-16" name = "__codelineno-2-16" href = "#__codelineno-2-16" > < / a >
< a id = "__codelineno-2-17" name = "__codelineno-2-17" href = "#__codelineno-2-17" > < / a > < span class = "sx" > proc< / span > < span class = "w" > < / span > < span class = "sx" > decode(_< / span > :< span class = "w" > < / span > < span class = "sx" > type< / span > < span class = "w" > < / span > < span class = "sx" > Metric< / span > ,< span class = "w" > < / span > < span class = "sx" > buf< / span > :< span class = "w" > < / span > < span class = "sx" > seq[byte]): Result[Metric< / span > ,< span class = "w" > < / span > < span class = "sx" > ProtoError] =< / span >
< a id = "__codelineno-2-18" name = "__codelineno-2-18" href = "#__codelineno-2-18" > < / a > < span class = "sx" > var< / span > < span class = "w" > < / span > < span class = "sx" > res< / span > :< span class = "w" > < / span > < span class = "sx" > Metric< / span >
< a id = "__codelineno-2-19" name = "__codelineno-2-19" href = "#__codelineno-2-19" > < / a > < span class = "w" > < / span > < span class = "sx" > let< / span > < span class = "w" > < / span > < span class = "sx" > pb< / span > < span class = "w" > < / span > < span class = "sx" > = initProtoBuffer(buf)< / span >
< a id = "__codelineno-2-20" name = "__codelineno-2-20" href = "#__codelineno-2-20" > < / a > < span class = "sx" > # " getField" will< / span > < span class = "w" > < / span > < span class = "sx" > return< / span > < span class = "w" > < / span > < span class = "sx" > a< / span > < span class = "w" > < / span > < span class = "sx" > Result[bool< / span > ,< span class = "w" > < / span > < span class = "sx" > ProtoError].< / span >
< a id = "__codelineno-2-21" name = "__codelineno-2-21" href = "#__codelineno-2-21" > < / a > < span class = "sx" > # The< / span > < span class = "w" > < / span > < span class = "sx" > Result< / span > < span class = "w" > < / span > < span class = "sx" > will< / span > < span class = "w" > < / span > < span class = "sx" > hold< / span > < span class = "w" > < / span > < span class = "sx" > an< / span > < span class = "w" > < / span > < span class = "sx" > error< / span > < span class = "w" > < / span > < span class = "sx" > if< / span > < span class = "w" > < / span > < span class = "sx" > the< / span > < span class = "w" > < / span > < span class = "sx" > protobuf< / span > < span class = "w" > < / span > < span class = "sx" > is< / span > < span class = "w" > < / span > < span class = "sx" > invalid.< / span >
< a id = "__codelineno-2-22" name = "__codelineno-2-22" href = "#__codelineno-2-22" > < / a > < span class = "sx" > # The< / span > < span class = "w" > < / span > < span class = "sx" > Result< / span > < span class = "w" > < / span > < span class = "sx" > will< / span > < span class = "w" > < / span > < span class = "sx" > hold< / span > < span class = "w" > < / span > < span class = "sx" > " false" if< / span > < span class = "w" > < / span > < span class = "sx" > the< / span > < span class = "w" > < / span > < span class = "sx" > field< / span > < span class = "w" > < / span > < span class = "sx" > is< / span > < span class = "w" > < / span > < span class = "sx" > missing< / span >
< a id = "__codelineno-2-23" name = "__codelineno-2-23" href = "#__codelineno-2-23" > < / a > < span class = "w" > < / span > < span class = "sx" > #< / span >
< a id = "__codelineno-2-24" name = "__codelineno-2-24" href = "#__codelineno-2-24" > < / a > < span class = "sx" > # We< / span > < span class = "w" > < / span > < span class = "sx" > are< / span > < span class = "w" > < / span > < span class = "sx" > just< / span > < span class = "w" > < / span > < span class = "sx" > checking< / span > < span class = "w" > < / span > < span class = "sx" > the< / span > < span class = "w" > < / span > < span class = "sx" > error< / span > ,< span class = "w" > < / span > < span class = "sx" > and< / span > < span class = "w" > < / span > < span class = "sx" > ignoring< / span > < span class = "w" > < / span > < span class = "sx" > whether< / span > < span class = "w" > < / span > < span class = "sx" > the< / span > < span class = "w" > < / span > < span class = "sx" > value< / span >
< a id = "__codelineno-2-25" name = "__codelineno-2-25" href = "#__codelineno-2-25" > < / a > < span class = "w" > < / span > < span class = "sx" > # is< / span > < span class = "w" > < / span > < span class = "sx" > present< / span > < span class = "w" > < / span > < span class = "sx" > or< / span > < span class = "w" > < / span > < span class = "sx" > not< / span > < span class = "w" > < / span > < span class = "sx" > (default< / span > < span class = "w" > < / span > < span class = "sx" > values< / span > < span class = "w" > < / span > < span class = "sx" > are< / span > < span class = "w" > < / span > < span class = "sx" > valid).< / span >
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< a id = "__codelineno-2-26" name = "__codelineno-2-26" href = "#__codelineno-2-26" > < / a > < span class = "sx" > discard< / span > < span class = "w" > < / span > < span class = "sx" > ?pb.getField(1< / span > ,< span class = "w" > < / span > < span class = "sx" > res.name)< / span >
< a id = "__codelineno-2-27" name = "__codelineno-2-27" href = "#__codelineno-2-27" > < / a > < span class = "sx" > discard< / span > < span class = "w" > < / span > < span class = "sx" > ?pb.getField(2< / span > ,< span class = "w" > < / span > < span class = "sx" > res.value)< / span >
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< a id = "__codelineno-2-28" name = "__codelineno-2-28" href = "#__codelineno-2-28" > < / a > < span class = "sx" > ok(res)< / span >
< a id = "__codelineno-2-29" name = "__codelineno-2-29" href = "#__codelineno-2-29" > < / a >
< a id = "__codelineno-2-30" name = "__codelineno-2-30" href = "#__codelineno-2-30" > < / a > < span class = "sx" > proc< / span > < span class = "w" > < / span > < span class = "sx" > encode(m< / span > :< span class = "w" > < / span > < span class = "sx" > MetricList): ProtoBuffer< / span > < span class = "w" > < / span > < span class = "sx" > =< / span >
< a id = "__codelineno-2-31" name = "__codelineno-2-31" href = "#__codelineno-2-31" > < / a > < span class = "sx" > result< / span > < span class = "w" > < / span > < span class = "sx" > = initProtoBuffer()< / span >
< a id = "__codelineno-2-32" name = "__codelineno-2-32" href = "#__codelineno-2-32" > < / a > < span class = "sx" > for< / span > < span class = "w" > < / span > < span class = "sx" > metric< / span > < span class = "w" > < / span > < span class = "sx" > in< / span > < span class = "w" > < / span > < span class = "sx" > m.metrics< / span > :
< a id = "__codelineno-2-33" name = "__codelineno-2-33" href = "#__codelineno-2-33" > < / a > < span class = "w" > < / span > < span class = "sx" > result.write(1< / span > ,< span class = "w" > < / span > < span class = "sx" > metric.encode())< / span >
< a id = "__codelineno-2-34" name = "__codelineno-2-34" href = "#__codelineno-2-34" > < / a > < span class = "sx" > result.finish()< / span >
< a id = "__codelineno-2-35" name = "__codelineno-2-35" href = "#__codelineno-2-35" > < / a >
< a id = "__codelineno-2-36" name = "__codelineno-2-36" href = "#__codelineno-2-36" > < / a > < span class = "sx" > proc< / span > < span class = "w" > < / span > < span class = "sx" > decode(_< / span > :< span class = "w" > < / span > < span class = "sx" > type< / span > < span class = "w" > < / span > < span class = "sx" > MetricList< / span > ,< span class = "w" > < / span > < span class = "sx" > buf< / span > :< span class = "w" > < / span > < span class = "sx" > seq[byte]): Result[MetricList< / span > ,< span class = "w" > < / span > < span class = "sx" > ProtoError] =< / span >
< a id = "__codelineno-2-37" name = "__codelineno-2-37" href = "#__codelineno-2-37" > < / a > < span class = "sx" > var< / span >
< a id = "__codelineno-2-38" name = "__codelineno-2-38" href = "#__codelineno-2-38" > < / a > < span class = "w" > < / span > < span class = "sx" > res< / span > :< span class = "w" > < / span > < span class = "sx" > MetricList< / span >
< a id = "__codelineno-2-39" name = "__codelineno-2-39" href = "#__codelineno-2-39" > < / a > < span class = "w" > < / span > < span class = "sx" > metrics< / span > :< span class = "w" > < / span > < span class = "sx" > seq[seq[byte]]< / span >
< a id = "__codelineno-2-40" name = "__codelineno-2-40" href = "#__codelineno-2-40" > < / a > < span class = "sx" > let< / span > < span class = "w" > < / span > < span class = "sx" > pb< / span > < span class = "w" > < / span > < span class = "sx" > = initProtoBuffer(buf)< / span >
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< a id = "__codelineno-2-41" name = "__codelineno-2-41" href = "#__codelineno-2-41" > < / a > < span class = "sx" > discard< / span > < span class = "w" > < / span > < span class = "sx" > ?pb.getRepeatedField(1< / span > ,< span class = "w" > < / span > < span class = "sx" > metrics)< / span >
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< a id = "__codelineno-2-42" name = "__codelineno-2-42" href = "#__codelineno-2-42" > < / a >
< a id = "__codelineno-2-43" name = "__codelineno-2-43" href = "#__codelineno-2-43" > < / a > < span class = "sx" > for< / span > < span class = "w" > < / span > < span class = "sx" > metric< / span > < span class = "w" > < / span > < span class = "sx" > in< / span > < span class = "w" > < / span > < span class = "sx" > metrics< / span > :
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< a id = "__codelineno-2-44" name = "__codelineno-2-44" href = "#__codelineno-2-44" > < / a > < span class = "w" > < / span > < span class = "sx" > res.metrics< / span > < span class = "w" > < / span > < span class = "sx" > & = ?Metric.decode(metric)< / span >
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< a id = "__codelineno-2-45" name = "__codelineno-2-45" href = "#__codelineno-2-45" > < / a > < span class = "sx" > ok(res)< / span >
< / code > < / pre > < / div > < / p >
< h2 id = "results-instead-of-exceptions" > Results instead of exceptions< / h2 >
< p > As you can see, this part of the program also uses Results instead of exceptions for error handling.
We start by < code > {.push raises: [].}< / code > , which will prevent every non-async function from raising
exceptions.< / p >
< p > Then, we use < a href = "https://github.com/arnetheduck/nim-result" > nim-result< / a > to convey
errors to function callers. A < code > Result[T, E]< / code > will either hold a valid result of type
T, or an error of type E.< / p >
< p > You can check if the call succeeded by using < code > res.isOk< / code > , and then get the
value using < code > res.value< / code > or the error by using < code > res.error< / code > .< / p >
< p > Another useful tool is < code > ?< / code > , which will unpack a Result if it succeeded,
or if it failed, exit the current procedure returning the error.< / p >
< p > nim-result is packed with other functionalities that you'll find in the
nim-result repository.< / p >
< p > Results and exception are generally interchangeable, but have different semantics
that you may or may not prefer.< / p >
< h2 id = "creating-the-protocol" > Creating the protocol< / h2 >
< p > We'll next create a protocol, like in the last tutorial, to request these metrics from our host
< div class = "highlight" > < pre > < span > < / span > < code > < a id = "__codelineno-3-1" name = "__codelineno-3-1" href = "#__codelineno-3-1" > < / a > < span class = "k" > type< / span >
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< a id = "__codelineno-3-2" name = "__codelineno-3-2" href = "#__codelineno-3-2" > < / a > < span class = "w" > < / span > < span class = "n" > MetricCallback< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > proc< / span > < span class = "p" > ():< / span > < span class = "w" > < / span > < span class = "n" > Future< / span > < span class = "o" > [< / span > < span class = "n" > MetricList< / span > < span class = "o" > ]< / span > < span class = "w" > < / span > < span class = "sx" > {.raises< / span > :< span class = "w" > < / span > < span class = "sx" > [], gcsafe.}< / span >
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< a id = "__codelineno-3-3" name = "__codelineno-3-3" href = "#__codelineno-3-3" > < / a > < span class = "w" > < / span > < span class = "n" > MetricProto< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "k" > ref< / span > < span class = "w" > < / span > < span class = "k" > object< / span > < span class = "w" > < / span > < span class = "k" > of< / span > < span class = "w" > < / span > < span class = "n" > LPProtocol< / span >
< a id = "__codelineno-3-4" name = "__codelineno-3-4" href = "#__codelineno-3-4" > < / a > < span class = "w" > < / span > < span class = "n" > metricGetter< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "n" > MetricCallback< / span >
< a id = "__codelineno-3-5" name = "__codelineno-3-5" href = "#__codelineno-3-5" > < / a >
< a id = "__codelineno-3-6" name = "__codelineno-3-6" href = "#__codelineno-3-6" > < / a > < span class = "k" > proc< / span > < span class = "w" > < / span > < span class = "nf" > new< / span > < span class = "p" > (< / span > < span class = "err" > _: typedesc[MetricProto], cb: MetricCallback): MetricProto =< / span >
< a id = "__codelineno-3-7" name = "__codelineno-3-7" href = "#__codelineno-3-7" > < / a > < span class = "w" > < / span > < span class = "kd" > var< / span > < span class = "w" > < / span > < span class = "n" > res< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "n" > MetricProto< / span >
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< a id = "__codelineno-3-8" name = "__codelineno-3-8" href = "#__codelineno-3-8" > < / a > < span class = "w" > < / span > < span class = "k" > proc< / span > < span class = "w" > < / span > < span class = "nf" > handle< / span > < span class = "p" > (< / span > < span class = "n" > conn< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "n" > Connection< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > proto< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "nb" > string< / span > < span class = "p" > )< / span > < span class = "w" > < / span > < span class = "sx" > {.async.}< / span > < span class = "w" > < / span > < span class = "o" > =< / span >
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< a id = "__codelineno-3-9" name = "__codelineno-3-9" href = "#__codelineno-3-9" > < / a > < span class = "w" > < / span > < span class = "k" > let< / span >
< a id = "__codelineno-3-10" name = "__codelineno-3-10" href = "#__codelineno-3-10" > < / a > < span class = "w" > < / span > < span class = "n" > metrics< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > res< / span > < span class = "p" > .< / span > < span class = "n" > metricGetter< / span > < span class = "p" > ()< / span >
< a id = "__codelineno-3-11" name = "__codelineno-3-11" href = "#__codelineno-3-11" > < / a > < span class = "w" > < / span > < span class = "n" > asProtobuf< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > metrics< / span > < span class = "p" > .< / span > < span class = "n" > encode< / span > < span class = "p" > ()< / span >
< a id = "__codelineno-3-12" name = "__codelineno-3-12" href = "#__codelineno-3-12" > < / a > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > conn< / span > < span class = "p" > .< / span > < span class = "n" > writeLp< / span > < span class = "p" > (< / span > < span class = "n" > asProtobuf< / span > < span class = "p" > .< / span > < span class = "n" > buffer< / span > < span class = "p" > )< / span >
< a id = "__codelineno-3-13" name = "__codelineno-3-13" href = "#__codelineno-3-13" > < / a > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > conn< / span > < span class = "p" > .< / span > < span class = "n" > close< / span > < span class = "p" > ()< / span >
< a id = "__codelineno-3-14" name = "__codelineno-3-14" href = "#__codelineno-3-14" > < / a >
< a id = "__codelineno-3-15" name = "__codelineno-3-15" href = "#__codelineno-3-15" > < / a > < span class = "w" > < / span > < span class = "n" > res< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > MetricProto< / span > < span class = "p" > .< / span > < span class = "n" > new< / span > < span class = "p" > (< / span > < span class = "o" > @[< / span > < span class = "s" > " /metric-getter/1.0.0" < / span > < span class = "o" > ]< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > handle< / span > < span class = "p" > )< / span >
< a id = "__codelineno-3-16" name = "__codelineno-3-16" href = "#__codelineno-3-16" > < / a > < span class = "w" > < / span > < span class = "n" > res< / span > < span class = "p" > .< / span > < span class = "n" > metricGetter< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > cb< / span >
< a id = "__codelineno-3-17" name = "__codelineno-3-17" href = "#__codelineno-3-17" > < / a > < span class = "w" > < / span > < span class = "k" > return< / span > < span class = "w" > < / span > < span class = "n" > res< / span >
< a id = "__codelineno-3-18" name = "__codelineno-3-18" href = "#__codelineno-3-18" > < / a >
< a id = "__codelineno-3-19" name = "__codelineno-3-19" href = "#__codelineno-3-19" > < / a > < span class = "k" > proc< / span > < span class = "w" > < / span > < span class = "nf" > fetch< / span > < span class = "p" > (< / span > < span class = "n" > p< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "n" > MetricProto< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > conn< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "n" > Connection< / span > < span class = "p" > ):< / span > < span class = "w" > < / span > < span class = "n" > Future< / span > < span class = "o" > [< / span > < span class = "n" > MetricList< / span > < span class = "o" > ]< / span > < span class = "w" > < / span > < span class = "sx" > {.async.}< / span > < span class = "w" > < / span > < span class = "o" > =< / span >
< a id = "__codelineno-3-20" name = "__codelineno-3-20" href = "#__codelineno-3-20" > < / a > < span class = "w" > < / span > < span class = "k" > let< / span > < span class = "w" > < / span > < span class = "n" > protobuf< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > conn< / span > < span class = "p" > .< / span > < span class = "n" > readLp< / span > < span class = "p" > (< / span > < span class = "mi" > 2048< / span > < span class = "p" > )< / span >
< a id = "__codelineno-3-21" name = "__codelineno-3-21" href = "#__codelineno-3-21" > < / a > < span class = "w" > < / span > < span class = "c" > # tryGet will raise an exception if the Result contains an error.< / span >
< a id = "__codelineno-3-22" name = "__codelineno-3-22" href = "#__codelineno-3-22" > < / a > < span class = "w" > < / span > < span class = "c" > # It' s useful to bridge between exception-world and result-world< / span >
< a id = "__codelineno-3-23" name = "__codelineno-3-23" href = "#__codelineno-3-23" > < / a > < span class = "w" > < / span > < span class = "k" > return< / span > < span class = "w" > < / span > < span class = "n" > MetricList< / span > < span class = "p" > .< / span > < span class = "n" > decode< / span > < span class = "p" > (< / span > < span class = "n" > protobuf< / span > < span class = "p" > ).< / span > < span class = "n" > tryGet< / span > < span class = "p" > ()< / span >
< / code > < / pre > < / div >
We can now create our main procedure:
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< div class = "highlight" > < pre > < span > < / span > < code > < a id = "__codelineno-4-1" name = "__codelineno-4-1" href = "#__codelineno-4-1" > < / a > < span class = "k" > proc< / span > < span class = "w" > < / span > < span class = "nf" > main< / span > < span class = "p" > ()< / span > < span class = "w" > < / span > < span class = "sx" > {.async.}< / span > < span class = "w" > < / span > < span class = "o" > =< / span >
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< a id = "__codelineno-4-2" name = "__codelineno-4-2" href = "#__codelineno-4-2" > < / a > < span class = "w" > < / span > < span class = "k" > let< / span > < span class = "w" > < / span > < span class = "n" > rng< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > newRng< / span > < span class = "p" > ()< / span >
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< a id = "__codelineno-4-3" name = "__codelineno-4-3" href = "#__codelineno-4-3" > < / a > < span class = "w" > < / span > < span class = "k" > proc< / span > < span class = "w" > < / span > < span class = "nf" > randomMetricGenerator< / span > < span class = "p" > ():< / span > < span class = "w" > < / span > < span class = "n" > Future< / span > < span class = "o" > [< / span > < span class = "n" > MetricList< / span > < span class = "o" > ]< / span > < span class = "w" > < / span > < span class = "sx" > {.async.}< / span > < span class = "w" > < / span > < span class = "o" > =< / span >
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< a id = "__codelineno-4-4" name = "__codelineno-4-4" href = "#__codelineno-4-4" > < / a > < span class = "w" > < / span > < span class = "k" > let< / span > < span class = "w" > < / span > < span class = "n" > metricCount< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > rng< / span > < span class = "o" > []< / span > < span class = "p" > .< / span > < span class = "n" > generate< / span > < span class = "p" > (< / span > < span class = "n" > uint32< / span > < span class = "p" > )< / span > < span class = "w" > < / span > < span class = "ow" > mod< / span > < span class = "w" > < / span > < span class = "mi" > 16< / span >
< a id = "__codelineno-4-5" name = "__codelineno-4-5" href = "#__codelineno-4-5" > < / a > < span class = "w" > < / span > < span class = "k" > for< / span > < span class = "w" > < / span > < span class = "n" > i< / span > < span class = "w" > < / span > < span class = "ow" > in< / span > < span class = "w" > < / span > < span class = "mi" > 0< / span > < span class = "w" > < / span > < span class = "p" > ..< / span > < span class = "o" > < < / span > < span class = "w" > < / span > < span class = "n" > metricCount< / span > < span class = "w" > < / span > < span class = "o" > +< / span > < span class = "w" > < / span > < span class = "mi" > 1< / span > < span class = "p" > :< / span >
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< a id = "__codelineno-4-6" name = "__codelineno-4-6" href = "#__codelineno-4-6" > < / a > < span class = "w" > < / span > < span class = "n" > result< / span > < span class = "p" > .< / span > < span class = "n" > metrics< / span > < span class = "p" > .< / span > < span class = "n" > add< / span > < span class = "p" > (< / span >
< a id = "__codelineno-4-7" name = "__codelineno-4-7" href = "#__codelineno-4-7" > < / a > < span class = "w" > < / span > < span class = "n" > Metric< / span > < span class = "p" > (< / span > < span class = "n" > name< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "s" > " metric_" < / span > < span class = "w" > < / span > < span class = "o" > & < / span > < span class = "w" > < / span > < span class = "o" > $< / span > < span class = "n" > i< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > value< / span > < span class = "p" > :< / span > < span class = "w" > < / span > < span class = "nb" > float< / span > < span class = "p" > (< / span > < span class = "n" > rng< / span > < span class = "o" > []< / span > < span class = "p" > .< / span > < span class = "n" > generate< / span > < span class = "p" > (< / span > < span class = "n" > uint16< / span > < span class = "p" > ))< / span > < span class = "w" > < / span > < span class = "o" > /< / span > < span class = "w" > < / span > < span class = "mf" > 1000.0< / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-8" name = "__codelineno-4-8" href = "#__codelineno-4-8" > < / a > < span class = "w" > < / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-9" name = "__codelineno-4-9" href = "#__codelineno-4-9" > < / a > < span class = "w" > < / span > < span class = "k" > return< / span > < span class = "w" > < / span > < span class = "n" > result< / span >
< a id = "__codelineno-4-10" name = "__codelineno-4-10" href = "#__codelineno-4-10" > < / a >
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< a id = "__codelineno-4-11" name = "__codelineno-4-11" href = "#__codelineno-4-11" > < / a > < span class = "w" > < / span > < span class = "k" > let< / span >
< a id = "__codelineno-4-12" name = "__codelineno-4-12" href = "#__codelineno-4-12" > < / a > < span class = "w" > < / span > < span class = "n" > metricProto1< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > MetricProto< / span > < span class = "p" > .< / span > < span class = "n" > new< / span > < span class = "p" > (< / span > < span class = "n" > randomMetricGenerator< / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-13" name = "__codelineno-4-13" href = "#__codelineno-4-13" > < / a > < span class = "w" > < / span > < span class = "n" > metricProto2< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > MetricProto< / span > < span class = "p" > .< / span > < span class = "n" > new< / span > < span class = "p" > (< / span > < span class = "n" > randomMetricGenerator< / span > < span class = "p" > )< / span >
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< a id = "__codelineno-4-14" name = "__codelineno-4-14" href = "#__codelineno-4-14" > < / a > < span class = "w" > < / span > < span class = "n" > switch1< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > newStandardSwitch< / span > < span class = "p" > (< / span > < span class = "n" > rng< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > rng< / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-15" name = "__codelineno-4-15" href = "#__codelineno-4-15" > < / a > < span class = "w" > < / span > < span class = "n" > switch2< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > newStandardSwitch< / span > < span class = "p" > (< / span > < span class = "n" > rng< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > rng< / span > < span class = "p" > )< / span >
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< a id = "__codelineno-4-16" name = "__codelineno-4-16" href = "#__codelineno-4-16" > < / a >
< a id = "__codelineno-4-17" name = "__codelineno-4-17" href = "#__codelineno-4-17" > < / a > < span class = "w" > < / span > < span class = "n" > switch1< / span > < span class = "p" > .< / span > < span class = "n" > mount< / span > < span class = "p" > (< / span > < span class = "n" > metricProto1< / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-18" name = "__codelineno-4-18" href = "#__codelineno-4-18" > < / a >
< a id = "__codelineno-4-19" name = "__codelineno-4-19" href = "#__codelineno-4-19" > < / a > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > switch1< / span > < span class = "p" > .< / span > < span class = "n" > start< / span > < span class = "p" > ()< / span >
< a id = "__codelineno-4-20" name = "__codelineno-4-20" href = "#__codelineno-4-20" > < / a > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > switch2< / span > < span class = "p" > .< / span > < span class = "n" > start< / span > < span class = "p" > ()< / span >
< a id = "__codelineno-4-21" name = "__codelineno-4-21" href = "#__codelineno-4-21" > < / a >
< a id = "__codelineno-4-22" name = "__codelineno-4-22" href = "#__codelineno-4-22" > < / a > < span class = "w" > < / span > < span class = "k" > let< / span >
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< a id = "__codelineno-4-23" name = "__codelineno-4-23" href = "#__codelineno-4-23" > < / a > < span class = "w" > < / span > < span class = "n" > conn< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > switch2< / span > < span class = "p" > .< / span > < span class = "n" > dial< / span > < span class = "p" > (< / span >
< a id = "__codelineno-4-24" name = "__codelineno-4-24" href = "#__codelineno-4-24" > < / a > < span class = "w" > < / span > < span class = "n" > switch1< / span > < span class = "p" > .< / span > < span class = "n" > peerInfo< / span > < span class = "p" > .< / span > < span class = "n" > peerId< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > switch1< / span > < span class = "p" > .< / span > < span class = "n" > peerInfo< / span > < span class = "p" > .< / span > < span class = "n" > addrs< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > metricProto2< / span > < span class = "p" > .< / span > < span class = "n" > codecs< / span >
< a id = "__codelineno-4-25" name = "__codelineno-4-25" href = "#__codelineno-4-25" > < / a > < span class = "w" > < / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-26" name = "__codelineno-4-26" href = "#__codelineno-4-26" > < / a > < span class = "w" > < / span > < span class = "n" > metrics< / span > < span class = "w" > < / span > < span class = "o" > =< / span > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > metricProto2< / span > < span class = "p" > .< / span > < span class = "n" > fetch< / span > < span class = "p" > (< / span > < span class = "n" > conn< / span > < span class = "p" > )< / span >
< a id = "__codelineno-4-27" name = "__codelineno-4-27" href = "#__codelineno-4-27" > < / a > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > conn< / span > < span class = "p" > .< / span > < span class = "n" > close< / span > < span class = "p" > ()< / span >
< a id = "__codelineno-4-28" name = "__codelineno-4-28" href = "#__codelineno-4-28" > < / a >
< a id = "__codelineno-4-29" name = "__codelineno-4-29" href = "#__codelineno-4-29" > < / a > < span class = "w" > < / span > < span class = "k" > for< / span > < span class = "w" > < / span > < span class = "n" > metric< / span > < span class = "w" > < / span > < span class = "ow" > in< / span > < span class = "w" > < / span > < span class = "n" > metrics< / span > < span class = "p" > .< / span > < span class = "n" > metrics< / span > < span class = "p" > :< / span >
< a id = "__codelineno-4-30" name = "__codelineno-4-30" href = "#__codelineno-4-30" > < / a > < span class = "w" > < / span > < span class = "n" > echo< / span > < span class = "w" > < / span > < span class = "n" > metric< / span > < span class = "p" > .< / span > < span class = "n" > name< / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "s" > " = " < / span > < span class = "p" > ,< / span > < span class = "w" > < / span > < span class = "n" > metric< / span > < span class = "p" > .< / span > < span class = "n" > value< / span >
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< a id = "__codelineno-4-31" name = "__codelineno-4-31" href = "#__codelineno-4-31" > < / a >
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< a id = "__codelineno-4-32" name = "__codelineno-4-32" href = "#__codelineno-4-32" > < / a > < span class = "w" > < / span > < span class = "n" > await< / span > < span class = "w" > < / span > < span class = "n" > allFutures< / span > < span class = "p" > (< / span > < span class = "n" > switch1< / span > < span class = "p" > .< / span > < span class = "n" > stop< / span > < span class = "p" > (),< / span > < span class = "w" > < / span > < span class = "n" > switch2< / span > < span class = "p" > .< / span > < span class = "n" > stop< / span > < span class = "p" > ())< / span >
< a id = "__codelineno-4-33" name = "__codelineno-4-33" href = "#__codelineno-4-33" > < / a > < span class = "w" > < / span > < span class = "c" > # close connections and shutdown all transports< / span >
< a id = "__codelineno-4-34" name = "__codelineno-4-34" href = "#__codelineno-4-34" > < / a >
< a id = "__codelineno-4-35" name = "__codelineno-4-35" href = "#__codelineno-4-35" > < / a > < span class = "n" > waitFor< / span > < span class = "p" > (< / span > < span class = "n" > main< / span > < span class = "p" > ())< / span >
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< / code > < / pre > < / div >
If you run this program, you should see random metrics being sent from the switch1 to the switch2.< / p >
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