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Glossary
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================
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.. glossary::
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metadatum
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A key-value pair included in the HTTP header. It is a
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2-tuple where the first entry is the key and the
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second is the value, i.e. (key, value). The metadata key is an ASCII str,
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and must be a valid HTTP header name. The metadata value can be
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either a valid HTTP ASCII str, or bytes. If bytes are provided,
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the key must end with '-bin', i.e.
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``('binary-metadata-bin', b'\\x00\\xFF')``
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metadata
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A sequence of metadatum.
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serializer
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A callable function that encodes an object into bytes. Applications are
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allowed to provide any customized serializer, so there isn't a restriction
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for the input object (i.e. even ``None``). On the server-side, the
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serializer is invoked with server handler's return value; on the
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client-side, the serializer is invoked with outbound message objects.
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deserializer
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A callable function that decodes bytes into an object. Same as serializer,
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the returned object doesn't have restrictions (i.e. ``None`` allowed). The
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deserializer is invoked with inbound message bytes on both the server side
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and the client-side.
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wait_for_ready
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If an RPC is issued but the channel is in TRANSIENT_FAILURE or SHUTDOWN
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states, the RPC is unable to be transmitted promptly. By default, gRPC
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implementations SHOULD fail such RPCs immediately. This is known as "fail
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fast," but the usage of the term is historical. RPCs SHOULD NOT fail as a
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result of the channel being in other states (CONNECTING, READY, or IDLE).
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gRPC implementations MAY provide a per-RPC option to not fail RPCs as a
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result of the channel being in TRANSIENT_FAILURE state. Instead, the
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implementation queues the RPCs until the channel is READY. This is known as
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"wait for ready." The RPCs SHOULD still fail before READY if there are
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unrelated reasons, such as the channel is SHUTDOWN or the RPC's deadline is
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reached.
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