81 lines
3.6 KiB
Python
81 lines
3.6 KiB
Python
import oxenmq
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import config
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import json
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import sys
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from datetime import datetime, timedelta
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omq, oxend = None, None
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def omq_connection():
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global omq, oxend
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if omq is None:
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omq = oxenmq.OxenMQ(log_level=oxenmq.LogLevel.warn)
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omq.max_message_size = 200*1024*1024
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omq.start()
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if oxend is None:
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oxend = omq.connect_remote(config.oxend_rpc)
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return (omq, oxend)
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cached = {}
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cached_args = {}
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cache_expiry = {}
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class FutureJSON():
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"""Class for making a LMQ JSON RPC request that uses a future to wait on the result, and caches
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the results for a set amount of time so that if the same endpoint with the same arguments is
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requested again the cache will be used instead of repeating the request.
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Cached values are indexed by endpoint and optional key, and require matching arguments to the
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previous call. The cache_key should generally be a fixed value (*not* an argument-dependent
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value) and can be used to provide multiple caches for different uses of the same endpoint.
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Cache entries are *not* purged, they are only replaced, so using dynamic data in the key would
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result in unbounded memory growth.
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omq - the omq object
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oxend - the oxend omq connection id object
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endpoint - the omq endpoint, e.g. 'rpc.get_info'
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cache_seconds - how long to cache the response; can be None to not cache it at all
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cache_key - fixed string to enable different caches of the same endpoint
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args - if not None, a value to pass (after converting to JSON) as the request parameter. Typically a dict.
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fail_okay - can be specified as True to make failures silent (i.e. if failures are sometimes expected for this request)
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timeout - maximum time to spend waiting for a reply
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"""
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def __init__(self, omq, oxend, endpoint, cache_seconds=3, *, cache_key='', args=None, fail_okay=False, timeout=10):
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self.endpoint = endpoint
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self.cache_key = self.endpoint + cache_key
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self.fail_okay = fail_okay
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if args is not None:
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args = json.dumps(args).encode()
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if self.cache_key in cached and cached_args[self.cache_key] == args and cache_expiry[self.cache_key] >= datetime.now():
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self.json = cached[self.cache_key]
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self.args = None
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self.future = None
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else:
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self.json = None
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self.args = args
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self.future = omq.request_future(oxend, self.endpoint, [] if self.args is None else [self.args], timeout=timeout)
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self.cache_seconds = cache_seconds
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def get(self):
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"""If the result is already available, returns it immediately (and can safely be called multiple times.
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Otherwise waits for the result, parses as json, and caches it. Returns None if the request fails"""
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if self.json is None and self.future is not None:
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try:
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result = self.future.get()
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self.future = None
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if result[0] != b'200':
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raise RuntimeError("Request for {} failed: got {}".format(self.endpoint, result))
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self.json = json.loads(result[1])
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if self.cache_seconds is not None:
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cached[self.cache_key] = self.json
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cached_args[self.cache_key] = self.args
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cache_expiry[self.cache_key] = datetime.now() + timedelta(seconds=self.cache_seconds)
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except RuntimeError as e:
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if not self.fail_okay:
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print("Something getting wrong: {}".format(e), file=sys.stderr)
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self.future = None
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return self.json
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