  In this paper, we introduce a general class of weighted spaces of holomorphic
Dirichlet series (with real frequencies) analytic in some half-plane and study
composition operators on these spaces. In the particular case when the symbol
inducing the composition operator is an affine function, we give criteria for
boundedness and compactness. We also study the cyclicity property and as a
byproduct give a sufficient condition so that the direct sum of the identity
plus a weighted forward shift operator on the Hardy space H^2 is cyclic.
